Hydrogeochemistry of the Mazamba and

Transcription

Technische Universität Bergakademie Freiberg
Fakultät für Geowissenschaften, Geotechnik und Bergbau
Institut für Geologie
Studiengang Geologie/Paläontologie
Diplomarbeit und Diplomkartierung
Hydrogeochemistry of the Mazamba and Nhambita spring
and springs at Gorongosa Mountain with special emphasis on
geothermal aspects, Gorongosa National Park, Mozambique
DIPLOMA THESIS
Luise Vogler
SUPERVISED BY
Prof. Dr. Broder Merkel
Dipl.-Geol. Franziska Steinbruch
TU Bergakademie Freiberg
Institut für Geologie
Lehrstuhl für Hydrogeologie
Freiberg, June 2009
Eidesstattliche Erklärung
Hiermit versichere ich, dass ich die vorliegende Diplomarbeit und Diplomkartierung
selbstständig und ohne unzulässige Hilfe Dritter angefertigt habe. Ich habe dazu
keine weiteren als die angeführten Hilfsmittel benutzt und die aus fremden Quellen
direkt oder indirekt übernommenen Gedanken sind als solche gekennzeichnet.
Freiberg, 22.06.2009
Luise Vogler
Table of contents
Table of contents
Abstract ................................................................................................................... iv
Illustration index ........................................................................................................v
Index of tables ........................................................................................................ vii
Index of appendices – CD...................................................................................... viii
Index of abbreviations ............................................................................................. xii
1. Introduction .......................................................................................................... 1
1.1. Research questions, objectives and deliverables * ...................................... 1
1.2. Study Area ................................................................................................. 3
1.2.1. Location .............................................................................................. 3
1.2.2. Geology and geomorphology* ............................................................. 5
1.2.3. Climate ..............................................................................................12
1.2.4. Vegetation and land use ....................................................................14
1.2.5. Soils ..................................................................................................15
1.2.6. Hydrology and hydrogeology* ............................................................16
1.2.7. Water uses ........................................................................................17
2. Methods ..............................................................................................................19
2.1. Field sampling and mapping* ....................................................................19
2.1.1. Sampling schedule and logistics* .......................................................19
2.1.2. Monitoring..........................................................................................19
2.1.3. Hydrology and hydrochemistry ..........................................................20
2.1.3.1. Electrochemical parameters* ........................................................20
2.1.3.2. Photometry* .................................................................................24
2.1.3.3. Measurement of discharge* ..........................................................27
2.1.3.4. Sample preservation ....................................................................29
2.1.3.5. Mapping* ......................................................................................29
2.1.4. Tectonic mapping* .............................................................................30
2.2. Laboratory analyses..................................................................................30
2.2.1. ICP-MS ..............................................................................................30
2.2.2. IC – anion ..........................................................................................30
*
Chapters are part of the field sampling and mapping project.
i
Table of contents
2.2.3. IC – cations .......................................................................................30
2.2.4. Stable isotopes ..................................................................................31
2.2.5. Carbon isotopes ................................................................................32
2.2.6. TIC / DOC..........................................................................................33
2.2.7. Investigation of ion conditions ............................................................33
2.3. Statistical techniques ................................................................................34
2.3.1. SiO2-geothermometer ........................................................................34
2.3.2. Calculation of the charge imbalance by PhreeqC ..............................35
2.4. “Digital Atlas – Mozambique 2008”*...........................................................36
3. Results ...............................................................................................................41
3.1. Geological and tectonic mapping* .............................................................41
3.1.1. Gorongosa Mountain* ........................................................................41
3.1.2. Mazamba region* ...............................................................................41
3.1.3. Nhambita hot spring region* ...............................................................43
3.2. Waterchemistry .........................................................................................44
3.2.1. Errors and uncertainties.....................................................................44
3.2.1.1. Calculation of the charge imbalance by PhreeqC.........................44
3.2.1.2. Comparison of photometry, ion chromatography (IC) and mass
spectrometry with inductively coupled plasma (ICP-MS) regarding to their
exactness .................................................................................................45
3.2.2. Introduction to water chemistry and references .................................46
3.2.2.1. Gorongosa Mountain ...................................................................47
3.2.2.2. Mazamba Karst spring .................................................................48
3.2.2.3. Nhambita hot spring region ..........................................................49
3.2.2.4. Site 1 and Sanctuary....................................................................52
3.2.3. Stable isotopes ..................................................................................54
3.2.4. Carbon isotopes ................................................................................55
3.3. Digital Atlas* ..............................................................................................55
3.3.1. Layers and features* ..........................................................................56
3.3.2. Legend of the layers and features*.....................................................58
4. Discussions ........................................................................................................61
4.1. Surface catchment characterization* .........................................................61
ii
Table of contents
4.1.1. Mazamba River surface catchment* ...................................................61
4.1.2. Rupice River surface catchment* .......................................................61
4.1.3. Gorongosa Mountain – surface catchments* ......................................62
4.2. Groundwater provinces and genesis .........................................................62
4.2.1. Groundwater – host rock interactions ................................................62
4.2.2. Elements with increased concentrations ............................................71
4.2.2.1. Phosphate ...................................................................................72
4.2.2.2. Total iron......................................................................................72
4.2.2.3. Manganese ..................................................................................72
4.2.2.4. Fluoride........................................................................................73
4.2.2.5. Mercury........................................................................................73
4.2.2.6. Ammonia .....................................................................................73
4.2.2.7. Sulfate .........................................................................................74
4.2.2.8. Chloride and sodium ....................................................................74
4.2.2.9. Calcium and magnesium .............................................................74
4.2.2.10. Nitrite .........................................................................................75
4.2.2.11. Aluminum ...................................................................................75
4.2.2.12. Uranium .....................................................................................75
4.2.3. Gorongosa Mountain springs classification ........................................76
4.2.4. Karst-associated springs ...................................................................77
4.2.5. Rift-associated springs ......................................................................78
4.2.6. River, creeks and stream water quality ..............................................80
4.2.7. Comparison of the group classification in the investigated areas .......82
4.3. Origin of groundwater ...............................................................................82
4.4. Groundwater aging ...................................................................................84
4.5. Pollution and geogen anomalies ...............................................................85
4.6. Water treatment ........................................................................................86
4.7. Database organization and information dissemination* .............................86
4.8. Errors and uncertainties ............................................................................87
5. Conclusions and recommendations ....................................................................89
6. References .........................................................................................................93
7. Acknowledgement ............................................................................................101
iii
Abstract
Abstract
The Gorongosa National Park in the Sofala Province of Central Mozambique is
located between Tete and Beira and covers an area about 5.300 km² with a
protective area about 1.500 km². The Park is located in the Urema Rift which is part
of the East African Rift System (EARS). The Urema Lake which gets provided by
rivers rising from the Gorongosa Mountain is one of the most important ecological
features of the Gorongosa National Park.
From April to July/August 2008, a detailed hydrochemical monitoring was performed
on four areas – Gorongosa Mountain, Mazamba region, Nhambita hot spring region,
and Site 1 and Sanctuary.
Gorongosa Mountain is located to the north-west of the Gorongosa National Park. It
is an isolated oval massif described as a complex of a felsic core surrounded by
mafic igneous rocks. The objective of this study was to map and geochemically
characterize springs to derive conclusions on groundwater recharge systems of the
region, to identify risks potentially affecting the springs and the potential of utilization
by the local communities.
The Mazamba Karst spring is located in the Mazamba River catchment in the
Cheringoma Province situated north-east of the Gorongosa National Park. The
Cheringoma Plateau forms the eastern edge of the Urema Trough. The goal was to
inspect catchment borders for the definition of the park buffer zone and the
geochemical description of the spring.
The Nhambita hot spring is only one of the sources with a possibly utilization of
geothermical energy directly in the case of balneological use. The investigations
more or less referred to the springs in the Rupice River catchment area. The
Nhambita hot spring region is situated at the southern border of the Báruè Midland,
a Precambrian geological Complex adjacent to the marginal sedimentary
Mozambique Basin. The goal was to measure quantity of thermal springs, their
origin and availability.
Site 1 is situated 6.4 km north and Sanctuary is located 11 km north-east of the
Nhambita hot spring at the southern border of the Báruè Midland. The investigation
comprises collecting water samples of all wells for checking the water quality and
quantity and to assess availability of the wells for inhabitants.
During four months of fieldwork springs, wells, rivers and creeks were investigated
for on-site parameters and photometry as well as sampled for further detailed
classification tests in the laboratory. Analysis of major ions, trace elements and
stable isotopes were conducted in laboratories in Germany and Canada.
iv
Illustration index
Illustration index
Figure 1:
Location of Mozambique........................................................................ 3
Figure 2:
Topographical map of Mozambique with the Gorongosa National Park
(TINLEY, 1977) ...................................................................................... 4
Figure 3:
Topographical map of the Urema Rift Valley (TINLEY, 1977) ................. 4
Figure 4:
Cross section of the Urema Rift (LÄCHELT, 2004) ................................. 6
Figure 5:
Location of Gorongosa Mountain in Central Mozambique...................... 7
Figure 6:
Geology of Gorongosa Mountain in Central Mozambique ...................... 8
Figure 7:
Location of Mazamba region in Central Mozambique ............................ 9
Figure 8:
Geological map of Mazamba region .....................................................10
Figure 9:
Location of Nhambita hot spring region in Central Mozambique ...........11
Figure 10: Geology of Nhambita hot spring region .................................................11
Figure 11: Average monthly rainfall for all major units in the investigation area;
derived from FAO LocClim Climate estimator (OWEN, 2004). ...............12
Figure 12: Precipitation vs. altitude ........................................................................13
Figure 13: a) Sampling procedure with a low flow pump and b) a discharge
measuring cell. .....................................................................................20
Figure 14: Summary diagram of hydrologic processes effecting oxygen and
hydrogen isotopic composition of water (www_3). ................................32
Figure 15: Example of a .pmf file – Digital Atlas – Mozambique 2008.pmf. ............37
Figure 16: Zooming into the Magnifier Window. .....................................................40
Figure 17: Calculated charge imbalance (by PhreeqC) for all taking samples in the
study area.............................................................................................44
Figure 18: Deuterium and oxygen-18 content of (a) Gorongosa Mountain
(April/May/June, 2008), (b) Mazamba Karst spring (June, 2008) and
Nhambita hot spring region (July, 2008), (c) Site 1 and Sanctuary
(July/August, 2008), and (d) rainfall of Chitengo and Gorongosa
(January/May/July/August, 2008) compared with the local meteoric
water line (δ2H=7.9*δ18O+13.3‰; STEINBRUCH & W EISE, 2008). .........54
Figure 19: a) Example for the Hydrochemistry – Limits b) Gorongosa Mountain with
measured samples showing the hydrochemistry limits..........................59
Figure 20: Example for the on-site parameters and all elements in the digital atlas
.............................................................................................................59
Figure 21: Example for the TIC & DOC concentrations in the digital atlas .............59
Figure 22: Example for the trace elements in the digital atlas ................................60
Figure 23: Example for the main cations in the digital atlas ...................................60
v
Illustration index
Figure 24: Example for the main anions in the digital atlas ....................................60
Figure 25: Contour line plot showing the spatial distribution of (I) nitrite, (II) total iron
(III) phosphate and (IV) bicarbonate; screenshot from “Digital Atlas –
Mozambique 2008” ...............................................................................63
Figure 26: Overview of the development of the temperature in the Nhambita hot
spring region.........................................................................................65
Figure 27 a: Contour line plot showing the spatial distribution of (I) EC, (II) pH, (III)
total iron, (IV) phosphate, (V) sulfate, (VI) manganese, (VII) sodium, and
(VIII) fluoride; screenshot from “Digital Atlas – Mozambique 2008” .......67
Figure 27 b: Contour line plot showing the spatial distribution of (IX) chloride, (X)
silicon, (XI) nickel, (XII) mercury, (XIII) bicarbonate, (XIV) calcium, and
(XV) magnesium; screenshot from “Digital Atlas – Mozambique 2008”. 68
Figure 28: Contour line plot showing the spatial distribution of (I) ammonia, (II)
potassium, (III) aluminum, and (IV) uranium, screenshot from “Digital
Atlas – Mozambique 2008” ...................................................................70
Figure 29: Bar plot showing the determination of the major anions and cations in
the springs of the Gorongosa Mountain ................................................76
the Mazamba Karst spring ....................................................................77
the creeks, spring discharges and springs of the Nhambita hot spring
region ...................................................................................................78
the wells of Site 1 and Sanctuary..........................................................79
the rivers of the Gorongosa Mountain ...................................................81
vi
Index of tables
Index of tables
Table 1:
Overview of the measurement procedures ...........................................46
Table 2:
Limit values for all important elements and parameters measured in the
investigation area including MCL MOZ, MCL EPA, MCL WHO and MCL
Germany...............................................................................................57
Table 3:
Summary of all elements which crossed the MCL.................................71
Table 4:
Comparison of all areas in the investigation area related to their groups
.............................................................................................................82
vii
Index of appendices – CD
Appendix A - Tables
Appendix A 1:
All mapped springs, wells, rivers, grab samples and outcrops of
the study area
Appendix A 2:
pH of natural systems (MERKEL, B. et al. 2005)
Appendix A 3:
Electrical conductivity for natural systems (*MERKEL, B. et al.
2005; °HÖLTING & COLDEWEY, 2005)
Appendix A 4:
Table of grab samples and outcrops detected in the investigation
area
Appendix A 5:
Detection limits for anion concentrations
Appendix A 6:
Detection limits for cation concentrations
Appendix A 7:
Device-specific characteristics for TIC/DOC analyses
Appendix A 8:
GPS points with coordinates and elevation [m]
Appendix A 9:
Organoleptic
characteristics
of
rivers,
creeks
and
spring
discharges (blue), springs (green) and wells (pink) of the entire
investigation area
Appendix A 10: On-site parameters measured in the investigation area
Appendix A 11: Analytical results of the Gorongosa Mountain
Appendix A 12: Analytical results of the Mazamba Karst spring (GNP-S 13)
Appendix A 13: Analytical results of the Nhambita hot spring region
Appendix A 14: Analytical results of Site 1 and Sanctuary
Appendix A 15: Discharge rates of the Gorongosa Mountain
Appendix A 16: Measuring data of the discharge of Mazamba Karst spring (GNP-S
13) and its flow channel
Appendix A 17: Discharge rates of the Nhambita hot spring region
Appendix A 18: 14C and 13C concentrations of GNP-W 11 (Site 1) and GNP-S.18
(Nhambita hot spring region
Appendix A 19: Saturation indices of all measured samples. Calculated with the
program PhreeqC, elements considered: T, pH, NO2, PO4, HCO3,
K, Na, Mg, Ca, Cl, SO4, SiO2, F, Mn, NO3, Li, Br, Al, Fe, Ni
Appendix A 20: Saturation indices for the relevant minerals of the different groups
in the areas of investigation
Appendix A 21: Ratios of the spring and well waters determined in the investigation
areas
Appendix A 22: SiO2-geothermometer – calculated temperatures
viii
Appendix B - Figures
Appendix B 1:
pH and redox values of natural occurring waters (MERKEL &
SPERLING, 1996)
Appendix B 2:
Limestone at GNP 23; layer-level-landscape; parallel-stratification
Appendix B 3:
Limestone with a transport direction of the upper moving rocks
recognized by harness plains (SE) (GNP 23)
Appendix B 4:
Calcarenite greywacke with two different dipping directions (GNP
24): one lamination (not in the picture) dips flat to S; second
lamination dips steeply to S (shown in picture)
Appendix B 5:
Limestone at GNP 25 is shaped by discharged water
Appendix B 6:
Rhyolith with milky white colored chalcedony
Appendix B 7:
a) Direction rose diagram of all measured layer plains in the
Mazamba region, Cleary to recognize is the NE-SW strike
direction. b) Pi-circle and pi-pin of all measured layer plains. Cleary
to recognize is the steep alternatively flat dipping of the layers in
the different outcrops
Appendix B 8:
a) Strike direction of GNP 32. b) In-situ gneiss with feldspar, quartz
and biotite
Appendix B 9:
a) Strike direction of GNP 33. b) The below laying gneiss contains
big lenses of quartz
Appendix B 10: Strike direction of quartz veins containing in the pegmatite
Appendix B 11: a) Quartz veins in pegmatite. b) Glimmer (muscovite) in the
pegmatite
Appendix B 12: Strike direction of GNP 35
Appendix B 13: Fault plain with granite, pegmatite and gneiss
Appendix B 14: Strike direction of GNP 36
Appendix B 15: Direction rose diagram of all measured layer plains. Clearly to
recognize is the N-S and EES-WWN direction
Appendix B 16: Overview of nitrite concentration at Gorongosa Mountain
Appendix B 17: Overview of total iron concentration at Gorongosa Mountain
Appendix B 18: Overview of phosphate concentration at Gorongosa Mountain
Appendix B 19: Electrical conductivity [µS/cm] versus time [sec] for the dilution
experiment in the discharge channel resulting in a discharge of
7.74 L/s on June, 18th 2008
Appendix B 20: Overview of phosphate concentration in Nhambita hot spring
region
Appendix B 21: Overview of sulfate concentration in Nhambita hot spring region
ix
Appendix B 22: Overview of chloride concentration in Nhambita hot spring region
Appendix B 23: SiO2-geothermometer calculated for two investigated areas:
springs of the Gorongosa Mountain and Nhambita hot spring
region
Appendix B 24: Piper diagram showing the distribution of major anions and cations
in springs of the Gorongosa Mountain
Appendix B 25: Map screenshot of the “Digital Atlas – Mozambique 2008”
containing flags showing group classification of springs of the
Gorongosa Mountain
Appendix B 26: Piper diagram showing the determination of the major anions and
cations in the Mazamba Karst spring
containing flags showing group classification of the Mazamba
Karst spring
cations in the creeks, spring discharges and springs of the
Nhambita hot spring region
containing flags showing group classification of Nhambita hot
spring region
cations in wells of Site 1 and Sanctuary
containing flags showing group classification of Site 1 and
Sanctuary
cations in rivers and creeks of the Gorongosa Mountain
containing flags showing group classification of rivers and creeks
of the Gorongosa Mountain
Appendix B 34: GNP-R 2 TM – Vunduzi River (701 m) at the Gorongosa Mountain
Appendix B 35: GNP-S 3 FH – Spring (319 m) at Gorongosa Mountain. The spring
is seen in the picture b) right of the piece of wood where the water
is turbid (red colored)
Appendix B 36: GNP-S 4 FH – Nhamucunga River with spring (381 m) at the
Gorongosa Mountain
Appendix B 37: GNP-S 5 FH – Spring (386 m) at Gorongosa Mountain
x
Appendix B 38: GNP-S 6 FH – Spring (447 m) at Gorongosa Mountain
Appendix B 39: GNP-R 10 FH – Muera River (510 m) at Gorongosa Mountain
Appendix B 40: GNP-S 12 TM – Muera Spring (1457 m) at Gorongosa Mountain
Appendix B 41: GNP-S 13 – Mazamba Karst spring (303 m) in the Mazamba
region. a) Mazamba Karst spring with the weir on the left side. b)
Mazamba Karst spring. c) Mazamba Karst spring and its flow
channel. d) Mazamba Karst spring and a worker who measured
the water height behind the weir
Appendix B 42: GNP-R 14 – Rupice River (54 m) in Nhambita hot spring region
Appendix B 43: GNP-S 16 and 17 – Spring 1 and 2 in river parallel to Nhambita hot
spring (42 m) in the Nhambita hot spring region. a) Shows both
springs (red circle). b) Shows GNP-S 16 right below the root (red
circle
Appendix B 44: GNP-S 18 – Spring (66 m) in Nhambita hot spring region. a) Creek
with the spring parallel to Nhambita hot spring. b) Spring (66 m).64
Appendix B 45: MOSA P1 – Nhambita hot spring which is located in the Nhambita
hot spring region
xi
Index of abbreviations
Index of abbreviations
3D
3 dimensional
OC
outcrops
AMS
accelerator mass spectrometry
PDF
portable document format
AOX
absorbable organic halogen
PET
potential evapotranspiration
compounds
PE
polyethylene
DEM
digital elevation model
pH
pH-value
DOC
dissolved organic carbon
PH
photometry
EARS
East African Rift System
pmf
published map file
EC
electrical conductivity
GS
grab samples
EH
redox potential
R²
R-square, coefficient of
EL
evaporation line
EMF
electromotive force or potential [mV]
R.O.A.
range of analyses
EPA
environmental protection agency
RV
rivers
ESRI
Environmental Systems Research
S
Sanctuary
Institute
S1
Site 1
GIS
geographical information system
SI
Saturation Index
GM
Gorongosa Mountain
SM
MERKEL & STEINBRUCH,
GMWL
global meteoric water line
GNP
Gorongosa National Park
SP
springs
GPS
Global Positioning System
SPSS
statistical package for the
IC
ion chromatography
ICP-MS
Inductively coupled plasma mass
T
temperature
spectrometry
TDS
total dissolved solids
IR
infrared sensor
TIC
total inorganic carbon
Kb
base capacity
TIN
triangulated irregular network
Ks
acid capacity
TOC
total organic carbon
LAWA
Länderarbeitsgemeinschaft Wasser
UFZ
Helmholtz-Zentrum für
LISS
low-imaging sensing satellite
Umweltforschung, Halle,
(multispectral satellite images)
Germany
determination
2006
social sciences
LMWL
local meteoric water line
UTM
Universe Transverse
MCL
maximum contamination level
MKS
Mazamba Karst spring
MOSA
Mozambique
MOZ
Mozambique
W
wells
MW
Magnifier Window
WGS
World Geodetic System
MWL
meteoric water line
WHO
World Health Organization
NR
Nhambita hot spring region
O2
dissolved oxygen
Mercator
VSMOW
Vienna Standard Mean
Ocean Water
xii
1. Introduction
1. Introduction
The diploma work describes the execution and results of a hydrogeologically
mapping around the Gorongosa National Park (GNP) in Central Mozambique. The
main investigation areas are Gorongosa Mountain, Mazamba region and Nhambita
hot spring region including Site 1 and Sanctuary. The field work was done from April
17th to August 2nd, 2008.
1.1. Research questions, objectives and deliverables
In Mozambique the water availability is strongly limited. Only hardly a third of the
population has access to clean drinking water – in rural areas the proportion is even
smaller. Women and children often walk long distances in order to get clean water
for their daily use. Due to rain falls the water is polluted by dirty leaves and waste.
The consequence is a high death rate in the population. Diarrhea, bilharzia and
cholera mostly hurt the weakest ones – the children. The country has one of the
highest infant mortality rates of the world: 246 of 1.000 children do not experience
their fifth birthday. During the past decades, wells were bored in different
development projects and water pumps were provided by different organizations
(e.g. World Vision) which are in need of reconstruction (www_1).
The field of functions was limited to four subareas which are in the premises of the
GNP. The goal of this study was to examine the springs on usability for the
inhabitants.
Objectives
The main objectives of this study were:
-
to collect information from previous projects, to analyze and partly reinterpret
them
The geological objectives were:
-
to augment the existing geological map by field observations in selective
outcrops
The hydrogeological objectives were:
-
to analyze four selected study areas for physicochemical measurements
-
to take samples for isotopic analyses on 2H/18O, 14C, ICP-MS, IC, TIC/DOC
-
to sample hot springs, karst springs, cold springs by taking water samples
and measuring on-site parameters
The mapping objectives were:
-
to present a multi-layer GIS (geographical information system) atlas with a
DEM (digital elevation model) and the thematic maps topography (base map
1
1. Introduction
including roads, borders of the GNP, wells, springs, catchments, rivers and
creeks, lakes), geology, tectonics, soil, potential use and different databases
with e.g. locations of the analyzed springs and wells, the examined
geological outcrops, geophysical sites, etc.
-
to present a characterization of all sampled springs with information on
location and previous chemical analyses
Deliverables
Related to the main objectives, the major deliverables of this study were focused as
following.
The geological deliverables were:
-
to improve the geological and especially the tectonic assessment of the rift in
order to comprehend the hydrogeological settings, detect geogenic
contamination sources, possible paths for anthropogenic contamination and
help to make an optimum choice for new well drillings regarding well depth,
well yield and water quality in the future
The hydrogeological deliverables were:
-
to develop a model about the existing springs and wells, their catchments,
the composition and possible connections between the springs
-
to ascertain damage
-
to estimate restrictions and limitations for water use
-
to protect the springs and wells in the future to reassure water quality
-
to calculate the discharge of the flowing inshore waters
-
to indicate a sustainable use of the springs
-
to reassure water quantity
Gorongosa Mountain:
-
to collect details of all springs for the development of new wells (origin and
characteristics)
-
to examine the correctness of the thesis that the springs are dry
-
to assess availability of the springs and wells for inhabitants
-
to inspect whether the springs of the Gorongosa Mountains could be used as
catchment area of the Nhambita hot spring
Nhambita hot spring region:
-
to measure quantity of thermal springs 2, their origin and availability
Mazamba region:
2
to inspect catchment borders for the definition of the park buffer zone
thermal springs = water with more than 40°C indicating that this water comes from larger depth
2
1. Introduction
-
geochemical description of the Mazamba Karst spring
Site 1 and Sanctuary
-
to check quality of well waters
-
to assess availability of the wells for inhabitants
1.2. Study Area
Chapter 1.2. presents a summary of existing knowledge concerning the study area
obtained from literature and previous projects.
1.2.1. Location
N
Figure 1: Location of Mozambique (red colored) (modified according to © Google – Kartendaten © 2008 Tele Atlas,
MapLink/Tele Atlas, AND, Europa Technologies).
