Atmospheric Chemistry Measurements at Whiteface Mountain, NY

Aerosol and Air Quality Research, 16: 873–884, 2016
Copyright © Taiwan Association for Aerosol Research
ISSN: 1680-8584 print / 2071-1409 online
doi: 10.4209/aaqr.2015.05.0376
Atmospheric Chemistry Measurements at Whiteface Mountain, NY: Ozone and
Reactive Trace Gases
Richard E. Brandt1, James J. Schwab1*, Paul W. Casson1, Utpal K. Roychowdhury1,
Douglas Wolfe1, Kenneth L. Demerjian1, Kevin L. Civerolo2, Oliver V. Rattigan2,
H. Dirk Felton2
1
Atmospheric Sciences Research Center, University at Albany, State University of New York, Albany and Wilmington, NY
12222, USA
2
Division of Air Resources, New York State Department of Environmental Conservation, Albany, NY 12233, USA
ABSTRACT
Measurements of ozone and reactive trace gases spanning four decades at the Whiteface Mountain summit observatory
are presented. Ozone (O3) measurements began in the mid-1970’s, and acid rain and O3 precursor gas measurements
became routine in the late 1980’s and early 1990’s. Measurements at the lower altitude lodge level have also been
performed routinely since about 2000. The 40-year O3 record shows up and down fluctuations through the 1980’s, a
relatively stable period into the early 2000’s, and indications of a decreasing trend over the past ten years. Sulfur dioxide
(SO2) and carbon monoxide (CO) trends are clearly decreasing over the roughly 25-year period of measurements at the
summit observatory. Oxides of nitrogen (NOy and NO2) show rather more complicated trends, increasing to a maximum in
the mid-2000’s, and decreasing sharply until 2011 with slight increases in concentration since then. Wind rose analysis
shows the greatest contribution to high concentrations of precursor gases are from the west, southwest, and southern
sectors, with SO2 and oxides of nitrogen having the most sharply defined high pollution sectors. Seasonal variations of
trace gas concentrations at the summit and lodge levels are also examined. Ozone concentrations are highest in the spring
months at both locations, and higher at the summit than the lodge. In contrast precursor gases (SO2 and NOx) show highest
concentrations in winter months with the lodge consistently higher than the summit.
Keywords: Air quality; Air pollution; Trend analysis; Seasonal variation; Pollution roses.
INTRODUCTION
Whiteface Mountain is located in the northern part of
the Adirondack State Park in upstate New York, North
America. On Whiteface summit (1483 m) is the University of
Albany’s Atmospheric Sciences Research Center’s (ASRC)
observatory, where meteorology and atmospheric chemistry
monitoring have taken place for over four decades. Trace
gas monitoring of ozone (O3) started in 1974 (Mohnen et
al., 1977); and measurements of carbon monoxide (CO),
sulfur dioxide (SO2), and oxides of nitrogen (NO, NO2 and
NOY) began in earnest in the late 1980’s to develop an
understanding of transport and chemical processing of
atmospheric pollutants; and to quantify the efficacy of
pollution control policy (Parrish et al., 1993; Trainer et al.,
*
Corresponding author.
Tel.: 518.437.8754; Fax: 518.437.8758
E-mail address: [email protected]
1993). Aerosol, precipitation, and cloud chemistry sampling
complement the trace gas monitoring and collectively these
observations contribute to our understanding of ozone and
PM2.5 pollution, acid precipitation chemistry and to the
deposition processes of atmospheric pollutants (Schwab et
al., 2016b). These measurements, and the trend data produced
over long measurement periods are important as states and
nations continue air pollution reductions to protect human
health and the environment, and mitigate climate change
(these pollutants variously act as absorbers or scatterers of
incoming and outgoing radiation, thereby affecting the
planet’s radiative balance).
As noted in our companion paper (Schwab et al., 2016a)
mountain top observatories offer a number of advantages
for air pollution measurements. Most importantly, this site
is located hundreds of km from any major pollution sources,
so it is a good indicator of regional background, air quality
and provides an opportunity to check the response to regional
emission controls as well as providing measurement data for
the validation of air quality modeling results. These
characteristics along with the long data record are the main
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Brandt et al., Aerosol and Air Quality Research, 16: 873–884, 2016
reason for the extensive use of Whiteface Mountain data in
numerous publications over the years (Logan, 1989; Lefohn
et al., 1990; Aneja and Li, 1992; Cooper et al., 2012; Cooper
et al., 2014). Whiteface summit is a lone massif peak, north
of the main group of Adirondack high peaks, and typically
influenced by aged air masses that predominantly flow
from the west and southwest transporting emissions from
source regions in the Midwest. Less typical northerly flows
are associated with clean air from Canada and the arctic.
These two distinct source regions provide a clear contrast
between polluted air masses originating in the south and
Midwest versus generally clean air from the north - which
is an indicator of background pollution levels. In this paper,
the Whiteface Mountain sites are presented as locations where
trace gas chemistry measurements have been performed for
decades and are ongoing.
