Acyl Peroxy Nitrates Link Oil and Natural Gas Emissions to High Ozone Abundances in the Colorado Front Range During Summer 2015

We present measurements of ozone (O ₃ ), acyl peroxy nitrates (APNs), and a suite of O ₃ precursors made at the Boulder Atmospheric Observatory in Erie, Colorado, during summer 2015. We employ an empirical analysis of the APNs and a previously described positive matrix factorization of the volatile organic compounds (VOCs) to investigate the contribution of different VOC sources to high O ₃ abundances at Boulder Atmospheric Observatory. Based on the ratio of peroxypropionyl nitrate (PPN) to peroxyacetyl nitrate (PAN), we find that anthropogenic VOC precursors dominate APN production when O ₃ is most elevated. Propane and larger alkanes, primarily from oil and natural gas emissions in the Colorado Front Range, drive these elevated PPN to PAN ratios during high O ₃ events. The percentage of OH reactivity associated with oil and gas emissions is also positively correlated with O ₃ and PPN/PAN. Idealized box model simulations are used to probe the chemical mechanisms potentially responsible for these observations. We find that observed abundances of long-lived oil and natural gas-related VOCs are likely high enough such that the oxidation of these VOCs in a single photochemical day produces sufficient peroxy radicals to contribute to O ₃ formation in the northern Colorado Front Range. Based on our empirical observations and box model simulations, we conclude that oil and natural gas emissions contribute to O ₃ production on high O ₃ days in this region during summer 2015.