The study areas are located around the GNP in the Sofala and Cheringoma
Province of Central Mozambique (Figure 1) which is located between 18°30’ S and
34°06’. Mozambique is situated in the southeast part of Africa between Tanzania
and South Africa. In 1975, it acquired its independence as the “People`s Republic of
Mozambique” under a Marxist presidency. Many years of civil war followed the
peace agreement of 1992. After the first free elections in 1994 Mozambique found
political stability. The consequences of the colonial age and the civil war, however,
are not yet resolved. 70 % of the approximately seventeen million inhabitants live in
the country side and in absolute poverty. GNP suffered a great deal from the
3
1. Introduction
consequences of the colonial age and civil war. The animal population was greatly
reduced and now, the park is getting increased in size through the assistance of
different organizations. The GNP is located 150 km north of Beira in the Urema Rift
which is part of the East African Rift System (EARS). The study area is divided into
four subareas shown in Figures 2 and 3.
1
2
3
Figure 2: Topographical map of Mozambique with the Gorongosa National Park (TINLEY, 1977) and three red
colored points: 1) Gorongosa Mountain, 2) Mazamba region, 3) Nhambita hot spring region, Site 1 and Sanctuary.
1
2
3
4
Figure 3: Topographical map of the Urema Rift Valley (TINLEY, 1977). The red circles mark the position of areas of
interest: 1) Gorongosa Mountain, 2) Mazamba region, 3) Nhambita hot spring region, 4) Site 1 and Sanctuary.
4
1. Introduction
1.2.2. Geology and geomorphology
All four areas of investigation are situated close to the southern end of the East
African Rift zone. The East African Rift stretches through East Africa from the Middle
East (Ethiopia) to Mozambique in southern Africa.
After MORLEY (1999), the East African Rift System (EARS) is formed primarily in the
zones of Precambrian organic belts and also late predominantly extensional events
during the Permo-Triassic, Jurassic, Cretaceous and Paleocene periods influenced
the location of the Tertiary rift system.
The Tertiary-Miocene EARS is characterized by the predominantly alkaline
volcanism. It is divided into two seismically and volcanically very differently active rift
arms: the eastern and the western rift. The western rift arm can be seen as a “good
model for a young continental rift” (MORLEY, 1999). Thereby the eastern rift arm can
be seen as a “mature continental rift system that has failed to produce oceanic
crust” (MORLEY, 1999). Both rift arms cut greatly elevated regions and they are
controlled in their process by the basement structures of east Africa which follow
usually the weak zones of the Mobile Belts 3. They can be characterized by large half
graben
systems
filled
by
fluvio-deltaic
and
lacustrine
sediments,
and/or
volcaniclasitcs. The eastern branch was probably developed in the Eocene;
therefore, the western branch is younger (late Miocene-recent) (MORLEY, 1999).
The western rift arm is less volcanically rich but more seismically active with deeper
earthquakes (down to about 30-40 km) than the eastern rift arm.
Volcanism in the EARS is strongly connected with the structure geological
development of the rift (MORLEY, 1999). Rifting includes mainly volcanic pipes,
grabens and fractures. In Mozambique the southern part of the EARS, in the Urema
Rift zone, geological work has been carried out.
After GTK CONSORTIUM (2006a), Mozambique has encountered different tectonic
physiographic zones or cycles
-
Mountainous Zone or Gondwana Cycle,
-
Large Plateau Zone or African Cycle,
-
Intermediate Plateau Zone or Zumbo Cycle and
-
Coastal Plain Zone or Congo Cycle.
The Gondwana Cycle was developed as a consequence of the PermoCarboniferous movements which was the onset of the Karoo Event. It mainly
affected the crystalline basement and refers to the plateau which lies between 1,500
and 1,800 meters above sea level. It distributes along the border of Malawi. “This
3
Mobile Belts = A long, relatively narrow crustal region of tectonic activity.
5
1. Introduction
cycle is responsible for a major phase of peneplanation of the African continent
during an extensive erosional period from the Upper Karoo till the Upper
Jurassic/Lower Cretaceous” (GTK CONSORTIUM, 2006a).
The African Cycle is an Early Cretaceous erosional phase which enounced the
beginning of the EAR event. During this cycle the Large Plateau Zone was
developed. It conforms to an erosion level at altitudes between 500 and 1,200
meters above sea level.
During the Zumbo Cycle, a phase of Middle Tertiary epeirogenesis the Intermediate
Plateau Zone was developed. Its altitude ranges from 200 to 500 meters. This zone
is developed along the Zambezi Valley and its larger tributaries. “This cycle almost
completely eroded the Karoo terrains and the Tete Gabbro-Anorthosite Suite. In the
area of Precambrian rocks, including Matambo, Missawa-Mândiè, Guro-Macossa,
Marínguè and Changara-Vanduzi, inselbergs 4 were formed” (GTK CONSORTIUM,
2006a).
The Coastal Plain Zone developed during the Congo Cycle and forms the end of the
erosional process.
Several parts of the mountainous western area earn their elevation to EAR
movements cutting the Precambrian crystalline basement.
Figure 4 shows the halbgraben-like profile of the Urema Rift which is due to
differences in timing and amount of displacement at the western and eastern
boundary faults. The Urema Rift has an N-S extension of 280 km. It ranges from the
Zambeze-Chire junction to the Indian Ocean at Beira.
Figure 4: Cross section of the Urema Rift (LÄCHELT, 2004). Legend: 1 – Mazamba Sandstone, 2 – Cheringoma
Limestone, 3 – Grudja Formation, 4 – Sena Sandstone, 5 – Sena Igneous Members, 6 – Belo Formation, 7 –
Stormberg Basalts, 8 – Gorongosa Granite, 9 – Basement Complex.
4
Inselberg = An isolated rock hill, knob, ridge or small mountain that rises abruptly from a gently sloping or virtually
level surrounding plain (HÖLTING & COLDEWEY, 2005).
6
1. Introduction
The Gorongosa Mountain, also called Serra da Gorongosa, is located in NW of the
GNP (Figure 5). It is an isolated oval massif about 30 km (N-S) long and 20 km (EW) wide. The highest point is the Gogogo peak with 1,862 m. This point dominates
the surrounding plateau which is underlain by lithologies of the Báruè Complex.
Figure 5: Location of Gorongosa Mountain (red colored) in Central Mozambique (map created with ArcGis by
Franziska Steinbruch). WGS 1984, UTM Zone 36S.
HUNTING (1984) described the structure of Gorongosa Mountain as a complex of a
felsic core surrounded by mafic igneous rocks. Rock investigations proved the
presence of micro pegmatite-granite with albite, orthoclase, quartz, clinopyroxene,
hornblende, chlorite and biotite. The felsic part consists of tholeiitic gabbro with
labradorite and clinopyroxene, and some norite and olivine-gabbro (GTK
CONSORTIUM, 2006a).
First the gabbros were intruded along a sub-horizontal contact between the
basement and a cover rock sequence – likely in the shape of a lopolith. Later it was
intruded by a granitic diapir. It deformed the gabbros’ layering while a partial rim
syncline was produced. In conclusion, a slander sub-vertical sheet of gabbroic rocks
intruded into the central granite core (GTK CONSORTIUM, 2006a). The dark green,
fine-to-medium-grained gabbro intrudes micaceous and calc-silicate gneisses of the
Báruè Complex southwest of the Muera village. Medium-grained and massive
gabbro is exposed on the southwestern slope of the Gorongosa Mountain. The core
of Gorongosa Mountain is formed from pinkish, medium-grained, massive granite.
The so-called syenite granite comprises a major mineralogy of quartz, albite,
hornblende, orthoclase and clinopyroxene.
The Gorongosa region is combined with a large swarm of basically NNE-SSW
trended felsic and mafic dykes. They radiate north and south of the region over long
7
1. Introduction
distances (up to 50 km). They are recognizable by their sharp-edged form. Some
major fault zones extend from 50 km north of the Gorongosa Suite to 70 km south of
it. They are associated with apparent lateral faults of close to 10 km. On the one
hand it represents extensive block faulting with significant vertical movement that
has taken place on some of the faults and on the other hand the facies interfaces in
the Báruè Complex are overall dipping weakly (GTK CONSORTIUM, 2006a). During
the work of GTK CONSORTIUM (2006a), a syenite sample of the mountain was
dated. Two analyzed zircon fractions show a Lower Jurassic age of 181±2 Ma. The
geological map is shown in Figure 6.
Figure 6: Geology of Gorongosa Mountain in Central Mozambique (map created with Arc View GIS 3.2). WGS
1984, UTM Zone 36S.
The Mazamba region consists of the Mazamba Karst spring which is located in the
Mazamba River catchment in the Cheringoma Province. It is situated NE of the GNP
inside the buffer zone (Figure 7). It is one of many karst springs in the Cheringoma
Plateau, also called Cuesta. The Cheringoma Plateau forms the eastern edge of the
Urema Trough and it rises to 394 m at its scarp crest near Inhaminga Town.
After SCHEIDERER (2006), a karst spring is a source, which is part of a karst
system. In addition, the underground drainage of a larger area belongs to it which
leads to the fact that karst springs have very large delivery. Karst springs are usually
the end of a cave system where a cave river reaches the earth’s surface. The most
important characteristic of karst springs results from the fact that caves transfer the
water quickly. Thus, it comes to a minimum cleaning of the water and to a small
balance of variable delivery.
8
1. Introduction
Figure 7: Location of Mazamba region (blue colored) in Central Mozambique (modified according to map created
with ArcGis by Franziska Steinbruch). WGS 1984, UTM Zone 36S.
The Cheringoma Plateau is a big monocline structure predominantly intersected by
a NNE-SSW system of faults. These are caused by the uplift of the block between
Pungue and Zambezi according to the big monocline structure directed from 3-5°
towards the sea with climax at about 300 meters. In the west, the structure is joined
with the Urema rift with a series of faults. The general inclination of the terrain varies
from branch to slightly hilly in the central range of the Plateau, whereby it is easily
decreased to E and W. The facile streams of the plateau are divided by a
hydrographic watershed along a narrow climax which runs from NNE-SSW into one
area in the ESE and another area in the WNW. The hydrographic network flowing
into the available cleaving system is determined by tectonic structures. The
Cheringoma Plateau belongs to the Mozambican sedimentary basin extending from
the delta of Zambezi in the N down to the border with South Africa in the S. On the
Cheringoma Plateau occur Late Tertiary sandstones (7 – 26 Ma).
The geological map of the Mazamba region is illustrated in Figure 8. The
lithostratigraphical sequence is divided in the Cheringoma Plateau, a sedimentary
series of Cretaceous to Quaternary age, underlying the Mazamba Formation which
consists of Pleistocene, Miocene and Pliocene sediments.
9
1. Introduction
Figure 8: Geological map of Mazamba region (modified according to map created with Arc View GIS 3.2). WGS
1984, UTM Zone 36S.
The Mazamba Formation is divided into two different sections: the Cheringoma
limestone (TTs1 – normal discordance, red sandstone, middle-grain size) and the
Inhaminga sandstone (TTs2 – arkosic and conglomeratic sands containing relics of
mollusks). The Middle-Upper-Eocene Cheringoma Formation (TTi) is affected by a
glauconitic and calcareous sandstone, calcarenites and compact nummulitic
limestone. After OWEN (2004), the limestone bedrock of the Cheringoma Plateau
has caused the development of karst features which result in the interrupted
drainage system (sinkholes, pans). The Grudja Formation (Ksm – upper Senonian
to lower Eocene) characterized by glauconitic calcareous sandstones with
foraminifers, is located on the top of the Sena Formation (Ksc). The Albian/Senonian
Sena Formation is distinguished by reddish sandstones.
The Nhambita hot spring region consists of the Nhambita hot spring which was
analyzed before by B. MERKEL and F. STEINBRUCH in 2006. It is situated in the
Rupice River catchment SW of the GNP inside the buffer zone (Figure 9). The
Rupice River catchment reaches the border of the GNP. Beside the Gorongosa
Mountain, the Nhambita hot spring region is also located in the Sofala province
situated 55 km south of Gorongosa Mountain at an altitude of about 40 m (MERKEL
& STEINBRUCH, 2006). The Nhambita hot spring region is situated at the southern
border of the Báruè Midland, a Precambrian geological Complex, adjacent to the
10
1. Introduction
marginal sedimentary Mozambique Basin. This area is part of the former Miocene
planation surface and characterized by metamorphic gneisses and migmatites with
swarms of granophyres and dolorite dikes and has an altitude of about 400 m
(TINLEY, 1977). The Nhambita hot spring region is located in an area of
Precambrian gneisses with pegmatite veins.
Figure 9: Location of Nhambita hot spring region (green colored) in Central Mozambique (modified according to map
created with ArcGis by Franziska Steinbruch). WGS 1984, UTM Zone 36S.
Site 1
Figure 10: Geology of Nhambita hot spring region (modified according to map created with Arc View GIS 3.2). WGS
1984, UTM Zone 36S.
On the strength of strike slip movements related to the rift forming major fault and
dike systems have developed. With reference to the Urema rift, faults parallel to the
Urema trench (SW-NE and NW-SE) can be expected. Spring discharges and creeks
show the main directions of both fault trends. Both young trends appear with an
11
1. Introduction
older N-S-directed fault system (TINLEY, 1977). The Nhambita hot spring is situated
more or less on the triple junction of the SW-NE fault system which is located on the
NW flank of the Urema Graben and the NW-SE fault systems which are eroded and
deepened by the Pungue River (TINLEY, 1977). The geology of the Nhambita hot
spring region is shown in Figure 10.
Additionally, both Site 1 and Sanctuary were also hydrogeological examined. Site 1
is situated 6.4 km N and Sanctuary is located 11 km NE of the Nhambita hot spring.
Both Site 1 and Sanctuary are located inside the GNP. Site 1 is an apartment
mechanism for the workers of the Camp Chitengo. Houses were developed and a
borehole for water supply was constructed. The fenced Sanctuary comprises 6,200
hectares of ideal herbivore habitat in the Park. Animals get released into it and stay
there to breed until the population is large and strong enough to roam freely in the
Park (www_9). The same as Nhambita hot spring, Site 1 and Sanctuary are situated
at the southern border of the Báruè Midland. Both are located in an area of
Precambrian gneisses with pegmatite veins.
1.2.3. Climate
Mozambique has a sub-tropical monsoon climate characterized by two well-defined
seasons: a dry season from April to November and a rainy season from December
to March (GTK CONSORTIUM, 2006a). After TINLEY (1977), Gorongosa Mountain,
Báruè platform (Nhambita hot spring region, Site 1, Sanctuary), Cheringoma Plateau
(Mazamba region) and Rift Valley are regions with different physiographical
features. The average monthly rainfall for all major units is shown in Figure 11.
.
Figure 11: Average monthly rainfall for all major units in the investigation area; derived from FAO LocClim Climate
estimator (OWEN, 2004).
12
1. Introduction
Four types of climate can be differentiated in Mozambique: (1) tropical rainfall
climate; (2) dry bushland-savannah climate; (3) tropical highland climate and (4)
mountain climate. The climate in the area of interest depends mainly on altitude, and
the water availability of the area depends strongly on altitude, geology and
landscape units (GTK CONSORTIUM, 2006a).
Central Mozambique falls within tropical savannah climate, except for Gorongosa
Mountain with a warm temperature rainy climate (TINLEY, 1977). After OWEN
(2004), the Rift Valley is the driest part of the study area and Gorongosa Mountain is
the wettest part (Figure 12). All areas of interest have wet-season surpluses and
dry-season deficits.
Gorongosa Mountain
Rift Valley
Cheringoma Plateau
Nhambita hot spring
region, Site 1 and
Sanctuary
Figure 12: Precipitation vs. altitude. High rainfall on Gorongosa Mountain and low rainfall in the Rift Valley (OWEN,
2004).
Precipitation values of Gorongosa Mountain (highest rainfall) reach 1,800 to 2,200
mm/yr because it is the only high elevation in the region. The mountain area is a
dominant groundwater recharge area. It presents springs for four major rivers:
Nhandare, Chitunga, Muera and Vunduzi. It has the highest water availability in the
study area. On Gorongosa Mountain the wet season average ranges from around
550 to 1,050 mm/yr and the dry season shows a deficit of 150 to 400 mm/yr.
The Báruè platform (Nhambita hot spring region, Site 1 and Sanctuary) has a
precipitation range of 800 to 1,200 mm/yr (OWEN, 2004). It lies E of the Rift Valley.
Its rainfall varies strongly. Rainfall decreases with distance from the sea but it is also
subject to orographic effects towards the W (TINLEY, 1977). The Báruè Plateau has
similar climate with the Cheringoma Plateau even though they are on different
sides of the rift. For the dry season, the deficit of the Báruè platform is from -400 to 700 mm and of the Cheringoma Plateau it is from -600 to -750 mm. The average for
the wet season is 150 to 550 mm for Báruè platform and 150 to 300 for Cheringoma
13
1. Introduction
Plateau. After OWEN (2004), it is clear that Gorongosa Mountain has a strong
influence on the Báruè platform climate.
Rift flanks include both the westward and the eastward facing flanks of the rift
valley. The rainfall is less than the high rainfalls measured on Gorongosa Mountain.
But it is higher than the rainfall measured in the Rift Valley Floor, a flat-lying plain
consisting of recent to tertiary unconsolidated sediments. This is the driest section of
the described regions. It is part of the Wet-Dry Tropical Savannah Climates with a
moist part. The annual precipitation is from 600 to 1,000 mm/yr (OWEN 2004).
Chitengo, situated in the rift floor, has an average annual temperature of 25.7°C
(winter: 21.5°C; summer: 28.6°C). On the contrary, the Rift Valley floor has the
lowest water availability. The wet season surplus is from 0 to 150 mm/yr and the dry
season deficit is from 700 to 850 mm/yr (results from global FAO LocClim Climate
estimator [OWEN, 2004]).
The eastern coastal zone extends from the edge of the rift valley to the coast. It
includes the Cheringoma Plateau (Mazamba region), the coastal plains and the
Zambezi delta. Precipitation values reach 1,000 to 1,400 mm per year. The wet
season surplus amounts to 250 mm and the deficit of the dry season from 550 to
600 mm.
1.2.4. Vegetation and land use
Vegetation of the investigation area comprises a stepped sequence of moist and dry
formations depending mainly on climate and soil type. Plateaus and valleys
subjected to Karoo and younger rocks are characterized by different flora (GTK
CONSORTIUM, 2006a):
-
high and intermediate forests in valleys formed by the more deeply incised
rivers,
-
savannah-like dry parklands in compact and sandy terrains,
-
shrub and bush savannah in terrains with a clayey-sandy soil or areas with
coarse grained, clastic sediments.
The greater part of Gorongosa Mountain is covered by rain forest, also dense
Miombo (Brachystegia; a genus of tree comprising a large number of species) and
cleared and agriculturally productive land. Cause of the improved rainfall and better
climate, the mountain has attracted settlers. The mountain slopes and foothills are
generally more densely populated than the surrounding areas. The area has also
developed a reputation for food production.
14
1. Introduction
In the Rift Valley Floor, mixed woodland exists on the rift flanks and grasslands,
wetlands and lakes in the rift bottom. Beside well-developed Miombo woodland
(classified in tropical and subtropical grasslands, savannahs and shrublands biome)
on Cheringoma (Mazamba region) in the Eastern Coastal Zone forest, grasslands
and wetlands on coastal plains are present. The typical vegetation cover of the
Báruè platform (Nhambita hot spring region, Site 1 and Sanctuary) is Miombo and
cleared land.
This complexity of types is a change of dominant species or aspects of the same
formation. The vegetation across the investigation area tends to be abundant,
verdant and healthy (OWEN, 2004). The water balance and the nature and volume
of the available water control the type and density of the plant cover.
1.2.5. Soils
The ground of the investigation area is subject to different developing forms. For
example, the soil of Gorongosa Mountain and the Midlands developed under the
influence of denudation and colluvation. Otherwise, soils of the Rift Valley developed
by accretion and hydromorphism (TINLEY, 1977). Soils of the Cheringoma Plateau
are influenced by eluviations and illuviation.
At Gorongosa Mountain, on the fine-grained acid granite ferrallitic soils developed.
On the basis of intensive weathering which led to the soil formation – this gave rise
to the leaching of bases.
The Rift Valley Floor is built up by fluvio-lacustrine alluvium (DNA, 1987). Due to
alluvial fan formation or shifting of river courses different, sorts of coarse and fine
sediments occurred in the floor (TINLEY, 1977).
The crystalline Báruè Midlands (Nhambita hot spring region, Site 1 and Sanctuary)
contain gneisses and migmatites which were the base for the formation of the
mostly sandy skeletal ferrallitic soils (TINLEY, 1977). Their over-permeability results
in rapid infiltration and, therefore, it is responsible for the strongly seasonal nature of
the rivers which originate in the Midlands.
The material of the Cheringoma Plateau (Mazamba region) was cemented by
calcic clay of the Mazamba formation (TINLEY, 1977). When the calcareous material
was leached laterally and downward, impermeable clayey illuvial subsoil with lime
concretions was formed.
15
1. Introduction
1.2.6. Hydrology and hydrogeology
In Central Mozambique marine and terrestrial waters meet and alternate with
seasons and tides over a broad ecotone formed by the overlap of shallow water with
low coastal plains (TINLEY, 1977).
At the Gorongosa Mountain, there are five constant streams that flow from the
mountain catchment. These streams flow both southwards into the Pungue River
catchment or eastwards into the Urema drainage and afterwards southwards into
the Pungue River (TINLEY, 1977). As a result of the higher orographic rainfall on the
mountain, a perennial radial drainage follows from the Gorongosa Mountain.
Because of steep slopes and large areas of bare rock, the runoff coefficients are
expected to be higher than those on the Báruè Platform (TINLEY, 1977).
In
the
Rift
Valley
Floor
disequilibrium
dominates
between
potential
evapotranspiration (PET) and rainfall. In face of this fact, the lowest parts of the rift
floor stay wet most of the year. From both rift flanks the Rift Valley Floor receives
surface runoff via drainage. The drainage comprises the Gorongosa Mountain, the
Báruè Platform and the Cheringoma Plateau. The floor consists of recent to tertiary
sediments. At the rift margins are course-grained sands grading into fine silts and
clays in the central valley bottom – the surface flows do not exist because the
external drainage water infiltrates as groundwater into the course sediments
occurring at the rift margins. Only the larger streams (Vunduzi, Nhandue) continue
as surface streams through the rift. They exit into the Pungue drainage. The surface
flows in the rift floor are also buffered by extensive wetlands in the upper Urema
drainage and by lake storage in Urema Lake reducing surface runoff (OWEN, 2004).
The Báruè Midlands (Nhambita hot spring region, Site 1 and Sanctuary) drains
either northwards into the Zambezi or southwards into the Pungue River either
directly or via the Rift Valley Floor. The Báruè is largely underlain by impermeable
and shallow-weathered crystalline gneisses which result in high runoff coefficients.
Larger streams of the Báruè Midlands are perennial while the smaller streams are
seasonal. The groundwater levels are very shallow and located either in fractures in
the bedrock or in the weathered regolith in valley bottoms (OWEN, 2004).
The Cheringoma Plateau (Mazamba region) is underlain by a suite of sedimentary
and limestone formations that dip gently eastwards towards the ocean. The eastern
margin of the Cheringoma Plateau is covered by recent coastal sands and highly
permeable. These sands are generally flat and low lying. As a result there is rapid
16
1. Introduction
infiltration. A few of the larger streams are perennial while the smaller streams are
mostly seasonal. In the north, the plateau is underlain by limestones which give rise
to sinkholes and other karst features. Groundwater levels are deep. The crest of the
Cheringoma Plateau forms a water divide between streams flowing westwards into
the rift and eastwards to the ocean. It is accepted that the sedimentary and
limestone strata occurring in the Cheringoma Plateau are likely to form an important
regional aquifer (TINLEY, 1977).
The Rift Flanks are divided into the eastern rift flanks which is the western edge of
the Cheringoma Plateau and the western rift flanks. As mentioned before, the crest
of the Cheringoma Plateau forms a water divide between streams flowing
westwards and eastwards. The streams of the western rift flanks follow the regional
drainage slope towards E (TINLEY, 1977).
The factors that control the drainage patterns and the relationships between rainfall,
runoff and infiltration are the nature of the geological bedrock, the degree and
density of fracturing and the thickness of the weathered regolith. The hydrology of
the study area is basically controlled by the geology. The crystalline rocks are
permeability medium; in contrast, the sediments in the rift and E of the rift have
generally higher permeability. On the Cheringoma Plateau, the groundwater levels
are deep while the shallow groundwater in the Gorongosa district is common.
After LÄCHELT (2004), 53 thermal springs exist in Mozambique. MARTINELLI et al.
(1995) have characterized the thermal water in Sofala and Manica District by
chloride-sulfate alkaline water with chloride as the major anion and sodium as the
major cation. Silica contents are below 100 mg/kg. After MERKEL & STEINBRUCH
(2006), the Nhambita hot spring located in the southwestern part of the buffer zone
of GNP is thermal water with a temperature of 62°C and a considerably low
mineralization. Major anions are chloride and sulfate and the major cation is sodium.
This water is about 11,000 years old because of the δ14C concentration. Low
concentration of arsenic, lead, cadmium, mercury, beryllium, selenium, antimony,
and uranium and high concentrations of fluoride were measured by MERKEL &
STEINBRUCH (2006). They speculate that the water comes from the Gorongosa
Mountain which is to be examined in these investigations.
