NO2/NOx volume ratio in three tunnels in Norway

Transcription

Norwegian Public
Roads Administration
15.5.2013
NO2/NOx volume ratio in
three tunnels in Norway
Observations 2007 - 2013
No. 173
Statens vegvesen
NO RWE GIAN PUBLIC RO ADS ADMIN IS T RA T I ON
Statens vegvesens rapportar
NPRA reports
Norwegian Public Roads Administration
Tittel
Registrering av volumandel NO2/NOx i tre
norske tunnelar
Title
Observations of NO2/NOx volume ratio in
three tunnels in Norway
Undertittel
2007 - 2013
Subtitle
2007 - 2013
Forfattar
Gunnar Lotsberg
Author
Gunnar Lotsberg
Avdeling
Ressursavdelinga
Department
Planning and Engineering Services Department
Seksjon
Prosjekteringsseksjonen
Section
Detailed Design Section
Rapportnummer
Nr. 173
Report number
No. 173
Godkjent av
Gunnar Søderholm
Approved by
Gunnar Søderholm
Emneord
Tunnel, ventilasjon, luftkvalitet, bileksos,
emisjonsfaktor, diesel, bensin, NO2, NO, NOx,
PM, PM10
Samandrag
Formålet med denne rapporten er å studere
utviklinga av giftige gassar i bileksosen dei
siste åra. Dette er nyttig kunnskap ved planlegging av ventilasjon i nye tunnelar og ved
vurdering av konsekvensar for miljøet rundt
tunnelportalane.
Rapporten inneheld målingar av NO og NO2
i tre tunnelar i Region vest frå 2007 til 2013.
Registreringane viser at utsleppet av støv og
NO2 frå tunge køyretøy har gått ned etter
innføring av partikkelfilter som oppfyller Euro
5-krava. Men det har vore ei negativ utvikling
i NO2-utslepp frå personbilar på grunn av den
sterke auken i talet på bilar med dieselmotor.
I tunnelar med stor utfartstrafikk medfører
dette høgt NO2-nivå fredag ettermiddag og
søndag kveld. I bytunnelar kan det ventast
høgst NO2-nivå i morgon- og ettermiddagsrushet.
Key words
Tunnel, ventilation, air quality, car exhaust,
emission factor, diesel, petrol, gasoline, NO2,
NO, NOx, PM, PM10
Summary
The purpose of this report is to study the
development of toxic gases in car exhaust in
recent years. This is useful knowledge when
planning ventilation in new tunnels and for the
assessment of environmental impact around
the tunnel portals.
The report contains observations of NO and
NO2 in three Norwegian tunnels from 2007 to
2013. Emission of dust and NO2 from heavy
duty vehicles have been reduced after introduction of particulate filters that meet the Euro
5 requirements. However, there has been a
negative trend in NO2 emissions from passenger cars because of the significant increase in
the number of diesel-powered cars in Norway.
In tunnels with large weekend-traffic, this
results in high NO2 concentrations on Friday
afternoon and Sunday evening. The highest
NO2 levels in urban tunnels can be expected
during rush hours.
Tal sider
Pages 67
67
Dato 15.5.2013
Date 15.5.2013
INDEX
Introduction ............................................................................................................................................. 4
1.
Nitrogen oxides (NOx), ozone (O3) and particulate matters.................................................... 5
1.1
Air quality guidelines for NO2 and Particulate matters (PM) .................................................. 5
1.2
Main sources for nitrogen oxides (NOx) in road tunnels ........................................................ 6
1.3
Some observations of NO2 in long Norwegian tunnels ........................................................... 8
1.4
Nitrogen oxides (NOx) ........................................................................................................... 10
1.5
Ozone (O3) and oxides of nitrogen (NOx) .............................................................................. 12
1.6
Particulate matters (PM) and relative humidity (Rh) ............................................................ 14
1.7
Diesel Particulate Filters (DPF) and NO2/NOx-ratio .............................................................. 15
1.8
NO2-sensors, measurement principles and detection limits ................................................. 16
2
Observations of NO2 / NOx volume ratio in the Laerdal tunnel ............................................. 19
2.1
The ventilation system .......................................................................................................... 19
2.2
Observations of NO and NO2 in September 2007 and 2008 ................................................. 20
2.3
Observations of NO and NO2 in July - September 2011 ........................................................ 31
2.4
NOx-emission from heavy duty vehicles in December 2012................................................. 36
2.5
NOx-emission from passenger cars in March 2013 ............................................................... 40
3
Observations of NO and NO2 in the Fodnes tunnel ............................................................... 46
3.1
Observations of NO2/NOx volume ratio in 2010 ................................................................... 46
3.2
3.3
4
Observations of PM10 and NOx in the Knappe tunnel in Bergen ........................................... 60
4.1
Particulate matters (PM) and relative humidity (Rh) ............................................................ 60
4.2
Observations of NO2 and NO in January 2012....................................................................... 63
4.3
Observations of NO2 and NO in March 2013......................................................................... 65
5
Concluding remarks ............................................................................................................... 66
6
References ............................................................................................................................. 67
1
Figures
Figure 1: Trends in emission of nitrogen oxides from road traffic in Norway [] ...................................................... 6
Figure 2: Average driving length for vehicles in Norway (www.ssb.no) ................................................................. 7
Figure 3: Road traffic volumes in Norway (www.ssb.no) ........................................................................................ 7
Figure 4: Diesel cars had 10 times higher NOx-emission than gasoline cars in 2001 ............................................. 7
Figure 5: European emission limits varies with fuel type and weight of vehicles ................................................... 8
Figure 6: Observed NO2 / NOx-ratio in the Laerdal tunnel in December 2012 ....................................................... 9
Figure 7: Observed and calculated NO-oxidation in the Laerdal tunnel ................................................................. 9
Figure 8: Time required for half NO in air ............................................................................................................. 10
Figure 9: Calculated NO2-production from oxidation of NO during 24 hours ....................................................... 10
Figure 10: Calculated production of NO2 from 2 – 10 ppm NO ............................................................................ 11
Figure 11: Nitrogen dioxide (NO2), ozone (O3) and particulate matters (PM) in January 2012 ............................ 12
Figure 12: Air quality in Bergen in January 2012 (www.luftkvalitet.info/) ........................................................... 13
Figure 13: Relationship between relative humidity and temperature.................................................................. 14
Figure 14: Length profile of the Knappe tunnel in Bergen .................................................................................... 14
Figure 15: Comparison of NO-values from a Dräger sensor with values from a precision instrument ................ 17
Figure 16: Comparison of NO2 values from a Dräger sensor and a precision instrument .................................... 17
Figure 17: Calculated NO2 / NOx volume ratios from two instruments ................................................................ 18
Figure 18: Ventilation principle in the Laerdal tunnel........................................................................................... 19
Figure 19: Example of natural ventilation during 12 hours before the fans started............................................. 20
Figure 20: Example of growth of NO2 / NOx volume ratio in the morning before the fans started ..................... 20
Figure 21: Example of low night traffic and start of ventilation at 03:00 because of NO-oxidation .................... 21
Figure 22: Example of low ventilation level and high NO2 / NOx volume ratio on Monday afternoon ............... 22
Figure 23: Example of high NO2 / NOx volume ratio on Saturday afternoon ........................................................ 22
Figure 24: Average concentration of NO2 and NO in week no. 37 in 2007 ........................................................... 23
Figure 25: Daily traffic in week no. 37 in 2007 and week no. 38 in 2008 ............................................................. 23
Figure 26: Average concentration of NO2 in week no. 37 in 2007 and week no. 38 in 2008 ............................... 24
Figure 27: Ventilation level and air velocity from Aurland on a Sunday in September 2007 and 2008 ............... 24
Figure 28: Average concentration of NO in week no. 37 in 2007 and week no. 38 in 2008 ................................. 25
Figure 29: NO2 / NOx volume ratio at 9.4 km in week no. 37 in 2007 and week no. 38 in 2008 ......................... 26
Figure 30: NO2 / NOx volume ratio at 17 km in week no. 37 in 2007 and week no. 38 in 2008 .......................... 26
Figure 31: NO2 and NO concentration 9.4 km and 17 km from Aurland on Monday 2007-09-10 ........................ 27
Figure 32: NO2 and NO concentration 9.4 and 17 km from Aurland on Sunday 2007-09-16 ............................... 28
Figure 33: NO2 / NOx volume ratio at 9.4 km and 17 km from 13 August to 16 September 2007 ....................... 28
Figure 34: Average NO2 / NOx volume ratio in week no. 33 – 37 in 2007 ............................................................ 29
Figure 35: NO2 / NOx volume ratio at 9.4 km and 17 km 1 – 21 September 2008................................................ 30
Figure 36: Average NO2 / NOx volume ratio 1 – 21 September 2008 ................................................................... 30
Figure 37: Average concentration of NO2 in week no. 29, 33 and 36 in 2011 ...................................................... 31
Figure 38: Average concentration of NO in week no. 29, 33 and 36 in 2011 ....................................................... 32
Figure 39: Average NO2 / NOx volume ratio at 9.4 km and 17 km in week no. 29 - 36 in 2011 ............................ 33
Figure 40: Daily traffic and ratio of heavy duty vehicles in week no. 29 - 37 in 2011........................................... 33
Figure 41: Average NO2 / NOx volume ratio from 2011-07-18 to 2011-09-17 ..................................................... 34
Figure 42: NO2 / NOx volume ratio 9.4 km from Aurland in week no. 29 and 36 in 2011 .................................... 35
2
Figure 43: NO2 / NOx volume ratio 17 km from Aurland in week no. 29 and 36 in 2011 ..................................... 35
Figure 44: Observed NO-concentration at five points in the south half of the tunnel ......................................... 36
Figure 45: Observed NO-concentration in the north half of the tunnel during 60 minutes ................................. 36
Figure 46: Traffic in the Laerdal tunnel on Monday 2012-12-10 .......................................................................... 37
Figure 47: Observed NO-concentrations from Aurland during two hours............................................................ 38
Figure 48: High NO2-concentration on Monday 2012-12-10 ................................................................................ 38
Figure 49: Variations in NO2 / NOx volume ratio from Saturday to Tuesday ........................................................ 38
Figure 50: Growth of NO2-concentration from oxidation of NO ........................................................................... 39
Figure 51: Variations of NO2 / NOx volume ratio during two hours ..................................................................... 39
Figure 52: Daily traffic and average NO2 / NOx volume ratio 2 weeks in March 2013 ......................................... 40
Figure 53: Normal growth of NO2 / NOx volume ratio from weekend-traffic on Friday afternoon...................... 40
Figure 54: Traffic variations on Friday 2013-03-08 ............................................................................................... 41
Figure 55: Traffic and NO2 / NOx volume ratio, March - April 2013 ..................................................................... 41
Figure 56: Traffic and NOx at the start of Easter holidays in 2013 ....................................................................... 42
Figure 57: Traffic and NOx on Easter Sunday in 2013 ........................................................................................... 43
Figure 58: Traffic and NOx on Monday 2013-04-01 .............................................................................................. 44
Figure 59: Traffic and NO2 / NOx volume ratio one week after Easter 2013 ........................................................ 45
Figure 60: Average NO2 / NOx volume ratio in the Fodnes tunnel 9 - 14 March 2010 ......................................... 46
Figure 61: Average NO2 / NOx volume ratio in the Fodnes tunnel 17 - 22 March 2010 ....................................... 46
Figure 62: Natural ventilation and average NO2 / NOx volume ratio on Friday 2010-03-12................................. 47
Figure 63: Ventilation level and average NO2 / NOx volume ratio on Sunday 2010-03-14 ................................... 48
Figure 64: Ventilation level and average NO2- and NO-concentration on Thursday 2010-03-18 ......................... 48
Figure 65: NO2- concentration on Thursday 2010-03-18 ...................................................................................... 49
Figure 66: Ventilation level and average NO2- and NO-concentration on Friday 2010-03-19 .............................. 49
Figure 67: NO2- and NO-concentration on Saturday 2010-03-20 ......................................................................... 50
Figure 68: Variations in traffic and NO2 / NOx volume ratio from week no. 29 to week no 37 in 2011 ............... 51
Figure 69: Variations in traffic and NO2 / NOx volume ratio in March – April 2013.............................................. 52
Figure 70: Daily variations of the NO2 / NOx volume ratio during week no. 11 in 2013 ....................................... 53
Figure 71: Ventilation and NO2 / NOx volume ratio on Wednesday 2013-03-13.................................................. 54
Figure 72: Ventilation level and NO2 / NOx volume ratio on Wednesday 2013-03-27 ......................................... 55
Figure 73: Traffic, ventilation and NO2 / NOx volume ratio on Friday 2013-03-08 ............................................... 56
Figure 74: Traffic, ventilation and NO2 / NOx volume ratio on Friday 2013-03-15 ............................................... 57
Figure 75: Ventilation and NO2 / NOx volume ratio on Saturday 2013-03-23 ...................................................... 58
Figure 76: Ventilation level and NO2 / NOx volume ratio on Easter Sunday 2013-03-31 ..................................... 59
Figure 77: PM10-values and air velocity in the Knappe tunnel in January 2011 .................................................... 60
Figure 78: PM10-values and air velocity in the Knappe tunnel in September 2011 .............................................. 61
Figure 79: PM10-values in the Knappe tunnel in January 2012 ............................................................................. 62
Figure 80: Daily variations of NO2, NO and NO2/NOx in the north direction in January 2012 .............................. 63
Figure 81: Daily variations of NO2, NO and NO2/NOx in the south direction in January 2012.............................. 64
Figure 82: NO2, NO and NO2/NOx on Wednesday 2012-01-04 ............................................................................. 64
Figure 83: NO2, NO and average NO2/NOx in south direction in March 2013 ...................................................... 65
