NH3 Monitoring in the Upper Green River Basin, Wyoming

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NH3 Monitoring in the Upper Green River Basin,
Wyoming
John V. Molenar1 H. James Sewell2 Jeffrey
Collett3 Cassie Archuleta1 Mark Tigges1 Florian
M. Schwandner3 Suresh Raja3 1 Air
Resource Specialists, Inc 2 Shell Exploration
Production Company 3 Department of Atmospheric
Science, Colorado State University Background
image courtesy of Dave Bell Photos PO Box 1738
Pinedale, WY 82941 ww.davebellphotos.com
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• Background oil gas development in Upper Green
  River Basin
• Monitoring Laboratory Procedures
• Results Interpretation

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Upper Green River Valley

• Nestled between the high peaks of western
  Wyoming's Wind River, Gros Ventre and Wyoming
  Ranges, the valley is home to
• More than 100,000 big game animals
• Largest mule deer herd in U.S.
• Continental America's longest big game migration
  route and a crucial link to the Greater
  Yellowstone Ecosystem (GYE)
• Largest publicly-owned big game winter range in
  the GYE
• One of the west's last best sage grouse habitats
  and a world-class fishery
• One of the largest natural gas reserves in the
  U.S.

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1986
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1999
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2007
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Oil Gas Emissions

• Particulates roads disturbed land
• VOCs drilling fluids, separation, dehydration,
  produced water, gas venting, gas compression
• NOx diesel drilling rigs, gas compression,
  vehicles, flaring

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WRAP BART CALPUFF Modeling

• The Interagency Workgroup on Air Quality
  Modeling (IWAQM, 1998) recommends three
  background values for CALPUFF modeling
• 0.5 ppb for forested lands
• 1.0 ppb for arid lands and
• 10 ppb for grasslands.
• Most of the western U.S. Class I areas are
  characterized by arid and forested lands,
  consequently a 1.0 ppb background ammonia value
  was selected for the WRAP RMC BART CALPUFF
  modeling.

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WRAP BART CALPUFF Modeling

• The complex non-linear sulfate-nitrate-ammonia
  system is highly dependent on availability of
  ammonia - NH3(g)
• SO2(g) ? H2SO4(g)
• NH3(g) H2SO4(g) ? (NH4)2SO4(p)
• NO2(g) ? HNO3(g)
• NH3(g) HNO3(g) ? NH4NO3(p)

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Monitoring Plan
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Objectives of the Upper Green River Basin Ammonia
Air Monitoring Project

• measure background ammonia (NH3) concentration
  for one year for use in refined visibility
  analyses
• measure concentrations of other related gases and
  particles to provide information about the local
  nitrogen budget
• attempt to identify the source regions
  attributable to these gases and particulates.

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Monitoring Constraints

• sample at existing monitoring site
• desire to use well known and accepted sampling
  and analysis protocols
• a priori assumption that NH3 would be at low
  concentrations
• cost

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Monitoring Instrumentation

• URG dual annular denuder system (Model 3000CA),
  mounted at a sample height of 1.5 meters
• A dual channel URG denuder/filter pack sampler is
  used to collect samples of ambient trace gas
  (ammonia, nitric acid, and nitrate) and PM2.5
  aerosol species (ammonium, nitrate, and sulfate)
• The prepared denuder/filter pack set is shipped
  to the site operator on a weekly basis, who
  installs it into the URG sampler according to a
  defined twice-weekly schedule that results in
  alternating 3-day and 4-day integrated samples
• The spent denuder/filter pack is shipped to the
  atmospheric science laboratory at CSU.

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Shipping Case
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Laboratory Analyses

• The denuders are extracted immediately upon
  arrival at CSU and the extracts are refrigerated
  until further analysis
• The filters are also unloaded immediately and
  stored frozen until extraction and analysis
• Samples are analyzed by ion chromatography on a
  monthly basis
• Data is validated according to EPA protocols and
  consist of concentrations in µg/m3 and ppbv for
  gases

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Results
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Neutralization

• Convert mass to molar values
• Ratio NH4 / NO3- 2SO42
• Then
• ratio 1 fully neutralized
• ratio lt 1 acidic lt 0.5 very acidic
• ratio gt 1 excess NH4

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Source Regions
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Residence Time Analysis

• Ammonia weighted back trajectories were used to
  identify the geographic source areas most likely
  to contribute to the highest measured ammonia
  days.
• Trajectories were generated using the
  Hybrid-Single Particle Lagrangian Integrated
  Trajectory (HYSPLIT) model developed by the
  National Oceanic and Atmospheric Administrations
  (NOAA) Air Resources Laboratory (ARL). Detailed
  information regarding the trajectory model and
  these data sets can be found on NOAAs Web site
  (http//www.arl.noaa.gov/ready/hysplit4.html).
• Three back trajectories were generated per day,
  including end times of 0400, 1200 and 2000 MST
  and end heights of 100 m. Each hourly point
  along a 72-hour back trajectory paths was
  weighted with measured ammonia concentration
  corresponding to the end date of each trajectory.
  The ammonia values associated with each hourly
  point were then summed and normalized into 1/4
  degree horizontal grid cells of latitude and
  longitude.

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Conclusions

• NH3 concentrations are highly seasonally
  dependent. Ranging from near detectable limits
  Dec-Feb, to peak values of 1.5 ppb during the
  summer.
• 2007 average NH3 was 0.24 ppb
• Residence time analysis indicates that NH3 is
  transported into the region primarily from the
  west along the Snake River Valley and Southwest
  along the Wasatch front.