Winter Photochemistry Underlying High Ozone in an Oil and Gas Producing Region

Monday, 15 December 2014: 10:35 AM
Steven S Brown1, Peter M Edwards2, James M Roberts3, Ravan Ahmadov4, Robert M Banta3, Joost A De Gouw5, William P Dube6, Robert Alexander Field7, Jessica Gilman8, Martin Graus9, Detlev Helmig10, Abigail Koss4, Andrew O'Neil Langford8, Barry L Lefer11, Brian M Lerner12, Stuart A McKeen3, Shao-Meng Li13, Shane M Murphy7, David D Parrish14, Christoph J Senff14, Jochen Stutz15, Chelsea R Thompson10, Michael Trainer5, Patrick R Veres6, Carsten Warneke6, Robert J Wild16, Cora Young17, Bin Yuan2, Robert J Zamora18 and Rebecca A Washenfelder6, (1)NOAA Earth System Research Lab, Chemical Sciences Division, Boulder, CO, United States, (2)CIRES, Boulder, CO, United States, (3)NOAA/ESRL, Boulder, CO, United States, (4)University of Colorado at Boulder, Boulder, CO, United States, (5)NOAA Earth System Research Lab, Boulder, CO, United States, (6)NOAA Boulder, Boulder, CO, United States, (7)University of Wyoming, Laramie, WY, United States, (8)NOAA ESRL, Boulder, CO, United States, (9)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (10)University of Colorado at Boulder, Institute of Arctic and Alpine Research, Boulder, CO, United States, (11)University of Houston, Earth and Atmospheric Sciences, Houston, TX, United States, (12)NOAA, Earth System Research La, Boulder, CO, United States, (13)Environment Canada Toronto, Toronto, ON, Canada, (14)NOAA, Boulder, CO, United States, (15)University of California Los Angeles, Los Angeles, CA, United States, (16)Colorado University/NOAA/ESRL, Boulder, CO, United States, (17)Memorial University of Newfoundland, St John's, NL, Canada, (18)NOAA/OAR R/PSD2, Boulder, CO, United States
Ozone formation during wintertime in oil and gas producing basins of the Rocky Mountain West now accounts for some of the highest ozone pollutant concentrations observed in the U.S. These events are scientifically challenging, occurring only during cold, snow covered periods when meteorological inversions concentrate pollutants near the surface, but when incident solar actinic flux that initiates photochemical reactions is at or near its minimum. A near-explicit chemical model that incorporates detailed measurements obtained during three successive winter field studies in the Uintah Basin, Utah, accurately reproduces the observed buildup of ozone and other photochemically generated species. It also identifies the sources of free radicals that drive this unusual photochemistry, and quantifies their relative contributions. Although sharing the same basic atmospheric chemistry, winter ozone formation differs from its summertime, urban counterpart in its dependence upon the relative concentrations of volatile organic compounds (VOCs) and nitrogen oxide (NOx) precursors. Observed NO­­x mixing ratios in the Uintah basin are lower than is typical of urban areas, while VOC levels are significantly larger. These extreme VOC concentrations allow for nearly optimal efficiency of ozone production from the available NO­x. This analysis will inform the design of mitigation strategies and provide insight into the response of winter ozone to primary air pollutants in other regions, particularly those where oil and gas development is contemplated.