3
Introduction
The purpose of this report is to provide a sound basis for detailed planning of the ventilation
system for the new Rogfast tunnel and other long road tunnels in Norway. The Rogfast tunnel
which is being planned on the coastal road between Stavanger and Bergen, is a 25 km long
subsea road tunnel with two tubes. The tunnel will be divided into four ventilation sections by
three double ventilation shafts. Each section will have a longitudinal ventilation system with
jet-fans.
The report is referring to observations of NO and NO2 and in three Norwegian tunnels:
Length
Daily traffic in 2012
% heavy duty vehicles
Laerdal tunnel
24.5 km
1 896
26 %
Fodnes tunnel
6.6 km
1 959
18 %
Knappe tunnel
2.5 km
19 153
5%
Gas measurements in multiple tunnels in Norway have given new knowledge about the
changes in NOx emissions from heavy duty vehicles and passenger cars since 2007. The
introduction of particulate filters that meet the Euro 5 requirements, have reduced the
emission of dust and NO2 from buses and trucks. However, there has been an opposite trend
in NO2 emissions from passenger cars because of higher numbers of new passenger cars with
diesel engines over the last years. In tunnels with large excursion traffic, the emissions from
diesel powered cars are giving the highest NO2 levels on Friday afternoon and Sunday
evening. The highest NO2 levels in urban tunnels have been observed during rush hours from
Monday to Friday when there is a low share of heavy duty vehicles.
4
1. Nitrogen oxides (NOx), ozone (O3) and particulate matters
1.1
Air quality guidelines for NO2 and Particulate matters (PM)
The first standards for NO2 were set by the US Environmental Protection Agency (EPA) in
1971. The EPA set both a primary standard (to protect health) and a secondary standard (to
protect the public welfare) at 0.053 parts per million, averaged annually. The Agency has
reviewed the standards twice since that time, but chose not to revise the standards at the
conclusion of each review. 0.053 PPM is equal to 100 μg/m3 at 11 °C (at standard air
pressure). A new 1-hour standard at a level of 100 ppb[1] was introduced by EPA in 2010 to
supplement the existing annual standard.
The EU air quality Directive 2008/50/EC sets concentration limits for nitrogen dioxide (NO2)
and particulate matter (PM10):
Nitrogen dioxide
(NO2)
Hourly limit value for the protection of human health
Annual limit value for the
protection of human health
Annual critical level for the protection of
vegetation and natural ecosystems
Upper assessment
threshold
70 % of limit value (140 µg/m3,
not to be exceeded more than
18 times in any calendar year)
80 % of limit value
(32 µg/m3)
80 % of critical level
(24 µg/m3)
Lower assessment
threshold
50 % of limit value (100 µg/m3,
not to be exceeded more than
18 times in any calendar year)
65 % of limit value
(26 µg/m3)
65 % of critical level
(19.5 µg/m3)
Particulate matters
(PM10 and PM2.5)
24-hour average PM10
Annual average PM10
Annual average PM2.5
Upper assessment
threshold
70 % of limit value (35 µg/m3, not to be exceeded more
than 35 times in any calendar year)
70 % of limit value
(28 µg/m3)
70 % of limit value
(17 µg/m3)
Lower assessment
threshold
50 % of limit value (25 µg/m3, not to be exceeded more
than 35 times in any calendar year)
50 % of limit value
(20 µg/m3)
50 % of limit value
(12 µg/m3)
The current WHO guideline value of 40 µg/m3 (annual mean) was set to protect the public
from the health effects of gaseous NO2. Epidemiological studies have shown that symptoms
of bronchitis in asthmatic children increase in association with long-term exposure to NO2.
Reduced lung function growth is also linked to NO2 at concentrations currently measured (or
observed) in cities of Europe and North America[2]. Continued exposure to high NO2 levels
can contribute to the development of acute or chronic bronchitis. The current WHO guideline
for 1-hour mean is 200 μg/m3 which is equal to 0.1 ppm at 21 °C (at standard air pressure).
The Norwegian government has given national targets and limit values for NO2 and PM10:
Nitrogen dioxide and particulate matters
Hour average limit value (NO2)
Annual average limit value
(NO2)
24 hour average limit value (PM10)
Annual average limit value
(PM10)
150 µg/m3, not to be exceeded
more than 8 hours in any calendar
year
40 µg/m3, not to be exceeded
50 µg/m3, not to be exceeded more
than 7 days in any calendar year
40 µg/m3, not to be
exceeded
1
2
100 ppb = 0,10 ppm
WHO: Air quality guidelines, Global update 2005
5
Upper threshold values for NO2 in tunnels shorter than 10 km are given in the Norwegian
design guide for tunnels. A tunnel with longitudinal ventilation shall be closed if the NO2concentration in the middle exceeds 0.75 ppm (equal to 1500 μg/m3 at 15 oC) for more than 15
minutes. The threshold value in the middle of the tunnel is regarded as an average value for
the NO2-concentration in long tunnels with longitudinal ventilation. The upper threshold
value in a 10 km long tunnel is set 10 times higher than the national hourly limit value for
NO2. This has been accepted because of the limited exposure time in the majority of
Norwegian tunnels.
The limit values and gas-concentrations in Norwegian tunnels are given as Parts Per Million
(ppm) which is a dimensionless value. Ppm is useful for presentation of gas measurements
because of the independency of temperature and pressure for ideal gases. To convert ppm to a
metric expression like µg/m3, the density of the concerning gas is needed. Since gas density
varies with temperature and pressure, both these parameters must be known in order to
convert ppm to µg/m3. The conversion of one ppm at different temperatures at standard
pressure (1 bar) is given in the following table:
o
3
1 ppm NO2 in µg/m
3
Air temperature C
Air density, kg/m
1 ppm NO in µg/m
21
1,20
1 953
1 242
0
1,29
2 103
1 338
-12
1,35
2 200
1 399
3
1.2 Main sources for nitrogen oxides (NOx) in road tunnels
Heavy duty vehicles with diesel engines have been the main source of nitrogen oxides for
many years. The total emission from road traffic in Norway is illustrated in figure 1. There
has been a significant decline in the emission from heavy duty vehicles after 2007 because of
stricter emission standards for new vehicles and improvement in motor technology since the
first Euro-norm for NOx-emission was implemented in 1988 [3]. The upper limit for NOx
emission from new heavy duty vehicles was gradually reduced from 16 g/kWh in 1988 to
maximum 2.0 g/kWh when Euro 5 came into force in 2009. A further decline in the emission
from heavy duty vehicles can be expected as the oldest trucks and buses are replaced with
new vehicles.
NOx-emission from road traffic in Norway
Tonn / year
30 000
Heavy duty
vehicles
Passenger
cars, gasoline
Passenger
cars, diesel
Others, diesel
20 000
10 000
0
2000
2002
2004
2006
2008
2010
Passenger cars and fuel type
2 000 000
1 500 000
Petrol
Diesel
1 000 000
500 000
Others,
gasoline
Figure 1: Trends in emission of nitrogen oxides from road traffic in Norway
0
2005
2006
2007 2008
2009
2010
2011
2012
[4]
New cars in Norway are generally driven more than older cars, and diesel-powered passenger
cars are driven more than cars with petrol fuel. Passenger cars less than five years old, were
driven an average of 16 000 kilometres in 2011. The average mileage was 16 600 km for
passenger cars with diesel engine and 10 700 km for petrol cars. The total share of dieselpowered passenger cars on Norwegian roads was 49.1 % in 2011.
3
4
Euro 1: 9 g NOx/kWh in 1992, Euro 2: 7 g/kWh in 1996: Euro 3: 5 g/kWh in 2000: Euro 4: 3.5 g/kWh in 2005
Sources: www.klif.no and www.ssb.no
6
Kms / year
Average driving length per vehicle in Norway in 2011
70 000
60 000
50 000
40 000
30 000
20 000
10 000
0
0-4
Million kms / year
Figure 2: Average
driving length for
vehicles in Norway
(www.ssb.no)
Passenger cars
Vans and small lorries
Buses
Heavy lorries and road tractors
Avarage of all vehicle types
5-9
10 - 14
15 - 19
20 - 24
Age of vehicles (years)
> 24
All vehicles
Road traffic volumes in Norway 2005 - 2011
All passenger cars
40 000
Petrol
Diesel
Figure 3: Road
traffic volumes in
Norway
(www.ssb.no)
30 000
20 000
10 000
0
2005
2006
2007
2008
2009
2010
2011
The decline in pollution emission from cars with gasoline fuel started when the first generation of catalytic converters was introduced in 1975. The two-way-converter reduced the
emission level of carbon monoxide (CO) and unburned hydrocarbons (HC). The next
generation of catalytic converters use a ceramic or metallic substrate with an active coating
incorporating alumina, ceria and other oxides and combinations of the precious metals
platinum, palladium and rhodium.
Three-way catalysts operate in a closed-loop system including a lambda or oxygen sensor to
regulate the air:fuel ratio on petrol engines. The catalyst can then simultaneously oxidise CO
and HC to CO2 and water while reducing NOx to nitrogen (N2).
g / km
The effective three-way catalyst has been mandatory on new cars with gasoline fuel in Europe
since Euro 1 entered into force in 1992. The emissions of CO and NOx have been gradually
reduced by introduction of new motor technology and improvement of the exhaust control
systems. The emission of lead has been eliminated as a side effect of the catalyst, because
lead fuel additive would have destroyed the catalyst.[5]
0,50
0,40
0,30
0,20
0,10
0,00
NOx-emission from new cars and vans in 2001. (Source: Miljøheimevernet)
Gasoline
Diesel
0,03
0,24
Small cars < 1050 kg
0,38
0,44
0,38
0,04
0,03
Small middle class
1050 - 1260 kg
Large middle class
< 1400 kg
0,03
Large cars (SUVs and
vans) > 1370 kg
Figure 4: Diesel cars had 10 times higher NOx-emission than gasoline cars in 2001
5
Lead was used as an additive in petrol from the 1920s to the beginning of 2000 when European legislation
stopped normal sale and distribution of leaded gasoline
7
European NOx emission standards for vehicles < 3 500 kg
European NOx emission standards for heavy duty vehicles
0,5
1,00
gasoline < 1305 kg
0,4
gasoline 1305 - 1760 kg
diesel 1305 - 1760 kg
PM (g / kWh)
NOx (g/km)
Euro 0
diesel < 1305 kg
Euro 1
0,75
gasoline 1760 - 3500 kg
diesel 1760 - 3500 kg
0,50
Euro 2
Euro 5
Euro 6
Euro 1
0,3
0,2
0,25
Euro 4
0,1
Euro 2
Euro 3
Euro 4
Euro 5
Euro 3
0,00
1992
1995
1998
2001
2004
2007
2010
2013
0
2016
0
2
Year of registration
4
6
8
10
NOx (g/kWh)
Figure 5: European emission limits varies with fuel type and weight of vehicles
Since 2002 there have been an increasing number of passenger cars, SUVs and vans with
diesel engine in Norway. The sale of big diesel-powered cars was accelerated when the
Norwegian government changed the tax structure for new cars in favour of diesel from
January 2007. The diesel share increased from 16 % in 2005 to 42 % in 2011. 64 % of new
passenger cars in Norway had diesel engine in 2012. The upward trend is continuing in 2013
with more than 50 % diesel share from January to April.[6] From figures 1 - 5 it can be
assumed that the effect of replacement of old gasoline cars, will be balanced by the higher
NO2-emission from new cars with diesel-engine until 2014. Euro 6 is expected to give stricter
emission standards for diesel-powered cars with total weight under 1760 kg. However, after
2014 new vans and other heavy diesel powered vehicles will still have higher NO2-emission
than cars with gasoline engines.
1.3 Some observations of NO2 in long Norwegian tunnels
The first exact measurements of NO2 in tunnels were performed in the 7.5 km long Høyanger
tunnel in 1994 and 1995[7]. This tunnel was opened in 1982 in a longitudinal ventilation
system and automatic regulation of 28 impulse fans according to the CO-concentration at five
different points. There were no permanent detectors for NO or NO2 before the NOx-measurements started in 1994. NO2-concentrations above 5 ppm were observed several times before
the ventilation started at 50 ppm CO. The 50 ppm start parameter for CO had not been
changed since the tunnel was opened in 1982. 50 % NO2/NOx-volume ratios were observed
due to oxidation of NO when the longitudinal air speed was low.
The 11.5 km long Gudvanga tunnel which was completed in 1992, had five NO-sensors to
control the ventilation level during the first years. A sensor for NO2 was installed in the
middle of the tunnel for observation of the NO2/NOx-ratio. The lower detection limit for NO2
was about 0.5 ppm and the accuracy was assumed to be low compared with the NO-sensors.
Therefore the NO2-values were not used as parameters in the ventilation program during the
first ten years of operation.
In 1992 it was assumed that the NO2/NOx volume ratio would be approximately 10 % and the
air quality should therefore be acceptable as long as the NO-level was kept below 10 ppm at
the end of the tunnel. When the ventilation was running at constant speed, an average value
of 5 ppm NO and about 0.5 ppm NO2 should be expected in the middle of the tunnel.
However, alarms from the NO2-sensor in the middle of the tunnel became more frequent
every year. NO2-values higher than 0.75 ppm were often observed early in the morning when
6
7
www.ofv.no.
HSF-rapport 6/97: Luftkvalitet i Høyangertunnelen
8
there had been low traffic during the night and the levels of CO and NO were below the start
parameters for the ventilation system. Sometimes the natural ventilation direction changed
during the night, and a dense plug of NO2-gas could appear in the middle of the tunnel before
the fans started. About ten years ago when new NO2-sensors with better accuracy and lower
detection limit had been developed, all NO-sensors in the Gudvanga tunnel were exchanged
with NO2-sensors.
In the 24.5 km long Laerdal tunnel which was opened in 2000, NO and NO2 are used as
parameters for ventilation control. Oxidation of NO is giving a considerable growth in the
NO2-concentration in this tunnel, and the NO-limits have been set much lower than in any
other tunnel in Norway in order to delay the oxidation process. Figure 6 and 7 illustrate the
observed growth of NO2 from a start-concentration of 8 ppm NO in December 2012.
NO2 / NOx volume ratio in the Laerdal tunnel on Monday 2012-12-10
Vol. % NO2 / NOx
20%
15%
10%
5%
15:30
16:00
16:30
17:00
17:30
Figure 6: Observed NO2 / NOx-ratio in the Laerdal tunnel in December 2012
Oxidation of NO was the main reason for the increase of NO2/NOx volume ratio from 5 % at
15:45 to over 17 % one and a half hour later. Calculation of the NO2-level from a startconcentration of 8 ppm NO is illustrated in figure 7. There is good compliance between the
observed NO2-values at three different points and the calculated values from NO-oxidation.
The differences between observed and calculated NO2-values were caused by variations in the
air speed and new emissions from vehicles. More details from this incident are given in
chapter 2.4.
2,25
2,00
PPM NO2
1,75
1,50
1,25
Observed and calculated NO2-concentration on 10.12.2012
9.4 km
12.5 km
17.0 km
Calculated
1,00
0,75
0,50
0,25
15:40
16:00
16:20
16:40
Figure 7: Observed and calculated NO-oxidation in the Laerdal tunnel
9
17:00
17:20
1.4 Nitrogen oxides (NOx)
Nitrogen dioxide (NO2) is one of a group of highly reactive gasses known as oxides of nitrogen, or nitrogen oxides (NOx). Other nitrogen oxides include nitrous acid and nitric acid. The
reddish-brown toxic NO2-gas has a characteristic sharp, biting odor and is a prominent air
pollutant from road traffic.
At temperatures above 21 oC ozone is produced directly by photolysis of NO2 in bright
sunlight (hv) where the NO2-molecule is split and the excess energy is used to build an
oxygen molecule with three atoms:
NO2 + hv → NO + O
O + O 2 → O3
Nitrous acid (HNO2) is a weak and monobasic acid known only in solution and in the form
of nitrite salts. In anything other than very dilute, cold solutions, nitrous acid rapidly decomposes into nitrogen dioxide, nitric oxide, and water:
2 HNO2 → NO2 + NO + H2O
Nitric acid (HNO3) is a highly corrosive and toxic strong acid. NO2 decompose into nitric
acid and nitrous acid in aqueous solution[8]:
2 NO2 + H2O → HNO3 + HNO2
NO
concentration in
air
Time required for half NO
to be oxidized to NO2
(ppm)
(min)
(h)
10 000
0,35
0,006
1 000
3,5
0,06
100
35
0,58
10
350
5,8
1
3500
58
0.1
35000
25 days
NO-concentration, PPM
Nitric oxide (NO) is the most common form of nitrogen oxides. Nitric oxide reacts with
oxygen (O2 and O3) to form nitrogen dioxide (NO2). The time required varies with the start