Ozone trends at remote mountain sites have attracted
additional interest in recent years, and this has been
accentuated by the recent decision of the USEPA to lower
the National Ambient Air Quality Standard for ozone to 70
ppb over an eight hour period (EPA, 2015). Due to the fact
that such sites have large fetches and are sometimes or even
frequently sampling air from the free troposphere, scientists
often use these sites as an indication of the “North
American Background” ozone levels, defined as the ozone
levels that would be present in the absence of North American
anthropogenic emissions (Jaffe et al., 2004; Fiore et al.,
2014). This very important parameter has a large impact
on the ability of states and metropolitan areas to meet ever
more stringent ozone standards.
Over the course of these long term observations trace-gas
analyzers and data acquisition systems have been upgraded to
take advantage of improved accuracy and updated signal
processing and I/O with onboard digital computers. With a
general decrease in pollution levels, analyzers with enhanced
sensitivity, such as Thermo and Teledyne API trace-level
instruments have been implemented. Data acquisition and
storage, initially using on-site magnetic tape, have been
updated with internet capable dataloggers such as the
Campbell CR3000 that upload data files daily; and can be
accessed directly via a web interface which greatly improves
the response time to problems with the instrumentation and
data stream.
SITE DESCRIPTION
Whiteface Mountain’s summit is located at 44.366°N
73.903°W in northeast New York State (NYS) in the
Adirondack State Park at an elevation of 1483 m above sea
level. In 1970 the ASRC built a four story cylindrical
observatory on the summit of Whiteface Mountain to support
experimental studies in meteorology and atmospheric
chemistry. A collaboration of agencies have provided support
for the observatory including New York State Department
of Conservation (DEC) on whose property it resides, The
Olympic Regional Development Authority (ORDA)
provides power and logistical support, and long-term funding
support is from the New York State Energy Research and
Development Authority (NYSERDA). The summit is
surrounded by forested lands owned by NYS; the nearest
hamlet is Wilmington, population 1300, 10 km to the
southeast. Site operators travel to the observatory at least
weekly year-round to calibrate instrumentation, collect
samples, and provide upkeep.
ASRC operates two environmental monitoring sites at
this location. The Marble Mountain Lodge site is located
on the eastern shoulder of the Whiteface Massif at 44.393°N
and 73.859°W with an elevation of 604 m above sea level.
Headquarters, offices and laboratories for the operation are
located at the lodge level. The Marble Lodge measurement
site is situated in a clearing of a wooded area that consists
primarily of a mixed Northern Hardwood forest type.
Additional details and a map showing the location are in
our companion paper (Schwab et al., 2016a).
PARAMETERS MEASURED: INSTRUMENT,
SAMPLING, AND METHOD DESCRIPTION
Trace gases monitored at Whiteface include O3, CO,
SO2, NO, NO2 and NOY. Tables 1(a) and 1(b) list the gases
measured year round and pertinent information for the
summit and lodge sites, respectively. A timeline and
additional instrument and method details are presented in
Tables S1 and S2 (except for ozone, which is addressed
below). Other parameters not discussed in this paper are
also measured, and many of the condensed phase species
are presented and discussed in a companion paper (Schwab
et al., 2016b). Thermo Environmental (TEI) and Teledyne
API continuous trace gas analyzers have been the instruments
of choice due to the reliability and design modifications
employed to measure ever lower concentration levels. Even
these instruments are severely challenged to measure the
quite low concentrations often experienced at both summit
and lodge locations. In addition to the gas concentration
measurements, basic meteorological parameters such as
temperature, relative humidity, wind speed, wind direction,
and barometric pressure are measured and recorded at each
location.
Two TEI 42CTL analyzers monitor nitrogen oxides at
the summit, and both have been modified to 1) improve
specificity for NO2 through use of photolytic conversion to
NO; and 2) reduce sampling losses of nitric acid and other
“sticky” oxides of nitrogen by relocation of the heated
molybdenum converter. For NO2 conversion, an Air Quality
Design UV photolytic converter replaces the standard heated
molybdenum converter. For NOY conversion the heated
molybdenum converter has been moved out of the analyzer
to within 20 cm of the intake manifold to minimize sample
exposure to long inlet lines and valves and tubing within
the 42CTL.
At the summit observatory ambient air for the NOx (NO
+ NO2), SO2, and CO analyzers is sampled from a 6 m
FEP Teflon 36 mm diameter tube that extends 1.6 m above
the observatory’s roof with an FEP lined stainless-steel cap
to protect from precipitation. A Dayton blower capable of
50 CFM in free air is installed at the downstream end of
the sample manifold which is simply four press-fit holes in
the 36 mm FEP tube. Exhausts from the Dayton blower,
Brandt et al., Aerosol and Air Quality Research, 16: 873–884, 2016
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Table 1(a). List of gaseous parameters, methods, and instruments for current measurements at the Whiteface summit
observatory.