1.2.7. Water uses
Water is one of the most vital natural resource for all life on Earth. The availability
and quality of water always have played an important role in determining not only
where people can live but also their quality of life. Even though, there always has
17
1. Introduction
been plenty of fresh water on Earth, water has not always been available when and
where it is needed, nor it is always of suitable quality for all uses. Water must be
considered as a finite resource that has limits and boundaries to its availability and
suitability for use. It is constantly in motion by way of the hydrological cycle. It
evaporates as vapor from oceans, lakes and rivers; is transpired from plants;
condenses in the air and falls as precipitation; and then moves over and through the
ground into waterbodies where the cycle begins again (HÖLTING & COLDEWEY,
2005).
18
2. Methods
2. Methods
Chapter 2 presents the technical aspect of the field work from April to July/August
2008.
2.1. Field sampling and mapping
Field sampling were arranged between April 17th and August 2nd, 2008. Springs
were located and measured with hydrogeochemical (on-site) parameters and
photometry to acquire the first water information and to retrieve important samples
for further detailed classification tests in laboratory setups. Also, on-site parameters
were measured to be presented in a digital atlas. A description of mapping program
is shown in Chapter 2.4. Lab analysis conducted in Germany and Canada on the
samples is described in Chapter 2.2.
Rivers were selected randomly by considering the size of the river and the
availability of springs and wells in the surrounding area. Springs were chosen
randomized for physicochemical investigations. All springs were mapped and twelve
samples were taken for analyses. Furthermore, wells were chosen randomly by
considering the usability and functioning. All eye-catching pieces of rocks along
roads and walking paths were selected for mapping. Also, outcrops were selected
randomized. All outcrops in the study area were mapped and photographed.
2.1.1. Sampling schedule and logistics
The field work was conducted with the help of staff of GNP. The work at Gorongosa
Mountain (April to June 2008) was performed with a car and most of the time by foot
with the help of Regina Cruz and Tongai Castigo. In the Mazamba region, the field
work (June 2008) was performed by foot and bike with the help of Sicoche Patricio.
With the help of a worker of Nhambita, the field work (July 2008) in the Nhambita hot
spring region was also arranged by foot. A handhold GPS of the type GARMIN
eTrex (12 channel GPS) was used for the positioning.
2.1.2. Monitoring
By the discovering of Gorongosa Mountain three water samples of Muera River, two
water samples of Vunduzi River and six water samples of springs, creeks and rivers
of Gorongosa Mountain were taken for a variety of chemical compounds. In the
region of Mazamba only one water sample and in Nhambita hot spring region six
water samples were taken (comparing with the samples of MERKEL & STEINBRUCH,
2006). Also, four water samples of Site 1 and Sanctuary were taken (Appendix A 1).
Photometrical and on-site parameters were measured at the sampling place. Water
19
2. Methods
samples were taken by low flow pumping using a portable, battery-powered
aspirated Ismatec pump (12 Volt) and a discharge measuring cell (Figure 13). The
water was pumped from the river, creek, spring or well through a hose to the
discharge measuring cell holding the electrodes to read oxygen content (O2),
electrical conductivity (EC), pH, redox potential (EH), and temperature (T).
a)
b)
Figure 13: a) Sampling procedure with a low flow pump and b) a discharge measuring cell.
On the basis of this measurement setup, the reproducible conditions will be
guaranteed. These conditions cannot be obtained by putting sensors in flowing river
water. Water samples were taken for laboratory analyses and photometry which was
measured on site. Alkalinity and acidity were determined by titration (only on
Mazamba Karst spring).
2.1.3. Hydrology and hydrochemistry
Hydrology is the study of the movement, distribution, and quality of water throughout
the earth. It implicates both the hydrologic cycle and water resources.
Hydrochemistry is a subsection of hydrology and examines the materials arising in
natural water. In addition, water tests analyzed the contents of elements, dissociated
ions and undissociated connections. From the resulting mineralization and
distribution contents, conclusions about quality and origin of the water can be drawn.
2.1.3.1. Electrochemical parameters
In order to avoid corruption by physicochemical reactions (e.g. with oxygen, carbon
dioxide), physical and chemical parameters were measured directly on sampling
point by electrodes in a discharge measuring cell. The measuring instruments were
calibrated before each use and in the further course of the day in order to reduce the
measuring errors. The discharge measuring cell and the electrodes were purged by
the first liters of the sampled water over a period of five to ten minutes.
20
2. Methods
Subsequently, the discharge measuring cell was refilled under continuous circulation
of sample water and water samples were taken.
In contrast to the physical and chemical parameters the organoleptic parameters,
i.e. the parameter perceptible with human senses, are only qualitatively judgable.
With the analysis of surface water coloring, turbidity, smell and taste of the water are
considered. Due to the received inspection results are not measurable; their
comparability is not ensured due to the different sensory perceptions of the
examiners. Nevertheless, the organoleptic examination plays an important role as
an indicator of the water quality since e.g. many materials are smell intensive,
however, with measuring instruments to be only insufficiently seized.
Both O2 and pH measurements were performed with a portable measuring
instrument of the HG series (HQ40d Multi Meter). The pH electrode is a combination
SenTix 97/T electrode with an integrated temperature sensor. The pH meter was
calibrated with a two buffer solution (pH 4.01 and 7.00). Under these conditions the
accuracy of pH readings can be arranged to be within 0.1 pH units. After completion
of the measurements the electrode was kept in a protective cap filled with KCl. As a
result of large fluctuations of pH values in May/June the pH electrode was
exchanged by a WTW pH electrode. Statements about the solubility of materials and
the ion concentration of the water can be made by pH.
pH depends on [H3O+] and [OH-] ion concentrations, whereby an increase of the pH
of 1 means an increasing of [H3O+] ion concentration by tenfold. It is valid:
-
acid solution:
[H3O+] > [OH-]  pH < 7.0
-
neutral solution:
[H3O+] = [OH-]  pH = 7.0
-
basic solution:
[H3O+] < [OH-]  pH > 7.0
The pH determines the solubility and ion concentration of many materials. Only few
ions (e.g. Na+, K+, NO3, Cl) remain over the entire pH range in solution. Thus, e.g.
the solubilities of most metal ions depend on pH, in particular the elements those
reacting as both acid and base upon reaction partner (especially metals such as Zn,
Sn, Cr): These connections are easily soluble in a sour environment and fail at rising
pH value as hydroxide and/or salt; at more alkalescency they go under creation of
basic complexes again into solution (HÖLTING & COLDEWEY, 2005). The influence
of this parameter becomes clearly by relationship with the temperature, the redox
potential as well as the electrical conductivity (HÖLTING & COLDEWEY, 2005).
Order-of-magnitude-wise the pH is specified in Appendix A 2 for natural systems.
21
2. Methods
The O2 electrode is a luminescent-based oxygen sensor with an integrated
temperature probe. The sensor was pre-calibrated by HACH – there was no option
for manual calibration. Concentrations for oxygen were indicated in mg/L as well as
in percentage. Accuracy of the O2 readings can be arranged to be within 0.05 mg/L.
During the rating of the water quality the content of solved free oxygen has a central
position since it refers to oxidizing and/or reducing conditions in waters and so
affects the redox potential of the water. Its content is decisive for biochemical
processes in natural waters. The higher it is, the much better is the water quality.
The oxygen content [mg/l] decreases with increase of temperature and/or salt
content of the water and increases with increase of the air pressure. However, the
oxygen saturation [%] is independent of these variables; it can accept values >
100% at streams with high discharge rates in consequence of the air entry.
For the appointment of EH determined as EMF [mV], WinLab®Data-Line Windhaus
pH-meter with a silver : silver chloride (Ag/AgCl) Pt 4805/S7 sensor was used.
Similar to the pH electrode the EH electrode was protected by a cap filled with KCl
after completion of the measurements. Converting the measured EMF value to the
EH value, the following formula was used:
EH = EMFmeasured + (– 0.7443 · T + 224.98)
EH
redox potential [mV]
EMFmeasured
electromotive force [mV]
T
temperature [°C]
(1)
Many bio and geochemical processes of reduction and oxidation reactions lie at the
basis which can be described by electron transfer. Free electrons do not exist during
these procedures, i.e. oxidation and reduction always take place coupled. The
arising electrical tension, so-called redox potential, serves for the quantification of
the redox procedures – it is defined as voltage difference opposite a hydrogen
electrode. The amount of the potential depends on the respective reaction partners;
direction and speed of the process depend on the quantity of the nascent energy.
For the redox potential, solved oxygen is particularly important in the water.
However, the potential also depends on temperature and pH of the water.
Processes which lead to the oxygen consumption come to a decrease of the
potential. Thus, the redox potential is an important indication for aerobe and
anaerobic conditions in waters (HÖLTING & COLDEWEY, 2005).
22
2. Methods
-
aerobe, oxidizing conditions – redox potential > 400 mV
-
intersection, partly-reduced conditions – redox potential 0…400 mV
-
anaerobe, reduced conditions – redox potential < 0 mV
By means of a pH-EH diagram for naturally occurring water, a fundamental
classification of the water is possible regarding their origin (Appendix B 1).
Using the microprocessor conductivity meter LF 320 with the standard-conductivity
cell TetraCon®325 integrating a temperature sensor, the EC has been determined.
The equilibration was reached after ten minutes. The reading was controlled by a
0.01 mol/L KCl calibration standard (0.01 mol/L = 1413 µS/cm). Temperature of
25°C is the automatically recalculated temperature for the recorded EC. The used
measuring instrument has an automatic temperature-correcting function so that the
correct measured value could always be read off immediately. Accuracy of the EC
readings is within 1-2 µS/cm. As a result of large fluctuations of EC values in June
the conductivity meter was exchanged with conductivity meter LF 39 (Sensortechnik
Meinsberg GmbH). EC depends on water temperature as well as dissociation
degree of electrolytes. EC is specified in Appendix A 3 for natural systems. The total
dissolved solids (TDS) are in a close relationship with the electrical conductivity.
This includes all solved solids and becomes indicated in ppm. 1 μS/cm corresponds
approximately to 0.65 mg/l.
Water temperature was measured with three sensors mentioned before and one
different measurement especially for hot and deep-water springs. Conductivity meter
LF 320/LF 39, SenTix 97/T pH electrode/WTW pH electrode and HACH HQ 20
luminescent O2 sensor showed similar values with deviations less than 0.1°C. Thus,
a mean temperature was calculated from these three determinations. The
temperature of hot and deep-water springs was determined with a digital GMH 3350
(Greisinger electronic GmbH, Germany) sensor. The accuracy of the measurements
was ± 0.5°C. Since the solubility of solids and gases as well as the speeds of
physical and chemical reactions in the water depends strongly on temperature the
water temperature is to be measured as directly as possible locally.
The titration of inorganic carbon species (CO2-, HCO3) was only measured at the
Mazamba Karst spring directly at the field site. The adsorbent plays an important
role in natural waters as a buffer in relation to the acid entries. For the water quality,
it is of great importance that pH does not change despite entry of H+ and/or OHions. In the water, carbonic acid is formed by the solution of CO2:
CO2 + H2O
H2CO3
23
2. Methods
By the supply of water carbonic acid dissociate in two stages to bicarbonate and
CO3 whereby protons (H+) become free likewise:
1. dissociation step:
H2CO3 + H2O
2. dissociation step:
HCO3-
HCO3- + H+
CO2- + H+
The redundant H+ ions lead to an increase of pH and thus to the acidification of the
water. Adverse the carbonate system works mainly CO32-, HCO3- and CO2- as
buffers. To describe the buffer capacity and to determine the carbonic acid species
the following criteria are used:
-
Ks – acid capacity
-
Kb – base capacity
In water analytics, these serve as basis for the computation contents of bicarbonate
and carbonate ions, solved carbon dioxide and sum of inorganic carbon. The acid
capacity Ks is a measure of the quantity a certain water volume of H+ ions can
absorb. From this, how much hydrogen carbonate was contained in the sample can
be calculated. For the computation of the CO2 content in a sample the base capacity
Kb is important which represents a measure for the quantity of OH- ions in a certain
water volume (MERKEL, B. et al. 2005).
For the determination of the acid and base capacity, the Test KIT Digital Titrator of
the company HACH was used. With the help of the SenTix 97/T, pH electrode could
be titrated exactly to the desired pH values 4.3 and 8.2. These pH values are
important since they indicate that under a pH value of 4.3 only CO2 and over 8.2
only HCO is present.
For the determination of the acid and base capacity by an intake system,
hydrochloric acid (0.1 N HCL) or caustic soda solution (0.1 N NaOH) was supplied
automatically. Afterwards the acid and/or base capacity could be determined as
follows:
V·c
V·c
Ks =
Kb =
Vs
(2), (3)
Vs
V
volume of added HCl or NaOH in mg/L
c
concentration of HCl or NaOH in mol/L
Vs
sample volume in ml
2.1.3.2. Photometry
The definition of the redoxsensitive elements nitrate (NO3), nitrite (NO2), ammonia
(NH4), iron(II) (Fe2+), total iron (Fe), phosphate (PO4), sulfide (S2-), manganese (Mn),
and silica (Si) have been effected by adoption by HACH – Colorimeter DR/890 to
24
2. Methods
avoid both chemical and microbial oxidation during storage. Before measurement, a
100 ml cuvette were first washed with distilled water 5 and afterwards washed twice
with filtered sample water. Water samples have been filtered by hand with celluloseacetate filters stacked in the middle of the filter machine (Sartorius) by the pore size
of 0.2 µm (Sartorius AG, Göttingen/Germany) and replaced for each sample. For
each analysis of elements, the appendent powder pillows have been added. With
the relation to a blank sample, the results could be read on the colorimeter.
Successionally, the basics of the analyses methods are described.
Nitrate values are commonly reported as either nitrate (NO3) or as nitrate-nitrogen
(NO3--N). Nitrate was determined by method 8192 with a detection limit of 0.02 mg/L
NO3--N (cadmium reduction method). The standard variation for this method is ± 0.1
mg/L using a standard solution of 3.0 mg/L NO3--N. All reagents necessary for this
method are contained in the powder pillows NitraVer5®. Sample water was used as
blank with a quantity of 10 ml. The photometer indicates the content of nitrogen from
nitrate. In order to determine the nitrate content, the result of measurement is
multiplied by the factor 4.4268. Sources of error are up to disturbing substances
such as iron (III), nitrite, chloride, all strongly oxidizing and reducing substances
contained in water as well as pH (ANONYM (b)).
Nitrite was determined by method 8507. Nitrite has a detection limit of 0 and 0.35
mg/L NO2--N (diazotization method). The standard variation for this method is
± 0.001 mg/L using a standard solution of 0.25 mg/L nitrite nitrogen. The detection
limit is 0.005 mg/L. For the photometric regulation, all necessary reagents are
contained in the NitriVer3® powder pillows for 10 ml sample solution. Sample water
was used as blank with a quantity of 10 ml. Substantially, the nitrite concentration
depends on the redox potential of the water. High nitrite contents are a reference to
partly decomposed organic wastes (ANONYM (a)). Most disturbing substances are
metals, nitrate and all strongly oxidizing and reducing substances contained in water
(ANONYM (b)).
Ammonia (as NH4+-N) was determined by method 8155 with a detection limit
between 0 and 0.5 mg/L. The standard variation for this method is ± 0.02 mg/L using
a standard solution of 0.40 mg/L ammonia nitrogen. The detection limit is 0.02 mg/L.
For the determination of the ammonia content, 10 ml of the sample are shifted with
5
The used distilled water came from the air conditioner in the camp of Chitengo and drinking water of bottles bought
in the market in Beira.
25
2. Methods
an ammonia salicylat and an ammonia cyanorat powder pillow. Distilled water was
used as blank with a quantity of 10 ml.
Total iron was determined with method 8008 with a detection zone between 0 and
3.00 mg/L (FerroVer method). The standard variation for this method is ± 0.017
mg/L and the detection limit is 0.03 mg/L. It is the sum of solved iron in the aqueous
phase both Fe (II) and Fe (III). Iron II (Fe2+) (method 8146; 1.10-Phenantrolin
method) can be formed by reduced influences at the boundary layer between
sediment and water body of water which goes into solution. In deeper groundwater,
iron is often present in the oxidation state II (Fe2+). Under air effect it oxidizes easily
to Fe3+. The intensity of the color development is directly proportional to the iron
concentration (ANONYM (a)). The determination of the total iron content takes place
using iron reagent for 10 ml of the sample solution. For the determination of the
bivalent iron, 25 ml of the sample are shifted with 1.10-Phenantrolin indicator in the
form of powder pillows. The trivalent iron does not react with this method. By
subtraction of iron (II) of the total iron, the concentration of Fe (III) results (ANONYM
(a)). Interferences may appear at high levels of Mg (> 100,000 mg/L), Cl (>185,000
mg/L) and S2-.
Phosphor was determined with method 8048 with a detection zone between 0 and
2.5 mg/L PO43- (PhosVer3/ascorbic acid method). The standard variation for this
method is ± 0.05 mg/L. The detection limit is 0.05 mg/L. For determination of the
phosphate content 10 ml, filtered sample water is shifted with a PhosVer3® powder
pillow (ascorbic acid).
Sulfide was determined by method 8131 with a detection limit between 0 and 0.7
mg/L S2- (methylene blue method). The standard variation for this method is ± 0.02
mg/L using a standard solution of 0.73 mg/L sulphide. The detection limit is 0.01
mg/L. For determination of the sulphide content, 25 ml filtered sample water is
shifted with a PhosVer3® powder pillow (ascorbic acid). Distilled water was used as
blank with a quantity of 25 ml.
Manganese was determined by method 8149 with a detection range of 0 and 0.7
mg/L (PAN method). The standard variation for this method is ± 0.013 mg/L. The
detection limit is 0.007 mg/L. Ascorbic acid is used for the reduction of all forms of
manganese oxidized in Mg2+. An alkaline cyanide reagent is added to mask all
potential interferences. After adding the PAN indicator with the presence of
manganese, an orange coloring develops (ANONYM (a)). Interferences can appear
26
2. Methods
at high levels of aluminum (> 20 mg/L), iron (> 5 mg/L) and copper (> 50 mg/L).
Distilled water was used as blank with a quantity of 25 ml.
Silica was determined by method 8186 with a detection range of 0 and 1.6 mg/L
(heteropoly blue method). The standard variation for this method is ± 0.025 mg/L
and the detection limit is 0.02 mg/L. Under acid conditions silica acid and phosphate
react with the molybdation.
2.1.3.3. Measurement of discharge
Under discharge the water volume is defined which per time unit flows through a
defined aboveground discharge cross-section (e.g. river cross section); the unit is
indicated in l/s or m3/s. The determination of the discharge can take place by means
of measuring resistance, hydraulic current meter or with tracer tests.
The discharge measurement (Gorongosa Mountain, Nhambita hot spring region)
could be more or less only estimated since no suitable equipment could be
prepared. On the basis of a 50 ml PE bottle, the water velocity was detected with
measuring the width and depth of the source of water. The 50 ml PE bottle was half
filled with water in such a way that it was half submerged in the water. A start and
end point were specified, afterwards the time was measured the bottle needed from
point A to point B. Changes of discharge are led back on strong precipitation events,
seasonally caused thaw phases and infiltration and evaporation period. Short term
changes of weather can cause delays during the attitude of discharge equilibrium.
Calculation of discharge:
D=A·v
D
discharge [m³/s]
A
area of discharge profile [m²]
v
discharge velocity [m/s]
(4)
Discharge of the Mazamba Karst spring and flow channel was determined by
dilution test. With this test, hydraulic geological marking means (tracers) are used. It
can be natural (e.g. environmental isotopes, environmental organisms) or artificial
origin (e.g. salts, coloring materials). In the investigation area, for tracer
measurement a saline solution well-known concentration was entered by moment
impulse into running waters – this solution is diluted due to transport in running
waters. The measurement principle is based on the fact that the tracer concentration
is noted by proof of the electrical conductivity at the point of registration, measuring
27
2. Methods
point laid downstream, continuously. From this concentration passage the dilution
and the discharge can finally be computed. The distance lying between input and
measuring point is to serve and must the complete mixing of the tracer in waters.
The evaluation is made afterwards by concentration time graph. In addition by
means of syringe to the water test, a quantity was given to a defined saline solution
(1,000 g NaCl in 10 L water), and measured following the conductivity. The change
of conductivity was read in 1 to 10 seconds intervals about 13.5 m downstream until
2 m before the channel reaches another river. This step was repeated twice. The
disadvantage of the tracer tests is apart from the ecological risks regarding the
tracer concentration in the multiplicity of the possibilities of error, like mixing, e.g.
lacking, turbulences by the underground and change of the background conductivity.
The following formula was used:
c1 · V
Q=
∑t2t1 c · ∆t
(5)
Q
discharge [L/s]
c1
EC of the tracer solution (by adding NaCl) [µS/cm] (= 91,900 µS/cm)
V
amount of used water [L]
t2
end of tracer arrival at registration point [s]
t1
begin of tracer arrival at registration point [s]
c
EC at the registration point [µS/cm]
∆t
time lag between two tracer concentration measurements at registration
point [s]
At c the background had to be abstracted by the formula:
c = ECmeasured · ∆t – ∆t · ECnatural
(6)
c
corrected EC [µS/cm]
ECmeasured
measured EC [µS/cm]
∆t
time lag between two tracer concentration measurements at
registration point [s]
ECnatural
natural EC without supply of NaCl [µS/cm]
At the Mazamba Karst spring, the discharge was determined over a certain period
(04/28/2008 to 08/01/2008) with a measuring weir. The measuring weir made of
wood was installed about 3 m downstream of the spring. Approximately 1 m
upstream, a resident measured the water level each day; likewise he was
28
2. Methods
responsible for the maintenance of the weir. Due to the kind of the measurement
(arise from individual errors with measuring) an evaluation was not possible.
2.1.3.4. Sample preservation
For laboratory analysis, the following water samples were taken: For ICP-MS
(inductively-coupled-plasma mass-spectrometry) filtered water (0.2 µm) was filled in
a 30 ml polyethylene (PE) bottle and stabilized with nitric acid (HNO3) to avoid fail of
elements. 50 ml filtered (0.2 µm), unstabilized water was taken for major anions and
cations (IC). For stable isotopes, 0.2 µm filtered, unstabilized water was kept in 30
ml PE bottles. For tritium (3H), water was unfiltered and unstabilized sampled in
1,500 liter bottles and for radiocarbon (14C), water was filtered (0.2 µm) with mercury
chloride (HgCl2) stabilized and sampled in 500 ml glass or PE bottles. For the
measurement of TIC (total inorganic carbon) and DOC (dissolved organic carbon) a
100 ml glass bottle was filled with 0.2 µm filtered, unstabilized water. Before
collecting water samples, bottles were washed with filtered sample water twice
avoiding contamination. All samples were kept cool and dark in the refrigerator until
final analysis in the laboratory. Except on transport to Germany, it was not possible
to keep the bottles cool.
2.1.3.5. Mapping
While the monitoring work at the study area, mapping was done as a basis for the
digital atlas. The size of the mapping area can be divided into three main areas:
parts of Gorongosa Mountain with approximately 425 km² (60 % of the entire
Gorongosa Mountain – 720 km²), parts of Mazamba region with 95 km² (30 % of the
entire Mazamba region – 315 km²) and parts of Nhambita hot spring region with 30
km² (46 % of the entire Nhambita hot spring region – 65 km²). Additionally, Site 1
and Sanctuary were measured for hydrogeological aspects but no special mappings
have been done.
For the orientation, tracks and representative waypoints such as water springs,
wells, rivers, creeks, living places, grab samples and outcrops, a GPS of the type
GARMIN eTrex was utilized. The next consideration was to map all springs and
wells with information about location, owner, dimension and employment.
Hydrochemical information was obtained using on-site parameters and photometry.
Some information also came from owners or individuals living there. Depths of some
wells could not be read because the pumps were closed systems.
Altogether, 39 springs (SP), 20 wells (W), 90 rivers (RV), 45 grab samples (GS) and
15 outcrops (OC) have been mapped within the study area (Appendix A 1). 22
29
2. Methods
samples of water were sampled and analyzed for the complete chemistry program
mentioned before (Chapters 2.1.2.; 2.1.3.1.-2.1.3.3.).
2.1.4. Tectonic mapping
Tectonic mapping on outcrops as a basis of the digital atlas was done besides the
monitoring work in the investigated area. GPS equipment mentioned before and a
geologist compass (geologist structure compass of Freiberg, coordinated with the
southern hemisphere) were used. Eight outcrops have been determined in
Mazamba region. In Nhambita hot spring region, five outcrops were determined. All
outcrops of the study area are noted in Appendix A 4.
2.2. Laboratory analyses
Nine tritium samples were taken but due to information of expecting low tritium
values the tritium measurement did not take place.
2.2.1. ICP-MS
For the determination of trace elements, the procedure of the ICP-MS was used.
This analytic method is based on the ionization of the material in plasma which can
be analyzed. Therefore, 0.2 µm filtered and with HNO3- stabilized samples were sent
in 30 ml PE bottles to Activation Laboratories Ltd. in Ancaster, Ontario, Canada
without preservation. The samples were measured by code 6 – natural waters with
low TDS (< 0.05 %).
2.2.2. IC – anion
IC was used for identification of the concentrations of major anions such as fluoride
(F), chloride (Cl), bromide (Br), phosphate (PO4), nitrate (NO3), and sulfate (SO4).
Filtered water samples were analyzed at the home university in Freiberg, Germany.