concentration of NO in air as shown in figure 8:
Half-life for NO in air (2NO + O2 → 2NO2)
20
18
16
14
12
10
8
6
4
2
0
20 ppm: 3 hours
10 ppm: 6 hours
5 ppm: 12 hours
0
4
8
12
16
20
24
Half-time in hours
Figure 8: Time required for half NO in air
2NO + O2 → 2NO2
Time required for oxidation of NO to NO2
10
10
10 ppm
8.0 ppm
10 ppm
NO-concentration, ppm
8
6.0 ppm
5.0 ppm
4.0 ppm
8 ppm
3.0 ppm
2.0 ppm
1.0 ppm
6 ppm
8
5 ppm
6
6
4 ppm
3 ppm
4
4
2 ppm
2
2
0
0
6
12
18
24
Hours
0
0
6
12
18
24
Hours
Figure 9: Calculated NO2-production from oxidation of NO during 24 hours
8
Kameoka, Yohji; Pigford, Robert (February 1977): Absorption of Nitrogen Dioxide into Water, Sulfuric Acid,
Sodium Hydroxide, and Alkaline Sodium Sulfite Aqueous.
10
NO2-concentration, ppm
12 ppm
12 ppm
Nitric oxide, NO
2NO + O2 = 2NO2
1,2
9 ppm
1,0
8 ppm
7 ppm
0,8
6 ppm
5 ppm
0,6
4 ppm
3 ppm
2 ppm
0,4
NO2-concentration (ppm)
10 ppm
0,2
0,0
0
30
60
90
120
Minutes
Molecular weight (M)
30.006 g/mol[9]
Specific volume (V)
24.15483 l/mol
(1.013 bar and 21 °C)
0.805 m3/kg
Nitrogen dioxide, NO2
Molecular weight (M)
46.05 g/mol
Specific volume (V)
23.5776 l/mol
(1.013 bar and 21 °C)
0.512 m3/kg
Figure 10: Calculated production of NO2 from 2 – 10 ppm NO
The 16 gram difference in molecular weight between NO and NO2 correspond with the extra
oxygen atom in the NO2 molecule. O2 has a molecular weight of 31.9988 g/mol (~2 x 16).
Avogadro’s law for ideal gases says that equal volumes of gases contain the same number of
molecules at Standard Temperature and Pressure (STP). STP is defined as a condition of 100
kPa (1 bar) and 273.15 K (0°C). For other temperatures and pressures than STP, the molar
volume of ideal gases can be calculated by the ideal gas equation:
pV = nRT
where:
p = pressure (Pa)
V = molar volume (m3)
n = the chemical amount of gas (mol)
R = Universal gas constant [8.3144621 JK-1mol-1]
T = Temperature (Kelvin)
The molar volume of an ideal gas at STP is 0.02271 m3/mol (22.71 l/mol). The molar volume
expands to 24.5 litres when the gas is heated to 21 °C. Nitrogen dioxide (NO2) is far from an
ideal gas at normal air temperatures in Norwegian tunnels. NO2 is a liquid at all temperatures
between the boiling point (21 °C) and the melting point (-11.2 °C).
The normal air temperature in Norwegian tunnels is below the condensation point (21 oC),
and NO2 is compressed 424 times a short distance from the exhaust pipe. Despite this fact,
NO2 is often regarded as an ideal gas for actual air temperatures in tunnels and the expression
“NO2/NOx volume ratio” is used in this report without any comments about liquid- or gasphases. At low temperatures the NO2-molecules in solid or liquid state must of course be
heated to the boiling point in order to measure the gas-concentration as volume ratio NO2/air
in parts per million (ppm). Since oxygen and nitrogen also can be regarded as ideal gases at
temperatures between -11°C and 21 °C, the calculated volume ratio NO2/air will not change
with variations in pressure or temperature.
9
www.encyclopedia.airliquide.com
11
1.5 Ozone (O3) and oxides of nitrogen (NOx)
Ozone is a colourless and invisible gas, but often occurs along with oxides of nitrogen and
particulate matters in urban areas where ozone is the primary ingredient of photochemical
smog. Ozone is associated with extensive health effects, most notably associated with the
respiratory system.
Under normal conditions the gas is unstable and thus very reactive and a powerful oxidant.
Nitrogen dioxide is produced by a reaction between nitric oxide (NO) and ozone (O3):
NO + O3 → NO2 + O2
The molecular weight of ozone is 46.05 g/mol which give the same gas density as nitrogen
dioxide above 21.1 oC. At 1.013 bar and 21 oC the specific volume of O3 is 0.519 m3/kg. If
there is a start-concentration of 50 µg/m3 O3 at the tunnel entrance and available NO-gas
inside the tunnel, the equation above may produce 50 µg/m3 NO2 in addition to the NO2-gas
emitted from vehicles inside the tunnel.
NO2 and O3 in Bergen centre, 2012.01.29 - 2012.01.30
PM in Bergen centre, 2012.01.29 - 2012.01.30
120
50
NO2
100
PM10
40
O3
mg/m3
mg/m3
80
60
40
PM2,5
30
20
10
20
0
0
22
23
00
01
02
03
04
05
06
07
08
22
23
00
01
02
03
04
05
06
07
08
Figure 11: Nitrogen dioxide (NO2), ozone (O3) and particulate matters (PM) in January 2012
A normal drop in the NO2-level in the Bergen area because of low traffic during the night, is
illustrated in the left diagram in figure 13. The pollution of particulate matters was also low
during night time on 29. January 2012. However, the ozone level rose quickly in the evening
from near zero to 30 µg/m3, and the relationship between the levels of ozone and nitrogen
dioxide can be seen in the diagram. Nitric oxide from the first traffic in the morning gave a
sudden drop in the ozone concentration.
At night time there is no ozone formation, and loss of ozone through NOx titration becomes
the dominant process. The concentration of O3 at night in urban centres is often lower than in
the surrounding rural area for this reason[10]. The concentration of ozone is low in Norway
during the winter months. High ozone levels are very rare when temperatures are below
20 oC. However, there are some exceptions caused by long transported air pollution.
The concentration of nitrogen dioxide, ozone and particulate matters with diameter less than
10 µm and 2.5 µm in the Bergen area at the end of January 2012 is illustrated in figure 12 on
the next page. NO2 produced from the reaction between NO and ozone is often referred to as
background concentration of NO2 at the tunnel entrance.
10
Sillman, S., The relation between ozone, NOx and hydrocarbons in urban and polluted rural environments.
Millenial Review series, Atmos. Environ., 33, 12, 1821-1845, 1999.
12
Figure 12: Air quality in Bergen in January 2012 (www.luftkvalitet.info/)
13
1.6 Particulate matters (PM) and relative humidity (Rh)
There have been a gradually reduction of smoke particles in tunnels since the first Euro emission standards were entered into force. Since year 2000 visibility meters and dust detectors
have been removed from several tunnels because NO2 has become the dominant pollution
factor to be used in the regulation of ventilation systems. The amount of particulate matters in
tunnels varies with cleaning procedures in addition to traffic volume and speed. However, the
most important factor is the amount of water vapour in the air which is expressed in terms of
relative humidity (Rh). When it’s raining or snowing outside, the cars are transporting water
into the tunnel, and most of the road dust will stick to surfaces as long as the humidity inside
the tunnel is high. In the winter season a gradual increase of the dust level has been observed
in many tunnels after a period with rainy weather when the drying particles start moving with
wind and turbulence forces caused by the vehicles. When the relative humidity falls below
60 %, the amount of dust particles (PM) is often 3 – 5 times higher than in rainy weather
when the smallest dust particles from brakes, tyres and asphalt-wear may be stored inside the
tunnel for several days.
In the afternoon of 31 January the PM10-concentration near the city hall in Bergen reached
200 µg/m3 which was the highest observed value in January 2012. Dry weather and road dust
were the main contributors to the reduced city air quality that was observed several days this
week at two different locations in Bergen city. The observed dust level in the Knappe tunnel
was 4 – 5 times higher than the maximum level in the city centre.
g/m3
20
Temperature, relative humidity and H2O-vapour in 1,0 m3 air
ml/m3
20
100% Rh
90 % Rh
80 % Rh
15
15
70 % Rh
60 % Rh
10
10
50 % Rh
Difference 50 - 80 % Rh
5
5
0
Figure 13: Relationship
between relative humidity
and temperature
0
-10
-5
0
5
10
Temperature, oC
15
20
25
The relationship between temperature and relative humidity is plotted in figure 13. The geothermal heat is lifting the temperature inside Norwegian tunnels during the winter. The airstream in the north direction of the Knappe tunnel is also heated by the natural compression
caused by the downward gradient from Dolvik. The 600 Pa pressure difference between the
tunnel entrance and the deepest point in this tunnel is giving about 0.6 % compression and
0.3 oC natural temperature difference between Dolvik and the deepest point in the tunnel.
When there is no rain or snow outside, the moisture in the exhaust is too low to compensate
for the drying effect from higher temperatures, and the relative humidity in the tunnel will
change according to the curves in figure 13.
Knappe tunnel Dolvik - Sandeide
15
Dolvik
-5 0,0
-15
Sandeide
Straume
8%
5
5.9 %
0,5
2.4 %
1,0
1,5
2,0
2.6 %
0.7 %
-25
-35
14
2,5
Figure 14: Length profile of the
Knappe tunnel in Bergen
7%
(Dolvik – Sandeide = “north
direction”)
1.7 Diesel Particulate Filters (DPF) and NO2/NOx-ratio
Diesel particulate filter is a generic terms used to describe systems which reduce particulate
matter in diesel engine exhaust emissions. There are several categories of DPFs known as
Particulate trap (RT), continuously regenerated traps (CRTs), catalyzed continuously
regenerated traps (CCRTs) or catalysed DPFs (CDPF). The first generation of DPFs were
passive filters where all visible smoke and soot particles with a diameter above 2.5 µm
(PM10) were collected. These filters have no effect on the smallest and most harmful particles
to human health which have been linked to lung ailments, cancer and heart disease. The
smallest particles are often referred to as PM2.5 which means particulate matters smaller than
2.5 µm[11].
From 1997 to 2003 there was a statistically significant downward trend in NOx, averaged
across a network of 36 sites in London. In the same period the NO2/NOx volume ratio
increased from 5 – 6 % to about 17 %. 8000 buses in London were fitted with DPFs from
1999 to 2006[12]. A higher share of diesel-powered cars in the same period has also been
regarded as an explanation for the high NO2/NOx-ratio in London compared with other cities
in Europe.
The DPF has to be regularly cleaned or regenerated by driving at high rpm in order to rise the
temperature above the ignition temperature for soot and burn off the collected particles. About
ten minutes is needed for a complete regeneration in ordinary cross-country driving. The
burning of particles will create CO2 and a small amount of ash which will remain inside the
filter. The regeneration of passive filters without a catalyst has no effect on nitric oxides (NO)
or nitrogen dioxides (NO2).
The automatic regeneration of the filter will be interrupted if the motor is stopped or if the
exhaust temperature should fall under the ignition temperature for the collected soot particles
(> 500 oC). The exhaust temperature varies with driving conditions and will fall during long
down-hill descents (mountain roads and sub-sea tunnels), frequent driving in the low-load
range (congested traffic, idling at traffic lights and also in ordinary low speed city traffic).
Regeneration of active filters is started automatically by the system’s control unit when the
pressure loss through the filter has reached a certain limit. Specific measures are taken to rise
the filter temperature above 550 – 600 oC for 5 – 10 minutes. If the regeneration process is
interrupted by the driver, the control unit will start the process again on the next tour.
The new generation of DPFs are removing more of the smallest and most dangerous particles
from the exhaust. Ceramic wall-flow filters remove almost completely the carbon particulates,
including fine particulates less than 100 nanometre[13] diameter with an efficiency of 95 % in
mass and 99 % in number of particles over a wide range of engine operating conditions. The
soot trapped in the filter must be regularly burnt to clean or regenerate the filter. Almost all
active filter regeneration techniques operate by raising the temperature of the filter to around
600 °C. An exhaust gas temperature of approximately 550 °C is needed to start the
combustion.
The catalytic converters, which following the EURO 2 standard, became mandatory in 1996
on light duty diesel vehicles, are using NO2 to regenerate the filter. Unfortunately, this has led
to significant increase in NO2 emissions from new diesel-powered cars during the last years.
11
1 µm = 1/1000 mm = 1000 nm (nanometer)
David C. Carslaw: Evidence of an increasing NO2/NOx emission ratio from road traffic emissions (Atmospheric
Environment, vol, 39, 2005)
13
100 nanometer (nm) = 0,1 mikrometer (µm), 1 µm = 1/1000 mm
12
15
Regeneration of filter with oxygen:
C + O2 → CO2
Production of NO2 by catalyst:
2NO + O2 → 2NO2
Regeneration with NO2:
2C + 2NO2 → N2 + 2CO2
The amount of available oxygen varies with driving condition and motor load. The regeneration process becomes more effective with nitrogen dioxide because NO2 is a more effective
oxidizer than oxygen. If the exhaust gases have an ideal balance between particles and NOx,
no harmful nitrous gases should be emitted. However, this is only possible in the laboratory.
At normal driving conditions there is a surplus of NO2-gas emitted to the outside air. Therefore a higher NO2/NOx-ratio should be expected from diesel-powered cars with catalysed
DPFs because of the surplus NO2 from the catalyst and the reduced volume of NO-gas.
Selective Catalytic Reduction (SCR) is now fitted to new heavy-duty diesel engines in
Europe[14]. The efficiency of SCR for NOx reduction also offers a benefit for fuel consumption. It allows diesel engine developers to take advantage of the trade-off between NOx, PM
and fuel consumption and calibrate the engine in a lower area of fuel consumption than if they
had to reduce NOx by engine measures alone. Particulate emissions are also lowered, and
SCR catalytic converters can be used alone or in combination with a particulate filter.
In the SCR system, ammonia is used as a selective reductant, in the presence of excess
oxygen, to convert over 70 % (up to 95 %) of NO and NO2 to nitrogen over a special catalyst
system. Different precursors of ammonia can be used; one of the most common options is a
solution of urea in water (e.g. AdBlue®[15]) carefully metered from a separate tank and
sprayed into the exhaust system where it hydrolyses into ammonia ahead of the SCR catalyst.
The consumption of AdBlue® is typically 3 - 4 % of the fuel consumption for an Euro IV
engine, and 5 - 7 % for an Euro V engine, depending on driving, load and road conditions.
1.8
NO2-sensors, measurement principles and detection limits
When the 24.5 km long Laerdal tunnel was opened in 2000, the air quality was monitored by
means of nine electrochemical diffusion NO-sensors and two NO2-sensors from Dräger.
Product data for new sensors for Polytron 7000
(at 20 oC, 50 % RH and 1013 mb)
NO2
NO
Standard measuring range:
10 ppm
50 ppm
Lower detection limit:
0.3 ppm
3 ppm
Uncertainty of measured value
uncertainty minimum
±5%
± 0.1 ppm.
±4%
± 1.0 ppm.
Calibration interval:
6 months
6 months
The NO- and NO2-sensors were tested in the Laerdal tunnel together with a precision
instrument during four days in September 2007. This test gave new knowledge about the
accuracy and the real measuring range of the Dräger sensors.
The API M200A NOx analyzer used in the test, is designed to measure the concentration of
nitric oxide (NO), total oxides of nitrogen (NOx) and, by calculation, nitrogen dioxide (NO2).
14
15
http://www.aecc.be/en/Technology/Catalysts.html
AdBlue® is a solution of 32.5 % Urea in deionized water. Urea, chemical formula (NH2)2CO, is also known as
a fertilizer
16
The instrument measures the light intensity of the cheminiluminiscent gas phase reaction of
nitric oxide and ozone (O3) as follows:
NO + O3 → NO2* + O2
NO2* → NO2 +hv
The reaction of NO with ozone results in electronically excited NO2 molecules as shown in
the first equation above. The excited NO2 molecules release their excess energy by emitting a
photon and dropping to a lower energy level as shown in the second equation. It has been
shown that the light intensity produced is directly proportional to the NO concentration present. The analyzer samples the gas stream and measures the NO concentration by digitizing
the signal from the analyzer’s photomultiplier tube. A valve then routes the sample stream
through a converter containing heated molybdenum to reduce any NO2 present to NO. The