START DATE PARAMETER
1974
O3
1995
NO
PHASE
Gas
Gas
1994
NO2
Gas
1989
NOY
Gas
1989
CO
Gas
1992
SO2
Gas
METHOD AND INSTRUMENT
AGENCY FREQUENCY
UV optical absorption, TEI Model 49C
DEC
Continuous
Chemiluminescence, TEI Model 42CTL
ASRC
Continuous
Photolytic conversion, then
ASRC
Continuous
chemiluminescence, TEI Model 42CTL
Heated Mo conversion, then
ASRC
Continuous
chemiluminescence, TEI Model 42CTL
Gas filter correlation – NDIR, Teledyne API
ASRC
Continuous
Model 300EU
Pulsed fluorescence, TEI Model 43CTL
ASRC
Continuous
Table 1(b). List of gaseous parameters, methods, and instruments for current measurements at the Marble lodge site.
START DATE PARAMETER
1984
O3
2002
NO
PHASE
Gas
Gas
2002
NO2
Gas
2009
CO
Gas
METHOD AND INSTRUMENT
UV optical absorption, TEI Model 49C
Chemiluminescence, TEI Model 42i
Heated Mo conversion, then
chemiluminescence, TEI Model 42i
Gas filter correlation – NDIR,
TEI Model 48CTL
Pulsed fluorescence, TEI Model 43C
1984
SO2
Gas
Agency Acronyms for Table 1:
ASRC – Atmospheric Sciences Research Center;
DEC – Department of Environmental Conservation (New York State).
analyzers, and calibration systems are collected in a 10 cm
diameter PVC exhaust manifold, then exhausted through a
Soler & Palau in line duct fan. The exhaust fan is capable
of 293 CFM in free air to ensure wind caused pressure
differences will not cause flow reversal. The inlet to the O3
instrument is a 1/2" diameter PFA tube from the roof about
6 m length which is stepped to ¼" diameter with a PFA fitting
and an inline 5 m pore size PTFE Teflon filter feeding the
sample port of the analyzer. 5 m pore size PTFE Teflon
filters are also used on the sample lines for other analyzers
to avoid particulate contamination of the analyzer optics.
At the lodge level, the sampling manifold is a 5 cm diameter
glass manifold maintained by NYSDEC.
Two-point calibration of the trace gas analyzers is done
manually on a weekly schedule. DEC staff calibrates and
maintains the 49C O3 analyzers, while ASRC operates the
CO, SO2 NO/NO2 and NOY analyzers at the summit and
CO and NOx analyzers at the lodge. The 49C O3 analyzer is
checked, audited, and calibrated when required using a DEC
certified calibrator, while the other analyzers are calibrated
with custom dynamic dilution calibration systems that use
Tylan mass flow controllers set with Tylan control boxes,
Furon PTFE or Kip stainless steel valves, PTFE mixing
chambers and either Scott-Marin primary standard calibration
gas cylinders (CO and NO) or VICI certified permeation tube
systems (SO2 and NO2). The SO2 permeation device is kept
at a stable output using a flow and temperature controlled
Kin-Tek oven while the NO2 permeation device is installed
in a PTCS-2 oven with an internal Tylan mass flow controller.
Calibration valves are actuated either manually on site or
automatically by a Campbell CR3000 data logger. Automatic
AGENCY FREQUENCY
DEC
Continuous
ASRC
Continuous
ASRC
Continuous
ASRC
Continuous
DEC
Continuous
calibration checks for ASRC operated instruments (see
Table 1) occur four times daily at the summit observatory
and once daily at Marble lodge. Calibration worksheets,
based on pdf forms, are easily compiled to a database to
streamline data processing which uses calibration coefficients
and calibration checks to correct for analyzer drift and to
assign QA flags. Calibrator flow controllers are audited
annually and corrections are employed to ensure stable and
accurate calibrations. Analysis of raw 1-minute average
data collected with the CR3000 provides annual tables of
1-hour average data and QA flags following the format of
the North American Research Strategy for Tropospheric
Ozone (NARSTO) data archival protocol. Trace gas and
meteorological data are available as 1-hour averages with a
QA flag for each parameter. The data files are individual
annual compilations in NARSTO format and are delimited
with commas for convenient importing into data analysis
programs. These files are stored on an ASRC server and
are available upon request. Meteorological data include air
and dew point temperatures, wind speed, wind direction
and barometric pressure.
Constancy of calibration procedures and activities are
critical to the establishment of credible long-term data sets.
As mentioned above, the summit ozone analyzer is calibrated
and audited by NYS DEC using established procedures and
following US EPA protocols. The original ozone analyzer
was of the ethylene chemiluminescence type, and this method
remains the Federal Reference Method for measurement of
gaseous ozone. In 1985, the ozone analyzer changed to the
ultraviolet absorption method, and has been this method
since that time. The UV absorption method has been
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Brandt et al., Aerosol and Air Quality Research, 16: 873–884, 2016
designated a Federal Equivalence Method for measuring
gaseous ozone. Other gas analyzers are calibrated by ASRC
staff using certified gas standards and dynamic gas dilution
methods at least weekly. Certified standards include NIST
traceable gas mixtures and/or certified permeation devices.
Flowmeters used for calibrations are calibrated as needed,
and at least annually.