The ion chromatograph was an Eppendorf Biotronic IC 2001 using a conductivity
detector with a range of 100 µS/cm. The eluent was 1.8 mmol/L Na2CO3 + 0.6
mmol/L NaHCO3 (composed on September 2nd, 2008) with a discharge rate of 1.5
ml/min and pressure of 90 bars. On the basis of high and low anion concentrations,
samples were also analyzed at different dilutions (max. 21-fold) and evaporations
(max. 20-fold). The detection limits are shown in Appendix A 5.
2.2.3. IC – cations
IC was also used for identification of the concentrations of major cations such as
lithium (Li), sodium (Na), ammonia (NH4), manganese (Mn), potassium (K), calcium
30
2. Methods
(Ca), and magnesium (Mg). Filtered water samples were analyzed at the home
university in Freiberg, Germany. The ion chromatograph was a Merck HITACHI
system model 6000 A L5025. The eluent was 2 mM HNO3 + 1 mM Dipicolinacid +
0.25 mM Crown Ether (composed on September 2nd, 2008) with a discharge rate of
1 ml/min and pressure of 90 bars. On the basis of high and low cation
concentrations, samples were also analyzed at different dilutions (max. 21-fold) and
evaporations (max. 20-fold). The detection limits are shown in Appendix A 6.
2.2.4. Stable isotopes
0.2 µm filtered, unstabilized samples were sent in 30, 50 and/or 100 ml PE bottles to
the laboratory of the department of isotope hydrology of the Helmholtz Centre for
Environmental Research (Helmholtz-Zentrum für Umweltforschung – UFZ) in Halle,
Germany without preservation. The stable isotopes such as
18
O and 2H were
determined by a gas isotope mass spectrometer (type Delta S; Company Thermo
Finnigan in Bremen, Germany). The analytic accuracy of δ2H is ± 1 ‰ and of δ18O is
± 0.1 ‰. The results of the stable isotopes are named in the usual δ-notation as ‰deviation from international standards. For 2H and 18O, this is the sea water standard
VSMOW (Vienna Standard Mean Ocean Water). Since in most cases the isotope
ratio are depleted from sea water opposite meteorically water, i.e. RP/RS < 1, for
basic and precipitation water results a negative δ-value.
The isotopic compositions of water can be compared to a well-known relationship –
the meteoric water line (MWL). It expresses the worldwide relationship between
18
O
2
and H in meteoric waters as follows (CRAIG, 1961 [www_3]):
δ2H = 8 · δ18O + 10‰
The relationship between 2H and
(7)
18
O isotopic ratios of natural waters in any
particular area is defined as the local meteoric water line (LMWL). The generalized
MWL is often described as the global meteoric water line (GMWL) which is a global
average of many local meteoric water lines. The LMWL is used as basic information
when discussing water cycle processes in a particular area and for regional and
local investigations. For Mozambique, the LMWL is described as follows
(STEINBRUCH & W EISE, 2008):
δ2H = 7.9 · δ18O + 13.3‰
(8)
After CLARK & FRITZ (1997), factors such as salinity, wind speed, humidity and
temperature affect kinetic fractionation of water during evaporation. The lower the
31
2. Methods
relative humidity, the faster the evaporation rate and the greater the kinetic
fractionation. Humidity affects hydrogen and oxygen differently.
The slope of the evaporation line will vary due to changes in relative humidity. It will
be close to 4 at very low relative humidity (<25%), between 4 and 5 for moderate
humidity (25% to 75%) and approach 8 for relative humidity (>95%). Likewise,
relative humidity affects the isotopic composition of water vapor reflected in the d
value (deuterium excess) of the MWL. In arid regions (low humidity), the d value will
be high upwards of 20. In contrast, in humid regions (high humidity) the d value will
be low approaching 0 (Figure 14).
Figure 14: Summary diagram of hydrologic processes effecting oxygen and hydrogen isotopic composition of water
(www_3).
2.2.5. Carbon isotopes
0.2 µm filtered and with mercury-chloride (HgCl2) stabilized samples were sent in
500 ml PE bottles to the Leibniz laboratory for age determination and isotope dating
in Kiel, Germany without preservation. Approximately 100 ml water sample was
isotope-neutrally filtered by a 0.2 µm membrane filter with inert gas and acidified
with approximately 2 ml of 30% phosphoric acid. Subsequently, the CO2 was rinsed
with nitrogen and caught cryotechnically. Afterwards, the extracted CO2 was
reduced with H2 at 600 °C over an iron catalyst to graphite and the iron graphitic
mixture was pressed into a sample holder for the accelerator mass spectrometry
(AMS) measurement.
32
2. Methods
The 14C concentration of the samples results from comparison of the simultaneously
determined
14
C,
13
C and
12
C contents with those of the CO2 measuring standard
(oxalic acid II) as well as suitable background samples. The conventional
14
C age is
computed after STUIVER and POLACH (radio carbon, 19/3 (1977), 355
[STEINBRUCH & W EISE, 2008]) with a correction on isotope fractionation on the
basis of the
the
13
C/12C ratio measured at the same time with AMS. The uncertainty in
14
C result considers counting statistics, stability of the AMS machine and
uncertainty in the subtracted background.
2.2.6. TIC / DOC
The identification of TIC and DOC required a 0.2 µm filtration of sampled water
analyzed at the home university in Freiberg, Germany. Analyses were done by
liquiTOC (Elementar Analysensysteme GmbH) with a standard deviation of
± 0.05 mgCorg/L and a detection limit between 0.1 and 5000 mgCorg/L. Devicespecific characteristics are shown in Appendix A 7.
By means of calculations, the HCO3- can be calculated. The HCO3- depends on pH;
with pH below 6 almost all carbon is CO2. pH between 7 and 8, nearly all C is mainly
bicarbonate. pH above 10, the predominant part of C is present as carbonate. CO2
does not appear above pH 9 (www_1).
2.2.7. Investigation of ion conditions
Apart from the analysis of common ions such as sodium, calcium, potassium,
magnesium etc. as well as redox sensitive elements, halides (Cl-, Br-, I-, and F-) play
an important role by the investigation. These are generally regarded as conservative
elements which react only in very small measure by the water transport with their
environment.
Like all halides (halogens) chlorine is with load of -1 the most stable (chloride). In
this form it does not participate in important redox reactions. In addition, chloride
adsorbs badly at loam or clay. Furthermore, chloride minerals fail only starting from
Cl- concentrations > 200 g/L. Therefore, chloride is suitable also as tracer because it
does not participate like carbon, nitrogen and sulfur in biological cycles (biologically
inertly). Cracking processes between the two sturdy chlorine isotopes are caused
therefore by physical processes. Under mixture and evaporation processes in the
hydrologic cycle as well as by salt solution in the underground, in groundwater large
variation of the chloride concentration can be found (CLARK and FRITZ, 1997).
Thus, it is not sufficient the exclusive quantitative regulation of Cl- as indicator as
source of salinity.
33
2. Methods
More helpfully is the view of ion and/or abundance ratios as for example Ca/Cl,
δ18O/Cl, Br/Cl, and particularly Na/Cl. With their assistance, mixture processes,
groundwater movements and geochemical processes can be identified whereby a
statement is possible for the genesis of saliniferous waters. Thus, for example, the
Cl/Br relationship permits a conclusion on whether groundwater of marine or
evaporative origin (solution of salt deposit places in rocks). The relationship of
sodium and chloride is suitable particularly for the identification of a sea water
intrusion because during the dilution of groundwater the relationship receive remains
how it is to be found in sea water.
Halogens ingest in the crystal lattice prefer the place of the hydroxyl groups. With
beginning alteration they are extracted most easily from rock federation.
Iodide and bromide are inclined to enrich in marine vegetation. Thus, brown algae
and corals contain about 32,000 times more iodine than sea water (BONESS, 1990).
If an arm of the sea is cut off of the ocean and is subject afterwards to evaporation,
whereby the marine fauna and flora perishes the stored iodide and bromide are
again set free which leads relative to an enrichment to the chloride.
2.3. Statistical techniques
A hierarchical cluster analysis was performed for the statistical evaluation of the
major anions and cations with the statistical software SPSS 16.0. The analysis were
done with the Ward`s method.
A spearman rank correlation was done for testing the dissolved major elements of
significance with the statistical software SPSS 16.0. The statistical significance was
defined at the 5% level.
The saturation index (SI) was used to express whether a solution was in equilibrium
with a solid phase or if it was under or over saturated in relation to a solid phase
respectively. SI values ranging between -0.2 and 0.2 indicated that water was close
to equilibrium with respect to a certain mineral (MERKEL & PLANER-FRIEDRICH,
2005). SI values of more than 0.2 indicated water that was super saturated to the
corresponding mineral. SI values of less than -0.2 indicated water that was under
saturated with respect to the corresponding mineral. SI was calculated with the
program PhreeqC.
2.3.1. SiO2-geothermometer
On the attitude of a chemical equilibrium between minerals of the aquifer and the
deep water, the principle of the chemical geothermometer is based. The equilibrium
depends on multiplicity factors such as reaction kinetics, reservoir temperatures,
34
2. Methods
concentrations of elements in the water and retention time of the water in the
reservoir (MOTYKA, 1980). If the time of contact between water and host rock is too
short no equilibrium can be prepared. The temperature of the water changes faster
during the ascent than the equilibrium composition. If water changes its composition,
it depends on permeability, way and type of rock (with ascent). By eliminations with
ascending and cooling of the water, precipitation can appear whereby the chemical
composition deviates according to deep water. Ideally, the reservoir temperature
represents the original temperature. This is computed by the chemical composition
of the water.
The silicon geothermometer is based on the connection between silicon solubility,
temperature and pressure. By temperature-dependent reactions between thermal
water and minerals such as quartz, chalcedony, amorphous silicon and cristobalite,
silicon can be dissolved. According to FOURNIER (1973), quartz determines the
silicon equilibrium starting from temperatures over 150°C. At temperatures below
150°C chalcedony (sometimes also cristobalite or amorphous silicon) is in
equilibrium. The reservoir temperatures can be computed after FOURNIER (1973)
from silicon concentrations (www_5).
Since unfortunately no data about the geothermal gradient in the investigation area
were available, temperature increase with depth was estimated based on an
average of 3°C/100m.
FOURNIER & POTTER (1982) presented two equations calculating the temperature
of SiO2 formation depending on the modifications (quartz or chalcedony):
quartz
T°C = 1309 ÷ (5.19 – log SiO2) – 273.15
(9)
chalcedony
T°C = 1032 ÷ (4.69 – log SiO2) – 273.15
(10)
2.3.2. Calculation of the charge imbalance by PhreeqC
The water analyses from field site and laboratory were checked for accuracy by
calculating the charge imbalance with the hydrogeochemical modeling program
PhreeqC v2.15 using the Wateq4F-database. PhreeqC is a chemical speciation
code for natural waters that uses field measurements such as pH, EH, T, alkalinity,
and the chemical analyses of a water sample as input and calculate the distribution
of aqueous species, mineral saturation indices and ion activities. The program uses
the following equation for calculating the charge imbalance:
100 · (∑cations [meq/L] – ∑anions [meq/L])
Percent Error =
(∑cations [meq/L] + ∑anions [meq/L])
35
(11)
2. Methods
As a result of a wide range of possible error sources, values smaller than ± 10 %
can be seen as tolerable and values smaller than ± 5 % are considered as accurate
(LANGGUTH & VOIGT, 2004).
2.4. “Digital Atlas – Mozambique 2008”
The “Digital Atlas – Mozambique 2008” shows the results of hydrogeological and
hydrogeochemical field work at Gorongosa Mountain, Mazamba region, Nhambita
hot spring region and Site 1 and Sanctuary around the GNP in Mozambique
between April and July/August 2008.
The presentation of all data was building up with the help of the GIS software
ESRI® ArcMapTM, version 9.2. For the visualization of the digital atlas, ArcReader
was used. ArcReader is a free, easy-to-use desktop mapping product from ESRI®
ArcGIS for viewing, exploring and printing maps and globes. Preparing the digital
atlas, at first it was necessary to import satellite images of the study area. The map
layout contains 32 LISS Satellite Photos by a size of 32 km x 26 km. The map was
already georeferenced so no further refurbishment was necessary. The three
channels were combined for true color displaying. The boundaries for detailed
identification were the boundary of GNP and Gorongosa Mountain which already
existed and the boundary of the Rupice River surface catchment and Mazamba
River surface catchment. These two boundaries were compiled as polygon layers.
Rivers and roads were compiled as vector layers and the polygon layer of Lake
Urema already existed. Also, cities already existed as point layers. Waypoints were
taken by GPS coordinates. These coordinates were read out with OziExplorer. The
raster layers of geology, geomorphology, soils and land use also already existed
and compatible with the work in the area of interest. DEM was based on
topographical heights which already existed. These topographical heights were
interpolated to three different elevation models including Nhambita hot spring region,
Mazamba region and the entire investigation area. Also, a 3D model was compiled
for the entire investigation area. This based on the 3D Analyst. The topographical
heights were converted as raster surface to 3D shown as points in the map.
Thereafter, modifying the 3D points to a TIN showing a 3D model in the map.
The next step was to import further coordinates into ArcMap, divided in: wells
(marked as red dots in the atlas), springs (marked as dark orange dots in the atlas),
intermittent rivers (marked as orange dots in the atlas), permanent rivers (marked as
yellow dots in the atlas), grab samples (marked as light green dots in the atlas) and
outcrops (marked as green dots in the atlas). These coordinates were imported as
point layers standardized to the WGS 1984 Universal Transverse Mercator (UTM)
36
2. Methods
Zone 36S. Assigned to these point layers, additional tables with information such as
longitude, latitude, altitude, description, features and hydrochemistry (some also
hyperlinks) were imported as database. From these tables, three groups for
hydrochemistry were created: hydrochemistry of wells, hydrochemistry of springs
and hydrochemistry of rivers. Within these three groups, different notations were
chosen to illustrate hydrochemical features based on the internal feature tables. TIC
and DOC, main anions, main cations and trace elements were displayed as pie
charts. On-site parameters such as EC, EH, O2 content and saturation, pH, T, TDS
and all important elements are displayed as bubbles, size depending on the
represented concentration: small size for low concentrations, medium size for
moderate concentrations and big size for high concentrations. Each parameter was
colored differently. Isolines were compiled for all important elements (NO2-, NH4+,
PO43-, Fe, S2-, Mn, Li, F, Br, Al, Si, Ni, Hg, U, HCO3-, SO42-, Cl-, NO3-, Ca, Mg, Na, K)
by the ArcMap Extension Spatial Analyst. With the feature “Interpolate to Raster”, it
was possible to create such a grid with Inverse Distance Weighted. The spatial
distribution for all important elements is shown by contour lines also plotted with
ArcMap Extension Spatial Analyst with Surface Analysis. The contour interval was
chosen by each element. At the end, the four main layers were created: Overview
GNP, Study area Gorongosa Mountain, Study area Nhambita hot spring region, and
Study area Mazamba region.
ArcReader – quick start tutorial
The best way to learn ArcReader is to try it yourself. This quick start tutorial guides
you through some basic ArcReader skills as exploring a map of the GNP,
Mozambique.
ArcReader can open published map files (.pmf) that have been created in ArcMap
and/or ArcGlobe with the ArcGIS publisher extension (Figure 15).
Map Display
Table of Contents
Figure 15: Example of a .pmf file – Digital Atlas – Mozambique 2008.pmf.
37
2. Methods
ArcReader Toolbar:
Open published map document.
Recent files – click here to see all recent files.
Print map.
Toogle table of contents – click here to activate or inactivate the table of
contents at the left side.
The ArcReader Toolbar has tools to move around the map and query features on
the map:
Zoom In – click here, move the mouse pointer to the desired location, then
click and drag a box around an area of the map. When releasing the mouse
button, the map zooms into the selected area.
Zoom Out – click here to zoom out one level. Continue clicking until you
have zoomed out to the desired level.
Fixed Zoom In – click here to zoom in one level. Continue clicking until you
have zoomed in to the desired level.
Fixed Zoom Out – click here to zoom out one level. Continue clicking until
you have zoomed out to the desired level.
Pan – click here, then click and drag the map in any direction. Dragging
down – see more of the top; dragging up – see more of the button; dragging
right – see more of the left; dragging left – see more of the right.
Zoom to Full Extent – click here to return to the full extent of the map.
Go Back to the previous extent.
Go Next to the next extent.
Using the Identify tool to obtain spatial and tabular information, seeing which
features are at a specific location and also investigate the attributes of each feature.
Identify – click here, then click to any point, river, street etc. to see
information.
Find – click here to search for any layer, points etc.
Measure – click here, then click to one point on the map and pull the mouse
pointer to another point. A small window will open and you will see the
distance between the two desired points.
38
2. Methods
Hyperlinks – click here and select the input links at the map.
Scale Bar – Select the pull down arrow to change the scale of
the display.
Activating layers and turning features on and off:
The table of contents is where map layers are activated and features turned on and
off. Activating a layer, right-click on layer in the table of
contents. To display a feature, check the box next to the
feature’s name. To turn it off, uncheck the box. It is important
to remember that layers will draw on the map in the order
they appear on the table of contents. Clicking on the small
plus on the front of the feature a small scale bar appears
underneath the check box.
Obtaining information about layers and features:
Each of the layers and features in a map has a set of properties that can be viewed
allowing the functionality available for that layer and/or features to be learned.
Properties
Using the Magnifier Window:
There are times when not wanting to change the location displayed in the map but
still need to see more detail. The ArcReader Magnifier Window allows this to be
done.
1. Click Window and click Magnifier. The Magnifier Window (MW) will open.
2. Click the title bar of the MW and drag it over the map. While dragging it, the
MW will show crosshairs to indicate which part of the display will be
magnified.
39
2. Methods
Result while dragging.
Result after dropping.
3. When the crosshairs are over the portion of the map, release the mouse
button. An enlarged view of the location under the MW will appear.
It is possible to change several properties of the MW, such as the magnification
factor and what the MW displays.
4. Move the pointer near the edge of the MW until it turns into resizing arrows,
then click and drag the window in the direction to resize.
5. Place the pointer inside the MW and right-click. Point to Magnification Factor
and click e.g. 800 %. This will scale the data displayed in the MW by the
percentage chosen (Figure 16).
Figure 16: Zooming into the Magnifier Window.
6. Right-click the MW and click Lock Magnifier. Click and drag the title bar of
the MW to move it somewhere else. The picture keeps the snapshot.
7. To re-enable the magnifier, right-click the MW and click Lock Magnifier
again. The window redraws to magnify the section of the map. When
finished, click the close button.
40
3. Results
3. Results
Chapter 3 presents the geological and hydrochemical results obtained during field
work.
3.1. Geological and tectonic mapping
In the investigation area, grab samples and outcrops were investigated and briefly
accounted by geological aspects (Appendix A 4). The rock types were taken from
Carta Geológica (MARQUES, 1968). Except the so-called micropegmatite granite is
called syenite granite (GTK CONSORTIUM 2006a) in the following description.
3.1.1. Gorongosa Mountain
At the Gorongosa Mountain, the detected grab samples were granite, gneiss,
hornfels and gabbro. The syenite granite (description by GTK CONSORTIUM 2006a)
builds the uppermost part of the Gorongosa Mountain.
The syenite granite is a pinkish, massive, medium-grained granite which intrudes
gabbroic rocks. It consists of the main mixing products albite, orthoclase, quartz,
hornblende and clinopyroxene. The color of the rocks in the investigation area varies
between grey red to red. Also grab samples of gneiss were found in the
investigation area. The investigated gneiss can be classified as orthogneiss,
developed from magmatic parent material. The gneiss was a medium-grained
metamorphic rock with pronounced parallel structure. Main mixing products are
feldspar (orthoclase), quartz and mica (biotite, muscovite). In the investigation area,
the color was grey. Gabbro, a grey, fine to medium-grained depth rock, contains the
main mixing components plagioclase and pyroxene. On the western site of the
Gorongosa Mountain, a medium-grained, massive gabbro was discovered. Hornfels
are metamorphic rocks. They develop between 600 to 700°C. At these temperatures
the shale lost their schistosity and accepted the so-called hornfels structure. The
close and hard, compact rock possessed fine to middle grain size. The color was
grey and spotted. According to HUNTING (1984), the structure of Gorongosa
Mountain is described as a complex of a felsic core (granite) surrounded by mafic
igneous rocks (gabbro, gneiss, hornfels).
3.1.2. Mazamba region
The outcrops were located in the catchment of the Mazamba River. All outcrops
were in good conditions and partly weathered.
GNP 23, 26 and 27 were layer-level-landscapes. GNP 23 was located 560 m W of
Mazamba Karst spring. The layer plain of GNP 23, 26 and 27 were dipping with 041
3. Results
35° to SSE (Appendix B 2). Noteworthy was a parallel-stratification. According to the
geological map (Figure 8), a calcarenite greywacke was identified but a limestone
was outcropping. The limestone was a fine to medium-grained sedimentary rock
which consisted of a large extent of calcite (calcspar). At GNP 23, it was
recognizable that a transport of the upper rocks took place from NE to SW which
can be shown at the harness plain (Appendix B 3).
GNP 24 and 28 were located approximately 800-1000 m W of Mazamba Karst
spring. GNP 24 was characterized by two different dip directions. One lamination
dipped like GNP 23 – flat to S. And the other lamination dipped steeply to S
(Appendix B 4). These enormously difference can be explained by tectonics (e.g.
fault, block slide due to the karst system). Also here, a parallel-stratification exists.
The rocks in situ are calcarenites (lime sand brick). A calcarenite is a rock formed by
the percolation of water through a mixture of calcareous shell fragments and quartz
sand causing the dissolved lime to cement the mass together. A calcarenite is also
called a dune rock or dune limestone.
1.42 km SE of the Mazamba Karst spring, GNP 25 was located. The measured layer
plain had a main dip direction to SE and two secondary dip directions to SW and W.
Again, a parallel-stratification is dominant (Appendix B 5). The detected limestone
was shaped by discharged water.
GNP 29 and 30 were located 2.44 km NE of Mazamba Karst spring. The measured
layer plains dip flat to SSE. As well a parallel-stratification of the quartzitic
greywacke was found.
In the investigated area, grab samples like greywacke, calcarenite, conglomerate,
sandstone, reddish and quartzitic greywacke and rhyolith with chalcedony were
found. 7.45 km NW of the Mazamba Karst spring, GNP 31 was located. Layers
could not be measured because the rocks were broken and no rocks in situ were
found. The rhyolith had a phorphyritical texture with inclusion of quartz and feldspar.
The rock was compact and fine grained containing chalcedony with a milky white
color (Appendix B 6).
In the entire Mazamba region a parallel layering exist. In Appendix B 7 a), the NNESSW striking direction of the layers is recognized clearly. The striking direction
indicated the process to the fold axle at the same time. In Appendix B 7 b), the
uniform dipped to SSE can be easily reconstructed whereby there was a clear
difference between GNP 25 with a steep dipping of 55-75° and a flat dipping of 035° in the remaining outcrops. As mentioned before in Chapter 1.2.2., the
Cheringoma Plateau is a big monocline structure predominantly intersected by a
NNE-SSW system of faults. These are caused by the uplift of the block between
42
3. Results
Pungue and Zambezi according to the big monocline structure directed from 3-5°
towards the sea with climax at about 300 meters.
3.1.3. Nhambita hot spring region
The outcrops were located in the catchment of the Rupice River. All outcrops were
strongly weathered. In this area, gneiss, pegmatite, quartz veins and granite were
found partly folded indicating a complex structural geology.
The outcrop of GNP 32 was located 420 m S of Nhambita hot spring. It was
characterized by two different dip directions. The main lamination dipped with 70° to
E and the other lamination dipped with 135° to SE (Appendix B 8 a). The rock
outcropping was gneiss with feldspar, quartz and biotite (Appendix B 8 b).
GNP 33 was located 1.2 km S of Nhambita hot spring. The layer plain dipped with
205-210° to the SSW (Appendix B 9 a). The rock outcroppings were two different
kinds of rocks. The first rock type was gneiss and the other type was a pegmatite
with course-grained feldspar and quartz. The gneiss also contained big lenses of
quartz which had the same dip direction as the gneiss (Appendix B 9 b). Both rock
types were strongly weathered.
1.15 km SE of the Nhambita hot spring, GNP 34 was located. The rock in-situ was
also a pegmatite. But in these pegmatites small veins of quartz with a strike direction
of 5-10° to N were found (Appendix B 10). The pegmatite had no dip direction but it
contained partly areas of muscovite (Appendix B 11).
GNP 35 was located 1.1 km SE of Nhambita hot spring. The measured layer plains
stroke with 20-30° to N (Appendix B 12). As well course-grained feldspar, quartz and
muscovite were found. This location can be seen as a big fault plain. At the ground
granite was visible and right above the granite, a mixture of pegmatite and gneiss,
was recognizable (reworked material) (Appendix B 13).
GNP 36 was located 8.7 km N of Nhambita hot spring. Two kinds of rocks were
located – gneiss and pegmatite. The measured layer plains of gneiss dipped with
14-20° to N and the measured layer plains of the pegmatite dipped with 21-26° to N
(Appendix B 14). As well course-grained feldspar, quartz and muscovite were found.
In the investigation area, grab samples like gneiss, granite, quartz blocks and
pegmatite were found. In Appendix B 15, the different striking directions of the layers
are clearly seen. The main strike direction pointed to NNW-SSE and two other
directions stroke to NW-SE (Chapter 1.2.2.). Spring discharges and creeks show the
main directions of both fault trends.