analyzer now measures the total NOx concentration. The NO2 concentration is found by
subtracting the NO and NOx values from each other. The instrument has a lower detectable
limit of 0.4 ppb (0.0004 ppm) and a precision of 0.5 % of reading. The instrument was calibrated for a maximum value of 1000 ppb (1 ppm) NO2 before the test started.
NO-concentration 12.5 km from Aurland on Wednesday 2007-09-05
6
PPM NO
5
4
3
2
API M200A Nox analyser
1
0
00:00
Dräger Polytron 2
04:00
08:00
12:00
16:00
20:00
00:00
Figure 15: Comparison of NO-values from a Dräger sensor with values from a precision instrument
NO2-concentration 12.5 km from Aurland on Wednesday 2007-09-05
PPM NO2
0,6
Test of NO2-filter
Dräger Polytron 2
0,4
0,2
00:00
04:00
08:00
12:00
16:00
Figure 16: Comparison of NO2 values from a Dräger sensor and a precision instrument
17
20:00
00:00
One sample per minute is plotted in figures 15 and 16. The average NO-values during 24
hours were 0.26 ppm higher from the Dräeger sensor than the calculated NO-values from the
API-analyzer. The 24 hour average NO2–level from the Dräeger sensor was 0.08 ppm lower
than the API-values during the same period.
Calculated values for NO2/NOx volume ratio for Wednesday and Thursday are plotted in
figure 17. NO2-values below 0.25 ppm from the Dräeger sensor were excludes from the
calculation. The average difference between the two curves is 2.0 %.
It looks like the major part of this difference between the two instruments was caused by an
inaccurate zero-point-calibration of the Dräeger-sensors. All sensors are calibrated with new
gas every year, and it is assumed that the accuracy has been improved after 2007.
The NO-curves in figure 15 have a sudden drop from 5 ppm to 3 ppm about 13:00. At the
same time the NO2-level was reduced from 0.65 to 0.25 ppm. This reduction was caused by
activating the NO2-filter which is located 9.4 km from Aurland. The filter gave about 5 %
reduction of the NO2/NOx volume ratio in the middle of the tunnel [16].
Vol. % NO2 / NOx 12.5 km from Aurland on Wednesday 2007-09-05
16%
Test of NO2-filter
12%
8%
Dräger Polytron 2
4%
00:00
04:00
08:00
12:00
16:00
20:00
00:00
Vol. % NO2 / NOx 12.5 km from Aurland on Thursday 2007-09-06
16%
Test of NO2-filter
12%
8%
Dräger Polytron 2
4%
00:00
04:00
08:00
12:00
16:00
20:00
Figure 17: Calculated NO2 / NOx volume ratios from two instruments
16
Statens vegvesen: E16 Lærdalstunnelen. Kontroll av luftkvalitet og energibruk (2007-10-24)
18
00:00
2 Observations of NO2 / NOx volume ratio in the Laerdal tunnel
2.1 The ventilation system
2 shaftfans
32 jet-fans
Figure 18: Ventilation principle in the Laerdal tunnel
The longitudinal ventilation system in the Laerdal tunnel is illustrated in figure 18. The 24.5
km long tunnel is divided into two ventilation sections by a ventilation tunnel 18 km from the
Aurland portal. Two shaft fans with a total capacity of 500 m3/sec are extracting polluted air
through the ventilation tunnel.
The ventilation system is regulated in four levels. Values from nine NO-sensors and two NO2sensors were used in 2007:
Ventilation level
Start-parameter
NO
NO2
Speed of
shaft fans
Number of Air velocity
jet-fans
from Aurland
Air velocity
from Laerdal
1
4 ppm
0,7 ppm
350 rpm
0
1.0 m/s
2.5 m/s
2
6 ppm
0,9 ppm
550 rpm
6
2.0 m/s
3.5 m/s
3
9 ppm
1,2 ppm
750 rpm
16
3.0 m/s
4.5 m/s
4
15 ppm
1,5 ppm
990 rpm
32
4.5 m/s
5,5 m/s
The ventilation tunnel has a gradient of 11.1 % which is giving a considerable chimney-effect
during the winter and in other periods when the outside air temperature is below 10 - 15 oC.
19
Fresh air from both portals is heated by the surrounding rock which has a constant temperature of 17 oC in the middle of the tunnel. The natural ventilation forces caused by the 400 m
height difference between the tunnel portals and the outlet of the ventilation tunnel, are giving
sufficient ventilation in periods with low traffic from September to May.
There are great variations in the air velocity from Aurland and Laerdal depending on the
number of vehicles driving in each direction. A group of heavy duty vehicles driving in the
south direction, will reduce the air velocity from Aurland, and the air may sometimes move in
the opposite direction at low ventilation levels. Figure 19 show great variations in the natural
ventilation on a Sunday in August 2007 before the fans started after 12:00. The negative parts
of the velocity curve were caused by the piston-effect from vehicles. Negative air velocity
was also observed a few minutes in the evening when the shaft fans were running at low
speed.
m/s
4
Air velocity on Sunday 2007-08-26
Air velocity
3
III
Ventilation level
2
II
1
II
I
0
-1
00:00
03:00
06:00
09:00
12:00
15:00
18:00
21:00
00:00
Figure 19: Example of natural ventilation during 12 hours before the fans started
2.2 Observations of NO and NO2 in September 2007 and 2008
The concentration of NO and NO2 was measured every minute in the Laerdal tunnel during
five weeks in August – September 2007. The concentration of NO2 was measured at two
points in week no. 33 - 34 and at three points from week no. 35 - 37. NO2/NOx volume ratios
were calculated from the observations at 9.4 km, 12.5 km and 17 km from Aurland. The
values from 08:00 to 20:00 were used in the calculation of a daily average concentration of
NO, NO2 and a daily average NO2/NOx volume ratio. NO-values below 1.0 ppm and NO2values below 0.2 ppm were excluded from the calculation of NO2/NOx-ratio because of the
unknown accuracy of these values.
25%
17 km from Aurland: Vol. % NO2 / NOx on Wednesday 2007-08-22
% NO2 / NOx
NO2 / NOx
NO2 (PPM)
PPM
8
NO (PPM)
6
20%
4
15%
2
10%
0
00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00
Figure 20: Example of growth of NO2 / NOx volume ratio in the morning before the fans started
20
High NO2-production should be expected in the Laerdal tunnel from figures 8 - 10 in chapter
1.4 because of the long ventilation section from Aurland and long periods with low air
velocity. If the ventilation fans are turned off in the evening with 3 ppm NO in the air and
10 vol. % NO2/NOx and it takes more than six hours to ventilate the tunnel, we can expect
NO2-concentrations above 1.0 ppm in the morning without any contribution from traffic
during the night.
Start of ventilation during the night because of high NO2-concentration was observed several
times in 2007. An example of night ventilation because of NO-oxidation is given in figure 21.
The fans started because of 0.75 ppm NO2 at the sensor 17.5 km from Aurland when the night
traffic was less than 20 vehicles/hour. Examples of high NO2/NOx-ratios at low ventilation
levels in the afternoon are given in figures 22 and 23 on the next page.
Traffic volumes on Thursday 2007-08-30 ; 1714 vehicles, 24 % > 7,5 m
200
Veh. / hour
< 7.5 m
100
9
12
4 14
4
4
> 7.5 m
6
7
9
9
8
10 16
5
0
01:00
04:00
26 27
12
11
9
24
26 21
41
30
25 35
16
89 88
64 76 61
38 55
07:00
25
10:00
120 115 104 107
13:00
16:00
12
16 6
38 27 20
96 75
62
19:00
22:00
Air velocity and ventilation level, Thursday 2007-08-30
4
Air velocity
3
Ventilation level
m/s 2
II
1
0
I
I
-1
00:00
15%
03:00
I
06:00
09:00
II
II
15:00
18:00
12:00
21:00
00:00
PPM
12.5 km from Aurland: Vol. % NO2 / NOx on Thursday 2007-08-30
NO2 / NOx
% NO2 / NOx
II
I
NO2 (PPM)
NO (PPM)
6
4
10%
2
5%
00:00
20%
0
03:00
06:00
09:00
12:00
15:00
18:00
21:00
17 km from Aurland: Vol. % NO2 / NOx on Thursday 2007-08-30
NO2 (PPM)
PPM
8
NO (PPM)
% NO2 / NOx
NO2 / NOx
00:00
6
4
15%
2
10%
0
00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00
Figure 21: Example of low night traffic and start of ventilation at 03:00 because of NO-oxidation
21
m/s
4
Air velocity and ventilation level, Monday 2007-09-10
Air velocity
3
Ventilation level
2
1
0
-1
14:00
20%
II
I
I
15:00
I
16:00
17:00
17 km from Aurland: Vol. % NO2 / NOx on Monday 2007-09-10
NO2 / NOx
% NO2 / NOx
I
NO2 (PPM)
18:00
PPM
8
NO (PPM)
6
4
15%
2
0
10%
14:00
NO2 (PPM)
1,4
15:00
16:00
17:00
17 km from Aurland: NO2 and NO on Monday 2007-09-10
18:00
NO (PPM)
7
14:28
NO2/NOx = 12.6 %
5
1,0
0,6
NO2 (PPM)
NO (PPM)
16:56
NO2/NOx = 18.0 %
3
1
0,2
14:00
15:00
16:00
17:00
18:00
Figure 22: Example of low ventilation level and high NO2 / NOx volume ratio on Monday afternoon
20%
17 km from Aurland: Vol. % NO2 / NOx on Saturday 2007-09-15
% NO2 / NOx
NO2 / NOx
NO2 (PPM)
PPM
8
NO (PPM)
6
4
15%
2
10%
12:00
0
14:00
16:00
18:00
20:00
22:00
Figure 23: Example of high NO2 / NOx volume ratio on Saturday afternoon
The NO-concentration on Saturdays is often low because of reduced traffic of heavy duty
vehicles in the week-ends. A low ventilation level is giving a higher production of NO2 from
22
oxidation of NO. The average transport time for fresh air from Aurland to the shaft fans at 18
km was 2 hours and 40 minutes between 11:00 and 21:00 on Monday in week no. 37 (average
air velocity: 1.9 m/s). The average air velocity was reduced to 0.9 m/s and the time for oxidation of NO was lengthened to more than five hours on Saturday.
Trend-curves for average NO- and NO2-concentration from Monday to Thursday are plotted
in figure 24. The gradient of the NO-curve is declining in the upper part, and the oxidation
product is making a gradually steeper NO2-curve.
The average values on Sundays in 2007 were different from the first five days in the week.
The difference was explained by the high proportion of heavy duty vehicles from Monday to
Friday. The measurements were repeated in three weeks with similar traffic conditions in
August – September in 2008.
NO2 (ppm)
0,8
NO (ppm)
5
Average concentration of NO2, and NO, Monday - Thursday
NO2
NO
Average NO2-concentration
Average NO-concentration
0,6
0,4
4
3
2
0,2
1
0,0
0
0
2
4
6
8
10
12
Distance from Aurland (km)
14
16
18
Figure 24: Average concentration of NO2 and NO in week no. 37 in 2007
Daily traffic volumes in week no. 37, 2007
< 7.5 m
> 7.5 m
Vehicles / day
2 500
2 000
2 091
1 500
1 000
500
1 779
1 052 396
862
407
916
443
1 223 430
353
1 014
317
186
0
Monday
Tuesday
Wednesday
Thursday
Friday
Daily traffic volumes in week no. 38, 2008
Saturday
< 7.5 m
Sunday
> 7.5 m
Vehicles / day
2 500
2 000
1 500
1 000
500
2 090
1 820
1 069 428
872
483
906
430
1 265
422
356
889 150
252
0
Monday
Tuesday
Wednesday
Thursday
Figure 25: Daily traffic in week no. 37 in 2007 and week no. 38 in 2008
23
Friday
Saturday
Sunday
NO2 (ppm)
0,8
Average NO2-concentration in week no. 37, 2007
Monday
M
0,6
Thursday
T
Friday
F
Sunday
S
0,4
0,2
0,0
0
2
NO2 (ppm)
0,8
4
8
10
12
14
16
18
16
18
Monday
M
0,6
6
Thursday
T
Friday
F
Sunday
S
0,4
0,2
0,0
0
2
4
6
8
10
12
14
Figure 26: Average concentration of NO2 in week no. 37 in 2007 and week no. 38 in 2008
m/s
4
3
2
Air velocity and ventilation level, Sunday 2007-09-16
Air velocity
Ventilation level
II
1
I
0
-1
00:00
03:00
m/s
4
3
2
06:00
09:00
12:00
18:00
21:00
00:00
Air velocity and ventilation level, Sunday 2008-09-21
Air velocity
II
Ventilation level
II
1
II
II
I
0
-1
00:00
15:00
03:00
06:00
09:00
12:00
15:00
18:00
Figure 27: Ventilation level and air velocity from Aurland on a Sunday in September 2007 and 2008
24
21:00
00:00
Week-end traffic in the south direction on Sunday afternoon reduces the air velocity from
Aurland. On some occasions in 2007 the NO2-concentrations exceeded the upper threshold
limit (0.75 ppm) in the middle of the tunnel. Therefore the start-parameter for NO2 was
reduced from 0.7 ppm to 0.4 ppm in 2008. Earlier start of ventilation gave only small changes
in the average air quality from Monday to Friday. However, the average NO2-concentration
on Sunday was reduced by 0.2 ppm in week no. 38 in 2008 compared with the average level
in week no. 37 in the previous year. There was also a significant reduction of the NO-concentration on Sundays in 2008 compared with days with similar traffic in 2007. The average NOconcentrations in week no 37 in 2007 and week no 38 in 2008 are plotted in figure 28.
NO (ppm)
Average NO-concentration in week no. 37, 2007
5
4
3
2
1
Monday
M
0
0
2
NO (ppm)
6
4
Friday
F
8
10
12
Sunday
S
14
16
18
16
18
Monday
M
5
6
Thursday
T
Thursday
T
Friday
F
Sunday
S
4
3
2
1
0
0
2
4
6
8
10
12
14
Figure 28: Average concentration of NO in week no. 37 in 2007 and week no. 38 in 2008
Calculated NO2/NOx volume ratios 9.4 km and 17 km from Aurland are plotted in figures 29
and 30 on the next page. The highest values in both years were observed from Friday afternoon to Sunday, and it is obvious that there is a great difference in the chemical composition
of the exhaust gases from passenger cars and heavy duty vehicles. From the lowest values at
9.4 km from Monday to Friday, we can conclude that some heavy duty vehicles were producing NOx with about 6 % NO2 in 2007. The NO2/NOx volume ratio increased to over 15 % in
periods with weekend-traffic of passenger cars and low numbers of heavy duty vehicles.
There were small changes of the average values from 2007 to 2008. However, there was a
25
significant change of the highest values each day in the week. The most likely explanation for
the higher values at 9.4 km in 2008 is the increased number of diesel-powered passenger cars.
Vol. % NO2 / NOx 9.4 km from Aurland
20%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
15%
10%
5%
2007-09-10
2007-09-12
2007-09-14
2007-09-16
20%
15%
10%
Monday
5%
2008-09-08
Tuesday
Wednesday
Thursday
2008-09-10
Friday
Saturday
2008-09-12
Sunday
2008-09-14
Figure 29: NO2 / NOx volume ratio at 9.4 km in week no. 37 in 2007 and week no. 38 in 2008
20%
15%
10%
Monday
5%
2007-09-10
20%
Tuesday
Wednesday
Thursday
2007-09-12
Friday
Saturday
2007-09-14
Sunday
2007-09-16
15%
10%
Monday
5%
2008-09-08
Tuesday
Wednesday
Thursday
2008-09-10
Friday
Saturday
2008-09-12
Figure 30: NO2 / NOx volume ratio at 17 km in week no. 37 in 2007 and week no. 38 in 2008
26
Sunday
2008-09-14
Observations of NO and NO2 on Monday and Sunday in week no. 37 in 2007 are plotted in
figure 31 and 32 with ten times difference in the vertical scales. The NO- and NO2-curves are
close at 9.4 km with NO2/NOx volume ratios between 8 % and 12 %. From 9.4 km to 17 km
the NO2-concentration is increasing much faster than NO. It has been assumed that oxidation
of NO is the main reason. However, a higher NO2-emission between 12.5 km and 17 km
because of different vertical alignment before and after 12.5 km could be another possible
explanation. Se comments about the observed effect of vertical alignment in the Laerdal
tunnel in chapter 2.4.
Concentration of NO2 and NO at 9.4 km on Monday 2007-09-10
1,0
10
NO2
NO2 / NOx = 12 %
NO
NO2 / NOx = 11 %
8
NO2 / NOx = 8 %
0,6
6
NO2 / NOx = 12 %
0,4
PPM NO
PPM NO2
0,8
4
0,2
09:00
11:00
13:00
15:00
17:00
19:00
21:00
2
23:00
Concentration of NO2 and NO at 17.0 km on Monday 2007-09-10
1,6
16
1,4
PPM NO2
1,2
NO2 / NOx = 16 %
NO2 / NOx = 14 %
NO2 / NOx = 18 %
NO2 / NOx = 15 %
14
NO
12
NO2 / NOx = 17 %
1,0
10
0,8
8
0,6
6
0,4
4
0,2
09:00
11:00
13:00
15:00
17:00
19:00
21:00
PPM NO
NO2
2
23:00
Figure 31: NO2 and NO concentration 9.4 km and 17 km from Aurland on Monday 2007-09-10
The high NO2/NOx volume ratio on Sunday morning at 9.4 km in figure 32, were caused by
little traffic and low air velocity before the fans started at 12:00. A few hours later the Sunday
values were reduced to near 12 % at 9.4 km and 15 % at 17 km.
The average values for each day in the week are plotted in figure 33 and 34. There were only
small variations around 10 % from Monday to Thursday at the sensors located 9.4 km from
Aurland. From Friday to Sunday the values were 2 – 4 % higher at the same point. 17 km
from Aurland the average NO2/NOx volume ratios were 4 - 5 % higher. However, at 17 km
there was a falling tendency from week no. 33 to week no. 37 and greater variations.[17]
Average NO2/NOx volume ratios during three weeks in 2008 are plotted in figure 35 and 36.
There was no significant change of the average NO2/NOx-ratio from 2007 to 2008.
17
Test of the NO2-filter in week no. 36 reduced the average NO2/NOx-ratio from Monday to Friday
27
Concentration of NO2 and NO at 9.4 km on Sunday 2007-03-16
1,0
10
NO2 / NOx = 14 %
NO2
NO
8
NO2 / NOx = 12 %
NO2 / NOx = 15 %
0,6
6
NO2 / NOx = 10 %
0,4
PPM NO
PPM NO2
0,8
4
0,2
09:00
11:00
13:00
15:00
17:00
19:00
21:00
2
23:00
Concentration of NO2 and NO at 17.0 km on Sunday 2007-09-16
1,4
14
NO2 / NOx = 15 %
NO2 / NOx = 18 %
NO2 / NOx = 14 %
12
NO2
NO
1,0
10
0,8
8
NO2 / NOx = 13 %
0,6
6
0,4
4
0,2
09:00
11:00
13:00
15:00
17:00
19:00
21:00
2
23:00
Figure 32: NO2 and NO concentration 9.4 and 17 km from Aurland on Sunday 2007-09-16
15%
Vol. % NO2/NOx, 9.5 km from Aurland (average 08:00 - 20:00)