TRENDS ANALYSIS
Annual box plots of O3, NOy, CO, SO2, and NO2 mixing
ratios at the summit observatory are shown in Figs. 1–5,
with data completeness represented by the box shading. The
O3 data makes up the longest data record, with reasonably
complete data starting in 1976. A five year running mean
trace is added to this box plot as a guide to the eye for this
data set. There is some indication of year-to-year variability,
but such excursions are small – generally 1–2 ppb in the
mean value, and rarely more than 4 ppb. The earliest part
of the data record is the exception to this relative slow
variation, exhibiting a large increase (~10 ppb) in the late
1970’s followed by equally large decrease through 1983,
before slowly rising again in the late 1980’s that lasted
about 15 years. The relatively lower data completeness for
those initial years may impact the mean values, although
examination of the 1976 data showed the missing data was
fairly well distributed throughout the year. The last ten years
(2005–2014) have seen a decrease in the annual average
ozone of about 4 ppb at the summit, as well as a decrease
in the standard deviation of ozone values (Fig. S1). The
decrease in standard deviation is due to the reduction of
regional emitted ozone precursor gases (most notably NOx),
and the corresponding reduced frequency of summertime
high concentration ozone events, as well as the increasing
convergence of summertime and wintertime ozone levels
which will discussed later. We will show later that the
decrease in annual average is not spread equally across all
seasons, but is most dramatic in the warm season.
This and numerous other long-term data sets for remotely
observed tropospheric ozone are presented and discussed
by Cooper et al. (2014). Whiteface is similar to the other
eastern U.S. sites in that study for the period 1980–2010
with a slightly positive, but statistically insignificant trend
in ozone. Like Whiteface, the eastern U.S. and European
stations are more likely to exhibit downward ozone trends
since 1990 or 2000, but many of these nascent trends are
not statistically significant (Cooper et al., 2014). This can
be contrasted with long-term sites in the western U.S. and
mid-Pacific (namely Lassen National Park (CA), Joshua
Tree National Park (CA), and Mauna Loa (HI)), where the
ozone trend is increasing (and statistically significant) up
to 2010.
The SO2 trend shown in Fig. 2 provides a clear picture
of the success, albeit sometimes in fits and starts, of Clean
Air Act (CAA) regulation of major point source emissions
of SO2 (these sources are dominated by power plants or
electricity generating units). After SO2 concentrations at
the summit observatory peaked in the early 1990’s, there
was a marked drop in the late 1990’s after the phased in
implementation starting in 1995 of the 1990 CAA
Amendments Title IV Phase 1 reductions, followed by a
flattening out over the next few years due to relatively high
emission caps and trading of emissions allowances. Phase
II of the CAA Amendments began in 2000, and another
Fig. 1. Whiteface Mountain Summit O3 annual box plot for the period 1975 to 2014. The box encompasses the interquartile
range of hourly values, and mean and medians are shown as horizontal line segments.
Brandt et al., Aerosol and Air Quality Research, 16: 873–884, 2016
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Fig. 2. Whiteface Mountain Summit SO2 annual box plot for the period 1992 to 2014. The details are as in Fig. 1. The
years noted with the shaded bars labeled P1 and P2 are the implementation periods for Phase I and Phase II of the SO2
emission reductions mandated by the Clean Air Act Amendments of 1990.
strong decrease in emissions shows up after 2005, when the
regulations were fully implemented. These implementation
periods are denoted on Fig. 2 with shaded bars labeled P1
and P2. Emissions for SO2 are shown for the Northeast
U.S. in Fig. S2 and more completely for the entire U.S. by
Hand et al. (2012). On the whole, the measured ambient
concentrations reflect the emissions from large electricity
generating units in the Midwest and northeast states of the
U.S. As shown in our companion paper (Schwab et al.,
2016a), and in greater detail in Fig. S2 for the period 1990–
2010 and S3 for the period 1994–2010, there is a strong
association between the gaseous SO2 measurements at the
summit observatory, and the northeast U.S. emissions of
SO2 taken from Xing et al. (2013). These two quantities are
correlated with an R2 (coefficient of determination) of 0.88.
Fig. 3 shows that CO, also emitted from combustion
sources, has also been trending down since the 1990’s.
Whereas SO2 is mainly from electricity generating units,
CO emissions are mostly from motor vehicles. This means
that CO emissions cannot be as easily and completely
regulated as SO2 emissions, but the downward trend clearly
indicates more efficient combustion in the areas upwind of
Whiteface. We have not found a suitable explanation for
the seemingly anomalous CO mixing ratios measured in
2000, but consider that year an outlier.