43
3. Results
3.2. Waterchemistry
3.2.1. Errors and uncertainties
During the field work, four sampling sites were investigated with 22 water samples of
wells, springs, rivers and creeks. At the sampling site, photometrical as well as onsite parameters were determined (Chapter 2.1.3.1. and 2.1.3.2.). As mentioned
before in Chapter 2.2., major cations, anions, TIC and DOC were analyzed in the
water lab of the Technische Universität Bergakademie Freiberg, Germany. Missing
values were labeled by the general code -999 and values below detection limit were
replaced by 0.3 * detection limit for further evaluation.
Uncertainty and error introducing sources were identified. They consist of parameter
uncertainty, errors in sampling and chemical analysis and uncertainties due to
computational and numerical procedures.
3.2.1.1. Calculation of the charge imbalance by PhreeqC
Figure 17: Calculated charge imbalance (by PhreeqC) for all taking samples in the study area.
For sixteen water samples the considered parameters for PhreeqC were T, pH, pe
(16.9 * EH), totals such as Ca, Cl, F, Fe2+, Fe3+, HCO3-, K, Mg, Na, NH4+, NO2-, NO3-,
PO43-, and SO42-. Only six water samples (GNP-S 13, 18, GNP-R 19, GNP-W 20, 21
and 22) were measured by ICP-MS. The results of this measurement were used for
the PhreeqC calculation. The considered parameters were T, pH, pe and totals such
as Ba, Br, Ca, Cl, F, Fe2+, Fe3+, HCO3-, I, K, Li, Mg, Mn, Na, NH4+, NO3-, PO43-, Rb,
SO42- and Si. The results of the accuracy check are shown in Figure 17. About 85
44
3. Results
water samples were only investigated by photometrical measurements and on-site
parameters. Due to missing information about anions and cations, high errors (80 to
95 %) resulted from the PhreeqC calculation. These values were not used for any
further evaluation.
The percent error for fifteen water samples were less than ± 5 %, for four water
samples less than ± 10 % and for three samples more than ± 10 % and thus not
used for further evaluation.
3.2.1.2. Comparison of photometry, ion chromatography (IC) and mass
spectrometry with inductively coupled plasma (ICP-MS) regarding to their
exactness
In the whole investigation area all waters were measured with photometry and ion
chromatography (IC). Only waters of GNP-S 13, GNP-S 18 and GNP-R 19 (also
MOSA P1, P3 and P4) were measured with ICP-MS. With different measuring
procedures raises the question which used procedure is the best and more detailed
one.
The definition of the redoxsensitive elements nitrate, nitrite, ammonia, iron(II), total
iron, phosphor, sulfide, manganese, and silica have been effected by photometry to
avoid both chemical and microbial oxidation during storage. Possible source of
errors during measurement with a photometer can be soiled cuvettes which are to
be examined before for fingerprints and contamination. Further the use of wrong
coat thickness, turbidity of solution, light reflection at the edge of the cuvette,
temperature influences, device-dependent errors, and solvent absorption. This
makes an initial blank sample inevitably (KRAUSE, 2003).
With IC, mainly all major anions and cations have been measured. Each substance,
whose retention time agrees with the one of the examined ions, can represent a
source of error. For example, at the nitrate identification source of error is bromide
(CASTELLUCCI, 2004).
The ICP-MS measurement procedure was mainly used to measure trace elements.
Coincidental errors are pulsating sample supply, atomizer noise, noise in plasma
and detector. Biased errors are wrong standards, errors and analyte looses during
sampling preparation, blank values, matrix effects, equipment drifts, and isobar
overlays of analyte isotopes (W OLLENWEBER, 2000).
Iron was measured with both photometer, IC and ICP-MS. In the groundwater iron is
normally present in the oxidation state II (Fe2+). Under air effect it oxidizes easily to
Fe3+. Therefore, photometry is the better and more exact procedure measuring iron.
45
3. Results
For nitrate, nitrite, ammonia, phosphate, manganese, sodium, potassium, calcium,
and magnesium, IC results are preferred since IC is specialized on the major anions
and cations. ICP-MS results are more exactly for bromide and lithium and all other
trace elements since ICP-MS is concentrated on trace elements. Table 1 shows the
measurement procedures in overview.
Table 1: Overview of the measurement procedures. X shows the relative measured
procedure which was used and the green colored small boxes show the chosen procedure
for each element.
NO3
NO2
NH4
Fe (total)
2+
Fe
PO4
Mn
Li
Na
K
Ca
Mg
Br
Photometer
X
X
X
X
X
X
X
IC
X
X
X
X
X
X
X
X
X
X
X
X
X
ICP-MS
X
X
X
X
X
X
X
X
3.2.2. Introduction to water chemistry and references
As mentioned before in Chapter 2.1.3.5., mapping was done putting results from
hydrochemical monitoring at the field site (Chapter 2.1.2.) into a broader context in
relation to a spatial spreading of water components such as cations, anions, redox
sensitive elements and field parameters in the surrounding area.
In the following sections the on-site parameters and the analytical results will be
presented. Mozambican water standard (2004), US EPA (2003), WHO (2004), and
the Drinking Water Ordinance of Germany (2001) were used as reference. GPS
points with coordinates and elevations are listed in Appendix A 8. All organoleptic
characteristics are listed in Appendix A 9 and all on-site parameters are listed in
Appendix A 10. The analytical results of the Gorongosa Mountain are listed in
Appendix A 11, the analytical results of the Mazamba Karst spring are listed in
Appendix A 12, the analytical results of the Nhambita hot spring region are listed in
Appendix A 13, and the analytical results of Site 1 and Sanctuary are listed in
Appendix A 14. Pictures of the relative sampling points are shown in Appendix B 34
to 45.
46
3. Results
3.2.2.1. Gorongosa Mountain
The examined water of the Gorongosa Mountain showed no organoleptic
characteristics; the water of all springs, rivers and creeks was clear and odorless,
without coloring and turbidity as well as characterized by an only – very small
amount of suspended matter. Nevertheless, there were exceptions: GNP-S 3 FH
exhibited an easily musty smell and GNP-S 6 FH exhibited a strongly musty smell
and some turbidity.
EH of the rivers was within the range of 274.6 mV and 359.2 mV. The EH of the
springs was between 32.5 mV and 502.5 mV. According to the pH-EH-diagram
(Appendix B 1), the water occurring in the investigation area was a mixture of
groundwater and river water. The EC of the rivers was between 33.5 µS/cm and
409.0 µS/cm and of the springs the EC was between 39.1 µS/cm and 186.8 µS/cm.
The MCL MOZ of 50-2000 µS/cm was crossed by GNP-R 7 FH, GNP-S 8 TM, 9 TM,
and 12 TM. The MCL Germany of 2500 µS/cm was not crossed. During the
measurement, both oxygen content and saturation were measured. The oxygen
contents of the rivers were between 8.2 mg/L and 9.1 mg/L. The oxygen contents
of the springs varied between 0.4 mg/L and 8.4 mg/L. The oxygen saturation of the
rivers was between 93.1 % and 97.9 %. The oxygen saturation of the springs varied
between 4.6 % and 86.0 %. The pH of the rivers was between 6.94 and 8.53, and
for the springs pH varied between 5.95 and 7.94. The MCL MOZ and EPA of 6.5-8.5
were crossed by GNP-S 4 FH, 5 FH, 6 FH, 8 TM, and GNP-R 10 FH. T in the rivers
was between 15.4°C and 20.9°C. A variety between 15°C and 24.4°C occurred in
the springs.
In Appendix A 15 the discharge is specified. The discharge of the rivers had an
average of 1.78 L/s and was between 0.37 L/s and 7.50 L/s. The discharge of the
springs was between 0.31 L/s and 1.87 L/s.
Below, the results of the laboratory water analysis measured by non dispersive IR,
IC and ICP-MS are presented. Only the contents exceeding the maximum
contamination level (MCL) will be discussed in detail.
Nitrite (NO2) was measured by both IC and photometry showing comparable
results, IC measurement was preferred (Chapter 3.2.1.2.). Nitrite in the rivers was
between 0.01 mg/L and 0.05 mg/L. The nitrite contents of the springs were between
0.02 mg/L and 1.4 mg/L. The concentrations did not cross the MCL MOZ and WHO
of 3 mg/L. But GNP-S 3 FH, 6 FH, and 8 FH crossed the EPA MCL of 1 mg/L and
Germany MCL of 0.5 mg/L. The process of the nitrite distribution is shown in
Appendix B 16.
47
3. Results
Total iron (Fe) was measured with photometry and IC showing compatible results,
photometry was preferred (Chapter 3.2.1.2.). The MCL MOZ of 0.3 mg/L was easily
crossed only by GNP-S 3 FH and the MCL Germany of 0.2 mg/L was crossed by
GNP-S 3 FH and GNP-R 7 FH. In Appendix B 17 total iron concentrations are
plotted.
Phosphate (PO4) was measured by IC and photometry showing deviating results,
IC measurement was preferred (Chapter 3.2.1.2.). The value at GNP-R 2 TM
measured by photometry was 0.8 mg/L and measured by IC showed a value of 2.0
mg/L. Only GNP-R 10 FH and GNP-S 12 TM did not cross the MCL MOZ of 0.1
mg/L (Appendix B 18). All other rivers and springs crossed the MCL’s.
The concentrations of bicarbonate (HCO3-) of the rivers were between 11.6 mg/L
and 207.1 mg/L and of the springs they varied between 2.6 mg/L and 151.3 mg/L.
3.2.2.2. Mazamba Karst spring
The Mazamba Karst spring (GNP-S 13) was investigated for five days taking three
readings each day. However, only little differences were observed. Three days after
the five days observation the spring was investigated again. The results are
described in the following.
The Mazamba Karst spring water was clear and odorless, without coloring and
turbidity.
The EH was within the range of 311.73 mV and 392.88 mV. According to the pH-EHdiagram (Appendix B 1) it is reflected that river water was present in the
investigation area. The EC was between 923 µS/cm and 993 µS/cm. The oxygen
content was between 4.0 mg/L and 4.6 mg/L. The average oxygen saturation was
55.4 %. The oxygen saturation was between 49.8 % and 57.7 %. In the Mazamba
Karst spring, the pH was between 7.37 and 7.39. The MCL MOZ and EPA of 6.5-8.5
and the MCL Germany of 6.5-9.5 were not crossed. The water temperature of the
spring had an average of 25.9 °C.
From the dilution test a total discharge of 7.74 L/s for the section up to the point
where the channel almost crossed another river was calculated from the integral of
the tracer concentrations (Appendix B 19). 1000 g dissolved NaCl was used as
tracer and the increasing of the EC was measured. Up to the arrival of the tracer at
the 13.5 m downstream convenient point of registration 230 seconds were passed.
In Appendix A 16 the measuring data of the discharge are specified.
In the following, the results of the laboratory water analyses measured by non
dispersive IR, IC and ICP-MS are presented. Only the concentrations exceeding the
MCL were discussed.
48
3. Results
Total iron (Fe) was measured with photometry, IC and ICP-MS. Results from
photometry were preferred because elements have been affected by photometry
avoiding both chemical and microbial oxidation during storage (Chapter 3.2.1.2.). At
the Mazamba Karst spring the content was 1.6 mg/L. The MCL MOZ of 0.3 mg/L
was crossed fivefold and the MCL Germany of 0.2 mg/L was crossed eightfold.
Phosphate (PO4) was measured by both photometry and IC. With IC, PO4 could not
be detected. In the investigated spring the phosphate had a concentration of 1.2
mg/L. This value crossed the MCL MOZ of 0.1 mg/L.
Manganese (Mn) was measured by photometry and ICP-MS showing different
results, photometry was preferred (Chapter 3.2.1.2.). The concentration was 0.4
mg/L and it crossed the MCL MOZ of 0.1 mg/L and the MCL EPA and Germany of
0.05 mg/L.
The acid capacity (Ks) of the karst spring was 7.5 mmol/L while the base capacity
(Kb) was 2.25 mmol/L. On the basis of the acid and base capacities measured in the
investigation area, the carbonic acid species can be computed from the pH. Nearly
the same results were determined on the basis of the measurement bicarbonate.
The concentration of bicarbonate (HCO3-) was 392.7 mg/L (6.43 mmol/L).
The ions Ca2+ and HCO3- make up the major part of dissolved components in karst
waters. Calcium (Ca) value was 60.1 mg/L (measured with IC) and above the MCL
MOZ of 50 mg/L. In the water sample of the Mazamba karst spring, a strontium
content > 0.2 mg/L (> 200 µg/L) was measured with the ICP-MS. The barium (Ba)
content was > 0.4 mg/L (> 400 µg/L). Therefore, no further conclusion can be made
exactly.
3.2.2.3. Nhambita hot spring region
The area of interest was investigated before by MERKEL & STEINBRUCH (2006).
MERKEL & STEINBRUCH (2006) determined water of the Nhambita hot spring and
its water channel. However, one task of the thesis was to examine the environment
of the hot spring and to compare the results with those of MERKEL & STEINBRUCH
(2006). The Nhambita hot spring was classified as thermal and mineral water (ALBU
et al., 1997).
The Nhambita hot spring region water had some organoleptic characteristics. The
water of GNP-R 14 and 15 was brown and turbid. GNP-R 14 was colorless and
clear. GNP-S 16 and 17 were waters with a color between clear and brown, with
strong turbidity and a musty smell. These were small springs developing in mud.
Both GNP-S 18 and GNP-R 19 were colorless with light turbidity. At GNP-S 18, an
iron accumulation was developed.
49
3. Results
The EH in the creeks was within the range of 252.5 mV and 306.3 mV, and of the
springs it varied between 70.1 mV and 321.0mV. After MERKEL & STEINBRUCH
(2006), the EH values in the Nhambita hot spring and its channel were between -5.6
mV and 301.6 mV. According to the pH-EH-diagram (Appendix B 1) it is reflected
that a mixture of groundwater and river water occurred in the investigation area.
In the creeks, the values of the EC were between 1813 µS/cm and 2480 µS/cm. The
EC in the springs varied between 1651 µS/cm and 1688 µS/cm. The values of
MERKEL & STEINBRUCH (2006) were in the same range – between 1643 µS/cm and
1680 µS/cm. The MCL MOZ of 50-2000 µS/cm was crossed by GNP-R 14 and 19
but the MCL Germany of 2500 µS/cm (20°C) was not crossed. The oxygen
contents in the creeks were between 2.7 mg/L and 5.6 mg/L and at the springs they
varied between 0.5 mg/L and 4.9 mg/L. Comparing with MERKEL & STEINBRUCH
(2006), the values were in the same range (0.42 mg/L to 5.58 mg/L). The oxygen
saturation of the creeks was between 31.2 % and 73.4 %. The oxygen saturation in
the springs varied between 8.5 % and 75.4 %, the same range as the water samples
of MERKEL & STEINBRUCH (2006). The pH in the creeks was between 6.83 and
7.46 and in the springs, it was between 6.47 and 7.46. The values of MERKEL &
STEINBRUCH (2006) were a bit above the sampling point measurements. The MCL
MOZ and EPA of 6.5-8.5 and the MCL Germany of 6.5-9.5 were crossed at the
lower limit by GNP-S 16 and 17 with a pH value of 6.49 and 6.47. The
temperatures in the creeks were between 19.1°C and 29.1°C. The springs
exhibited temperatures in the range of 41.0°C and 41.7°C. Comparing these values
with MERKEL & STEINBRUCH (2006), it is remarkable that the temperature of the
spring of MOSA P1 was much higher (61.2°C) than all other measurement. MOSA
P1 is the Nhambita hot spring whereas the other points are only channels or other
small springs.
In Appendix A 17 the discharge is specified. At the spring discharges and creeks,
the discharge was 0.11 L/s. The springs exhibited discharges between 0.02 L/s and
0.12 L/s.
In the following, the results of the laboratory water analyses measured by non
dispersive IR, IC and ICP-MS (only GNP-S 18 and GNP-R 19 were measured (+
MOSA P1, P3, P4)) are presented. Only the contents exceeding the MCL were
discussed.
Ammonia (NH4) was measured with IC and photometry, IC was preferred (Chapter
3.2.1.2.). MCL Germany of 0.5 mg/L was crossed by GNP-R 15 and GNP-S 16.
Total iron was measured with photometry, IC and ICP-MS, photometry was
preferred (Chapter 3.2.1.2.). Measurements of photometry and IC showed the same
50
3. Results
values and in comparison with ICP-MS the values were different. The values of
MOSA P1, P3 and P4 were between 0.06 mg/L and 0.15 mg/L. The concentrations
of the creeks in the investigated area varied between 1.4 mg/L and 3.2 mg/L and the
springs showed contents between 0.1 mg/L and 0.9 mg/L. The MCL MOZ of 0.3
mg/L and the MCL Germany of 0.2 mg/L were crossed by GNP-R 14, 15, 19, and
GNP-S 16, 18.
Phosphate (PO4) was measured with IC and photometry showing the same results,
IC measurement was preferred (Chapter 3.2.1.2.). GNP-R 19 was below the
detection limit 0.05 mg/L (photometry) and 0.1 mg/L (IC). Concentrations of the
creeks varied between 0.4 mg/L and 2.8 mg/L and those of the springs, they were
between 0.3 and 0.5 mg/L. Only GNP-R 19 did not cross the MCL MOZ of 0.1 mg/L
(Appendix B 20).
Sulfate (SO4) was measured with IC. The content in the brooks was between 387.8
mg/L and 504.1 mg/L and in the springs, it was between 348.8 mg/L and 362.9 mg/L
(Appendix B 21). The values measured by MERKEL & STEINBRUCH (2006) were
between 309.1 mg/L and 333.2 mg/L. All measuring points crossed the MCL MOZ
and EPA of 250 mg/L and the MCL Germany of 240 mg/L.
Manganese (Mn) was measured with photometry, IC and ICP-MS, IC measurement
was preferred (Chapter 3.2.1.2.). The values of the creeks were between 0.1 mg/L
and 0.8 mg/L and the values of the springs varied between 0.1 mg/L and 0.6 mg/L.
MOSA P1, P3 and P4 had values at 0.05 mg/L. Comparing the manganese values
of the spring discharges, creeks and springs of the Nhambita hot spring region with
the MCL MOZ of 0.1 mg/L, the conclusion is permissible that GNP-R 14, 19 and
GNP-S 16, 18 crossed the limit. Also, the MCL EPA and Germany (0.05 mg/L) got
crossed by all sampling points. The MCL WHO (0.4 mg/L) got crossed by GNP-S 16
and GNP-R 19.
The contents of bicarbonate (HCO3-) in the creeks were between 46.0 mg/L and
82.0 mg/L and the contents of the springs were between 37.8 mg/L and 66.4 mg/L.
Sodium (Na) contents of the creeks were between 334.2 mg/L and 467.3 mg/L and
the contents of the springs varied between 295.4 mg/L and 309.3 mg/L (measured
with IC). Values measured by MERKEL & STEINBRUCH (2006) were between 295
mg/L and 300 mg/L. All measuring points did not correspond to the requirements of
the MCL MOZ and the MCL Germany of 200 mg/L.
Fluoride (F) was measured by IC. The values of the creeks were between 9.0 mg/L
and 11.1 mg/L, the values of the springs were between 7.8 mg/L and 8.7 mg/L. The
values of MERKEL & STEINBRUCH (2006) were between 8.6 mg/L and 9.5 mg/L. All
51
3. Results
values crossed the MCL MOZ, WHO and Germany of 1.5 mg/L, also the MCL EPA
with 4 mg/L.
Chloride (Cl) was measured by IC. The determined chloride concentrations are
specified in Appendix B 22. The chloride contents of the creeks varied between
285.9 mg/L and 389.9 mg/L and the contents of the springs were between 262.3
mg/L and 264.3 mg/L. After MERKEL & STEINBRUCH (2006), the values ranged
between 228.2 mg/L and 241.0 mg/L. All measured points crossed the MCL MOZ,
EPA and Germany of 250 mg/L except MOSA P1, P3 and P4.
The following parameters were measured only by ICP-MS; only GNP-S 18, GNP-R
19, MOSA P1, P3 and P4. Not all parameters are considered but only those which
are relevant for the elaboration of the investigation area (high values).
The nickel (Ni) value of GNP-S 18 was 1.2 µg/L and GNP-R 19 the value was 8.6
µg/L. After MERKEL & STEINBRUCH (2006) the values were between 27 µ/L and 35
µg/L. MOSA P1, P3 and P4 crossed the MCL MOZ and Germany of 20 µg/L. The
MCL WHO of 70 µg/L was not crossed.
The strontium contents at GNP-S 18 and GNP-R 19 were above 200 µg/L. But
MOSA P1, P3, and P4 showed values between 800 µg/L and 820 µg/L. For
strontium no MCL was specified in the drinking water regulation after MOZ, EPA,
WHO or Germany.
The concentration of mercury was 1.3 µg/L (GNP-S 18) and 2.3 µg/L (GNP-R 19)
and crossed the MCL MOZ and Germany of 1 µg/L and the MCL EPA of 2 µg/L. The
concentrations of MOSA P1, P3 and P4 were < 2 µg/L and they were replaced with
0.3 * 2 = 0.6 for statistical evaluation (Chapter 3.2.1.).
3.2.2.4. Site 1 and Sanctuary
Site 1 and Sanctuary are groundwater wells. GNP-W 11 was measured on June 3rd,
2008 and GNP-W 20, 21 and 22 were measured on August 28th, 2008 (by Franziska
Steinbruch). The results are shown in Appendix A 9, A 10 and A 14 described
beneath.
The examined water of the investigation area pointed generally to some
organoleptic characteristics. The water of GNP-W 11 and 20 was colorless but
provokes itching on skin which points to allergy and high contents of dissolved
matter. GNP-W 22 had a green color which points to algae.
The EH in the analyzed water was within the range of 122.98 mV and 686.98 mV.
According to the pH-EH-diagram (Appendix B 1), it is reflected that GNP-W 11, 20
and 21 were classified to lake and river water and GNP-W 22 was classified to
ocean water. The EC was between 424 µS/cm and 1283 µS/cm. The MCL MOZ of
52
3. Results
50-2000 µS/cm and the MCL Germany of 2500 µS/cm (20°C) were not crossed. The
pH was between 7.22 and 8.49. The MCL MOZ and EPA of 6.5-8.5 and the MCL
Germany of 6.5-9.5 were not crossed. T ranged between 26.7°C and 21.5°C.
In the following, the results of the laboratory analyses measured by non dispersive
IR, IC and ICP-MS are presented. Only the contents exceeding the MCL were
discussed.
Ammonia (NH4) was measured with IC and photometry, IC measurement was
preferred (Chapter 3.2.1.2.). The NH4 concentrations varied between 0.02 mg/L and
14.1 mg/L. MCL MOZ of 1.5 mg/L and MCL Germany of 0.5 mg/L were crossed by
GNP-W 22.
The total iron (Fe) was determined with photometry, IC and ICP-MS; photometry
was preferred (Chapter 3.2.1.2.). For ICP-MS only GNP-W 20, 21, and 22 were
measured. The concentrations were between 0.03 mg/L and 0.4 mg/L. GNP-W 20
and 21 were beneath detection limit (< 0.01 mg/L). The MCL MOZ of 0.3 mg/L and
the MCL Germany of 0.2 mg/L were crossed by GNP-W 22.
Phosphate (PO4) was measured with IC and photometry showing same results, IC
measurement was preferred (Chapter 3.2.1.2.) – only GNP-W 11 was measured.
The value was about 0.3 mg/L and crossed the MCL MOZ of 0.1 mg/L.
Manganese (Mn) was measured with photometry, IC and ICP-MS. GNP-W 11 was
measured with both photometry and IC. At both measurements this sampling point
was beneath detection limit. GNP-W 20, 21, and 22 were measured with ICP-MS.
The concentrations varied between 0.0002 mg/L (GNP-W 21) and 0.0327 mg/L
(GNP-W 22). Only GNP-W 22 was measured again by IC. The value differed
strongly to the ICP-MS value – IC values were preferred (Chapter 3.2.1.2.). It was
tenfold bigger than the value of ICP-MS. The value was about 0.36 mg/L and
crossed the MCL MOZ of 0.1 mg/L, the MCL EPA and Germany (0.05 mg/L) and the
MCL WHO (0.4 mg/L).
Bicarbonate (HCO3-) was between 260.4 mg/L and 706.1 mg/L. Calcium (Ca)
values ranged between 17.4 mg/L and 115.1 mg/L (measured with IC). GNP-W 11
and 20 crossed the MCL MOZ of 50 mg/L. Magnesium (Mg) values were between
10.4 mg/L and 163.7 mg/L (measured with IC). GNP-W 11, 20, and 21 crossed the
local drinking water standard of 50 mg/L. Fluoride (F) was measured by IC. The
concentrations of the wells were between 0.8 mg/L and 2.5 mg/L. GNP-W 11
crossed the MCL MOZ, WHO and Germany of 1.5 mg/L, but it did not cross the
MCL EPA with 4 mg/L. Aluminum (Al) was measured only by ICP-MS. The values
were between 2 µg/L and 318 µg/L and exceeded the MCL EPA of 50 to 200 µg/L
and the MCL WHO of 200 µg/L. The concentration of mercury varied between 5.8
53
3. Results
µg/L and 6.2 µg/L and crossed the MCL MOZ and Germany of 1 µg/L and the MCL
EPA of 2 µg/L. The uranium content was between 1.98 µg/L and 70.90 µg/L. GNPW 20 crossed the drinking water MCL of EPA of 30 µg/L by more than the double
and the MCL of WHO of 15 µg/L by more than the fourfold.
