NH 3 Monitoring in the Upper Green River Basin, Wyoming John V. Molenar 1 H. James Sewell 2 Jeffrey Collett 3 Cassie Archuleta 1 Mark Tigges 1 Florian M. Schwandner 3 Suresh Raja 3 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 ww.davebellphotos.com

Background: oil & gas development in Upper Green River Basin Monitoring & Laboratory Procedures Results & Interpretation

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.

1986

1999

2007

Oil & Gas Emissions Particulates – roads & disturbed land VOCs – drilling fluids, separation, dehydration, produced water, gas venting, gas compression NO x – diesel drilling rigs, gas compression, vehicles, flaring

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.

WRAP BART CALPUFF Modeling The complex non-linear sulfate-nitrate-ammonia system is highly dependent on availability of ammonia - NH 3 (g) SO 2 (g) ↔ H 2 SO 4 (g) NH 3 (g)+ H 2 SO 4 (g) ↔ (NH 4 ) 2 SO 4 (p) NO 2 (g) ↔ HNO 3 (g) NH 3 (g) + HNO 3 (g) ↔ NH 4 NO 3 (p)

Monitoring Plan

Objectives of the Upper Green River Basin Ammonia Air Monitoring Project measure background ammonia (NH 3 ) 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.

Monitoring Constraints sample at existing monitoring site desire to use well known and accepted sampling and analysis protocols a priori assumption that NH 3 would be at low concentrations cost

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 PM 2.5 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.

Ammonia Sampler Air Temperature Controller and MFC Flow Recorders Controller Housing PM 2.5 Size-Selective Inlets Temperature-Controlled Housing for Denuders and Filters Air Quality Station Shipping Case

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

Results

Neutralization Convert mass to molar values Ratio [NH 4 + ] / [NO 3 - ] + 2[SO 4 2+ ] Then: ratio = 1 fully neutralized ratio < 1 acidic < 0.5 very acidic ratio > 1 excess NH 4 +

Source Regions

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 Administration’s (NOAA) Air Resources Laboratory (ARL). Detailed information regarding the trajectory model and these data sets can be found on NOAA’s Web site ( 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.

Conclusions NH 3 concentrations are highly seasonally dependent. Ranging from near detectable limits Dec-Feb, to peak values of 1.5 ppb during the summer average NH 3 was 0.24 ppb Residence time analysis indicates that NH 3 is transported into the region primarily from the west along the Snake River Valley and Southwest along the Wasatch front.