week no. 33
week no. 34
week no. 35
week no. 36
week no. 37
10%
5%
Monday
20%
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Vol. % NO2/NOx, 17 km from Aurland (average 08:00 - 2:00)
week no. 33
week no. 34
week no. 35
week no. 36
week no. 37
15%
10%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Figure 33: NO2 / NOx volume ratio at 9.4 km and 17 km from 13 August to 16 September 2007
28
Sunday
PPM NO
PPM NO2
1,2
NO2 / NOx = 14 %
Vol. % NO2 / NOx in week no. 33 , 2007 (Average 08:00 - 20:00)
20%
9.4 km
17.0 km from Aurland
16,9 %
13,8 %
15,9 %
12,2 %
15,0 %
11,9 %
13,1 %
9,5 %
15,3 %
10,5 %
15,0 %
10,6 %
15,7 %
10%
10,4 %
15%
5%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
20%
9.4 km
16,1 %
13,8 %
15,5 %
12,6 %
16,0 %
11,5 %
14,7 %
10,1 %
17,2 %
12,2 %
14,7 %
9,9 %
15,1 %
10%
10,1 %
15%
5%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
20%
9.4 km
12.5 KM
9,5 %
10,2 %
12,7 %
10,1 %
11,3 %
13,7 %
10,4 %
11,7 %
14,0 %
11,9 %
14,2 %
16,0 %
13,1 %
14,2 %
15,3 %
13,2 %
9,4 %
13,7 %
10%
9,8 %
15%
Wednesday
Thursday
Friday
Saturday
Sunday
5%
Monday
Tuesday
20%
9.4 km
12.5 KM
9,7 %
9,4 %
12,3 %
10,0 %
9,1 %
11,9 %
10,1 %
9,4 %
12,7 %
10,6 %
10,6 %
13,2 %
10,4 %
11,9 %
14,8 %
13,4 %
14,1 %
15,7 %
10%
9,5 %
9,6 %
11,5 %
15%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
5%
20%
9.4 km
12.5 KM
9,5 %
10,7 %
14,1 %
10,1 %
11,2 %
13,7 %
9,8 %
10,8 %
14,3 %
11,1 %
11,6 %
15,0 %
12,0 %
12,4 %
14,5 %
12,9 %
13,9 %
15,2 %
10%
10,2 %
11,4 %
14,5 %
15%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
5%
Figure 34: Average NO2 / NOx volume ratio in week no. 33 – 37 in 2007
29
Vol. % NO2/NOx, 9.4 km from Aurland (average 08:20:00)
15%
week no. 36
week no. 37
week no. 38
10%
5%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Vol. % NO2/NOx, 17 km from Aurland (average 08:00 - 20:00)
20%
week no. 36
week no. 37
week no. 38
15%
10%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Figure 35: NO2 / NOx volume ratio at 9.4 km and 17 km 1 – 21 September 2008
20%
9.4 km
12.5 KM
16,1 %
13,1 %
13,8 %
16,0 %
12,4 %
12,4 %
15,1 %
12,0 %
12,3 %
14,2 %
11,2 %
11,1 %
13,6 %
10,0 %
9,8 %
13,7 %
10,4 %
9,8 %
14,5 %
11,0 %
10%
10,3 %
15%
5%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
20%
9.4 km
12.5 KM
15,8 %
13,5 %
14,0 %
15,6 %
11,7 %
12,1 %
15,5 %
13,0 %
13,6 %
14,5 %
11,0 %
10,7 %
14,5 %
11,1 %
10,9 %
14,5 %
11,0 %
10,9 %
14,7 %
11,3 %
10%
11,0 %
15%
5%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
20%
9.4 km
12.5 KM
15,4 %
12,9 %
13,3 %
15,5 %
11,8 %
12,1 %
14,6 %
11,1 %
11,7 %
14,2 %
11,1 %
11,1 %
13,8 %
10,2 %
9,9 %
13,9 %
10,4 %
10,1 %
13,9 %
10,6 %
10%
10,3 %
15%
5%
Monday
Tuesday
Wednesday
Thursday
Figure 36: Average NO2 / NOx volume ratio 1 – 21 September 2008
30
Friday
Saturday
Sunday
2.3 Observations of NO and NO2 in July - September 2011
The concentration of NO and NO2 was measured every five minutes during nine weeks in
order to observe the changes in NOx-emission from passenger cars and heavy duty vehicles.
The traffic growth in week no. 37 was about 20 %. from 2007 to 2011. The average NO2/NOx
volume ratios for three weeks are plotted in figure 37. There was less difference between the
values on Monday and Sunday in 2011 than in 2008.
NO2 (ppm)
0,8
Monday
M
0,6
Thursday
T
Friday
F
Sunday
S
0,4
0,2
0,0
0
2
4
NO2 (ppm)
8
10
12
14
16
18
16
18
16
18
0,8
Monday
M
0,6
6
Thursday
T
Friday
F
Sunday
S
0,4
0,2
0,0
0
2
NO2 (ppm)
4
8
10
12
14
0,8
Monday
M
0,6
6
Thursday
T
Friday
F
Sunday
S
0,4
0,2
0,0
0
2
4
6
8
10
12
Figure 37: Average concentration of NO2 in week no. 29, 33 and 36 in 2011
31
14
The average NO-concentrations at 17 km in figure 38 were reduced by one ppm compared
with the values for 2008 (in figure 28 on page 25). NO2-emission from new diesel-powered
passenger cars gave a higher ventilation level in 2011 and lower average NO-values on
Sundays. Higher air velocity in 2011 reduced the effect of NO-oxidation between the gassensors at 9.4 km and 17 km.
NO (ppm)
5
Monday
M
4
Thursday
T
Friday
F
Sunday
S
3
2
1
0
0
2
4
NO (ppm)
5
8
10
12
14
16
18
16
18
16
18
Monday
M
4
6
Thursday
T
Friday
F
Sunday
S
3
2
1
0
0
2
NO (ppm)
5
4
8
10
12
14
Monday
M
4
6
Thursday
T
Friday
F
Sunday
S
3
2
1
0
0
2
4
6
8
10
12
Figure 38: Average concentration of NO in week no. 29, 33 and 36 in 2011
32
14
The gradual reduction of average NO2/NOx volume ratio from July to September is illustrated
in figure 39. In the same period there was a good correlation between reduction of NO2/NOx
and reduced traffic of passenger cars from Monday to Thursday. From Monday to Thursday
in week no. 36, the average NO2/NOx volume ratio at 9.4 km was near 10 % which means
that there had been no significant change in the exhaust from heavy duty vehicles since week
no. 33 – 37 in 2007 (Figure 33 on page 28).
20%
16%
Vol. % NO2 /NOx, 9.4 km from Aurland (average 08:00 - 20:00)
week 29
week 34
week 30
week 35
week 31
week 36
week 32
week 37
week 33
Wednesday
Thursday
Friday
12%
8%
Monday
20%
Tuesday
Saturday
Sunday
Vol. % NO2 /NOx, 17 km from Aurland (average 08:00 . 20:00)
week 29
week 34
week 30
week 35
week 31
week 36
week 32
week 37
week 33
Wednesday
Thursday
Friday
16%
12%
8%
Monday
Tuesday
Saturday
Sunday
Figure 39: Average NO2 / NOx volume ratio at 9.4 km and 17 km in week no. 29 - 36 in 2011
Daily traffic in week no. 29 - 37 in 2011
4 000
3 000
2 000
1 000
0
week 29
week 34
Monday
week 30
week 35
Tuesday
Wednesday
week 31
week 36
Thursday
week 32
week 37
Friday
week 33
Saturday
Sunday
% of vehicles with length > 7.5 m in week. no. 29 - 37 in 2011
40%
week 29
week 32
week 35
30%
20%
week 30
week 33
week 36
week 31
week 34
week 37
10%
0%
Monday
Tuesday
Wednesday
Thursday
Friday
Figure 40: Daily traffic and ratio of heavy duty vehicles in week no. 29 - 37 in 2011
33
Saturday
Sunday
12.5 KM
13,0 %
13,8 %
15,8 %
12,9 %
13,3 %
15,3 %
13,4 %
13,5 %
15,1 %
14,0 %
14,3 %
16,4 %
10%
13,0 %
13,7 %
15,3 %
15%
Monday
Tuesday
Wednesday
Thursday
Friday
17,0 %
16,8 %
18,2 %
9.4 km
17,8 %
17,2 %
18,6 %
20%
Saturday
Sunday
5%
12.5 KM
11,3 %
12,3 %
14,5 %
11,8 %
13,0 %
15,1 %
11,1 %
12,2 %
14,6 %
13,3 %
14,0 %
16,2 %
10%
13,5 %
14,2 %
16,0 %
15%
Monday
Tuesday
Wednesday
Thursday
Friday
17,2 %
17,1 %
18,4 %
9.4 km
17,0 %
16,8 %
18,1 %
20%
Saturday
Sunday
5%
20%
9.4 km
12.5 KM
11,4 %
12,3 %
14,5 %
13,3 %
14,0 %
15,8 %
Tuesday
Wednesday
Thursday
Friday
16,3 %
17,0 %
17,7 %
10,2 %
11,4 %
13,8 %
Monday
15,5 %
16,3 %
17,7 %
12,0 %
12,9 %
14,7 %
10%
10,6 %
11,9 %
14,3 %
15%
Saturday
Sunday
5%
20%
9.4 km
12.5 KM
9,3 %
10,2 %
12,8 %
9,4 %
10,6 %
12,9 %
10,6 %
11,2 %
13,8 %
12,4 %
13,0 %
15,1 %
13,0 %
14,1 %
16,2 %
15,5 %
16,2 %
17,7 %
10%
10,2 %
11,2 %
13,8 %
15%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
5%
20%
9.4 km
12.5 KM
9,5 %
9,5 %
12,4 %
9,0 %
8,9 %
12,0 %
11,0 %
10,9 %
13,2 %
13,0 %
12,4 %
14,2 %
14,7 %
14,3 %
15,6 %
10%
10,1 %
10,1 %
13,0 %
15%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
5%
Figure 41: Average NO2 / NOx volume ratio from 2011-07-18 to 2011-09-17
34
25%
Vol. % NO2 / NOx 9.4 km from Aurland in week no. 29, 2011
20%
15%
10%
Monday
5%
2011-07-18
20%
Tuesday
Wednesday
Thursday
2011-07-20
Friday
2011-07-22
Saturday
Sunday
2011-07-24
15%
10%
Monday
5%
2011-09-05
Tuesday
Wednesday
Thursday
2011-09-07
Friday
2011-09-09
Saturday
Sunday
2011-09-11
Figure 42: NO2 / NOx volume ratio 9.4 km from Aurland in week no. 29 and 36 in 2011
25%
20%
15%
10%
Monday
5%
2011-07-18
20%
Tuesday
Wednesday
Thursday
2011-07-20
Friday
2011-07-22
Saturday
Sunday
2011-07-24
15%
10%
Monday
5%
2011-09-05
Tuesday
Wednesday
Thursday
2011-09-07
Friday
2011-09-09
Figure 43: NO2 / NOx volume ratio 17 km from Aurland in week no. 29 and 36 in 2011
35
Saturday
Sunday
2011-09-11
2.4 NOx-emission from heavy duty vehicles in December 2012
When the Laerdal tunnel was opened at 15:22 on Monday 2012.12.10 after a traffic accident
on Sunday evening, there were 100 heavy duty vehicles and 50 passenger cars waiting near
the portals. 30 minutes later the NO-concentration had increased to 8 ppm near the Aurland
portal and 13 ppm near Laerdal. The fast growth of NO-concentrations in the tunnel section
from 2 – 17 km from Aurland is plotted in figure 44. The highest values at the Aurland side
were observed at the NO-sensor located 2.0 km from the portal. The NO-emission five
minutes after start was 10 - 15 % higher than the average emission-values in the middle of the
tunnel. This cold-start-effect was gradually reduced during the first ten minutes and was
negligible after 9.4 km.
6 ppm is equal to a NO-volume of 336 l/km since the average tunnel profile is 56 m2. The
observed NO-concentration at 2 km corresponds to an average NO-emission of 7.5 l/km from
heavy duty vehicles in the south section where the uphill gradient is 2.3 %. The average
downhill NO-emission from heavy duty vehicles was less than 1.0 l/km in this section.
PPM
NO-concentration 2.0 - 12.5 km from Aurland, 2012.12.10
15:42
5.79 ppm
15:39
4.6 ppm
8
15:37
6.07 ppm
6
4
15:46
5.15 ppm
15:44
5.29 ppm
2
2.0 km
9.4 km
0
15:25
15:30
15:35
15:40
4.0 km
12.5 km
15:45
15:50
7.5 km
15:55
16:00
Figure 44: Observed NO-concentration at five points in the south half of the tunnel
16
NO-concentration 17 - 22 km from Aurland om 2012-12-10
15:45 13.01 ppm
14
PPM NO
12
10
8
6
4
Air from Aurland
until 15:55
2
0
15:30
15:40
15:50
16:00
NO 22.0 km
NO 18.5 km
NO 17.0 km
NO 14.5 km
16:10
Figure 45: Observed NO-concentration in the north half of the tunnel during 60 minutes
36
16:20
16:30
The lowest NO-values in figure 44 and 45 were observed 14.5 km from Aurland. The average
NO-emission factor for heavy duty vehicles was near 3.7 l/km in this section.
The average NO-emission factors from heavy duty vehicles from the Laerdal side were
10 l/km at 22 km and 8.7 l/km at 18.5 km. There was no detectable NO-emission from heavy
duty vehicles driving downhill towards Laerdal from 18.5 to 24.5 km.
Gradient
0 - 7.5
2.3 %
7.5 - 11.5 12.5 - 14.5 14.5 - 17
2.3 %
-0.7 %
-0.7 %
NO-emission, north direction
7.4 l/km
7.0 l/km
2.8 l/km
NO-emission, south direction
Average NO-emission-factor
Effect of cold-start and load
1.0 l/km
4.2 l/km
13 %
1.0 l/km
4.0 l/km
6%
4.7 l/km
3.7 l/km
0%
18.5 - 22
-2.7 %
22 - 24.5
-2.7 %
2.8 l/km
0
0
5.8 l/km
4.3 l/km
16 %
8.7 l/km
4.3 l/km
16 %
10.1 l/km
5.0 l/km
36 % (?)
Higher emission rates were expected in the south direction near Laerdal because of 2.7 %
uphill gradient and heavier loaded vehicles driving from Oslo to Bergen. The effect of coldstart during the first ten minutes is uncertain. Heavy loaded trucks may be another likely
explanation for the high NO-emission in the uphill section from the Laerdal portal.
Traffic from Aurland on 2012-12-10
Vehicles / hour
100
80
60
> 15.9 m
12.4 - 15.9 m
5.6 - 7.5 m
< 5.6 m
13
2
11
1
34
40
14
5
20
7.5 - 12.4 m
8
3
0
15:00
17:00
18:00
19:00
20:00
Traffic from Laerdal on 2012-12-10
100
Vehicles / hour
16:00
80
60
> 15.9 m
12.4 - 15.9 m
5.6 - 7.5 m
< 5.6 m
6
10
7.5 - 12.4 m
55
16
40
7
20
12
0
15:00
16:00
17:00
18:00
19:00
20:00
Figure 46: Traffic in the Laerdal tunnel on Monday 2012-12-10
The NO-concentration was almost constant during the first hour after the two vehicle columns
had driven through the tunnel. There were few vehicles the next hour. However, the growth of
NO2-concentration continued. The extreme values are plotted in figure 48 together with
normal NO2-values from Saturday to Tuesday.
37
12
PPM NO
10
NO-concentration 2 - 17 km from Aurland om 2012-12-10
NO 2.0 km
NO 12.5 km
NO 4.0 km
NO 14.5 km
NO 7.5 km
NO 17.0 km
NO 9.4 km
8
20 min.
3.8 m/s
6
19 min.
4
4.8 m/s
2
0
15:30
16:00
16:30
17:00
17:30
Figure 47: Observed NO-concentrations from Aurland during two hours
PPM NO2
2,25
High NO2-concentration in the Laerdal tunnel on 2012.12.10
2,00
9.4 km
1,75
12.5 km
17.0 km
1,50
1,25
Saturday
Sunday
Monday
1,00
Tuesday
0,75
0,50
0,25
08.12.2012
09.12.2012
10.12.2012
11.12.2012
Figure 48: High NO2-concentration on Monday 2012-12-10
NO2 / NOx volume ratio in the Laerdal tunnel
20 %
Vol. % NO2 / NOx
9.4 km
12.5 km
17.0 km
15 %
10 %
Saturday
5%
8.12.2012
Monday
Sunday
9.12.2012
10.12.2012
Figure 49: Variations in NO2 / NOx volume ratio from Saturday to Tuesday
38
Tuesday
11.12.2012
Observed NO2-concetrations every minute at 9.4 km, 12.5 km and 17.0 km from Aurland, are
plotted in figure 50. The average NO2-emission from heavy duty vehicles driving in the north
direction at 9.4 km and 12.5 km was 0.35 l/km. The average NO2-emission rate for both
directions from 12.5 km to 17 km was 0.25 l/km which give a total NOx-emission value near
4.0 l/km for vehicles with length over 7.5 m. (3.75 l NO + 0.25 l NO2)/km.
There was no significant change of the NO2/NOx-ratio caused by the variations in vertical
alignment. Change of vertical alignment after 11.5 km and 60 % of the heavy duty vehicles
driving in the south direction, gave higher NO2-values at 17 km than at 9.4 km and 12.5 km.
However, the NO-emission was also higher from vehicles driving in the south direction in the
middle of the tunnel.
The three control points in figure 51 had almost identical increase of NO2/NOx volume ratio
caused by oxidation of NO during the first hour after the tunnel was opened. The average
NO2/NOx volume ratio from the first 40 heavy duty vehicles from Aurland varied between
5 % and 6 %.
2,25
2,00
1,75
17:19: 2.25 ppm
9.4 km
16:59: 1.93 ppm
12.5 km
16:44: 1.73 ppm
17.0 km
PPM NO2
1,50
NO2-concentration 9.4 - 17.0 km from Aurland on 10.12.2012
20 min.
1,25
15 min.
1,00
0,75
22 min.
0,50
3.8 m/s
3.5 m/s
3.4 m/s
0,25
15:30
16:00
16:30
17:00
17:30
Figure 50: Growth of NO2-concentration from oxidation of NO
20 %
NO2 / NOx volume ratio in the Laerdal tunnel on 2012.12.10
9.4 km
16 %
12.5 km
17.0 km
12 %
8%
4%
15:30
16:00
16:30
Figure 51: Variations of NO2 / NOx volume ratio during two hours
39
17:00
17:30
2.5 NOx-emission from passenger cars in March 2013
The natural ventilation forces in the Laerdal tunnel are strongest in cold periods. High natural
air velocity is reducing the available time for oxidation of NO in periods with little traffic.
Small differences between NO2/NOx volume ratios were observed between the sensors at 9.4
km and 17 km during two weeks in March 2013. The values from Monday to Thursday in
figure 52 were similar to the values in week no. 35 – 37 in 2011. (Figure 41 on page 34).
However, the 2013-values from Friday to Sunday at 9.4 km were higher than the observed
values in 2011. Reduction of the NO2/NOx volume ratio at 17 km from 2011 to 2013 was
caused by higher ventilation levels because of increased traffic and shorter periods with high
NO-oxidation. Low ventilation levels and traffic of passenger cars gave NO2/NOx volume
ratios above 25 % on Friday afternoon in figure 53.
Daily traffic in the Laerdal tunnel, 8 - 22 March 2013
4 000
Vehicles / day
Length > 7.5 m
3 000
333
213
2 000
1 000
401
Length < 7.5 m
431
490
508
499
395
119
1 868
1 835
806
1 411 1 319 1 408 1 677
2 024
245
118
507
457
504
517
3 065
1 931
819
1 465 1 328 1 507
1 855
0
Fri
Sun Mon Tue Wed Thu
Fri
Sat
Sun Mon Tue Wed Thu
Fri
8 - 22 March 2013: Vol. % NO2/NOx (Average 08:00 - 20:00)
20%
NO2 / NOx
Sat
9.4 km
12.5 km
15%
10%
5%
Fri
Sat
Sun Mon Tue Wed Thu
Fri
Sat
Sun Mon Tue Wed Thu
Fri
Figure 52: Daily traffic and average NO2 / NOx volume ratio 2 weeks in March 2013
30%
NO2 / NOx
% NO2 / NOx
PPM
4
9.4 km from Aurland: Vol. % NO2 / NOx on Friday 2013-03-08
NO2 (PPM)
NO (PPM)
25%
3
20%
2
15%
1
10%
5%
08:00
0
10:00
12:00
14:00
16:00
18:00
Figure 53: Normal growth of NO2 / NOx volume ratio from weekend-traffic on Friday afternoon
40
20:00
15 % of 2 168 vehicles were longer than 7.5 m on Friday 2013-03-08
Vehicles/hour
200
26 16
Length > 7.5 m
100
16 14 17
0
9
3
6
3
6
19 18
9
01:00
04:00
16
8
27
Length < 7.5 m
13 11
11
6
16
18 19
23
18
82 72 82 100
47 55 63
41
23 23
11
07:00
10:00
13:00
131 145
169
146
13
126
83
16:00
19:00
7
58
12
25 23
22:00
Figure 54: Traffic variations on Friday 2013-03-08
Typical traffic variations on Friday are illustrated in figure 54. 15 % NO2/NOx-volume ratio
in the morning in figure 53 was caused by NO-oxidation because of low air velocity before
the fans started. The growth of NO2/NOx volume ratio after 17:00 was caused by reduced
traffic of heavy duty vehicles and higher NO2-emission from passenger cars.
Reduced traffic of heavy duty vehicles gave higher NO2/NOx volume ratios during the Easter
week in 2013 except for Monday and Tuesday. Detailed observations are given in figures 55 –
58. Cold weather gave high natural ventilation and average air velocity near 2 m/s during the
