Influence of Oil\nand Gas End-Use on Summertime Particulate\nMatter and Ozone Pollution in the Eastern US

The influence of oil and gas end-use activities on ambient\nair\nquality is complex and understudied, particularly in regions where\nintensive end-use activities and large biogenic emissions of isoprene\ncoincide. In these regions, vehicular emissions of nitrogen oxides\n(NO<sub><i>x</i></sub>NO + NO<sub>2</sub>) modulate\nthe oxidative fate of isoprene, a biogenic precursor of the harmful\nair pollutants ozone, formaldehyde, and particulate matter (PM<sub>2.5</sub>). Here, we investigate the direct and indirect influence\nof the end-use emissions on ambient air quality. To do so, we use\nthe GEOS-Chem model with focus on the eastern United States (US) in\nsummer. Regional mean end-use NO<sub><i>x</i></sub> of 1.4\nppb suppresses isoprene secondary organic aerosol (OA) formation by\njust 0.02 μg m<sup>–3</sup> and enhances abundance of\nthe carcinogen formaldehyde by 0.3 ppb. Formation of other reactive\noxygenated volatile organic compounds is also enhanced, contributing\nto end-use maximum daily mean 8-h ozone (MDA8 O<sub>3</sub>) of 8\nppb. End-use PM<sub>2.5</sub> is mostly (67%) anthropogenic OA, followed\nby 20% secondary inorganic sulfate, nitrate and ammonium and 11% black\ncarbon. These adverse effects on eastern US summertime air quality\nsuggest potential for severe air quality degradation in regions like\nthe tropics with year-round biogenic emissions, growing oil and gas\nend-use and limited environmental regulation.