3.2.3. Stable isotopes
The values of δ2H and δ18O measured in the investigation area were compared only
with the local meteoric water line (LMWL).
Figure 18: Deuterium and oxygen-18 content of (a) Gorongosa Mountain (April/May/June, 2008), (b) Mazamba
Karst spring (June, 2008) and Nhambita hot spring region (July, 2008), (c) Site 1 and Sanctuary (July/August,
2008), and (d) rainfall of Chitengo and Gorongosa (January/May/July/August, 2008) compared with the local
meteoric water line (δ2H=7.9*δ18O+13.3‰; STEINBRUCH & WEISE, 2008).
Figure 18 shows δ18O versus δ2H plots in a Craig diagram for the water samples of
(a) Gorongosa Mountain (April, May, June 2008), (b) Mazamba Karst spring (June
2008) and Nhambita hot spring region (July 2008), (c) Site 1 and Sanctuary (July,
August 2008), and (d) rainfall of Chitengo and Gorongosa (January, May, July, and
August 2008). Mazamba Karst spring was only one sample; therefore, it was
summarized with measurements of the Nhambita hot spring region because they fall
in the same part of points. All other isotope data were grouped by the location. A
local meteoric water line (LMWL) is also shown. The water samples of the
54
3. Results
investigation areas are plotted not linear. Therefore a trend line (regression line) was
added for the better understanding of the relationship of δ18O and δ2H. The result of
linear regression analysis suggested a correlation between δ18O and δ2H (the
correlation coefficients are between 0.87 and 1) and the slopes of the regression
lines were 7.4 (Gorongosa Mountain), 6.3 (Nhambita hot spring region), 7.4 (Site 1
and Sanctuary) and 8.1 (rainfall in Chitengo and Gorongosa), respectively, showing
smaller values than the slope of LMWL (7.9) except the rainfall of Chitengo and
Gorongosa.
3.2.4. Carbon isotopes
The sample of GNP-W 11 (Site 1) contained approximately 1.0 mg carbon and the
sample of GNP-S 18 (Nhambita hot spring region) contained 0.7 mg carbon. Both
amounts of C were still sufficient carbon for AMS determination of
14
C. For specified
facts see Appendix A 18.
The δ13C ratios were at -13.7 ‰ (GNP-S 18) and -12.63 ‰ (GNP-W 11). Plotting
radiocarbon activities versus
13
C ratios a tendency became apparent. GNP-W 11
showed a lower activity (58.93 ± 0.42 pmC) but a higher
13
C-value. Compared with
GNP-S 18, it showed a higher activity (75.43 ± 0.31 pmC) but a lower 13C-value. The
corrected mean residence time in the subsurface of the GNP-S 18 water was 4,250
± 60 years. And the corrected mean residence time of the water of GNP-W 11 was
2,265 ± 35 years. Exchange processes in the subsurface, sulfate reduction and
methane genesis were not taken into account by the calculation of mean residence
time but there was so far no evidence for such processes.
3.3. Digital Atlas
The digital atlas contains five layers. The first layer “Digital Atlas – Mozambique
2008” is only the page layout and the starting point. The second layer contains all
important features for the GNP. The third, fourth and fifth layers contain study areas
of Gorongosa Mountain, Nhambita hot spring region including Site 1 and Sanctuary,
and Mazamba region. “Overview of the Gorongosa National Park” contains 32 LISS
Satellite Photos by a size of 32 km x 26 km and a georeferenced base map to give
an overview about the location. Moreover, detailed information including geology,
geomorphology, soils and land use are given in further features. Different chart
types and contour line-plots present the hydrogeochemical situation at the
investigation area and give a spatial summary for water components like anions,
cations, trace elements and field parameters. These features and additional
information and/or data are included in tables belonging to the vector objects. All
55
3. Results
layers are based on the same design. ArcReader version 9.3 provides the basis for
the digital atlas.
3.3.1. Layers and features
The digital atlas is subdivided in five layers with several features that are further
separated in different features. Altogether these ten features can be abstracted into
two thematic categories: the basis cartographic information comprising of DEM,
geology, geomorphology, soils and land use, and the hydrochemistry of sampling
points for mapping including the spatial distribution of selected chemical elements.
All features were georeferenced by the map date WGS 1984 with the map projection
Universal Transverse Mercator (UTM) Zone 36S.
Below, the features are described in order of the digital atlas from top to bottom. The
navigation is described in Chapter 2.4.
Group classification: contains five features with groups of water type: Gorongosa
Mountain – springs; Gorongosa Mountain – rivers, creeks; Mazamba Karst spring;
Nhambita hot spring region; Site 1 and Sanctuary.
Hydrochemistry of wells: contains six features with current features with
hydrochemical attributes of the mapped wells. The trace elements, main anions and
cations are presented in pie charts and on-site parameters are displayed as different
colored sized pins. For displaying on-site parameters, all measured sampling points
for wells were taken. Instead, for displaying TIC & DOC, trace elements, main
anions, cations and all elements, only four sampling points were taken.
Hydrochemistry of springs: same as “Hydrochemistry of wells”. This feature
relates to the measured springs in the area of investigation. For displaying on-site
parameters all measured sampling points for springs were taken. Instead, for
displaying TIC & DOC, trace elements, main anions, cations and all elements, only
four sampling points were taken.
Hydrochemistry of permanent rivers: same as “Hydrochemistry of wells”. This
feature relates to the measured permanent rivers in the investigation area. For
displaying on-site parameters all measured sampling points for the permanent rivers
were taken. Instead, for displaying TIC & DOC, trace elements, main anions, cations
and all elements, only four sampling points were taken.
Hydrogeology – Limits: contains eighteen point features showing drinking water
standards for EC, pH, TDS, sodium, magnesium, calcium, chloride, manganese,
56
3. Results
total iron, sulfate, phosphate, ammonia, nitrite, fluoride, aluminum, nickel, mercury,
and uranium by pie charts and different colors (green: < MCL; red: > MCL MOZ;
dark orange: > MCL EPA; yellow: > MCL WHO; orange: > MCL Germany). For
displaying the limits of pH, TDS and EC, all measured sampling points of wells,
springs and rivers/brooks were taken. For displaying the limit of all elements only 24
sampling points were taken (Table 2).
Table 2: Limit values for all important elements and parameters measured in the
investigation area including MCL MOZ, MCL EPA, MCL WHO and MCL Germany.
EC [µS/cm]
pH
TDS [ppm]
Na [mg/L]
Mg [mg/L]
Ca [mg/L]
Cl [mg/L]
Mn [mg/L]
Fe [mg/L]
2SO4 [mg/L]
3PO4 [mg/L]
+
NH4 [mg/L]
NO2 [mg/L]
F [mg/L]
Al [mg/L]
Ni [mg/L]
Hg [mg/L]
U [mg/L]
MCL MOZ
50-2,000
6.5-8.5
1,000
200
50
50
250
0.1
0.3
250
0.1
1.5
3
1.5
20
1
-
MCL EPA
6.5-8.5
500
250
0.05
250
1
4
0.05-0.2
2
30
MCL WHO
0.4
3
1.5
0.2
70
6
15
MCL Germany
2,500
6.5-9.5
200
250
0.05
0.2
240
0.5
0.5
1.5
20
1
-
The relative tables in the digital atlas show only values, if one of the MCL was
crossed. If the MCL was not crossed, there is a zero behind the relative MCL. If the
MCL was crossed, e.g. MCL MOZ and MCL Germany were crossed, behind both
MCLs there are the same values because both MCLs were crossed with the relative
value.
Base Map: contains six features with current features: Specification of waypoints,
cities and elevation, roads, rivers, Lake Urema, boundaries and satellite photos.
Surface catchments: contains three features: Muera River Catchment, Vunduzi
River Catchment, Nhandare River Catchment
DEM: contains six raster features showing the different DEM in the area of interest:
Contour_3D_Model, 3D_Model, Contour_InvestArea, InvestArea, DEM Nhambita
and DEM Mazamba.
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3. Results
Geology: contains two vector features and two raster features describing the
geology of the investigation area: faults, veins, geology – formation and geology of
Mozambique.
Geomorphology: is a raster feature displaying the geomorphology of the
investigation area.
Soils: is a raster feature displaying the soils in the area of interest.
Land Use of Central Mozambique: is a raster feature displaying the land use of
central Mozambique including the investigation area.
Contours: contains five features with current features showing the contours of each
parameter and/or element: on-site parameters, TIC and DOC, main anions, main
cations and trace elements.
Contour lines: contains five features with current features showing the contour
lines of each parameter and/or element. The layout is the same as Contours.
Additional, hyperlinks were compiled in the map. First clicking on
in the toolbar
showing all hyperlinks as blue areas or points in the map. Clicking on Gorongosa
Mountain, Rupice River surface catchment, Mazamba River surface catchment, or
GNP a PDF-File for the selected area will open. The location and geology will be
described shortly. Activating the three important layers (areas of interest), also
clicking on different sampling points a picture about the selected point will open.
3.3.2. Legend of the layers and features
The layers and features of the “Digital Atlas – Mozambique 2008” are selfexplanatory by legends and symbols. In the following, these layers and features will
be explained briefly, starting from top to bottom.
The feature Hydrochemistry – Limits contains pie-charts for all important elements
which cross the MCL MOZ (red colored), MCL EPA (dark orange colored), MCL
WHO (light orange colored) and/or MCL Germany (yellow colored). This illustration
type only serves as perspective on which sampling points the limits got crossed. The
four limits are different from each other independent limit values. If the pie is total
green colored, the limits are not crossed. If the pie is e.g. red and yellow colored, the
limits of MOZ and Germany were crossed. Coloring for each MCL was chosen as
follows (Figure 19):
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3. Results
N
a)
b)
Figure 19: a) Example for the Hydrochemistry – Limits, showing the measured values as green colored, the values
above MCL MOZ red colored, the values above MCL EPA dark orange colored, the values above MCL WHO
orange colored, and the values above MCL Germany yellow colored. b) Gorongosa Mountain with measured
samples showing the hydrochemistry limits (“Digital Atlas – Mosambique 2008”).
The legend shown in ArcReader for the base map, elevation, geology,
geomorphology, soils, land use, contours and contour lines are clearly to read.
Therefore, no further legend explanation was necessary.
The atlas contains three chemistry groups: hydrochemistry of wells, hydrochemistry
of springs and hydrochemistry of permanent rivers. Each chemistry group comprises
the same kind of features, exemplified by the group hydrochemistry of springs,
containing features for on-site parameters, TIC & DOC, trace elements, main
cations, main anions and all elements. In the following, these features will be
explained, starting from top to bottom.
The features On-site parameters and All elements contain
all important parameters and elements measured in the
investigation area. For both features, sized pins were
chosen (Figure 20). The smallest pin shows the lowest and
the biggest pin shows the highest concentrations.
Figure 20: Example for the on-site parameters and all elements in the digital atlas. For both layers, sized pins were
chosen.
The feature TIC & DOC contains pie-charts for main total
inorganic carbon (TIC) and dissolved organic carbon (DOC).
Coloring was chosen as follows (Figure 21):
Figure 21: Example for the TIC & DOC concentrations in the digital atlas. Pie charts were chosen.
59
3. Results
The feature Trace elements contains pie-charts for trace
elements. Coloring for each element was chosen as follows
(Figure 22):
Figure 22: Example for the trace elements in the digital atlas. Pie charts were chosen.
The feature Main Cations contains pie-charts for major cations.
Coloring for each element was chosen as follows (Figure 23):
Figure 23: Example for the main cations in the digital atlas. Pie charts were chosen. Ca –
green, Mg – light green, Na – yellow, K – red.
The feature Main Anions contains pie-charts for major anions.
Coloring for each element was chosen as follows (Figure 24):
Figure 24: Example for the main anions in the digital atlas. Pie charts were chosen. HCO3
– yellow, SO4 – orange, Cl – pink, NO3 – blue.
60
4. Discussions
4. Discussions
4.1. Surface catchment characterization
Water fluxes in catchments are controlled by physical processes and material
properties that are complex, heterogeneous and poorly characterized by direct
measurements. Each catchment is characterized by a number of morphology (e.g.
area, slope, and aspect), climate, land cover and runoff characteristics. A detailed
study of the catchment areas of Mazamba River and Rupice River (Nhambita hot
spring region) has been carried out using LISS data and the DEM with the help of
GIS technology.
4.1.1. Mazamba River surface catchment
The Mazamba karst spring is situated in the Mazamba River surface catchment with
a size of approximately 315 km² (max. length of 33 km; max. width of 19 km [“Digital
Atlas – Mozambique 2008”]). The upstream part of the Mazamba River surface
catchment responses only to local rainfall events with slow discharges and
thereafter drying up quickly. Therefore, it can be assumed that a porous aquifer
exists and permeable rocks dominate in the Mazamba River catchment. The rocks
around the karst spring are limestones which lead to an artesian calcareous
carbonate aquifer. Karst catchments are predominantly drained via underground
channels or conduits created by widening of fractures in soluble rocks such as
limestone or dolomite. As a consequence surface water is scarce on karst plateaus.
These water resources are particularly vulnerable to anthropogenic contamination
because of the typically thin soil layers and high permeability of the karstified host
rock which lead to short residence times and low natural attenuation capacities
(www_2).
4.1.2. Rupice River surface catchment
As mentioned before in Chapter 1.2.2., the Nhambita creeks and springs are
situated in the Rupice River surface catchment draining into the Pungue River
catchment which has an area of 31,150.5 km² with 1,460.7 km² (4.7 %) in Zimbabwe
and 29,689.8 km² (95.3 %) in Mozambique (SWECO & ASSOCIATES_I, 2004). The
Rupice River surface catchment has a size of approximately 65 km² with a maximal
length of 16 km and a maximal width of 7 km (“Digital Atlas – Mozambique 2008”).
As MERKEL & STEINBRUCH (2006) reported, the upstream part of the catchment of
Nhambita hot spring only response to local rainfall events with quick discharges and
thereafter drying up immediately. The same is valid for all other spring discharges
and creeks except of some parts of the Rupice River. As mentioned before in
61
4. Discussions
Chapter 1.2.5., gneiss is the base for the formation of the mostly sandy skeletal
ferrallitic soils. Therefore, pore aquifers are located in this region. Pungue River
floods do not reach the Nhambita hot spring even at very high stands.
4.1.3. Gorongosa Mountain – surface catchments
The three most important rivers at the Gorongosa Mountain are Vunduzi, Nhandare
and Muera. All three rivers consist of a surface catchment.
The Nhandare River surface catchment has a size of approximately 812 km² with a
maximal length of 63 km and a maximal width of 26 km (“Digital Atlas –
Mozambique 2008”). The Nhandare River flows southwards into the Pungue River.
The size of the Vunduzi River surface catchment is approximately 1470 km² with a
maximal length of 71 km and a maximal width of 47 km (“Digital Atlas –
Mozambique 2008”). The Vunduzi River flows into the Urema Lake and drainage
which has a catchment area of 8755 km² (BÖHME, 2005). After BÖHME (2005), to
the Urema drainage the rivers of Vunduzi, Nhandugue and Sungue are included.
The Muera River surface catchment shows a size of approximately 161 km². The
maximal length is 20 km and the maximal width is 17 km (“Digital Atlas –
Mozambique 2008”). The Muera Rivers flows northwards into the Nhandugue River
which has a catchment area of 5935 km² (BÖHME, 2005). The Nhandugue River is
the longest tributary within the catchment of Lake Urema (BÖHME, 2005).
As a result of the higher orographic rainfall on the mountain, a perennial radial
drainage follows from the Gorongosa Mountain. Because of the steep slopes and
large areas of bare rock, the runoff coefficients are expected to be higher than those
on the Báruè Platform (TINLEY, 1977). The rivers located on the mountain are feed
by precipitation. It is well-known from Chapter 1.2.3. that the mountain has the
largest precipitation rate in the environment due to its elevation. The up- and
downstream parts of the river catchments response to precipitation with fast
discharges (Chapter 3.1.1.) and consistently wetness. Cause of non-permeable
rocks like granite, it can be assumed that fracture aquifers exist.
4.2. Groundwater provinces and genesis
4.2.1. Groundwater – host rock interactions
The sample points of Gorongosa Mountain can be divided in rivers, creeks and
springs. The rivers and creeks show EC in the range of MCL Mozambique and
Germany except of one water sample (< 50 µS/cm), partly reduced to
oxidizing/aerobe conditions, oxygen contents above 8 mg/L and oxygen saturations
above 90 %, weak acid to basic pH and temperatures between 15°C and 21°C. The
62
4. Discussions
analyzed springs show EC below 50 µS/cm, partly reduced conditions, anaerobe to
aerobe conditions, acid to weak basic pH and temperatures ranging between 15°C
and 24°C (Appendix A 10).
With PhreeqC calculated charge imbalance shows percent errors > ± 10 % in GNPS 6 FH and GNP-S 8 TM. Therefore, these two sampling points were considered
with attention. GNP-S 3 FH and GNP-S 8 TM showed high concentrations of nitrite
(Appendix A 11). GNP-S 3 FH and GNP-R 7 FH showed high concentrations of
total iron. And all springs except of GNP-S 10 FH and all rivers and brooks except
of GNP-R 12 TM showed high concentrations of phosphate. The waters of the
springs were low in TIC which is a clear indication that the waters were not in
contact with a still active volcanism. The water is also low in natural toxic elements
like arsenic, lead, cadmium, mercury, beryllium, selenium, antimony and uranium.
The spatial distributions of nitrite, total iron, phosphate and HCO3- at Gorongosa
Mountain are represented in Figure 25. The interpolations for the spatial distribution
were calculated by the investigated sampling points of the chosen rivers and/or
springs. Green areas mark no and/or low concentrations of the relative elements
and the white areas mark the highest concentrations.
I
II
N
N
III
IV
N
N
Figure 25: Contour line plot showing the spatial distribution of (I) nitrite, (II) total iron (III) phosphate and (IV)
bicarbonate; screenshot from “Digital Atlas – Mozambique 2008”. Enlargement scale: 1:175,000; WGS 1984, UTM
Zone 36S. Mapping points are displayed as colored dots without a sample code. Rivers are displayed blue, Gogogo
Peak is a red point, and the boundary of the Gorongosa Mountain is grey lined. For detailed information see the
digital atlas.
63
4. Discussions
GNP-R 10 FH showed an increased EC (409 µS/cm) compared to the other rivers
and creeks of Gorongosa Mountain. As mentioned before in Chapter 2.1.3.1., the
EC depends on water temperature as well as the dissociation degree of the
electrolytes. The temperature at this point was 20.9°C – no difference to the other
measured rivers. But pH at this point was about 8.5, increased to the other rivers.
Therefore, it is possible that with increasing pH also EC increased.
By comparing the molar ratios of Cl/Br, Cl/F, and F/Br with seawater the origin of the
springs can be evaluated (Appendix A 21). In general, it is defined that waters with
ratios below seawater ratio are fresh water affected and with ratios above seawater
ratio are deepwater affected. In the springs of the Gorongosa Mountain the Cl/Br
ratio was between 158 and 403 with a mean of 256 whereby the ratio of the
seawater is about 288. Ratios of GNP-S 3 FH, GNP-S 4 FH and GNP-S 5 FH were
below the ratio of seawater whereby the ratio of GNP-S 12 TM was above. The ratio
of Cl/F showed a mean of 67. The ratios of GNP-S 3 FH, GNP-S 4 FH, GNP-S 5 FH
and GNP-S 8 TM were below seawater ratio and the ratio of GNP-S 6 FH was
above. Seawater shows a ratio of about 551. However the ratio of GNP-S 12 TM
was equal to seawater ratio. The ratios of F/Br varied between 4 and 6 in the springs
with a mean of 5 whereby seawater shows a ratio of about 0.5. The ratio of F/Br was
above seawater ratio.
The water of the Mazamba Karst spring shows EC between ranges of
Mozambican and German standards, partly reduced conditions decreasing with
reducing temperature, aerobe conditions decreasing with rising temperatures,
oxygen saturations below 50 % which points to oxygen consumptive disassembly
processes in the groundwater, a weak basic pH and a mean temperature of 26°C
(Appendix A 10).
The spring water was high in total iron, phosphate, manganese and calcium
(Appendix A 12). The spring water was high in TIC which is a clear indication that
solution processes have been executed (CO2- solution). The water had still high
values of HCO3- and it is also low in natural toxic elements like arsenic, lead,
cadmium, mercury, beryllium, selenium, antimony and uranium. As mentioned
before, it is defined that waters with ratios below seawater ratio are fresh water
affected and with ratios above seawater ratio are deepwater affected (Appendix A
21). In the Mazamba Karst spring, the Cl/Br ratio was about 516 (seawater ratio:
288), the ratio of Cl/F was 83 (seawater ratio: 551) and the F/Br ratio of the karst
spring was 6 (seawater ratio: 0.5). The ratios of the Mazamba Karst spring were
above the ratios of seawater.
64
4. Discussions
No spatial distribution of nameable elements was possible because one water
sample is not representative for the investigated area.
The water of the Nhambita hot spring region can be divided in springs, brooks and
spring discharges. The brooks and spring discharges (Appendix A 10) show EC
ranging in the MCL of MOZ and Germany (50 – 2000 µS/cm) except of two rivers
with values < 50 µS/cm, partly reduced and anaerobe to aerobe conditions, weak
acid to weak basic pH and temperatures between 19°C and 29°C. The analyzed
springs showed EC in the range of 50 – 2000 µS/cm, partly reduced and anaerobe
to aerobe conditions, weak acid to weak basic pH and temperatures between 41°C
and 42°C which is classified as mesothermal water (ALBU et al., 1997). After ALBU
et al. (1997), the discovered springs with temperatures between 36 and 42°C at
origin point are classified as mesothermal waters and springs with temperatures
> 42°C at origin point are classified as hyperthermal waters. The temperature
gradient is represented in Figure 26.
mesothermal: 36-42°C
hyperthermal: > 42°C
Figure 26: Overview of the development of the temperature in the Nhambita hot spring region.
According to Appendix A 13, GNP-R 14, 15, 19 and GNP-S 16 and 18 showed high
concentrations of total iron. All sampling points except GNP-R 19 had high
concentrations of phosphate. GNP-S 18 and GNP-R 19 exhibits high mercury
concentrations and GNP-R 15 and GNP-S 16 exhibit high ammonia contents.
Additionally, all sampling points were high in manganese, sulfate, sodium,
fluoride and chloride. The waters of the springs were low in TIC which is a clear
indication that the waters were not in contact with a still active volcanism. The result
is the same as MOSA P1. The water is also low in natural toxic elements like
65
4. Discussions
arsenic, lead, cadmium, beryllium, selenium, antimony and uranium, except of
mercury.
The spatial distributions of EC, pH, total iron, phosphate, sulfate, HCO3-,
manganese, calcium, magnesium, sodium, fluoride, chloride, silicon, nickel and
mercury in the Nhambita hot spring region are represented in Figure 27. The
interpolations for the spatial distribution in the Nhambita hot spring region were
calculated by investigated sampling points of the chosen brooks and/or springs.
Green areas mark no and/or low concentrations of the relative elements and the
white areas mark the highest concentrations. It is only an estimation because six
water samples are usually to less for a specified interpolation.
According to MERKEL & STEINBRUCH (2006), the Nhambita hot spring water has
seen a depth of about 1,700 m and deeper. It was speculated that the Nhambita
thermal water was saturated with chalcedony at 132°C. Therefore, it must originate
from more than 5,000 m depth (MERKEL & STEINBRUCH, 2006). Older literatures
e.g. MARTINELLI (1995) or BOND (1953) also support this statement. After MERKEL
& STEINBRUCH (2006), another explanation for heat discharge can be the existence
of a mantle plume in the area of the Gorongosa Mountain. The existence of a deep,
connected fault system parallel to the Urema Rift can be approved by the major fault
directions. It is speculated that the groundwater is recharged north of the Pungue
River in the area of Gorongosa Mountain and Báruè Midlands. Based on this
statement, it was necessary to analyze spring water from Gorongosa Mountain. The
origin of the Nhambita thermal water has a Br/Cl and I/Cl ratio of 2.5x10-3. GNP-S 12
located at the top of the Gorongosa Mountain has also a Br/Cl ratio of about
2.5x10-3. The other springs at the foothills of the Gorongosa Mountain have Br/Cl
ratios between 3.8x10-3 and 6.3x10-3. No iodine was measured. These springs have
not the same origin. Only GNP-S 12 is an indicator for the statement that the
Nhambita thermal water possibly origins from Gorongosa Mountain. These ratios
are indicators for a very long subsurface residence time of the water in a silicate-rich
rock formation, the same as Nhambita hot spring. Data on Gorongosa Mountain are
unsufficient and the source of the heat remains still speculative. More study work
has to be done to prove this statement. As mentioned before, it is defined that
waters with ratios below seawater ratio are fresh water affected and with ratios
above seawater ratio are deepwater affected (Appendix A 21). The springs
measured in the Nhambita hot spring region showed a Cl/Br ratio showed a mean of
511 (seawater ratio: 288), a Cl/F mean ratio of 32 (seawater ratio: 551) and a F/Br
mean ratio of 16 (seawater ratio: 0.5). The ratios of the springs in the Nhambita hot
spring region were partly above and below the seawater ratios.
66
4. Discussions
I
N
II
N
III
N
IV
N
V
N
VI
N
VII
N
VIII
N
Figure 27 a: Contour line plot showing the spatial distribution of (I) EC, (II) pH, (III) total iron, (IV) phosphate, (V)
sulfate, (VI) manganese, (VII) sodium, and (VIII) fluoride; screenshot from “Digital Atlas – Mozambique 2008”.