night and no sign of NO2 from oxidation in the morning. The NO2/NOx volume ratio at 17 km
was lower than at 9.4 and 12.5 km for all days in figure 55 except Monday and Tuesday. The
most likely explanation is that passenger cars are producing less NO2 at the low gradient
section from 11.5 to 17 km compared with the first tunnel section from Aurland. The 30 %
NO2/NOx-ratio at 9.4 km on Easter Sunday was probably a combination of NO-oxidation and
NO2-emission from diesel-powered passenger cars. The ratio varied between 20 % and 25 %
after start of ventilation.
Daily traffic in the Laerdal tunnel, 23 March 7 April 2013
162
2013-03-29
2013-04-01
2013-04-04
1 461
947
1 549
904
374
243
356 521 502
153
1 213
2 733
3 430
63
1 267
1 768
2 985
1 690
82
2013-04-07
23 March - 7 April 2013: Vol. % NO2/NOx (Average 08:00 - 20:00)
25%
NO2 / NOx
2013-03-26
91
1 358
0
2013-03-23
1 509
1 000
190 245 456 456
1 777
2 000
Length > 7.5 m
Length < 7.5 m
270
3 000
1 030
282
2 066
Vehicles / day
4 000
9.4 km
12.5 km
20%
15%
10%
5%
Sat
Sun Mon Tue Wed Thu
Fri
Sat
Figure 55: Traffic and NO2 / NOx volume ratio, March - April 2013
41
Sun Mon Tue Wed Thu
Fri
Sat
Sun
8 % of 3 530 vehicles were longer than 7.5 m on Wednesday 2013-03-27
32
300
19
0
Length > 7.5 m
16
12
8
38
55
166
107
11:00
m/s
Length < 7.5 m
10
13
09:00
223
253
13:00
300
333
332
10
331
237
15:00
17:00
183
19:00
6
127
78
21:00
5
7
43
30
23:00
Air velocity and ventilation level on Wednesday 2013-03-27
6
5
4
3
2
1
0
08:00
30%
III
IV
IV
4
III
III
3
III
III
II
10:00
III
III
2
II
Air velocity
1
Ventilation level
I
12:00
14:00
16:00
I
18:00
0
22:00
20:00
PPM
3
9.4 km from Aurland: Vol. % NO2 / NOx on Wednesday 2013-03-27
NO2 / NOx
% NO2 / NOx
18
10
200
100
13
18
22
NO2 (PPM)
Ventilation level
Vehicles / hour
400
NO (PPM)
25%
2
20%
1
15%
10%
08:00
NO2
0,70
0
10:00
12:00
14:00
16:00
18:00
20:00
22:00
NO
12.5 km from Aurland: NO2 and NO on Wednesday 2013-03-27
NO2 (PPM)
NO (PPM)
3
0,60
0,50
2
0,40
0,30
0,20
08:00
% NO2 / NOx
30%
1
10:00
12:00
14:00
16:00
18:00
20:00
22:00
17 km from Aurland: Vol. % NO2 / NOx on Wednesday 2013-03-27
NO2 / NOx
NO2 (PPM)
NO (PPM)
PPM
5
4
25%
3
20%
2
15%
10%
08:00
1
0
10:00
12:00
14:00
16:00
Figure 56: Traffic and NOx at the start of Easter holidays in 2013
42
18:00
20:00
22:00
4 % of 3 748 vehicles were longer than 7.5 m on Easter Sunday 2013-03-31
Length > 7.5 m
400
Length < 7.5 m
300
0
1
1
18
34
09:00
9
26
2
371
329
370
10
286
285
208
152
60
11:00
13:00
15:00
17:00
19:00
145
21:00
9
5
64
53
23:00
Air velocity and ventilation level on Sunday 2013-03-31
4
III
III
III
3
Ventilation level
3
2
2
II
1
0
08:00
35%
% NO2 / NOx
357
265
Air velocity
4
17
15
10
379
5
m/s
5
17
9
5
200
100
13
II
II
II
II
10:00
12:00
1
I
I
14:00
16:00
18:00
20:00
22:00
0
00:00
PPM
9.4 km from Aurland: Vol. % NO2 / NOx on Easter Sunday 2013
NO2 / NOx
NO2 (PPM)
Ventilation level
Vehicles / hour
500
NO2 (PPM)
2
30%
25%
1
20%
15%
10%
12:00
NO2
0,70
0
14:00
16:00
18:00
20:00
22:00
NO
12.5 km from Aurland: NO2 and NO on Easter Sunday 2013
NO2 (PPM)
NO (PPM)
3
0,60
0,50
2
0,40
0,30
0,20
12:00
% NO2 / NOx
35%
1
14:00
16:00
18:00
20:00
22:00
17 km from Aurland: Vol. % NO2 / NOx on Easter Sunday 2013
NO2 / NOx
NO (PPM)
NO2 (PPM)
PPM
4
30%
3
25%
2
20%
1
15%
12:00
0
14:00
16:00
18:00
Figure 57: Traffic and NOx on Easter Sunday in 2013
43
20:00
22:00
8 % of 3 239 vehicles were longer than 7.5 m on Monday 2013-04-01
100
24
13
200
0
7
7
26
09:00
2
214
11:00
13:00
256
13
283
23
20
212
217
15:00
Length < 7.5 m
24
22
238
17:00
180
19:00
13
9
52
39
106
21:00
5
23:00
4
IV
3
Ventilation level
3
17
Air velocity and ventilation level on Monday 2013-04-01
Air velocity
4
321
297
Length > 7.5 m
31
108
59
m/s
5
III
III
2
II
1
0
08:00
30%
% NO2 / NOx
18
16
300
2
II
II
I
11:00
1
I
14:00
17:00
20:00
0
23:00
9.4 km from Aurland: Vol. % NO2 / NOx on Monday 2013-04-01
NO2 / NOx
Ventilation level
Vehicles / hour
400
NO (PPM)
NO2 (PPM)
25%
PPM
3
2
20%
1
15%
10%
11:00
NO2
0,70
0
13:00
15:00
17:00
19:00
21:00
NO
12.5 km from Aurland: NO2 and NO on Monday 2013-04-01
NO2 (PPM)
NO (PPM)
3
0,60
0,50
2
0,40
0,30
0,20
12:00
% NO2 / NOx
30%
1
14:00
16:00
18:00
20:00
17.0 km from Aurland: Vol. % NO2 / NOx on Monday 2013-04-01
NO2 / NOx
NO (PPM)
NO2 (PPM)
22:00
PPM
5
4
25%
3
20%
2
15%
10%
12:00
1
0
14:00
16:00
18:00
Figure 58: Traffic and NOx on Monday 2013-04-01
44
20:00
22:00
Daily traffic in the Laerdal tunnel, 30 March - 7 April 2013
Length < 7.5 m
0
Vol. % NO2 / NOx
2013-03-31
521
2013-04-02
502
374
2013-04-04
153
1 461
356
947
270
1 549
162
1 030
1 000
904
2 000
Length > 7.5 m
1 213
3 000
2 733
3 430
Vehicles / day
4 000
243
2013-04-06
Vol. % NO2/NOx 31 March - 7 April 2013 (Average 10:00 - 20:00)
25%
9.4 km
20%
12.5 km
15%
10%
5%
Sun
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Figure 59: Traffic and NO2 / NOx volume ratio one week after Easter 2013
The low number of heavy duty vehicles during the Easter week made it possible to calculate
an average NOx-emission factor for passenger cars. Emission factors from December 2012
were used in the calculation of total NOx-emission from heavy duty vehicles in the table
below. Observations from Monday and Tuesday were not included in the table because more
than 70 % of the total NOx-volume came from heavy duty vehicles these days. The average
NOx-emission factor in the table is 0.29 l/km for vehicles with length under 7.5 m. The same
factor was found at 9.4 and 17 km on Easter Sunday when only 4 % of the vehicles were
longer than 7.5 m.
Date
2013-03-23
2013-03-24
2013-03-27
2013-03-28
2013-03-29
2013-03-30
2013-03-31
2013-04-01
Sensor
NOx-volume m3/(10:00 – 20:00)
Vehicles
location
> 7.5 m
Total (m3)
L > 7.5 m
L < 7.5 m
9.4 km
10.15
4.09
6.07
8%
17.0 km
16.05
7.31
8.74
9.4 km
9.02
4.09
4.92
11 %
17.0 km
16.02
8.18
7.85
9.4 km
16.28
7.36
8.92
8%
17.0 km
25.18
12.42
12.77
9.4 km
6.68
1.44
4.74
5%
17.0 km
10.25
3.64
6.61
9.4 km
4.96
1.62
3.35
6%
17.0 km
8.34
3.20
5.14
9.4 km
4.28
1.04
3.24
5%
17.0 km
7.45
2.28
5.17
9.4 km
7.62
1.87
5.75
4%
17.0 km
14.82
4.59
10.22
9.4 km
9.41
4.07
5.34
8%
17.0 km
17.81
8.61
9.20
Average NOx-emission-factor for vehicles shorter than 7.5 m:
45
Emission factor
l / km / vehicle
0.30
0.24
0.31
0.28
0.31
0.25
0.31
0.24
0.32
0.27
0.35
0.31
0.29
0.29
0.30
0.29
0.29
3 Observations of NO and NO2 in the Fodnes tunnel
The Fodnes tunnel is 6.6 km long with a vertical gradient about 1.0 % from Laerdal towards
Fodnes. The north end is located 2.0 km from the ferry connection between Fodnes and
Mannheller. The average traffic volume varies between 1500 vehicles/day in November March to over 3000 vehicles/day in July. 18 % of the vehicles (346 vehicles/day) were longer
than 7.5 m in 2012 compared with 26 % (493 vehicles/day) in the Laerdal tunnel. Therefore a
higher NO2/NOx-ratio could be expected in the Fodnes tunnel.
The tunnel has gas-sensors installed at three points located 1.1 km, 3.5 km and 5.5 km from
Laerdal. The average NO2/NOx volume ratio has been calculated for NO2-concentrations
above 0.25 ppm and NO-values over 1.0 ppm.
3.1
Observations of NO2/NOx volume ratio in 2010
Observed NO2/NOx-volume ratios in two 6-day-periods in March 2010 are plotted in figure
60 and 61. In figure 60 the tunnel was ventilated towards Fodnes from Tuesday to Thursday.
Low air velocity and oxidation of NO gave 3 - 5 % higher NO2/NOx ratio near Fodnes than at
the sensors located 1.1 km from the Laerdal portal. When the direction of ventilation changed
towards Laerdal from Friday to Sunday, the highest ratio was found near Laerdal. In figure 61
there is 5 % increase in the NO2/NOx ratio from 1.1 km to 5.5 km on Wednesday when the
tunnel was ventilated towards Fodnes. The ventilation direction changed several times the
next days, and the lowest values were observed in the middle of the tunnel. No extra NO2emission was observed during the first minutes after cold-start on the ferry. The average
NO2/NOx ratio near Fodnes was not higher than in the Laerdal end of the tunnel.
March 9 - 14 2010: Vol. % NO2/NOx (Average 08:00 - 22:00)
30%
1.1 km
3.4 km
5.5 km from Laerdal
25%
20%
15%
10%
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Figure 60: Average NO2 / NOx volume ratio in the Fodnes tunnel 9 - 14 March 2010
30%
March 17 - 22, 2010: Vol. % NO2/NOx (Average 08:00 - 22:00)
1.0 km
3.5 km
5.5 km from Laerdal
25%
20%
15%
10%
Wednesday
Thursday
Friday
Saturday
Figure 61: Average NO2 / NOx volume ratio in the Fodnes tunnel 17 - 22 March 2010
46
Sunday
Monday
The start direction for the longitudinal ventilation system varies with wind, temperature and
traffic. Natural air velocity over 1.0 m/s is often sufficient for ventilation of this tunnel
without start of jet-fans. The ferry frequency is one tour per 20 minutes, and the traffic
column of 50 – 100 vehicles from the ferry often turns the airflow in the tunnel for 5 – 10
minutes. Sometimes fresh air is blown up to the gas-sensors located 1.1 km from the tunnel
portals. In the diagrams on the next pages this effect can be seen as a short drop in the
concentration of nitrous gases at 1.1 and 5.5 km.
The highest NO2/NOx volume ratios were observed in periods with low natural ventilation
when the NO-level was below the start-parameter for ventilation. Examples are given in
figures 62 and 63. The natural ventilation was towards Laerdal in figure 62. However, the
NO-values 5.5 km from Laerdal show that the direction of ventilation has been unstable. The
low air velocity in the tunnel gave high NO-oxidation in the afternoon and 5 – 10 % increase
of the NO2/NOx volume ratio from 3.4 km to 1.1 km.
The NO2/NOx ratio was also high on Sunday in the same week until the traffic of heavy
goods vehicles gave increased NO-concentration after 17:00 in figure 63 on the next page.
% NO2 / NOx
30%
NO2 (ppm)
20%
2
NO (ppm)
1
15%
30%
% NO2 / NOx
PPM
3
Vol. % NO2 / NOx
25%
10%
08:00
0
10:00
12:00
14:00
16:00
18:00
20:00
3.4 km from Laerdal: Vol. % NO2 / NOx on Friday 2010-03-12
Vol. % NO2 / NOx
NO2 (ppm)
NO (ppm)
25%
22:00
PPM
3
2
20%
1
15%
10%
08:00
35%
% NO2 / NOx
0
10:00
12:00
14:00
16:00
18:00
20:00
Vol. % NO2 / NOx
NO2 (ppm)
NO (ppm)
22:00
PPM
3
30%
2
25%
20%
1
15%
10%
08:00
0
10:00
12:00
14:00
16:00
18:00
Figure 62: Natural ventilation and average NO2 / NOx volume ratio on Friday 2010-03-12
47
20:00
22:00
% NO2 / NOx
35%
Vol. % NO2 / NOx
NO2 (ppm)
NO (ppm)
PPM
3
30%
2
25%
1
20%
15%
12:00
40%
% NO2 / NOx
3.4 km from Laerdal: Vol. % NO2 / NOx on Sunday 2010-03-14
0
13:00
14:00
15:00
16:00
17:00
18:00
19:00
20:00
21:00
22:00
1.1 km from Laerdal: Vol. % NO2 / NOx on Sunday 2010-03-14
Vol. % NO2 / NOx
NO2 (ppm)
NO (ppm)
PPM
3
35%
2
30%
1
25%
20%
12:00
0
13:00
14:00
15:00
16:00
17:00
18:00
19:00
20:00
21:00
22:00
Figure 63: Ventilation level and average NO2 / NOx volume ratio on Sunday 2010-03-14
Ventilation level in the Fodnes tunnel on Thursday 2013-03-18
Jet-fans
8
Direction Laerdal
Direction Fodnes
4
0
09:00
12:00
4
15:00
18:00
21:00
8
Concentration of NO2 and NO, 3.35 km from Laerdal on Thursday 2010-03-18
NO2 / NOx = 15 %
0,9
NO2 / NOx = 16 %
4,5
NO2 / NOx = 18 %
NO2 / NOx = 17 %
NO2
3,5
NO
0,5
2,5
0,3
1,5
0,1
09:00
PPM NO
PPM NO2
0,7
0,5
11:00
13:00
15:00
17:00
19:00
21:00
23:00
Figure 64: Ventilation level and average NO2- and NO-concentration on Thursday 2010-03-18
The start parameters for the ventilation system are adjusted to keep the NO2-concentration
below the upper threshold limit. Values above 0.75 ppm in the middle of the tunnel are
accepted for maximum 15 minutes before the tunnel is closed. High values are often observed
when the ventilation direction is changed during the day. The fans started towards Laerdal at
11:20 and 14:36 in figures 64 and 65. Then the natural ventilation changed before the next
48
start at 17:02 and backflow of air increased the NO2-concentration in the middle of the tunnel
from 0.6 ppm to 0.85 ppm after a few minutes. This triggered start of 100 % ventilation with
an average air velocity of 3 m/s towards Fodnes. The highest gas concentration reached the
NO2-sensor at 5.5 km about 12 minutes later.
PPM NO2
NO2 in the Fodnes tunnel on Thursday 2010-03-18
1.1 km
3.4 km
5.5 km from Laerdal
Upper threshold limit
1,00
0,80
0,60
0,40
0,20
09:00
11:00
13:00
15:00
17:00
19:00
21:00
23:00
Figure 65: NO2- concentration on Thursday 2010-03-18
Ventilation level in the Fodnes tunnel on Friday 2013-03-19
Jet-fans
8
Direction Laerdal
4
Direction Fodnes
0
09:00
4
11:00
13:00
15:00
17:00
19:00
21:00
23:00
8
Concentration of NO2 and NO, 3.35 km from Laerdal on Friday 2010-03-19
0,8
NO2 / NOx = 20 %
NO2 / NOx = 15 %
4
NO2 / NOx = 21 %
NO2
3
0,4
2
PPM NO
PPM NO2
NO
0,6
0,2
09:00
1
11:00
13:00
15:00
17:00
19:00
21:00
23:00
PPM
5.5 km from Laerdal: Vol. % NO2 / NOx on Friday 2013.03-19
% NO2 / NOx
35%
NO2/NOx
NO2
4
NO
30%
3
25%
2
20%
1
15%
10%
09:00
0
11:00
13:00
15:00
17:00
19:00
21:00
Figure 66: Ventilation level and average NO2- and NO-concentration on Friday 2010-03-19
49
23:00
Ventilation level in the Fodnes tunnel on Saturday 2013-03-20
Jet-fans
8
Direction Laerdal
Direction Fodnes
4
0
09:00
11:00
4
13:00
15:00
17:00
19:00
21:00
23:00
8
NO2/NOx
40%
% NO2 / NOx
PPM
3
1.1 km from Laerdal: Vol. % NO2 / NOx on Saturday 2010-03-20
45%
NO2
NO
2
35%
30%
1
25%
20%
15%
09:00
0
11:00
13:00
15:00
17:00
19:00
21:00
23:00
Concentration of NO2 and NO, 3.5 km from Laerdal on Saturday 2010-03-20
0,6
NO2
NO
4
21:18
NO2 > 0.75 ppm
NO2 / NOx = 30 %
NO2 / NOx = 19 %
3
NO2 / NOx = 16 %
0,4
2
0,2
09:00
35%
1
11:00
13:00
15:00
17:00
19:00
21:00
23:00
PPM
4
NO2/NOx
NO2
NO
30%
% NO2 / NOx
PPM NO
PPM NO2
0,8
3
25%
2
20%
1
15%
10%
09:00
0
11:00
13:00
15:00
17:00
19:00
21:00
23:00
Figure 67: NO2- and NO-concentration on Saturday 2010-03-20
NO2/NOx volume ratio over 40 % was observed on Saturday 2013-03-20. Low air velocity
and change of natural ventilation direction several times after 17:00 gave almost no replacement of air in the tunnel from 17:00 to 21:00 in figure 67. All the fans started at 21:15 when
the NO2-concentration in the middle of the tunnel reached 0.75 ppm. The NO2-concentration
at 5.5 km increased to 0.76 ppm 16 minutes later and fell below the detection limit at 21:42.
50
3.2 Observations of NO2/NOx volume ratio in 2011
Calculations of the average NO2/NOx-ratio at two points in the Fodnes tunnel for nine weeks
from July to September in 2011 are plotted in figure 71. Unfortunately the NO-sensor near
Fodnes was not in working order these weeks. The correlation between NO2/NOx-ratio and
the reduced traffic volume of passenger cars from July to September is similar to the observed
values in the Laerdal tunnel in figures 39 – 40 on page 33. Traffic of heavy duty vehicles was
almost constant from Monday to Friday and low on Saturday and until noon on Sunday. The
weekend traffic of passenger cars started on Friday afternoon and gave the highest NO2/NOx
volume ratio in this period. The lowest average NO2/NOx-values from Monday to Thursday
were about 5 % higher than in the Laerdal tunnel (figure 52 on page 40).
4000
Traffic in the Fodnes tunnel July - August 2011
Monday
Vehicles/day
Tuesday
3000
Wednesday
2000
Thursday
Friday
1000
Saturday
0
Sunday
Week 29 Week 30 Week 31 Week 32 Week 33 Week 34 Week 35 Week 36 Week 37
% of vehicles with length > 7.5 m in week no. 29 - 37, 2011
% of vehicles > 7.5 m
Monday
18%
Tuesday
Wednesday
14%
Thursday
Friday
10%
Saturday
Sunday
6%
11.7. 18.7. 25.7.
1.8.
8.8.
15.8. 22.8. 29.8.
5.9.
12.9.
Date
Fodnes tunnel: Average Vol. % NO2 / NOx, 3.5 km from Laerdal
% NO2 / NOx
35%
Monday
Tuesday
30%
Wednesday
25%
Thursday
Friday
20%
Saturday
Sunday
15%
Week 29 Week 30 Week 31 Week 32 Week 33 Week 34 Week 35 Week 36 Week 37
Figure 68: Variations in traffic and NO2 / NOx volume ratio from week no. 29 to week no 37 in 2011
51
08:00 - 22:00
Observations of NO2/NOx volume ratio in 2013
3.3
Normal heavy duty traffic around 15 – 20 % in March 2013 gave NO2/NOx volume ratios
near 15 %. Few heavy duty vehicles in the weekends and during the Easter holidays gave 10 –
20 % higher values. Cold weather and high natural air velocity gave low average NOoxidation from the middle of the tunnel to the sensors near Fodnes in March – April this year.
Daily traffic in the Laerdal tunnel, 8 - 22 March 2013
1 660
295
1 448
303
1 272
299
1 085
228
1 444
131
912
73
1 815
234
1 610
289
1 404
300
1 262
286
1 341
291
1 362
104
1 000
862
86
2 000
2 363
Length > 7.5 m
247
Length < 7.5 m
1 736
203
Vehicles / day
3 000
0
8.3.
10.3.
14.3.
16.3.
18.3.
20.3.
22.3.
8 - 22 March 2013: Average vol. % NO2/NOx 08:00 - 20:00
