Synergistic contributions of typical photochemical reactive species to ozone pollution in the southeastern coastal city of China.

Surface ozone (O3) pollution has emerged as a regional environmental issue. Photochemical reactive species significantly impact O3 photochemical formation by regulating radicals and atmospheric oxidation capacity. This study focuses on O3 pollution in a southeastern coastal city, utilizing coordinated methods of filed observations and Photochemical Box Model to explore the pollution mechanisms and sensitivity analyses of typical reactive species (PAN, HCHO, and isoprene). The photolysis of O3 (37 %), HCHO (29 %), and other oxygenated volatile organic compounds (OVOCs) (21 %) are the main primary sources of radicals. For ROx radical cycling, the reaction of VOCs with OH· (5.89 ppbv·h-1) producing RO2· is a crucial pathway, with the isoprene oxidation by OH· contributing approximately 40 %. Furthermore, PAN production rate reached 4.5 ppbv·h-1. Based on the Relative Incremental Reactivity (RIR), the control of isoprene (RIR: 0.22), HCHO (0.19), and PAN (0.12) would lead to the reduction in O3. In fact, PAN chemistry demonstrated a suppressive effect (11 %) on O3 production in our study, and the 20 % reduction of isoprene and HCHO could cost-effectively reduce O3 formation by 5.93 %. This conclusion provides a scientific basis for exploring the photochemical mechanisms and for the prevention and control of O3 pollution in coastal areas.