Oxides of nitrogen, NOy and NO2, shown in Figs. 4 and 5,
have a quite different and complicated variation over time
when compared to the previous three species. Fig. 4 shows
that NOy mixing ratios at the summit observatory increased
slowly through the 1990’s and early 2000’s, peaking in the
mid-2000’s. Large reductions in NOy concentrations were
realized in the late 2000’s, due at least in part to the US
EPA’s NOx Budget Program and the Clean Air Interstate
Rule. These programs only account for a fraction of the total
NOx emissions in the US, since mobile source account for
nearly 60% of the NOx emissions in the latest 2011 National
Emissions Inventory (http://www.epa.gov/ttnchie1/net/20
11inventory.html). Although the increase that is showing up
over the last three years for both NO2 and NOy is difficult to
fully explain, note that regulated NOx emissions have
largely leveled out since 2009, and there was even a slight
uptick in 2010 (http://www3.epa.gov/airmarkets/progress/
reports/emissions_reductions_nox.html#figure1), which means
that year to year variations could produce one or more years
with higher concentration than the previous year. The three
consecutive years of increased values would be unlikely
even in this scenario, and no definitive explanation of this
level of sustained increase has been found. Still, even with
these recent puzzling results, the NOy trend over the last
ten and even the last twenty years is downward, as would be
expected from the emissions reductions in the U.S. required
by EPA.
Gas concentrations measured at the Marble lodge site
have a much shorter data record, beginning in earnest around
2000. An interquartile range box plot of the O3 measurements
at the Marble lodge site form 2001–2014 is presented as
Fig. 6. Peak O3 mixing ratios, as reflected in the 90th
percentile whiskers, show a statistically significant decrease
over this period (p = 3.7 × 10–5), while average O3 mixing
ratios have been relatively flat.
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Fig. 3. Whiteface Mountain Summit CO annual box plot for the period 1989 to 2014. The details are as in Fig. 1.
Fig. 4. Whiteface Mountain Summit NOY annual box plot for the period 1989 to 2014. The details are as in Fig. 1.
WIND SECTOR ANALYSES
An important tool for beginning to understand the source
of pollutant gases to a location is the wind sector analysis
technique, in which mean pollutant concentrations for a
given set of wind direction ranges is displayed on a radial
plot. What is important here is the notion of prevailing
mean wind direction over relatively long transport distances
(10’s of km and more). Unfortunately, wind sensors located
at the summit of Whiteface often experience strong local
Brandt et al., Aerosol and Air Quality Research, 16: 873–884, 2016
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Fig. 5. Whiteface Mountain Summit NO2 annual box plot for the period 1994 to 2014. The details are as in Fig. 1.
Fig. 6. Marble Lodge O3 annual box plot for the period 2001 to 2014
perturbations and turbulence, due to mountain orography,
radiative effects, and other flow disturbing phenomenon. For
this reason we have elected to use 3-hour National Center
for Environmental Prediction/North American Regional
Reanalysis (NCEP/NARR) reanalysis data for the wind
directions at Whiteface summit (Mesinger et al., 2006).
Fig. 7 illustrates the pollution roses over eight wind sectors
for the Whiteface summit trace gas measurements from the
beginning of record through 2010. SO2 has a highly
skewed radial distribution of pollutants, NO, NO2 and NOy
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Brandt et al., Aerosol and Air Quality Research, 16: 873–884, 2016
distributions are moderately skewed, and CO and O3
distributions are much closer to radially symmetric. Fig. 9
shows the change over time of the directional component
of the SO2 mixing ratio. For SO2 the dominant contribution is
consistently from the west and southwest sectors, but the
change in magnitude is striking, and appears even more
impressive than shown in Fig. 2. The largest SO2 sources
in the EPA power plant emissions database are to the
southwest, as shown in Fig. S7 (http://www.epa.gov/airm
arkets/progress/datatrends/index.html). The largest sources
in this region have reduced their collective emissions by an
average of greater than 90% between 1990 and 2014. Time
evolution pollution rose plots for other gases are in the
supplementary material (see Figs. S4–S6).
SEASONAL DEPENDENCE OF TRACE GAS
CONCENTRATIONS
Monthly averaged O3 mixing ratios for the ten-year period
2005–2014 measured at both the summit and lodge stations
are presented in Fig. 9. Ozone is significantly higher in the
spring as compared to all other seasons at these locations,
Fig. 7. Whiteface Mountain Summit mean directional trace gas mixing ratio for each trace gas from the beginning of
record to 2010. Wind direction retrieved from 3-hour NCEP reanalysis data.
Fig. 8. Whiteface Mountain Summit mean directional SO2 mixing ratio for three time periods from 1989 to 2010.
Brandt et al., Aerosol and Air Quality Research, 16: 873–884, 2016
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Fig. 9. Whiteface Mountain Summit and Lodge O3 averaged by month for the consolidated period 2005 to 2014.
due in part to enhanced transport from the stratosphere
(which is greatest in the spring, but only accounts for a
very small increment at Whiteface – see Mohnen et al.,
1977), and in part due to the enhanced spring production
while NOx is still high and biogenic VOC’s are entrained
in a somewhat lower boundary layer than during summer.
Ozone is lowest in late fall and early December as might
be expected due to lower photochemical activity, but the
higher mixing ratios in January and February do not fit the
standard picture of higher ozone in the warm season. We
speculate that very low boundary layer heights during winter,
combined with snow enhanced albedo for photochemistry,
may lead to higher than expected wintertime ozone
production on a much smaller scale than that seen in the
Unitah Basin in Utah (Ahmadov et al., 2014). Summit O3
is systematically higher than lodge O3, from roughly two
to as many as five ppb on average. A major contributor to
this difference is the much greater surface deposition to the
forested surroundings of the lodge site as contrasted with
the rocky summit. Since NOx reacts with and titrates O3,
the higher NOx at the Lodge could be a contributing factor
for lower O3. Also the seasonal differences in the boundary
layer as mentioned below likely impacts the O3.
