Photochemistry of Volatile Organic Compounds in the Yellow River Delta, China: Formation of O3 and Peroxyacyl Nitrates

Abstract

AbstractAn extensive set of primary and secondary pollutants was measured at a ground site in a remote location in the Yellow River Delta, China during the Ozone Photochemistry and Export from China Experiment (OPECE) from March to April 2018. The measurements include volatile organic compounds (VOCs), peroxyacyl nitrates (PANs), ozone (O3), particulate species, nitrogen oxides (NOx), and SO2. Observed VOC mixing ratios were comparable to those measured in heavily polluted cities in the U.S. and China. The VOC source signatures suggest a strong influence from Oil and Natural Gas (O&NG) emissions with potentially large contributions from Liquified Petroleum Gas (LPG) sources as well. Consistently elevated concentrations of O3, PAN, and its rarely measured homologs peroxybenzoylic nitric anhydride (PBzN) and peroxyacrylic nitric anhydride (APAN) at the OPECE site indicate complex photochemistry in a heterogeneous VOC environment. Diagnostic 0‐D box model simulations are used to investigate the budgets of ROx (OH + HO2 + RO2), and the rate and efficiency of O3 production. Model sensitivity calculations indicate that O3 production at OPECE site is VOC limited in spring. This suggests that reduction in VOCs should be a priority for reducing O3, where production and fugitive emissions from O&NG provide an attractive target. While initial reductions in NOx might increase O3 production, reduction of NOx along with VOCs will be a necessary step to achieve long‐term ozone reduction.