Modeling Studies of Air Quality in the Four Corners Region National Park Service U.S. Department of the Interior Cooperative Institute for Research in the Atmosphere Marco Rodriguez 1, Michael Barna 2, Tom Moore 3 1 CIRA, Colorado State University, Fort Collins, CO 2 National Park Service, Fort Collins, CO 3 Western Regional Air Partnership, Western Governors’ Association, Fort Collins, CO Workshop on Regional Emissions and Air Quality Modeling Studies July 2008

Motivation Ozone in the Western U.S is becoming an increasing problem in remote areas Many Class I areas will be confronted with ozone concentrations that are trending towards the EPA's acceptable limits The growing development of oil and gas extraction operations throughout the West is essential to understand the potentially negative impact on air quality in some of the nation's protected areas

Methodology CAMx simulations at NPS-CIRA 2002 annual simulations (36 km) Emissions, meteorology from WRAP-RMC Model performance Evaluation Evaluate oil & gas impacts

Methodology Significant increases in NOx and VOC for oil and gas development in WRAP region –largest emission increases in NM, CO, UT, WY To evaluate contribution to regional air pollution (e.g., ozone and fine nitrate PM) from O&G, consider two CAMx simulations –base emissions –base emissions minus O&G run SMOKE’s MRGGRID to combine all base02 emission categories except O&G

Methodology The difference between these two runs represents the impact of O&G emissions Results reflect an ‘emissions sensitivity test’, not a true source apportionment (CAMx’s OSAT better suited for that analysis)

NOx VOC Oil and gas emissions within WRAP: NOx: 125,000 tons/yr (3% of total) VOC: 363,000 tons/yr (2% of total) Emissions from oil and gas in WRAP region

ParameterChoice 36 km domainNo nesting Vertical Layers19 sigma vertical layers (surface up to ~ 14 km). Initial Conditions15 days spin up time Boundary ConditionsDirichlet set by GEOS-Chem GCM Chemical MechanismCarbon Bond IV CAMx Simulation

Model Performance Evaluation Evaluation relies on Mean Fractional Bias (MFB) and Mean Fractional Error (MFE) estimates MFB and MFE “Bugle Plots” MFB and MFE Spatial distributions

Ozone error and bias for all WRAP fractional error fractional bias

Ozone performance stats for all WRAP EPA goalAll sites (Western U.S) Mean Observation47 Mean Estimation44 Standard deviation Obs.13 Standard deviation Est.12 Mean Bias Error-3 Mean Normalized Bias Error (%) < ±15%-1.6 Mean Absolute Gross Error 10 Mean Absolute Normalized Gross Error (%) < 35%22.7 Mean Fractional Error (%)23 Mean Fractional Bias (%)-5.8

NO3 error and bias for all WRAP fractional error fractional bias

Annual Spatial Distribution SO 4 Fractional BiasSO 4 Fractional Error

Annual Spatial Distribution NO 3 Fractional BiasNO 3 Fractional Error

Annual Spatial Distribution NH 4 Fractional BiasNH 4 Fractional Error

Example summertime ozone 6 August 2002 Mesa Verde NP: 65 ppb max hourly concentration

Ozone at Mesa Verde fractional error fractional bias

Example ozone increase from O&G emissions, 6 August 2002

Ozone enhancements at Mesa Verde from O&G July – August 2002 August 6

Ozone max. 8hr average in 2002 Concentrations Base caseConcentrations O&G impacts

Ozone max. 8hr average O&G impacts Concentrations O&G impactsConcentrations Base case

Ozone enhancements - Time Series Base Case O&G enhancement

Summary Acceptable ozone performance in WRAP –47 ppb (observed) vs. 44 ppb (predicted) –fractional error: 0.23, fractional bias –biases overpredict: fall through spring underpredict: summer low concentrations are overestimated

Summary (cont’d) Nitrate performance not as good, but falls within bugle plot limits –wintertime overpredictions, summertime underpredictions Largest impacts from O&G emissions on regional ozone occur in Four Corners –at Mesa Verde NP on 6 August ppb ozone enhancement peak ozone concentrations of 65 ppb

Summary (cont’d) Limitations of this work: –O&G emissions inventory has undergone several updates from the one used here –No effects in CO because O&G emissions in phase I were accounted in the area emissions not O&G emissions –Study does not provide information about the contributing sources (need for OSAT simulations)

Acknowledgments Western Regional Air Partnership –Tom Moore –Mohammad Omary UNC-Chapel Hill, Carolina Environmental Program –Zac Adelman ENVIRON International Corporation –Ralph Morris –Chris Emery