Influence of oil and gas field operations on spatial and temporal distributions of atmospheric non-methane hydrocarbons and their effect on ozone formation in winter

摘要

Emissions from oil and natural gas development during winter in the UpperGreen River basin of Wyoming are known to drive episodic ozone (O₃)production. Contrasting O₃ distributions were observed in the winters of2011 and 2012, with numerous episodes (hourly O₃ ≥ 85 ppbv) in2011 compared to none in 2012. The lack of O₃ episodes in 2012 coincidedwith a reduction in measured ambient levels of total non-methane hydrocarbons(NMHC). Measurements of speciated NMHC, and other air quality parameters,were performed to better understand emission sources and to determine whichcompounds are most active in promoting O₃ formation. Positive matrixfactorization (PMF) analyses of the data were carried out to help achievethese goals. PMF analyses revealed three contributing factors that wereidentified with different emission source types: factor 1,combustion/traffic; factor 2, fugitive natural gas; and factor 3, fugitivecondensate. Compositional signatures of the three contributing factors wereidentified through comparison with independently derived emission sourceprofiles. Fugitive emissions of natural gas and of condensate were the twoprincipal emission source types for NMHC. A water treatment and recyclingfacility was found to be a significant source of NMHC that are abundant incondensate, in particular toluene and m+p-xylene. Emissions from watertreatment have an influence upon peak O₃ mixing ratios at downwindmeasurement sites.