Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 15, 411-429, 2015
© Author(s) 2015. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
14 Jan 2015
Understanding high wintertime ozone pollution events in an oil- and natural gas-producing region of the western US
R. Ahmadov1,2, S. McKeen1,2, M. Trainer2, R. Banta2, A. Brewer2, S. Brown2, P. M. Edwards1,2,*, J. A. de Gouw1,2, G. J. Frost1,2, J. Gilman1,2, D. Helmig3, B. Johnson2, A. Karion1,2, A. Koss1,2, A. Langford2, B. Lerner1,2, J. Olson1,2, S. Oltmans1,2, J. Peischl1,2, G. Pétron1,2, Y. Pichugina1,2, J. M. Roberts2, T. Ryerson2, R. Schnell2, C. Senff1,2, C. Sweeney1,2, C. Thompson3, P. R. Veres1,2, C. Warneke1,2, R. Wild1,2, E. J. Williams2, B. Yuan1,2, and R. Zamora2 1Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO, USA
2Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
3Institute for Arctic and Alpine Research, University of Colorado at Boulder, Boulder, CO, USA
*now at: Department of Chemistry, University of York, York, UK
Abstract. Recent increases in oil and natural gas (NG) production throughout the western US have come with scientific and public interest in emission rates, air quality and climate impacts related to this industry. This study uses a regional-scale air quality model (WRF-Chem) to simulate high ozone (O3) episodes during the winter of 2013 over the Uinta Basin (UB) in northeastern Utah, which is densely populated by thousands of oil and NG wells. The high-resolution meteorological simulations are able qualitatively to reproduce the wintertime cold pool conditions that occurred in 2013, allowing the model to reproduce the observed multi-day buildup of atmospheric pollutants and the accompanying rapid photochemical ozone formation in the UB.

Two different emission scenarios for the oil and NG sector were employed in this study. The first emission scenario (bottom-up) was based on the US Environmental Protection Agency (EPA) National Emission Inventory (NEI) (2011, version 1) for the oil and NG sector for the UB. The second emission scenario (top-down) was based on estimates of methane (CH4) emissions derived from in situ aircraft measurements and a regression analysis for multiple species relative to CH4 concentration measurements in the UB. Evaluation of the model results shows greater underestimates of CH4 and other volatile organic compounds (VOCs) in the simulation with the NEI-2011 inventory than in the case when the top-down emission scenario was used. Unlike VOCs, the NEI-2011 inventory significantly overestimates the emissions of nitrogen oxides (NOx), while the top-down emission scenario results in a moderate negative bias. The model simulation using the top-down emission case captures the buildup and afternoon peaks observed during high O3 episodes. In contrast, the simulation using the bottom-up inventory is not able to reproduce any of the observed high O3 concentrations in the UB. Simple emission reduction scenarios show that O3 production is VOC sensitive and NOx insensitive within the UB. The model results show a disproportionate contribution of aromatic VOCs to O3 formation relative to all other VOC emissions. The model analysis reveals that the major factors driving high wintertime O3 in the UB are shallow boundary layers with light winds, high emissions of VOCs from oil and NG operations compared to NOx emissions, enhancement of photolysis fluxes and reduction of O3 loss from deposition due to snow cover.

Citation: Ahmadov, R., McKeen, S., Trainer, M., Banta, R., Brewer, A., Brown, S., Edwards, P. M., de Gouw, J. A., Frost, G. J., 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.: Understanding high wintertime ozone pollution events in an oil- and natural gas-producing region of the western US, Atmos. Chem. Phys., 15, 411-429, doi:10.5194/acp-15-411-2015, 2015.
Publications Copernicus
Short summary
High 2013 wintertime O3 pollution events associated with oil/gas production within the Uinta Basin are studied using a 3D model. It's able quantitatively to reproduce these events using emission estimates of O3 precursors based on ambient measurements (top-down approach), but unable to reproduce them using a recent bottom-up emission inventory for the oil/gas industry. The role of various physical and meteorological processes, chemical species and pathways contributing to high O3 are quantified.
High 2013 wintertime O3 pollution events associated with oil/gas production within the Uinta...