Impacts of Oil and Gas Exploration Activities on SOA formation in the Colorado Front Range
Tuesday, 15 December 2015: 15:01
3014 (Moscone West)
Oil and gas exploration activities (O&G) in Wattenberg Field, located north of the Denver Metropolitan area, have expanded in the last few years. Although VOC emissions and the potential for ozone formation in the area from these sources have been studied previously, no information is available on the impact on secondary organic aerosol (SOA) formation. During the Front Range Air Pollution and Photochemistry Experiment (FRAPPE), airborne measurements of trace gases and aerosol composition were made in the northern Front Range during July-August 2014. We present analyses on evolution of organic aerosol (OA) and their precursors in order to assess the impact of urban vs. O&G emissions on SOA formation. Significant contribution of SOA to total OA was observed in pure urban and urban plumes mixed with O&G emissions. Under an OH-exposure of 2.8×1011 molecule cm-3 s, enhancement ratios of OA relative to carbon monoxide (ΔOA/ΔCO) increased by factors of ~3.6-5.4; however, (ΔSOA/ΔCO)urban+O&G was 87% higher than (ΔSOA/ΔCO)urban. Predicted ΔSOA/ΔCO values from the oxidation of C7-C11 alkanes, C6-C9 aromatics, and biogenics were about a factor of 10-15 too small compared to the measurements. Predicated alkane-derived SOA contributed to 38% (16%) of anthropogenic ΔSOA/ΔCO values in urban+O&G- (urban-) influenced air masses.