30%
Vol. % NO2 / NOx
12.3.
3.4 km
25%
5.5 km
20%
15%
10%
Fri
Sat
Sun
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Mon
Tue
Wed
Thu
Fri
Daily traffic in the Laerdal tunnel, 23 March - 7 April 2013
Length < 7.5 m
2 000
1 000
Length > 7.5 m
1 785
115
1 383
134
1 799
257
1 811
290
2 463
227
1 462
65
1 193
55
1 186
60
2 310
82
2 221
151
1 580
270
1 434
299
1 494
294
1 796
241
1 032
98
1 370
124
Vehicles / day
3 000
0
Vol. % NO2 / Nox
23.3.
25.3.
27.3.
29.3.
31.3.
2.4.
4.4.
6.4.
23 March - 7 April in 2013: Average vol. % NO2/NOx 08:00 - 20:00
30%
Easter Sunday
Palm Sunday
25%
3.4 km
5.5 km
20%
15%
10%
Sat
Sun Mon Tue Wed Thu
Fri
Sat
Sun Mon Tue Wed Thu
Figure 69: Variations in traffic and NO2 / NOx volume ratio in March – April 2013
52
Fri
Sat
Sun
Vol. % NO2 / NOx 3.4 km from Laerdal
30%
25%
20%
15%
10%
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
5%
2013-03-11
2013-03-13
2013-03-15
2013-03-17
Figure 70: Daily variations of the NO2 / NOx volume ratio during week no. 11 in 2013
Normal variations of the NO2/NOx volume ratio in the middle of the Fodnes tunnel during
one week are plotted in figure 70. Values below 10 % were observed when the traffic was
dominated by heavy duty vehicles. Detailed observations during six days in March are given
on the next pages.
Figure 71 and 72: Wednesday 2013-03-13 and 2913-03-27
15 % heavy duty vehicles gave NO2/NOx ratio variations around 15 % on Wednesday 13
March. Similar values were observed in the morning of Wednesday two weeks later. Doubled
traffic of passenger cars in the afternoon lifted the NO2/NOx volume ratio to 25 – 30 %.
0.4 ppm NO2 in the middle of the tunnel started two fans towards Fodnes 10:53 in figure 72.
Average air velocity around 1.0 m/s was sufficient until the NO2-level in the middle of the
tunnel reached 0.6 ppm 14:43 and three new fans started.
Figure 73 and 74: Friday 2013-03-08 and 2913-03-15
Two jet-fans gave sufficient ventilation on Friday 2013-03-08. The fans started four times
when the NO2- concentration reached 0.40 ppm at 3.4 km. The last start at 18:00 was caused
by 0.60 ppm NO2 at 5.5 km. The NO2/NOx volume ratio was near 15 % in the morning and
increased to over 20 % from 11:00 to 13:00. Values near 30 % were observed several times in
the afternoon when the number of heavy duty vehicles was low. The same tendency was
observed on Friday in the following week in figure 74.
Figure 75: Saturday 2013-03-23
Low traffic of heavy duty vehicles gave the highest NO2/NOx volume ratios this week.
Values around 30 % were observed several times at 3.4 km and 5.5 km. The production of
NO2 from oxidation was negligible because the NO-concentration in the south half of the
tunnel was below 1.0 ppm and the average air velocity was over 1.0 m/s.
Figure 76: Easter Sunday 2013-03-31
Easter Sunday had the lowest traffic of heavy duty vehicles in this period with only 3 %
average. Variations of NO2/NOx volume ratios between 30 and 35 % were observed from
13:00 to 18:30. The values are slightly higher than the values at 9.4 km in the Laerdal tunnel
(figure 57 on page 43).
53
Vehicles / hour
200
15
17
21
10
100
94
88
74
7
74
16
25
87
95
26
Length > 7.5 m
18
Length < 7.5 m
22
115
123
18
127
70
71
0
09:00
15:00
18:00
10
39
36
12
46
21:00
Ventilation level in the Fodnes tunnel on Wednesday 2013-03-13
4
Jet-fans
12:00
14
Direction Laerdal
0
06:00
08:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00
4
Direction Fodnes
8
0,80
PPM NO2
NO2 (PPM)
3
0,40
2
25%
% NO2 / NOx
NO (PPM)
0,60
0,20
08:00
1
10:00
12:00
14:00
16:00
18:00
20:00
22:00
3.4 km from Laerdal: Vol. % NO2 / NOx on Wednesday 2013-03-13
NO2/NOx
NO2
NO
PPM
4
3
20%
2
15%
10%
08:00
25%
1
0
10:00
12:00
14:00
16:00
18:00
20:00
NO2/NOx
% NO2 / NOx
PPM NO
4
3.4 km from Laerdal: NO2 and NO on Wednesday 2013-03-13
NO2
22:00
PPM
4
NO
3
20%
2
15%
10%
08:00
1
0
10:00
12:00
14:00
16:00
Figure 71: Ventilation and NO2 / NOx volume ratio on Wednesday 2013-03-13
54
18:00
20:00
22:00
300
14
Vehicles / hour
Length > 7.5 m
Length < 7.5 m14
200
14
56
0
7
9
10
10
13
16
100
150
111
87
09:00
Jet-fans
9
19
14
194
12:00
212
238
243
226
15:00
8
221
166
155
18:00
105
80
21:00
Ventilation level in the Fodnes tunnel on Wednesday 2013-03-27
4
Direction Laerdal
0
08:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00
4
Direction Fodnes
8
PPM NO2
0,8
0,6
NO2
NO
2
0,2
08:00
35%
30%
PPM NO
4
3
0,4
% NO2 / NOx
14
1
10:00
12:00
14:00
16:00
18:00
20:00
NO2 / NOx
NO2
22:00
PPM
3
NO
2
25%
20%
1
15%
10%
08:00
35%
0
10:00
12:00
14:00
16:00
18:00
20:00
NO2/NOx
NO2
NO
22:00
PPM
3
% NO2 / NOx
30%
2
25%
20%
1
15%
10%
08:00
0
10:00
12:00
14:00
16:00
18:00
Figure 72: Ventilation level and NO2 / NOx volume ratio on Wednesday 2013-03-27
55
20:00
22:00
300
Vehicles / hour
Length > 7.5 m
200
100
0
17
6
11
10
7
12
42
75
90
80
07:00
81
90
10:00
10
19
15
12
210
139
104 120
13:00
8
7
156 137
16:00
95
8
79
4
5
54
54
19:00
22:00
4
Jet-fans
21
Length < 7.5 m
Direction Laerdal
0
06:00
08:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00
4
Direction Fodnes
8
0,60
PPM NO2
NO2 (PPM)
NO (PPM)
2
0,40
0,20
06:00
30%
1
08:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00
PPM
3
NO2 / NOx
% NO2 / NOx
PPM NO
3
3.4 km from Laerdal: NO2 and NO on Friday 2013-03-08
NO2 (PPM)
NO (PPM)
25%
2
20%
1
15%
10%
06:00
30%
0
08:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00
PPM
3
NO2 / NOx
NO2 (PPM)
NO (PPM)
% NO2 / NOx
25%
2
20%
1
15%
10%
06:00
0
08:00
10:00
12:00
14:00
16:00
Figure 73: Traffic, ventilation and NO2 / NOx volume ratio on Friday 2013-03-08
56
18:00
20:00
22:00
300
Vehicles / hour
Length > 7.5 m
15
Length < 7.5 m
200
18
100
0
13
48
18
68
14
9
20
8
13
93
126 123 116 104 149
10:00
13:00
87
07:00
188
15
6
155 126
118
16:00
70
3
10
50
40
19:00
22:00
4
Jet-fans
7
17
11
Direction Laerdal
0
06:00
08:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00
4
Direction Fodnes
8
30%
PPM
4
NO2 / NOx
NO2 (PPM)
NO (PPM)
3
% NO2 / NOx
25%
20%
2
15%
1
10%
06:00
30%
0
08:00
10:00
12:00
14:00
16:00
18:00
20:00
PPM
4
NO2 / NOx
NO2 (PPM)
22:00
NO (PPM)
3
% NO2 / NOx
25%
20%
2
15%
1
10%
06:00
0,80
0
08:00
10:00
12:00
14:00
16:00
18:00
20:00
PPM
4
5.5 km from Laerdal: NO2 and NO on Friday 2013-03-15
NO2 (PPM)
22:00
NO (PPM)
3
0,40
2
% NO2 / NOx
0,60
0,20
06:00
1
08:00
10:00
12:00
14:00
16:00
Figure 74: Traffic, ventilation and NO2 / NOx volume ratio on Friday 2013-03-15
57
18:00
20:00
22:00
6 % of 1 961 vehicles were longer than 7.5 m on Saturday 2013-03-23
300
Vehicles / hour
Length > 7.5 m
200
10
7
7
5
147
170
12
5
Length < 7.5 m
8
5
5
99
88
7
100
152
163
189
153
148
85
0
11:00
20:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00
4
Direction Fodnes
NO2 / NOx
% NO2 / NOx
39
Direction Laerdal
35%
NO2 (PPM)
NO (PPM)
PPM
3
30%
2
25%
20%
1
15%
10%
10:00
35%
% NO2 / NOx
46
0
8
0
12:00
14:00
16:00
18:00
20:00
NO2 / NOx
NO2 (PPM)
NO (PPM)
22:00
PPM
3
30%
2
25%
20%
1
15%
10%
10:00
0,80
0
12:00
14:00
16:00
18:00
20:00
22:00
PPM NO
4
5.5 km from Laerdal: NO2 and NO on Saturday 2013-03-23
NO2 (PPM)
PPM NO2
17:00
4
Ventilation level in the Fodnes tunnel on Saturday 2013-03-23
4
Jet-fans
14:00
6
NO (PPM)
0,60
3
0,40
2
0,20
10:00
1
12:00
14:00
16:00
Figure 75: Ventilation and NO2 / NOx volume ratio on Saturday 2013-03-23
58
18:00
20:00
22:00
3 % of 2 475 vehicles were longer than 7.5 m on Easter Sunday 2013-03-31
Vehicles / hour
300
Length > 7.5 m
Length < 7.5 m
200
9
3
13
9
9
3
5
5
1
100
0
6
2
2
21
09:00
33
230
256
245
229
195
222
214
165
125
78
12:00
15:00
18:00
4
6
106
98
21:00
Ventilation level in the Fodnes tunnel on Easter Sunday 2013-03-31
Jet-fans
4
Direction Laerdal
0
12:00
14:00
16:00
18:00
20:00
22:00
4
Direction Fodnes
8
PPM NO2
0,8
0,6
3.4 km from Laerdal: Vol. % NO2 / NOx on Easter Sunday 2013-03-31
PPM NO
4
NO2
NO
3
0,4
2
0,2
12:00
35%
1
14:00
16:00
18:00
22:00
PPM
3
NO2 / NOx
% NO2 / NOx
20:00
NO2 (PPM)
NO
30%
2
25%
1
20%
15%
12:00
40%
0
14:00
16:00
18:00
20:00
22:00
NO2 / NOx
NO2 (PPM)
NO
PPM
3
% NO2 / NOx
35%
2
30%
25%
1
20%
15%
12:00
0
14:00
16:00
18:00
Figure 76: Ventilation level and NO2 / NOx volume ratio on Easter Sunday 2013-03-31
59
20:00
22:00
4 Observations of PM10 and NOx in the Knappe tunnel in Bergen
4.1 Particulate matters (PM) and relative humidity (Rh)
The Knappe tunnel is a 2.5 km long city tunnel with two tubes on a ring road outside Bergen
centre. The average daily traffic in 2012 was 9500 vehicles/day in each direction. Only 5 % of
the vehicles are longer than 7.5 m. The piston-effect from vehicles is giving sufficient
ventilation without start of jet-fans.
The tunnel has two PM-meters with 300 m distance in the north direction and with 950 m
distance in the south direction. Typical PM10-variations and air velocity in both tubes in
January 2011 are plotted in figure 77. Observed values from a week with similar traffic
density in September 2011 are plotted in figure 78 on the next page. The air velocity in the
south part of the tunnel is about 2 m/s higher than the values in the diagram because of the
on/off ramps in the middle of the tunnel. (See length profile at page 14).
µg/m3
600
500
400
300
200
100
0
3.1. 12:00
µg/m3
600
500
400
300
200
100
0
3.1. 12:00
PM10-level in north direction from Monday to Thursday in week no 1, 2011
2.0 km from Dolvik
2.3 km from Dolvik
4.1. 12:00
5.1. 12:00
6.1. 12:00
PM10-level in south direction from Monday to Thursday in week no 1, 2011
1.3 km from Sandeide
4.1. 12:00
5.1. 12:00
6.1. 12:00
Air velocity from Monday to Thursday in week no 1, 2011
6
Wind, m/s
4
2
0
-2
3.1. 12:00
North direction
4.1. 12:00
South direction
5.1. 12:00
Figure 77: PM10-values and air velocity in the Knappe tunnel in January 2011
60
6.1. 12:00
µg/m3
PM10-level in north direction in week no 37, 2011
300
2.0 km from Dolvik
2.3 km from Dolvik
200
100
0
12.9. 16:00
µg/m3
13.9. 16:00
14.9. 16:00
15.9. 16:00
16.9. 16:00
17.9. 16:00
PM10-level in south direction in week no 37, 2011
300
200
100
0
12.9. 16:00
13.9. 16:00
14.9. 16:00
15.9. 16:00
16.9. 16:00
17.9. 16:00
Air velocity in week no 37, 2011
6
Wind, m/s
4
2
0
North direction
-2
12.9. 16:00
13.9. 16:00
14.9. 16:00
15.9. 16:00
South direction
16.9. 16:00
17.9. 16:00
Figure 78: PM10-values and air velocity in the Knappe tunnel in September 2011
From the great variations in PM10-values from one day to the next in week no 1 and 37, it is
clear that the predominant portion of PM10 comes from road dust and not from car exhaust.
The PM10-level varies with air velocity and traffic density. However, the daily variations of
the PM10-level are not proportional to the amount of traffic and do not increase according to
the driven distance from the tunnel entrance . For long periods there is almost no detectable
change of dust-level between the two control-points in each tube.
Use of studded winter tyres in Norway is causing a great difference in PM10-values between
summer and winter months. About 1/5 of the cars in Bergen are using studded tyres from
November to March[18].
18
Statens vegvesen&Bergen kommune: Luftkvalitet i Bergen 2010 (March 2011)
61
The majority of cars have travelled at least five minutes before entering the Knappe tunnel.
Therefore the influence of cold start has been assumed to be low. So far no evidence has been
found for a higher smoke production from the average car engine at low temperatures.
Shifting weather conditions with periods of cold and dry air is giving the highest values of
particulate matters in Norwegian tunnels. The lowest PM-values are often found at the end of
a rainy period when the relative humidity in the tunnel air is over 90 %. An example of high
PM10-values at the end of a cold and dry period in January 2012 is given in figure 79. Two
weeks later the PM10-level had fallen to the same low level as in September 2011.
At high relative humidity, H2O-molecules are absorbed by small dust particles, and the weight
of these particles will increase. Wet dust particles are deposited on all available surfaces in the
tunnel. When the weather changes and the evaporation rate wins over condensation, the small
particles will start flying again in the turbulence and wind from vehicles. In periods with high
PM10-concentrations, there is a significant reduction in the dust-level from morning to afternoon because the traffic is creating sufficient longitudinal wind speed to blow dry particles
out of the tunnel during the middle of the day. Low traffic during the night is creating less
turbulence and not enough wind speed to have any cleaning effect. In cold and dry weather,
the evaporation will continue throughout the night, and the dried dust particles will give a
higher PM10-level the next morning when the traffic produces higher longitudinal air speed
and enough turbulence to start moving of the particles.
µg/m3
PM10-level in north direction from Tuesday to Friday in week no. 5, 2012
1000
2.0 km from Dolvik
800
2.3 km from Dolvik
600
400
200
0
31.1.
µg/m3
1.2.
2.2.
3.2.
PM10-level in south direction from Tuesday to Friday in week no. 5, 2012
1000
800
600
400
200
0
1.31
2.1
2.2
Figure 79: PM10-values in the Knappe tunnel in January 2012
62
2.3
4.2 Observations of NO2 and NO in January 2012
Sensors for NO and NO2 in the northbound tube are located 2.2 km from the south entrance of
the Knappe tunnel after a nearly horizontal section. The sensors in the southbound tube are
located in the 5.9 % uphill section, 2.25 km from the north entrance. A high proportion of the
cars are using the tunnel at the same time every day from Monday to Friday. The morning
rush in the south direction is of same magnitude as the afternoon rush in the north direction.
Observations of NO2 and NO in January 2012 are plotted in figure 80 - 82. NO2-values below
0.20 ppm and NO-values below 0.50 ppm were excluded from the calculation of NO2/NOx
volume ratio because of the unknown accuracy for these values. However, the accuracy of
these calculations is low compared with Laerdal and Fodnes tunnels because the observed gas
values in the Knappe tunnel were below or near the lower detection limit for long periods.
The weekend NO2-level in 2012 was too low to calculate any NO2/NOx ratio with acceptable
accuracy.
PPM NO2
0,50
NO2-concentration in north direction
Wednesday
Thursday
Friday
0,40
0,30
0,20
0,10
2012-01-04
2,0
2012-01-05
NO-concentration in north direction
Wednesday
PPM NO
2012-01-06
Thursday
Friday
1,5
1,0
0,5
2012-01-04
40%
2012-01-05
2012-01-06
% NO2/NOx volume ratio in north direction
Wednesday
Thursday
Friday
30%
20%
10%
2012-01-04
2012-01-05
2012-01-06
Figure 80: Daily variations of NO2, NO and NO2/NOx in the north direction in January 2012
63
PPM NO2
NO2-concentration in south direction
0,50
Wednesday
Thursday
Friday
0,40
0,30
0,20
0,10
2012-01-04
2012-01-05
NO-concentration in south direction
2,0
Wednesday
PPM NO
2012-01-06
Thursday
Friday
1,5
1,0
0,5
2012-01-04
2012-01-05
2012-01-06
% NO2 / NOx volume ratio in south direction
40%
Wednesday
Thursday
Friday
30%
20%
10%
2012-01-04
2012-01-05
2012-01-06
Figure 81: Daily variations of NO2, NO and NO2/NOx in the south direction in January 2012
35%
PPM
NO2 and NO in the south direction on Wednesday, 2012-01-04
NO2 / NOx
NO2 (PPM)
1,80
NO (PPM)
% NO2 / NOx
30%
1,40
25%
1,00
20%
0,60
15%
10%
06:00
0,20
08:00
10:00
12:00
14:00
Figure 82: NO2, NO and NO2/NOx on Wednesday 2012-01-04
64
16:00
18:00
20:00
4.3 Observations of NO2 and NO in March 2013
Variations in the average NO2/NOx volume ratio from Monday to Friday around 16 to 18 %
are near the observed values in the Fodnes tunnel in figure 70 on page 53. The NO-concentration was low on Sunday in figure 83 compared with the values from Monday to Friday
because of very few heavy duty vehicles in the week-end.
NO2-concentration in south direction
0,50
PPM NO2
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
0,40
0,30
0,20
0,10
2013-03-03
2013-03-04
2013-03-05
2013-03-06
2013-03-07
2013-03-08
2013-03-09
NO-concentration in south direction
PPM NO
2,5
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
1,5
0,5
2013-03-03
2013-03-04
2013-03-05
2013-03-06
2013-03-07
2013-03-08
2013-03-09
Vol. % NO2 / NOx in south direction
30%
20%
10%
Sunday
0%
2013-03-03
25 %
Monday
2013-03-04
Sunday
Tuesday
2013-03-05
Wednesday
2013-03-06
2013-03-07
Vol. % NO2/NOx in south direction
Monday
Tuesday
Thursday
Wednesday
Friday
2013-03-08
Thursday
2013-03-09
Friday
20 %
15 %
24 %
17 %
16 %
18 %
10 %
Average 08:00 - 20:00
Figure 83: NO2, NO and average NO2/NOx in south direction in March 2013
65
18 %
18 %
5 Concluding remarks
Heavy duty vehicles (Vehicles > 7.5 m)