Enlargement scale: 1:85,000; WGS 1984, UTM Zone 36S.
67
4. Discussions
IX
N
X
N
XI
N
XII
N
XIII
N
XIV
N
XV
N
Figure 27 b: Contour line plot showing the spatial distribution of (IX) chloride, (X) silicon, (XI) nickel, (XII) mercury,
(XIII) bicarbonate, (XIV) calcium, and (XV) magnesium; screenshot from “Digital Atlas – Mozambique 2008”.
Enlargement scale: 1:85,000; WGS 1984, UTM Zone 36S. Mapping points are displayed as colored dots without a
sample code. Spring discharges and creeks are displayed blue, streets are black, and the boundary of the Rupice
River catchment is grey lined. For detailed information see the digital atlas.
68
4. Discussions
The analyzed wells of Site 1 and Sanctuary (close to Nhambita hot spring region)
showed EC in the range of the MCL MOZ and Germany with 50-2000 µS/cm, partly
reduced to oxidizing conditions, weak basic to basic pH and temperatures ranging
between 21°C and 27°C (Appendix A 10).
With PhreeqC calculated charge imbalance showed a percent error > ± 10 % in
GNP-W 21. Therefore, this sampling point was considered with attention. According
to Appendix A 14, GNP-W 11 showed high concentrations of phosphate, calcium,
fluoride and magnesium. GNP-W 20 was high in calcium, mercury, magnesium
and uranium. GNP-W 21 had high contents of mercury and magnesium. And GNPW 22 showed high total iron, manganese, mercury, ammonia and aluminum
concentrations. The waters of the wells were high in TIC which is a clear indication
whether solution processes have been executed (CO2- solution) or the waters were
chemical changed by deep water. The water is also high in natural toxic elements
like uranium and mercury. The same as the Nhambita hot spring region, according
to Chapter 1.2.5., gneiss is the base for the formation of the mostly sandy skeletal
ferrallitic soils. Therefore, pore aquifers are located in this region. The wells
investigated in Site 1 and Sanctuary were no spring waters but also they were
checked for the ion conditions. As mentioned before, it is defined that waters with
ratios below seawater ratio are fresh water affected and with ratios above seawater
ratio are deepwater affected (Appendix A 21). The wells showed a mean Cl/Br ratio
of 815 (seawater ratio: 288), a mean Cl/F ratio of 88 (seawater ratio: 551) and a
mean F/Br ratio of about 16 (seawater ratio: 0.5). The ratios of Site 1 and Sanctuary
were above seawater ratios.
The spatial distributions of ammonia, potassium, aluminum and uranium in Site 1
and Sanctuary are represented in Figure 28. Total iron, phosphate, manganese,
fluoride, silicon, HCO3-, calcium, magnesium and mercury are shown in Figure 27.
The interpolations for the spatial distribution were calculated by the investigated
sampling points of the chosen rivers and/or springs. Green areas mark no and/or
low concentrations of the relative elements and the white areas mark the highest
concentrations.
69
4. Discussions
I
II
N
N
III
IV
N
N
Figure 28: Contour line plot showing the spatial distribution of (I) ammonia, (II) potassium, (III) aluminum, and (IV)
uranium, screenshot from “Digital Atlas – Mozambique 2008”. Enlargement scale: 1:85,000; WGS 1984, UTM Zone
36S. Mapping points are displayed as colored dots without a sample code. Rivers are displayed blue, streets are
black, and the boundary of the Rupice River catchment is grey lined. For detailed information see the digital atlas.
Statement of on-site parameters
As expected, the oxygen saturation is much higher in rivers and creeks (Gorongosa
Mountain, Nhambita hot spring region) than in springs. This can be attributed to the
exchange between atmosphere and water as well as the oxygenation by the
photosynthesis-operating algae and plants. Since the sampling concerns exclusively
with surface water, this has a large influence and the values tend to the values
typical for surface water of around 10 mg/L and a saturation of 100 %. After
HÖLTING & COLDEWEY (2005), the oxygen index in surface waters should be >
70 %. The oxygen saturation of GNP-S 3 FH, 4 FH, 5 FH, 6 FH, GNP-R 14, GNP-S
16 and GNP-S 18 are, however, below 50% and point thus to reducing conditions.
This refers to oxygen consumptive disassembly processes in waters. The other
measuring points, however, are in the oxidizing environment, the oxygen supply of
the water organisms, thus, are not limited.
Possible reason for high pH values (pH = 8) in surface water could be the balance
with the pCO2 of the atmosphere or generally contamination through waste water,
e.g. by washing clothes. Also by the increased content of minerals (e.g. Site 1 and
Sanctuary), the pH rises automatically and the water becomes more basic.
70
4. Discussions
Despite the high accuracy of the temperature measurement, the received values
can be evaluated only insufficiently or compared since the measurement was
accomplished in too large time steps. So, increased values can be attributed e.g. to
low water levels and/or increased sun exposure, decreased measured values e.g.
shading effects.
4.2.2. Elements with increased concentrations
Comparing the relative investigated areas, it is remarkable that all waters were high
in phosphate and total iron. Mazamba Karst spring, water of Nhambita hot spring
region and well water of Site 1 and Sanctuary were all high in manganese. Water of
Nhambita hot spring region and well water of Site 1 and Sanctuary showed high
contents of fluoride, mercury and ammonia. Only water of Nhambita hot spring
region was high in sulfate, sodium and chloride. Mazamba Karst spring and well
water of Site 1 and Sanctuary were high in calcium. Only springs of Gorongosa
Mountain were high in nitrite. And only well water of Site 1 and Sanctuary showed
high concentrations of magnesium, aluminum and uranium. Table 3 shows the
summary of all elements which crossed the MCL.
Table 3: Summary of all elements which crossed the MCL. GM – Gorongosa Mountain, MKS
– Mazamba Karst spring, NR – Nhambita hot spring region, numbers in brackets are the
relative available water samples.
GM –
GM –
MKS
NR –
NR –
Site 1 and
rivers (4)
springs (7)
(1)
rivers (3)
springs (3)
Sanctuary (4)
phosphate
X (3)
X (6)
X (1)
X (2)
X (3)
X (1)
total iron
X (1)
X (1)
X (1)
X (3)
X (2)
X (1)
X (1)
manganese
X (3)
X (3)
X (1)
fluoride
X (3)
X (3)
X (1)
mercury
X (1)
X (1)
X (3)
ammonia
X (1)
X (1)
X (1)
sulfate
X (3)
X (3)
sodium
X (3)
X (3)
chloride
X (3)
X (3)
calcium
nitrite
X (1)
X (2)
X (2)
magnesium
X (3)
aluminum
X (1)
uranium
X (1)
71
4. Discussions
Some elements showed elevated concentrations in the area of investigation. In the
following, comparisons are made to the MCLs and background values from
literature.
4.2.2.1. Phosphate
The diffuse PO4 sources are erosion with leakage water into groundwater, lateral
erosion directly in surface water (solved materials), erosion of ground materials,
sediment suspension in rivers, avulsion of fertilizers, excreta from animals and
humans, wastes of all kinds and waste water which is neither treated nor piped.
Also, a direct entry by precipitation, strew, animal excreta, guano, animal feeds or
materials by bathing rank among the diffuse sources (MERKEL & SPERLING, 1996).
In all areas of interest, phosphate crossed the MCL MOZ of 0.1 mg/L. Phosphatic
rock can be a possible source of high phosphate concentrations in the water of the
investigated area. The Gorongosa Mountain consists of a felsic core surrounded of
mafic rock, also admits as granite (phosphatic). The karst area consists mainly of
sediments such as limestone and sandstone which is high in phosphate (Chapter
1.2.2.). Entry of phosphate by agriculture activities can only be speculated. In the
Mazamba Karst spring, also natural guano is considered as outstanding source of
phosphate.
4.2.2.2. Total iron
In all areas of interest, total iron crossed the MCL MOZ of 0.3 mg/L and the MCL
Germany of 0.2 mg/L. Iron appears geogenic in rock forming silicates. Furthermore
difficulty water soluble sulfides and oxides play an important role since they also
build interesting economical reservoirs. Iron is represented in all living organisms
(MERKEL & SPERLING, 1996). Due to illegal mining industry, sediment suspension
and heavy metal entry in rivers is also a considerable iron intrusion in rivers and
creeks.
4.2.2.3. Manganese
After W EDEPOHL (1978), the average value in rivers is up to 0.05 μg/l. In rivers of
the investigation area, the values are much higher (> 90 µg/L). Manganese enters
surface water by surface tributaries and mobilization of manganese from sediment
(MERKEL & SPERLING, 1996). Also, sediment suspension and heavy metal entry in
rivers due to illegal mining industry is a major manganese intrusion in rivers and
creeks. Manganese occurs not elementarily but as a component of different
minerals. It is possible that these high values occurred through ore deposits which
72
4. Discussions
were cut by faults (but no evidences are at hand). Manganese is particularly
represented in magmatic rocks in silicates. In the environment it arrives particularly
by decomposition, crushing and particularly by smelting of ores.
4.2.2.4. Fluoride
After MERKEL & SPERLING (1996), in groundwater concentrations vary with the type
of rock through the water discharges but do not usually exceed 10 mg/L. In
Nhambita hot spring region, Site 1 and Sanctuary, Fluoride concentrations
exceeded the MCL of 4 mg/L (EPA) and 1.5 mg/L (MOZ, WHO, Germany). All
relative sampling points are acceptable for geogenic sources. According to
Appendix A 13, only in Nhambita hot spring region e.g. GNP-R 14 showed a value >
10 mg/L (11.1 mg/L). Fluoride is contained in different minerals from which it
discharges by alteration processes in the water. The most important minerals are
apatite, mica and cryolite.
4.2.2.5. Mercury
After KOCH (1989), mercury contents in surface water are between 0.01 µg/L and
0.5 µg/L. Mercury in groundwater varies between 0.01 and 0.4 µg/L. One spring in
Nhambita hot spring region (GNP-S 18) showed a value of 1.3 µg/L and one river
(GNP-R 19) showed a value of 2.3 µg/L. Also wells of Site 1 and Sanctuary showed
high values (5.8-6.2 µg/L). The origin of mercury contents are not investigated now.
Only assumptions can be made. An assumption can be the tectonic in the
investigated area. All samples with high concentrations of mercury were taken in the
area where Nhambita hot spring is located. This region is characterized by tectonic
activities. According to Chapter 4.3., springs investigated in Nhambita hot spring
region have their origin in depths of approximately 3,100 to 3,600 m. Mercury
originates from cool, deep-epithermal residual liquid of hydrothermal mineralization.
Most occurrences lie in mobile zones (MERKEL & SPERLING, 1996). Further field
work is necessary to investigate the geogenic origin of mercury.
4.2.2.6. Ammonia
Natural levels in groundwater and surface water are usually below 0.2 mg/L.
Anaerobe groundwater may contain up to 3 mg/L (MERKEL & SPERLING, 1996).
Most disturbing substances are iron (all levels), nitrate (> 100 mg/L), calcium (>
1000 mg/L as CaCO3), nitrite (>12 mg/L) and all strongly oxidizing and reducing
substances contained in water (ANONYM (b)). Ammonia is a component of the
nitrogen cycle. It should not be present in drinking water because it is usually a
73
4. Discussions
reference to solid pollution with liquid manure or waste water. Only in nearly oxygenfree, so-called reduced water, it can be present in natural way. Microorganisms
oxidize ammonia to nitrate (MERKEL & SPERLING, 1996). GNP-W 22 showed a high
NH4 concentration of about 14.1 mg/L. This sampling point is a retention pond which
is re-filling with groundwater when it does not rain. This place is a good
accumulation point for bacterial, sewage and animal waste pollution.
4.2.2.7. Sulfate
After MERKEL & SPERLING (1996), the sulfate concentrations in natural waters are
usually between 10 and 150 mg/l, in surface water frequently at 100 mg/l.
Only in Nhambita hot spring region, high sulfate concentrations were measured
(348-504 mg/L). All rivers and springs crossed the MCL MOZ, EPA (250 mg/L) and
Germany (240 mg/L) by up to the double. It can be caused by natural geogenic
conditions (salt and gypsum deposits). It can also store by decomposition of sulfidic
ores (e.g. pyrites: FeS).
4.2.2.8. Chloride and sodium
Only in Nhambita hot spring region, sodium concentrations crossed the MCL MOZ
and Germany of 200 mg/L by up to the double. In water of humid areas, the sodium
content amounts to 1 to 50 mg/l (ALBRECHT, 1979). In surface waters the sodium
concentration lies usually over 10 mg/l (W ORCH, 1997), in rivers with an average of
39 mg/l (W EDEPOHL, 1978). Geogenic sodium ions are set free by release and/or
decomposition processes from silicates, salt deposit places and essentially remains
as free ions in solution. In Nhambita hot spring region, all investigated creeks and
springs crossed the MCL MOZ, EPA and Germany of 200 mg/L. Chloride ions are
contained only in badly permeable clay rocks as NaCl crystals and/or as NaCl
solutions. If halite dissolution took place, a Na/Cl ratio of 1 would have to expect.
The Na/Cl ratios of all rivers and springs investigated in the area around the GNP
have a Na/Cl ratio > 1 (Na/Cl ~ 1.05 – 1.44). Some values (e.g. GNP-S 13) show a
higher sodium concentration in comparison to chloride but other values (e.g. GNP-W
11) show higher chloride concentrations in comparison to sodium. Therefore,
sodium and/or chloride must have different sources like weathering of plagioclase,
ion exchange or impact of wastewater.
4.2.2.9. Calcium and magnesium
The Mazamba Karst spring showed an increased value of calcium (60.1 mg/L)
crossing the MCL MOZ of 50 mg/L. Also Site 1 with the sampling points GNP-W 11
74
4. Discussions
and 20 showed increased values of calcium (97-115 mg/L). The typical contents for
calcium in surface water are between 4 and 40 mg/L (MERKEL & SPERLING, 1996).
Site 1 and Sanctuary showed increased magnesium concentrations (52-164 mg/L).
After MERKEL & SPERLING (1996) typical contents in surface water for magnesium
are 0 to 50 mg/L. Calcium and magnesium are supplied to surface water in small
quantities by means of precipitation, the main part arrived with the decomposition of
calcium and magnesia minerals and maybe washing of fertilizers into surface water.
Magnesium occurs geogenic in carbonate rocks (e.g. dolomite, chlorite, Mg-calcite),
evaporite and minerals of salt deposit places (sulfates, chloride) and it is a
component of magmatite (olivine, pyroxene, amphibole, biotite). It is set free - like
calcium - by the siliceous decomposition of crystalline rocks.
4.2.2.10. Nitrite
Only two springs of Gorongosa Mountain are increased in nitrite (1.1-1.4 mg/L).
These values crossed only MCL EPA of 1 mg/L and MCL Germany of 0.5 mg/L.
High nitrite contents are a reference to partly decomposed organic wastes
(ANONYM (a)) and fecal contaminations. Most disturbing substances are metals,
nitrate and all strongly oxidizing and reducing substances contained in water
(ANONYM (b)).
4.2.2.11. Aluminum
GNP-W 22 (N-Pan, Sanctuary) showed an aluminum value of 318 µg/L crossing the
MCL EPA and WHO of 200 µg/L. As mentioned before, this sampling point is a
retention pond. In nature, aluminum is liberated with the decomposition of minerals
such as feldspar, orthoclase, anorthite/albite, mica and bauxite and reaches clay
minerals. The geological inventory around GNP-W 22 was not investigated.
However, the geological map (MARQUES, 1968) shows gneiss. Gneiss consists of
feldspar, quartz and mica. After MERKEL & SPERLING (1996), higher aluminum
contents arise in water with low and high pH. The measured pH of GNP-W 22 was
8.49. Therefore, the higher aluminum content can be explained by the increasing
pH.
4.2.2.12. Uranium
Uranium concentrations in natural waters are within a range from 0.01 to 100 µg/L
(MERKEL & SPERLING, 1996). It is enriched primarily in granites and gneisses.
GNP-W 20 (Site 1 Borehole – 70.1 µg/L, MCL EPA: 30 µg/L, MCL WHO: 15 µg/L) is
located in the region where Nhambita hot spring is situated. This region is
75
4. Discussions
characterized with tectonic activities. The origin of the uranium contents are not
investigated so far. Only assumptions can be made. The tectonic in the investigated
area is an assumption. Further field work is necessary to investigate the geogenic
origin of uranium.
4.2.3. Gorongosa Mountain springs classification
A hierarchical cluster analysis was performed for the statistical evaluation of major
anions and cations (Chapter 2.3.). The analysis divided seven water samples into
five major groups (Figure 29). A spearman rank correlation was done for testing the
dissolved major elements of significance (Chapter 2.3.). In the investigated area,
several correlations between dissolved elements were found. Appendix B 24 and 25
shows the spatial distribution of Gorongosa Mountain springs.
Group 1
Group 2
Group 3 Group 4
Group 5
Figure 29: Bar plot showing the determination of the major anions and cations in the springs of the Gorongosa
Mountain. Five groups: Group 1 – GNP-S 3; Group 2 – GNP-S 4, GNP-S 5; Group 3 – GNP-S 6; Group 4 – GNP-S
8; Group 5 – GNP-S 9, GNP-S 12.
Group 1 was a HCO3-Na-Ca-Cl-type. This group contained GNP-S 3 FH (Spring
[319 m]) located E of Gorongosa Mountain where basalt and weathered rocks are
present. A HCO3-Na-K-Ca-Mg-Cl-type was specified in group 2 including GNP-S 4
FH (Nhamucunga River with spring) and GNP-S 5 FH (Spring [386 m]). The spring
waters of group 2 are close together and situated SE of the mountain where also
basalt and weathered rocks are attendant. For group 3, a HCO3-Na-K-Cl-type was
determined comprising GNP-S 6 FH (Spring [447 m]). Group 4 was specified as a
HCO3-Na-Ca-Mg-Cl-SO4-type which contained GNP-S 8 TM (Nhambamba River
with spring). Group 3 and 4 are located separately S of the mountain. Gneiss is
76
4. Discussions
present where group 3 is situated and gabbro is attendant where group 4 is located.
A HCO3-Na-K-Ca-Cl-type was determined in group 5 including GNP-S 9 TM
(Vunduzi spring) and GNP-S 12 TM (Muera spring). The spring waters of group 5
are also located close together both at the top of the mountain in NNE. As
mentioned before (Chapter 1.2.2.), at the top of the mountain granite is present. The
group classification is well remarkable in location of the springs and also, geology
plays an important role.
At the Gorongosa Mountain, under saturated species were anhydrite, calcite,
dolomite, gypsum, halite and amorphous SiO2. Except of silicagel, it is only under
saturated in group 3 and 5 but super saturated in group 1, 2 and 4. Also quartz and
chalcedony were super saturated. The EC ranged between 39.1 µS/cm (group 4)
and 186.8 µS/cm (group 1). A general increasing or decrease was not determined.
There is no correlation between increasing salinity and phases.
The under saturations might be caused by the decay of organic matter which
produce CO2 and thus leads the water to under saturation. It must be expected that
some of the minerals being super saturated will precipitate with system changes
(pressure decrease or cooling). The water is not in calcite carbon dioxide
equilibrium. Therefore, it tends to be aggressive to metal pipes.
4.2.4. Karst-associated springs
A hierarchical cluster analysis was also performed for the statistical evaluation of the
major ions (Chapter 2.3.).
Figure 30: Bar plot showing the determination of the major anions and cations in the Mazamba Karst spring – HCO3Na-Ca-Mg-Cl-type.
77
4. Discussions
The group classification of the Mazamba Karst spring (GNP-S 13) is specified in
Figure 30. Appendix B 26 and 27 show the spatial distribution of Mazamba Karst
spring. The karst water was a HCO3-Na-Ca-Mg-Cl-type. The Mazamba Karst spring
is located in an area of lime and sandstone which is an indicator for the group
classification. HCO3 was the dominant species while sodium, calcium, magnesium
and chloride were increased.
The Mazamba Karst spring was under saturated in anhydrite, calcite, dolomite,
gypsum, halite and amorphous SiO2 and super saturated in quartz, chalcedony and
silicagel (Appendix A 20). The under saturations might be caused by the decay of
organic matter which produce CO2 and thus leads the water to under saturation. It
must be expected that some of the minerals being super saturated will precipitate
with system changes (pressure decrease or cooling).
4.2.5. Rift-associated springs
For the statistical evaluation of the major ions, a hierarchical cluster analysis was
performed (Chapter 2.3.). The analysis divided three spring water samples of
Nhambita hot spring region into one major group also including three river water
samples. A spearman rank correlation was done for testing the dissolved major
elements of significance (Chapter 2.3.).
Figure 31: Bar plot showing the determination of the major anions and cations in the creeks, spring discharges and
springs of the Nhambita hot spring region. Only one group is remarkable: Na-SO4-Cl-type.
Figure 31 shows the group classification of the brooks, spring discharges and
springs located in Nhambita hot spring region. Appendix B 28 and 29 show the
spatial distribution of Nhambita hot spring region. No division between brooks,
78
4. Discussions
spring discharges and springs was necessary because only one classification group
emerged. A Na-SO4-Cl-type was specified. Sodium, sulfate and chloride were
dominant, and calcium and bicarbonate showed a small increasing.
As mentioned before in Chapter 1.2.6., the thermal waters described by MARTINELLI
et al. (1995) were characterized by chloride-sulfate alkaline water with chloride as
major anion and sodium as major cation. The same is valid for the measured spring
waters in Nhambita hot spring region. It was characterized by chloride-sulfate
alkaline, and chloride and sodium were the major ions.
The creeks, spring discharges and springs of Nhambita hot spring region were
under saturated in anhydrite, calcite, dolomite, gypsum, halite and amorphous SiO2.
They were super saturated in quartz, chalcedony and silicagel. The under
saturations might be caused by the decay of organic matter which produce CO2 and
thus leads the water to under saturation. It must be expected that some of the
minerals being super saturated will precipitate with system changes (pressure
decrease or cooling).
The group classification of the wells located in Site 1 and Sanctuary is specified in
Figure 32. Appendix B 30 and 31 show the spatial distribution of Site 1 and
Sanctuary.
Group 1
Group 2
Group 3
Figure 32: Bar plot showing the determination of the major anions and cations in the wells of Site 1 and Sanctuary.
Three groups: Group 1 – GNP-W 11, GNP-W 20; Group 2 – GNP-W 21; Group 3 – GNP-W 22.
Four wells were divided into three groups. Group 1 was a HCO3-Na-Ca-Mg-Cl-type
including GNP-W 11 (Site 1) and GNP-W 20 (Site 1 Borehole). Site 1 and Site 1
Borehole are located in the same area. The water of Site 1 Borehole was measured
directly on borehole and the water of Site 1 was measured on the pipe thread right
79
4. Discussions
beside the borehole. A HCO3-Na-Ca-Mg-type was determined in group 2 containing
GNP-W 21 (Sanctuary Borehole Dam). And group 3 was a HCO3-Na-K-Ca-Cl-type
comprehending GNP-W 22 (Sanctuary N-Pan). N-Pan is a watershed which is fed
by groundwater and/or precipitation.
In the wells of Site 1 and Sanctuary, the following phases were under saturated in all
groups: anhydrite, calcite, gypsum and halite. Only in group 1 silicagel and
amorphous SiO2 were under saturated. The super saturated phase in all groups was
chalcedony. Quartz was only super saturated in group 1. Dolomite was under
saturated in group 3 and super saturated in group 1 and 2.
The EC varied between 424 µS/cm (group 3) and 1244 µS/cm (group 1). With
increasing salinity, it is remarkable that the anhydrite saturation index also increased
from -4.37 to -3.07. Also the saturation indices of calcite and gypsum increased with
increasing salinity. Calcite increased from -0.79 to 0.17 and gypsum increased from
-4.15 to -2.85. The under saturations might be caused by the decay of organic
matter which produce CO2 and thus leads the water to under saturation. It must be
expected that some of the minerals being super saturated will precipitate with
system changes (pressure decrease or cooling).
In the entire area in and around the GNP, seismic activity is present proved by the
presence of Nhambita hot springs. In the 1980s, shallow earthquakes were recorded
in the area of interest but no consequences were considered. For the hydrological
regime of the springs and rivers, it is possible that neo-tectonic movements can play
an important role (e.g. spillage, landslides). The area of interest is a tectonic
volcanically affected area. Lithium contents in the investigated springs varied
between 60 µg/L and 130 µg/L which give a reference to it.
4.2.6. River, creeks and stream water quality
For statistical evaluation of major anions and cations, a hierarchical cluster analysis
was also performed (Chapter 2.3.). A spearman rank correlation was done for
testing the dissolved major elements of significance (Chapter 2.3.).
The rivers and creeks of Gorongosa Mountain were divided into three groups.
Appendix B 32 and 33 show the spatial distribution of the rivers and creeks of
Gorongosa Mountain. According to Figure 33, group 1 was a HCO3-Na-K-Ca-Mg-Cltype containing GNP-R 1 TM (Muera River [1236 m]) and GNP-R 7 FH (Nhandare
River). Group 2 was a HCO3-Na-K-Cl-type including GNP-R 2 TM (Vunduzi River).
And group 3 was a HCO3-Ca-Mg-Cl-type comprising GNP-R 10 FH (Muera River
[510 m]). All three named rivers have their origin at the top of the mountain. The
80
4. Discussions
reason for the two different classifications of the Muera River is maybe the location
of the sampled waters. The Muera River with an elevation of 1236 m is located in an
area with no population but the river with an elevation of 510 m is situated in an area
where more population is present. For this reason the river water at 510 m could be
contaminated through e.g. wastes and bathing. The same is valid for Vunduzi River.