Fig. 10 presents the seasonal variation of SO2, a primary
pollutant gas, at both summit and Marble Lodge sites for
the years 2005–2014. The Marble Lodge data exhibit a very
strong seasonal dependence, with concentrations more than
twice as high in the cold season months of January and
February than in the warm season months of May, June,
and July. This typically seen seasonal pattern is due to 1)
more active photochemical removal in summer (both gas
phase and aqueous), combined with 2) stronger combustion
sources and 3) lower boundary layer heights in winter. The
seasonal variation at the summit is much less pronounced
with winter concentrations only about 50% higher than in
summer. The more regional character of the mountaintop
summit site helps to explain the smaller seasonal variation,
since more long range transport, and therefore greater
photochemical aging of the sampled air play much greater
roles. The reaction rates are faster in the summer months
(for both gaseous and aqueous oxidation) leading to lower
concentrations in the warm season. However, wintertime
local source and boundary layer height effects are much
reduced, resulting in a weaker seasonal dependence.
In contrast to O3, these primary pollutants are
systematically higher at the lodge site, which is more
influenced by local sources and more “connected” to the
surface boundary layer. The summit, in contrast, is much
more likely to be separated from the surface layer, residing in
the mixed layer and even at times the free troposphere. Hence
the summit, on average, reflects more aged and oxidized air,
with lower levels of precursor gases like SO2 and NOx.
The seasonal dependence of O3 measured at the summit
observatory over the full data record is presented in Fig. 11,
and as box plots in Figs. S8–S11. The most striking feature
in this figure is the opposite behaviors of the summer and
winter averages. The summer month average was just
slightly higher than the spring average for the first part of
the data record, until about 1990. Since then, the summer
period has experienced steadily decreasing O3 mixing ratios,
while there is little change in the spring period. The difference
in the mean O3 for the spring and summer periods is currently
greater than 5 ppb. Part or most of this summertime decrease
can be attributed to the NOx SIP call program issued in
1998 and implemented in 2003 (Aleksic et al., 2013). Cooper
et al. (2012) analyzed the O3 data for this and many other
rural North American sites for the period 1990–2010, and
found similar results. At the same time, O3 during the winter
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Brandt et al., Aerosol and Air Quality Research, 16: 873–884, 2016
Fig. 10. Whiteface Mountain Summit and Lodge SO2 averaged by month for the consolidated period 2005 to 2014.
Fig. 11. Whiteface Mountain Summit annual and seasonal mean O3 time-series smoothed using a 5-year running average.
months (DJF) has been slowly creeping up, approximately
2 or 3 ppb since the stable period in the late 1980’s and early
1990’s. From a simple p-value significance test, both the JJA
and DJF linear trends are significant (p-values of 0.00005
and 0.006, respectively). However, the r-squared values of the
trend lines are low (0.34 and 0.16), so these trends may not be
considered “statistically meaningful” (Bryhn and Dimberg,
2011). The wintertime increase, if it continues and reaches a
meaningful threshold, could indicate an increase in global
or continental background ozone, due to global emission
increases and/or changing climate (Lefohn et al., 1992;
IPCC, 2013; Eyring et al., 2013; Shindell et al., 2013).
SUMMARY
Whiteface Mountain has been an active center of longterm research quality measurements of O3 and related trace
gases with year-round measurement activity beginning in the
1970’s. The measurements of reactive trace gases occurs at
two locations on the mountain, the summit observatory site
and the Marble Mountain Lodge site; and is a collaborative
effort between the SUNY Albany Atmospheric Sciences
Research Center and the New York State Department of
Environmental Conservation. This research activity has
established long-term data sets on ozone and ozone precursors
Brandt et al., Aerosol and Air Quality Research, 16: 873–884, 2016
that provide an important window on the changing remote
background atmospheric environment in eastern North
America in the late 20th and early 21st centuries. The longest
continuous data record is for ozone mixing ratio measured
at the summit observatory, and this four decade time series
shows an increase in the late 1970’s, followed by a decrease
and recovery in the 1980’s. This was followed by a
roughly 20 year period of little change, and indications of a
decrease in starting around 2005. When examined as seasonal
averages, the summertime summit O3 concentrations exhibit
a clear decrease, especially in the past decade. In contrast,
wintertime O3 has not decreased, and even shows a
tendency toward increasing values.
Significant reductions in summit observatory SO2 and
CO concentrations (attributed to reduced emissions) have
been observed over the past two and a half decades. NOy
measured at the summit has decreased more modestly, and
there is no clear trend (and even hints of a recent increase)
in NOx concentrations. The same species measured at summit
and lodge level shows similar seasonal variation of monthly
averaged values. Ozone peaks in the spring, while primary
pollutants (SO2, NOx, and CO) peak during winter. Ozone
concentrations are systematically higher at the summit than
the lodge, while the opposite is true for SO2 and NOx.