The introduction of diesel particulate filters (DPFs) that meet the Euro 5 requirements
for heavy duty vehicles, has given significant reductions of visible air pollution (PM10)
in Norwegian tunnels.

Emission of visible smoke particles from new buses and trucks is negligible when they
are driving at constant speed and with warm engines (hot DPFs).

Road dust is the main contributor to PM10 in tunnels. The highest PM10-levels were
observed in periods with low air humidity.

The average NOx-emission from heavy duty vehicles in the Laerdal tunnel is 4.0 l/km.
This is 20 % below the emission-factor in the Norwegian design guide for tunnels.

The average NO2-emission from heavy duty vehicles is 0.25 l/km (≈ 0.50 g/km)

The average NO2/NOx-ratio in the exhaust gas from heavy duty vehicles is probably
less than 6 % for vehicles produced after 2009 (Euro 5).
Passenger cars (Vehicles < 7.5 m)

Diesel has been the dominant fuel type for new passenger cars since 2007. 42 % of the
passenger cars in Norway had diesel engines in 2012. However, new cars are driven
more than older cars, and the average percentage of diesel-powered passenger cars on
Norwegian roads reached 60 % in 2012.

The average NOx-emission is near 0.30 l/km (≈ 0.44 g/km). This is 100 % over the
emission-factor in the Norwegian design guide for tunnels (March 2010).

The average NO2-emission from passenger cars is 0.10 l/km (≈ 0.20 g/km)

The average NO2/NOx volume ratio has increased from 10 % to over 30 % over the
last ten years.

The average age at the time of scrapping in 2012 was 18.1 years for private cars and
15.0 years for vans[19]. Scrapping of diesel-powered cars from the years 2006 - 2013
(Euro 4 and 5) will give a gradual reduction of the average NO2-emission from
passenger cars from 2020 to 2030.
Appropriate measures
19

In order to provide safe control of air quality in long tunnels, the existing gas-sensors
for NO must be replaced with new sensors for detection of NO2.

The maximum NO-concentration in long tunnels without NO2-sensors should not be
higher than 5 ppm from Friday to Sunday.

The Draeger Polytron sensor for NO2 (tunnel variant) has given acceptable accuracy
for control of ventilation systems in tunnels.
www.ssb.no
66
6 References
AEA Technology:
The Impact of Changes in Vehicle Fleet Composition and Exhaust Treatment Technology on
the Attainment of the Ambient Air Quality Limit Value for Nitrogen Dioxide in 2010
(AEAT/ENV/R/2440 Issue 2)
ec.europa.eu/environment/air/quality/legislation/pdf/report_nox.pdf
Air liquide:
Gas Encyclopaedia www.encyclopedia.airliquide.com
Association for Emissions Control by Catalyst
www.aecc.be/en/Technology/Catalysts.html
(Norwegian) Climate and Pollution Agency
www.klif.no
Luftkvaliteten i Norge
www.luftkvalitet.info/
David C. Carslaw:
Evidence of an increasing NO2/NOx emission ratio from road traffic emissions (Atmospheric
Environment, vol, 39, 2005)
David C. Carslaw:
Road vehicle emissions of NOx and NO2.. Recent evidence concerning NOx and NO2
emissions from road vehicles. Wengen workshop (2011)
http://www.eurochamp.org/datapool/page/198/06%20carslaw%20.pdf
David Carslaw et al. (2011):
Trends in NOx and NO2 emissions and ambient measurements in the UK
http://uk-air.defra.gov.uk/reports/cat05/1108251149_110718_AQ0724_Final_report.pdf
Kameoka, Yohji; Pigford, Robert (February 1977):
Absorption of Nitrogen Dioxide into Water, Sulfuric Acid, Sodium Hydroxide, and Alkaline
Sodium Sulfite Aqueous.
Sillman, S:
The relation between ozone, NOx and hydrocarbons in urban and polluted rural environments.
Millenial Review series, Atmos. Environ., 33, 12, 1821-1845, 1999.
Statens vegvesen & Bergen kommune:
Luftkvalitet i Bergen 2010
Statens vegvesen, Region vest:
E16 Lærdalstunnelen. Kontroll av luftkvalitet og energibruk (2007-10-24)
Statistics Norway
www.ssb.no
TØI-rapport 1168/2011:
NO2-utslipp fra kjøretøyparken i norske storbyer. Utfordringer og muligheter frem mot 2025.
www.toi.no/article30722-4.html
WHO: Air quality guidelines, Global update 2005
www.who.int/phe/health_topics/outdoorair_aqg/en/
WHO: Health Aspects of Air Pollution with Particulate Matter, Ozone and Nitrogen Dioxide
Report on a WHO Working Group, Bonn, Germany, 13–15 January 2003.
www.euro.who.int/document/e79097.pdf
67
Statens vegvesen
Region vest
Ressursavdelinga
Askedalen 4 6863 LEIKANGER
Tlf: (+47 915) 02030
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ISSN: 1893-1162
vegvesen.no
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NO2/NOx volume ratio in three tunnels in Norway

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