The Nhandare River water was also measured at the foothills but there was no
population around.
207.1 mg/L
Group 1
Group 2
Group 3
Figure 33: Bar plot showing the determination of the major anions and cations in the rivers of the Gorongosa
Mountain. Three groups: Group 1 – GNP-R 1, GNP-R 7; Group 2 – GNP-R 2; Group 3 – GNP-R 10.
Appendix A 20 shows the calculated saturation indices of relevant minerals for the
different groups in the investigated area. In the rivers and creeks of Gorongosa
Mountain, the following phases were under saturated in group 1, 2 and 3: anhydrite,
calcite, dolomite, gypsum, halite, silicagel and amorphous SiO2. Chalcedony and
quartz were super saturated in all groups. The EC was ranging from 45 µS/cm
(group 1) to 409 µS/cm (group 3). In general, the anhydrite saturation index
increased with increasing salinity from -5.55 to -4.08. Gypsum and halite behaved in
the same way. Gypsum increased from -5.33 to -3.86 and halite increased from 9.55 to -8.38.
The rivers and creeks of the Nhambita hot spring region have been discussed
before in Chapter 4.2.5. Only one group was established together with springs.
81
4. Discussions
4.2.7. Comparison of the group classification in the investigated areas
Table 4: Comparison of all areas in the investigation area related to their groups. Colors in
the table show the conform groups.
Area
Gorongosa
Mountain –
rivers
Gorongosa
Mountain –
springs
group 1
HCO3-Na-K-Ca-MgCl-type
HCO3-Na-K-Cl-type
type
Cl-type
type
Cl-type
group 5
HCO3-Na-Ca-
HCO3-Na-
Mg-Cl-SO4-
K-Ca-Cl-
type
type
type
HCO3-Na-K-Cl-
HCO3-Na-Ca-Mg-
group 4
HCO3-Ca-Mg-Cl-
HCO3-Na-K-Ca-Mg-
Karst spring
spring region
group 3
HCO3-Na-Ca-Cl-
Mazamba
Nhambita hot
group 2
Na-SO4-Cl-type
Site 1 and
HCO3-Na-Ca-Mg-
HCO3-Na-Ca-Mg-
HCO3-Na-K-Ca-
Sanctuary
Cl-type
type
Cl-type
Comparing all groups of each area of interest, it is remarkable that some groups
correspond to other groups (Table 4). Group 1 of the Gorongosa Mountain rivers
shows the same water type as group 2 of the Gorongosa Mountain springs. Also,
group 2 of the Gorongosa Mountain rivers has the same water type than group 3 of
the Gorongosa Mountain springs. There is a correlation between group 5 of the
Gorongosa Mountain springs and group 3 of Site 1 and Sanctuary. At least, the
water type of Mazamba Karst spring is the same as group 1 of Site 1 and Sanctuary.
On the basis on different areas, geology and location, it is not expedient to compare
the groups of the different areas. It is just an advice that in different areas the same
type of water can appear.
In all groups the water is super saturated with chalcedony which is in agreement
with the later discussed SiO2-geothermometer (Chapter 4.3.).
4.3. Origin of groundwater
As it was described in Chapter 2.3.1., SiO2 was used as geothermometer to
determine the approximate circulation depth of the water types.
According to Chapter 2.3.1., generally the second equation was applied since in
most of the sampled waters chalcedony predominated as SiO2 modification while
amorphous SiO2 and silicagel were undersatured and quartz features higher supersaturated than chalcedony. The single records of saturation indices for quartz,
respectively chalcedony and the calculated temperatures are presented in Appendix
A 19. No SiO2 was measured for GNP-W 20, 21 and 22.
82
4. Discussions
For the spring of Gorongosa Mountain, the SiO2 concentrations showed a maxima
at about 171 mg/L (Appendix B 23). The calculated SiO2 formation tempratures
were between 33°C and 147°C. An average annual temperature of 25.7°C in the rift
floor has to be substracted from this calculated temperature. Therefore, the SiO2
formation temperature may have been between 7°C and 121°C. According to the
geothermal gradient of 3°C/100 m, the corresponding depth would be 230 - 4030 m.
The SiO2 temperatures calculated for the measured springs in Nhambita hot
spring region were between 121°C and 134°C (Appendix B 23). Substracting the
average annual temperature of 25.7°C, the SiO2 temperature was between 95°C
and 108°C. The corresponding depth would be 3100 - 3600 m.
As mentioned before in Chapter 2.3.1., the silica geothermometer is based on
attitude of a chemical equilibrium between the minerals of the aquifer and the deep
water. According to FOURNIER (1973), waters below 150°C are in equilibrium with
chalcedony. As mentioned above, the calculation by the silica geothermometer
showed temperatures in Gorongosa Mountain springs between 33°C and 147°C and
in Nhambita hot spring region springs between 121°C and 134°C. These are
temperatures at which equilibrium is established with chalcedony, respectively.
According to Figure 14 in Chapter 2.2.4., the isotopic composition of the sampled
water was intensively affected by evaporative loss. Figure 18 (a – Gorongosa
Mountain) (Chapter 3.2.3.) shows a more humid evaporative loss than Figure 18 (b
– Mazamba Karst spring, Nhambita hot spring region and/or c – Site 1 and
Sanctuary). Figure 18 (c) only shows 2 water samples, for detailed discussion it is
too less. In Nhambita hot spring region, the increase in δ18O was much smaller than
at Gorongosa Mountain or Site 1 and Sanctuary while the slope of EL was the
largest. The EL slope of the rainfall of Chitengo and Gorongosa (8.1) is higher than
the slope of the LWML (7.9). For the Mazamba Karst spring, only one sample was
taken and, therefore, no regression line could be plotted. In a karst system a dual
porosity may exist. On the one hand porosity occurs in small-scale fractures and the
porous matrix. And on the other hand porosity is in the high-velocity conduits
through the system – stable isotopes have the ability to travel through these two
systems (www_3).
As a result, it is suggested that isotopic enrichment of the sampled water is closely
related to evaporation of ponded water rather than the total evapotranspiration from
the field. This supports the possibility to separate evaporation and transpiration
using the isotope hydrological approach usually impossible by micrometeorological
83
4. Discussions
measurements. For more detailed and quantitative analysis, intensive field
observations of water balance and collection of water samples in the same area are
necessary.
4.4. Groundwater aging
The very low mineralization in the springs of the Gorongosa Mountain is an
indicator for a short residence time in the host rocks. Gorongosa Mountain is an
Inselberg existing of mainly granite. Cause of its elevation of about 1,862 m, the
precipitation is much higher at the mountain than at the surrounded area (Chapter
1.2.3.). The precipitation water normally has an EC of 2 – 40 µS/cm (Appendix A 3).
The spring water from the mountain has an EC value ranging between 39 – 187
µS/cm – only slightly higher as the precipitation values. Cause of fault zones above
and around the mountain water leaks as springs shortly after rainfall.
Also in the Mazamba Karst spring, the low mineralization is an indicator for a short
residence time in the host rocks which is usual for a karst system. As mentioned
before in Chapter 1.2.2., the most important characteristic of karst springs results
from the fact that caves transfer the water quickly. It comes to a minimum cleaning
of the water and to a small balance of variable delivery.
The springs located in the Nhambita hot spring region and the wells of Site 1 and
Sanctuary are very high in mineralization. This is an indicator for long residence
time in the host rocks which are gneisses. The high mineralization is also
abandoned by the geology. The corresponding origin depths are 3100 - 3600 m
(Chapter 4.3.). The longer water flows through and along rocks, the longer is the
contact between water and rock, and the more minerals are rinsed from the rock
and absorbed in the water. MERKEL & STEINBRUCH (2006) examined the Nhambita
hot spring (MOSA P1) for
14
C and identified an average residence time of 11,310 ±
45 years. If comparing GNP-S 18 (4,250 ± 60 years), a hot spring in Nhambita hot
spring region, with MOSA P1, it is close to the fact that both springs do not have the
same origin since they exhibit different ages (Chapter 3.2.4.). In addition, the
13
C
value of MOSA P1 lies in the normal range for fresh water bicarbonate (equilibrium
with terrestrial carbonates). Instead, the
13
C value of GNP-S 18 lies in the fresh
water range and corresponds to a mixture of soil CO2 and marine carbonate.
84
4. Discussions
4.5. Pollution and geogen anomalies
The polluted water in the investigated areas goes back particularly to animal and
human excreta, fertilizers, sediment suspension in rivers and illegal mining industry
(sedimentation, heavy metal). It can lead to substantially health damage. Some
important elements were described in the following:
Studies clearly established that fluoride primarily produces effects on skeletal
tissues like bones and teeth. In many regions with high fluoride exposure, fluorosis
is a significant cause of morbidity.
High mercury content can be in the long term health-endangering. It can come to
irreversible malfunctions because mercury is accumulated in the body and can
damage the nervous system and kidney.
Ammonia in drinking-water is a indicator for fecal contamination. No health-based
guideline value after WHO or EPA is proposed. Toxicological effects are observed
only at exposures above 200 mg/kg of body weight. However, ammonia can
compromise disinfection efficiency, result in nitrite formation in distribution systems,
cause the failure of filters for the removal of manganese and cause taste (1.5 and 35
mg/L) and other problems.
Since water with higher sulfate concentration taste not only unpleasant but also
stomach, intestine disturbances and damage to buildings can be caused
(ALBRECHT 1979; WORCH 1997).
There is little indication that orally ingested aluminum is acutely toxic to humans
despite the widespread occurrence of the element in foods, drinking-water and
many antacid preparations. It has been hypothesized that aluminum exposure is a
risk factor for the development or acceleration of onset of Alzheimer disease in
humans (KÖLLE, 1998).
Uranium is estimated as strongly poisonous since uranium causes liver and kidney
damage.
Around the GNP, the water-use cycle is influenced by human activity. Withdrawal
pipes in rivers and groundwater wells reveal that humans have a small impact on
the water cycle. In the water-use cycle, water moves from a source to a point of use,
and partly to a point of disposition (e.g. Inhaminga Town, Chitengo). The sources of
water are either surface water or groundwater. Water in the investigated area was
used by animals and there living people for cleaning, washing, cooking, preparing
food and drinks, and putting out fires to save people and properties. Humans use
the relative water without knowing the water quality and thinking of their health.
More than 13 % of dead are caused by lacking hygiene, missing sanitary
85
4. Discussions
constructions, and dirty drinking water. A big problem is the missing education in
respect to hygiene and transfer of diseases through water. Another problem is the
water treatment after use. There are no wastewater treatment plants, draining wells,
open air defecation, etc. Therefore the waste water flows through groundwater or
directly into rivers where it is used again for daily uses.
4.6. Water treatment
Due to limited utilization because of high initial and operating costs of the
conditioning measurement procedures (e.g. ion exchanger, reverse osmosis,
charcoal, batcher), toxically rest salts and no conversion for logistic reasons in rural
regions, a cheaper aspect should be considered.. A “LifeStraw” of the Danish
enterprise “Vestergaard Frandsen” was manufactured. The 160 gram heavy
equipment filters bacteria from dirty water. The straw costs only three US Dollar per
piece. Nevertheless, the 31 centimeters straw cleans dirty water for up to one year
and can be stored according to manufacturer data also up to three years. This is
possible due to three different filters which remove the bacteria. Thus it protects for
Cholera and the Ruhr (www_10). Also, the project with the name “Sodis” (Solarly
Water Disinfection) is cheap and simple. Researchers of the Swiss water research
institute “Eawag” had the idea to fill water into conventional PET bottles and to
suspend it the UV-radiation of the sun. Only after six hours, at least the exciters of
diarrhea were already eliminated in the dirty water. But dark and glass bottles are
suitable for the cleaning according to statement of the water researchers (www_10).
A completely different way goes the physicist Shuji Nakamura, professor of the
University of California in Santa Barbara. In the 1990s, the Japanese scientist built
the first blue laser diode and used for this the material gallium nitride. This special
LED radiates very much UV light. UV light possesses very high photon energy, kills
the bacteria in the water and cleans it in such a way. UV LEDs are very cheap and
cost approximately a dollar per piece. Besides they are easy and efficient. If
someone gets dirty river water, the water can be drank with the help of a special
hose which is put on the drinking cup and in a filter with UV LEDs is assigned
(www_10).
4.7. Database organization and information dissemination
A major purpose of the digital atlas was thus to provide background information to
relate observations from the test field to a larger context and interpret them
considering the overall spatial distribution of hydrogeochemical parameters. The
digital atlas should be considered as a snapshot of the whole water problem at and
86
4. Discussions
surround the GNP. It is a summary of the whole diploma thesis. Hyperlinks compiled
in the map show a detailed characterization about location and geology of the
relative areas of interest.
4.8. Errors and uncertainties
Some uncertainties and errors are as follows:
-
All water samples were taken only once. Cause of uncertainties concerning
the reliability of the results, the analysis of the elements should be repeated
by a hydrochemical laboratory at least two times.
-
Filtering of the water samples was done in field. Cause of contamination due
to e.g. dirty fingers, the filtering may result to an error.
-
All water samples had to keep cool during storage and transport. Only during
storage in Chitengo, it was possible keeping the water cool in a refrigerator.
However, during transport there was no possibility preserving the water cool.
The samples were on transport for at least two weeks or more. In Germany,
they were stored in the refrigerator again.
-
In June, despite calibrations of the conductivity analyzer uncertainties arose
concerning to the measured values – these varied strongly. For this reason
another conductivity analyzer was taken. However, it is not clear, if the
preceding measured values were nevertheless correctly.
-
The used distilled water came from the air conditioner in the camp of
Chitengo and drinking water of bottles bought in the market in Beira.
Therefore, errors can appear for on-site parameters especially photometry
because distilled water was used as blanks.
-
Calculation of the charge imbalance by PhreeqC: Potential errors which sum
up and contribute to charge imbalance besides analytical problems are for
example errors in sample acidification, preservation, inaccurate dilution and
laboratory.
-
The discharge measurement of rivers, creeks, spring discharges and springs
at the Gorongosa Mountain and in the Nhambita hot spring region was done
with a flowing bottle (Chapter 2.1.3.3.). These data are by no means exact
and are to serve only as approximate value for the representation the order
of magnitude of the discharge.
-
Changes of discharge are led back on strong precipitation events, seasonally
caused thaw phases and infiltration and evaporation period. Short term
changes of weather can cause delays during the attitude of discharge
equilibrium.
87
4. Discussions
-
The tracer test at the Mazamba Karst spring: possibilities of errors are e.g.
mixing, lacking, turbulences by the underground and change of the
background conductivity.
-
At the Mazamba Karst spring, the discharge was determined with a
measuring weir. Due to the kind of the measurement (arise from individual
errors with measuring) an evaluation was not possible.
88
5. Conclusions and recommendations
The present report is based on field-work conducted in Mozambique. The field-work
was divided in three main investigation areas: Gorongosa Mountain, Mazamba
region, Nhambita hot spring region including Site 1 and Sanctuary. Various
problems and errors occurred and new ideas evolved for following studies. A short
summary follows:
Gorongosa Mountain:
In the investigated area of the Gorongosa Mountain, the goal was to collect details
of all springs for the development of new wells, to assess availability of the springs
and wells for inhabitants, and to inspect, if the springs of the Gorongosa Mountain
could be used as catchment area of the Nhambita hot spring. In the context of the
field work, it was possible to find springs, to measure on-site parameters and to take
water samples.
The rivers and brooks of the Gorongosa Mountain showed EC in the range of MCL
Mozambique and Germany except of one water sample (< 50 µS/cm), partly
reduced to oxidizing conditions, oxygen contents above 8 mg/L and oxygen
saturations above 90 %, weak acid to basic pH and temperatures between 15°C
and 21°C. The analyzed springs showed EC below 50 µS/cm, partly reduced and
anaerobe to aerobe conditions, acid to weak basic pH and temperatures ranging
Calculated charge imbalance shows percent errors > ± 10 % in GNP-S 6 FH and
GNP-S 8 TM. Therefore, these two sampling points were considered with attention.
GNP-S 3 FH and GNP-S 8 TM showed high concentrations of nitrite (Appendix
A 11). GNP-S 3 FH and GNP-R 7 FH showed high concentrations of total iron. And
all springs except GNP-S 10 FH and all rivers except GNP-R 12 TM showed high
concentrations of phosphate. The water of the investigated rivers, creeks and
springs is used for cooking, washing, cleaning, drinking etc. Also it was possible to
assess the availability of the springs and wells for inhabitants: At the Gorongosa
Mountain several wells were found. These wells are derelict and are partly in bad
state. Nevertheless, inhabitants are still using those wells which can cause
diseases.
For
these
wells
further
investigations
and
rehabilitations
are
recommended (withdrawal of water test and investigation, water purification
measures etc.). Due to time scarceness and logistic problems, no more springs at
the top of the mountain could be more explored. Therefore, more spring waters have
to be investigated in the same way. It is not for sure that the first conductivity meter
always measured correctly because in June, it had to be changed with another
89
conductivity meter due to no constant concentrations. Therefore, the electrical
conductivity should be measured again at sampling point GNP-S 12 TM (and GNPW 11).
In the investigated area of the Gorongosa Mountain grab samples of granite,
gneiss, hornfels and gabbro were taken.
Mazamba Karst spring:
The goal at the investigated area of the Mazamba region was to inspect catchment
borders for the definition of the park buffer zone and the geochemical description of
the spring. In the context of the field work, the surface catchment border could not
be inspecting exactly because of time scarceness, logistic problems, elevation
differences and inapproachability of the area. However, it was possible to calculate
the surface catchment of the Mazamba River with the help of ArcGIS 9.3. The
Mazamba Karst spring was measured by on-site parameters and water samples
were taken for further laboratory analyses.
The water of the Mazamba Karst spring showed EC between Mozambican standard
ranges, partly reduced conditions decreasing with reducing temperature, aerobe
conditions decreasing with rising temperatures, low oxygen saturations which points
to oxygen consumptive disassembly processes in the groundwater, a slightly basic
pH and a mean temperature of 26°C (Appendix A 10).
The spring water was high in total iron, phosphate, manganese and calcium
(Appendix A 12). On the basis of information by inhabitants, this spring is also used
for cooking, washing, cleaning, drinking etc.
The investigated area of the Mazamba region contains limestones, calcarenites
and quartzitic greywacke outcrops. Also grab samples like greywacke,
calcarenite, conglomerate, sandstone, reddish and quartzitic greywacke and a
rhyolith with chalcedony were present.
Nhambita hot spring region:
In the Nhambita hot spring region, the goal was to measure quantity of thermal
springs, their origin and availability. In the context of the field work, it was possible to
find two more hot springs and one cold spring measuring on-site parameters, taking
water samples for further analyses and getting information about origin and
availability. Springs, brooks and spring discharges were determined in the Rupice
River surface catchment calculated with ArcGIS 9.3.
The creeks and spring discharges (Appendix A 10) measured in the Rupice River
surface catchment showed EC ranging in the MCL of MOZ and Germany (50 – 2000
µS/cm) except of two rivers with values < 50 µS/cm, partly reduced and anaerobe to
90
aerobe conditions, weak acid to weak basic pH and temperatures between 19°C
and 29°C. The analyzed springs located in stream courses showed also EC ranging
in the MCL of MOZ and Germany (50 – 2000 µS/cm), partly reduced and anaerobe
to aerobe conditions, weak acid to weak basic pH and temperatures between 41°C
and 42°C which are classified as mesothermal waters (ALBU et al., 1997). On the
basis of Br/Cl ratio, GNP-S 12 TM is an indicator for the statement that the
Nhambita thermal water possibly origins from the Gorongosa Mountain.
GNP-R 14, 15, 19 and GNP-S 16, 18 showed high concentrations of total iron. All
sampling points except GNP-R 19 had high concentrations of phosphate. GNP-S
18 and GNP-R 19 exhibits high mercury concentrations and GNP-R 15 and GNP-S
16 exhibit high ammonia contents. Additionally, all sampling points were high in
manganese, sulfate, sodium, fluoride and chloride (Appendix A 13). Information
given by locals about the purpose, the spring is not always in use. Creeks and
spring discharges are in use for cooking, washing, cleaning, drinking etc. The
thermal springs in the Nhambita hot spring region can be used as geothermal
energy source. The direct use includes swimming, bathing, balneology (therapeutic
use), thermal heating, agricultural (animal farming, green house heating), industrial
processes and heat pumps.
Chemical analysis on main ions and trace elements like Hg, U, Sr, Zn, Ni, Al and Ba
should be checked again at least two times since they showed values which are
unusual. For further concepts in the Nhambita hot spring region, it is necessary to
arrange a long-term monitoring scheme at a drilled well with continuously readings
of pressure and key parameters such as EC, T, pH etc. in the geothermal system,
taking water samples for bacteriological check, complete ion analyses, strontium
and sulfur isotope analyses, 14C analyses and installing permanent weirs.
The geological goal was to augment the existing geological map by field
observations in selective outcrops. Therefore, outcrops and grab samples were
investigated and criticized. The investigation area of Nhambita hot spring region
consists of gneiss, pegmatite and granite with quartz veins. For closer analyzes
of the geology, geophysical sections are required. A systematic network of
geophysical sections through the entire investigation area is recommended in order
to check the depth. Especially in Nhambita hot spring region, geophysical sections
would help to identify where the origin of Nhambita hot spring is located, trying to
find out strike direction and depth of the fault. Seismic should be preferred to the
geoelectric since it covers greater depths. Heatflow could help to locate the fault
zone.
91
Site 1 and Sanctuary:
The investigation of Site 1 and Sanctuary comprises collecting water samples of all
wells for checking water quality and quantity and to assess availability of the wells
for inhabitants. In the context of the field work, it was possible to measure on- site
parameters and to take water samples for further laboratory analyses.
The analyzed wells of Site 1 and Sanctuary (close to Nhambita hot spring region)
showed EC in the range of the MCL MOZ and Germany with 50-2000 µS/cm, partly
reduced to oxidizing conditions, weak basic to basic pH and temperatures ranging
Calculated charge imbalance showed percent errors > ± 10 % in GNP-W 21.
Therefore, this sampling point was considered with attention. GNP-W 11 showed
high concentrations of phosphate, calcium, fluoride and magnesium. GNP-W 20
was high in calcium, mercury, magnesium and uranium. GNP-W 21 had high
contents of mercury and magnesium. And GNP-W 22 showed high total iron,
manganese, mercury, ammonia and aluminum concentrations (Appendix A 14).
Concerning hydrogeology, it would generally help for future interpretation, if a
database of all wells, springs, rivers and creeks existed accessible to all
researchers. Single information already exists but a complete network is missing.
For hydrogeochemistry, already many analyses have been done, unfortunately,
mostly without considering geology or hydrogeological setting (especially aquifers).
Chemical analysis should be checked for both dry and wet season. Concentrations
of pesticides have to be measured in all wells and rivers/creeks because inhabitants
take these waters for cooking and drinking. Groundwater flow and groundwater
recharge rate in Rupice River surface catchment and Mazamba River surface
catchment areas should be quantified. This will enable a more reliable calculation of
the water balance.
92
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7. Acknowledgement
7. Acknowledgement
While the stay in Mozambique did not proceed completely without problems, it was a
very interesting and unforgettable time. I gained many experiences and found
friends.
I like to thank the following people:
-
My first supervisor Prof. Dr. Broder J. Merkel (Chair for Hydrogeology) from
my home university in Freiberg who supported this work by professional
suggestions, helped with all technical problems and who was always
available for discussions. I also like to thank him for proof-reading.
-
Special thanks goes to Dipl. Geol. Franziska Steinbruch (Centro de
Informação Geográfica, Universidade Católica de Moçambique (CIG UCM),
Beira, Mozambique) for her amicable support in all situations not only
concerning scientific questions. Her engagement, experience in the field,
availability for asking as well as proof-reading was essential for finishing my
thesis. Her hospitality gave me a lot of inspiration and comfort.
-
During the work in and around the GNP, I relied on the help from the
National Park Staff. Therefore, a special thanks goes to Tongai Castigo and
Regina Cruz who were an indispensable help for the work at the Gorongosa
Mountain. Also, I would like to thank Carlos Lopes Pereira, Justino Carlos
Davane and Adolfo Júlio Ruco who made the field work more comfortable.
A great thanks goes to all other coworkers of the park who assisted me
during the time in Mozambique and made the life a little easier. Furthermore,
I appreciated the help of Sicoche Patriçio who supported my work at the
Mazamba Karst spring. A great thanks goes to Silvestre Meguegy who
helped me with GIS data and digital maps in the CIG UCM, Beira.
-
Thanks goes also to Opras Publicas, the local water authority in Beira and
Gorongosa, for providing me access to all their wells at the foothills of the
Gorongosa Mountain and their raining data.
-
I like to thank Hans-Joachim Peter and Dr. Sascha Kummer for their
support at the laboratory in Freiberg (Germany).
-
Special thanks goes to the Activation Laboratories Ltd. in Ancaster,
Ontario, Canada for examination the trace elements with ICP-MS, and P. M.
Grootes of the Leibniz laboratory for age determination and isotope dating in
Kiel, Germany for examination the carbon isotopes.
-
Regina van den Boogaart was a great help managing all problems while
constructing the digital atlas.
101
7. Acknowledgement
-
Especially, I like to thank my parents for financing my studies and always
believing in me, my family and friends for the permanent encouragement
during the difficult periods of my work and for just being there when I needed
them.
102

Hydrogeochemistry of the Mazamba and

Transcription

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