Analysis of pollution roses for the summit observatory
indicates the largest pollution sources for this location are
located in the west, southwest, and south sectors.
ACKNOWLEDGEMENTS
This work has been supported by the New York State
Energy Research and Development Authority (NYSERDA),
the United States Environmental Protection Agency
(EPA), the New York State Department of Environmental
Conservation (DEC), and others over the years. Special
thanks to Mr. Richard Lamica, Ms. Shari Kent, Mr. Kenneth
Eckhardt, and many others who have been part of the
Whiteface team. Thanks also to Conor Lahif of the National
Weather Service for providing the NCEP reanalysis winds.
DISCLAIMER
Although this manuscript was reviewed internally, it
does not necessarily reflect the views or policies of the
DEC or supporting agencies.
SUPPLEMENTARY MATERIALS
Supplementary data associated with this article can be
found in the online version at http://www.aaqr.org.
REFERENCES
Aleksic, N., Ku, J.Y. and Sedefian, L. (2013). Effects of
the NOx SIP Call Program on Ozone Levels in New
York. J. Air Waste Manage. Assoc. 63: 1335–1342, doi:
10.1080/10962247.2013.824392.
Ahmadov, R., McKeen, S., Trainer, M., Banta, R., Brewer,
A., Brown, S. Edwards, P.M., deGouw, J.A., Frost, G.J.,
883
Gilman, J., Helmig, D., Johnson, B., Karion, A., Koss,
A., Langford, A., Lerner, B. Olson, J., Oltmans,S., Peischl,
J., Pétron, G., Pichugina, Y., Roberts, J.M, Ryerson, T.,
Schnell, R., Senff, C., Sweeney, C., Thompson, C.,
Veres, P.R., Warneke, C., Wild, R., Williams, E.J., Yuan,
B. and Zamora, R. (2015). Understanding High Wintertime
Ozone Pollution Events in an Oil- and Natural Gasproducing Region of the Western US. Atmos. Chem.
Phys. 15: 411–429, doi: 10.5194/acp-15-411-2015.
Aneja, V.P. and Li, Z. (1992). Characterization of Ozone
at High Elevation in the Eastern United States: Trends,
Seasonal Variations, and Exposure. J. Geophys. Res. 97:
9873–9888.
Bryhn, A.A. and Dimberg, P.H. (2011). An Operational
Definition of a Statistically Meaningful Trend. PLoS
One 6: e19241, doi: 10.1371/journal.pone.0019241.
Cooper, O.R., Gao, R.S., Tarasick, D., Leblanc, T. and
Sweeney, C. (2012). Long-term Trends at Rural Ozone
Monitoring Sites across the United States, 1990-2010. J.
Geophys. Res. 117: D22307, doi: 10.1029/2012JD018261.
Cooper, O.R., Parrish, D.D., Ziemke, J., Balashov, N.V.,
Cupeiro, M., Galbally, I.E., Gilge, S., Horowitz, L.,
Jensen, N.R., Lamarque, J.F., Naik, V., Oltmans, S.J.,
Schwab, J., Shindell, D.T., Thompson, A.M., Thouret, V.,
Wang, Y. and Zhinden, R.M. (2014). Global Distribution
and Trends of Tropospheric Ozone: An Observation-based
Review. Elem. Sci. Anth. 2: 000029, doi: 10.12952/jour
nal.elementa.000029.
Environmental Protection Agency (EPA) (2015)
Regulatory Action for Ground Level Ozone.
http://www3.epa.gov/ozonepollution/actions.html.
Eyring, V., Arblaster, J.M., Cionni, I., Sedlacek, J., Perlwitz,
J., Young, P.J., Bekki, S., Bergmann, D., CameronSmith, P., Collins, W.J., Faluvegi, G., Gottschaldt, K.D.,
Horowitz, L.W., Kinnison, D.E., Lamarque, J.F., Marsh,
D.R., Saint-Martin, D., Shindell, D.T., Sudo, K., Szopa,
S. and Watanabe, S. (2013). Long-term Ozone Changes
and Associated Climate Impacts in CMIP5 Simulations.
J. Geophys. Res. 118: 5029–5060, doi: 10.1002/jgrd.50316.
Fiore, A.M., Oberman, J.T., Lin, M.Y., Zhang, L., Clifton,
O.E., Jacob, D.J., Naik, V., Horowitz, L.W., Pinto, J.P.
and Milly, G.P. (2014). Estimating North American
Background Ozone in U.S. Surface Air with Two
Independent Global Models: Variability, Uncertainties,
and Recommendations. Atmos. Environ. 96: 284–300,
doi: 10.1016/j.atmosenv.2014.07.045.
Hand, J., Schichtel, B.A., Malm, W.C. and Pitchford, M.L.
(2012). Particulate Sulfate ion Concentrations and SO2
Emission Trends in the United States from the Early
1990s through 2010. Atmos. Chem. Phys. 12: 10353–
10365, doi: 10.5194/acp-12-10353-2012.
IPCC (Intergovernmental Panel on Climate Change)
(2013). Working Group I Contribution to the IPCC Fifth
Assessment Report, “Climate Change 2013: The Physical
Basis”, http://www.ipcc.ch.
Jaffe, D., Price, H., Parrish, D., Goldstein, A. and Harris, J.
(2003). Increasing Background Ozone during Spring on
the West Coast of North America. Geophys. Res. Lett.
30: 1613, doi: 10.1029/2003GL017024.
884
Brandt et al., Aerosol and Air Quality Research, 16: 873–884, 2016
Lefohn, A.S., Shadwick, D.S. and Mohnen, V.A. (1990).
The Characterization of Ozone Concentrations at a
Select Set of High-Elevation Sites in the Eastern United
States. Environ. Pollut. 67: 147–178.
Lefohn, A.S., Shadwick, D.S., Feister, U. and Mohnen,
V.A. (1992). Surface-Level Ozone: Climate Change and
Evidence for Trends. J. Air Waste Manage. Assoc. 40:
136–144, doi: 10.1080/10473289.1922.10466975.
Logan, J.A. (1989). Ozone in Rural Areas of the United
States. J. Geophys. Res. 94: 8511–8532.
Mesinger, F., DiMego, G., Kalnay, E., Mitchell, K., Shafran,
P.C., Ebisuzaki, W., Jovic, D., Kistler, R. Woollen, J.,
Rogers, E., Berbery, E.H., Ek, M.B., Fan, Y., Grumbine,
R., Higgins, W., Li, H., Lin, Y., Manikin, G., Parrish,
D.D. and Shi, W. (2006). North American Regional
Reanalysis. Bull. Am. Meteorol. Soc. 87: 343–360, doi:
10.1175/BAMS-87-3-343.
Mohnen, V.A., Hogan, A. and Coffey, P. (1977). Ozone
Measurements in a Rural Area. J. Geophys. Res. 82:
5889–5895.
Parrish, D.D., Buhr, M.P., Trainer, M., Norton, R.B.,
Shimshock, J.P., Fehsenfeld, F.C., Anlauf, K.G.,
Bottenheim, J.W., Tang, Y.Z., Wiebe, H.A., Roberts,
J.M., Tanner, R.L., Newman, L., Bowersox, V.C.,
Olszyna, K.J., Bailey, E.M., Rodgers, M.O., Wang, T.,
Berresheim, H., Roychowdhury, U.K. and Demerjian,
K.L. (1993). The Total Reactive Oxidized Nitrogen Levels
and Partitioning between Individual Species at Six Rural
Sites in Eastern North America. J. Geophys. Res. 98:
2927–2939.
Schwab, J.J., Wolfe, D., Casson, P., Brandt, R., Demerjian,
K.L., Husain, L., Dutkiewicz, V.A., Civerolo, K.L. and
Rattigan, O.V. (2016a). Atmospheric Science Research
at Whiteface Mountain, NY: Site Description and
History. Aerosol Air Qual. Res. 16: 827–840.
Schwab, J.J., Casson, P., Brandt, R., Husain, L., Dutkewicz,
V., Wolfe, D., Demerjian, K.L., Civerolo, K.L., Rattigan,
O.V., Felton, H.D. and Dukett, J.E. (2016b). Atmospheric
Chemistry Measurements at Whiteface Mountain, NY:
Cloud Water Chemistry, Precipitation Chemistry, and
Particulate Matter. Aerosol Air Qual. Res. 16: 841–854.
Shindell, D.T., Pechony, O., Voulgarakis, A., Faluvegi, G.,
Nazarenko, L., Lamarque, J.F., Bowman, K., Milly, G.,
Kovari, B., Ruedy, R. and Schmidt, G.A. (2013).
Interactive Ozone and Methane Chemistry in GISS-E2
Historical and Future Climate Simulations. Atmos. Chem.
Phys. 13: 2653–2689, doi: 10.5194/acp-13-1653-2013.
Trainer, M., Parrish, D.D., Buhr, M.P., Norton, R.B.,
Fehsenfeld, F.C., Anlauf, K.G., Bottenheim, J.W., Tang,
Y.Z., Wiebe, H.A., Roberts, J.M., Tanner, R.L., Newman,
L., Bowersox, V.C., Meagher, J.F., Olszyna, K.J., Rodgers,
M.O., Wang, T., Berresheim, H., Demerjian, K.L. and
Roychowdhury, U.K. (1993). Correlation of Ozone with
NOy in Photochemically Aged Air. J. Geophys. Res. 98:
2917–2925.
Xing, J., Pleim, J., Mathur, R., Pouliot, G., Hogrefe, C.,
Gan, C.M. and Wei, C. (2013). Historical Gaseous and
Primary Aerosol Emissions in the United States from
1990 to 2010. Atmos. Chem. Phys. 13: 7531–7549, doi:
10.5194/acp-13-7531-2013.
Received for review, May 30, 2015
Revised, September 15, 2015
Accepted, November 6, 2015