Non-negligible contribution of high-level volatile sulphur compounds to ozone photochemical formation in an industry zone in the North China Plain

The increasing amount of ozone (O3) pollution in China is attracting extensive scientific attention globally. This study presents direct evidence that high concentrations of volatile sulphur compounds (VSCs) accelerate the photochemical production of O3. We analysed three high O3 cases (Cases I, II, and III) in which the O3 concentrations were high but the compositions of O3 precursors differed. An analysis of the O3 precursors and the magnitudes of the associated ROx (ROx = ·OH + ·HO2 + ·RO2) reactivities amongst three cases revealed that VSCs may play an important role in O3 production. Case I showed high loadings of VSCs, mainly dimethyl sulphide (DMS), and the simulated diurnal average concentration of radicals and the net O3 production rate were higher than those in Cases II and III, reflecting the higher photochemical reactivity and oxidation capacity of Case I. Although O3 was mainly produced from the oxidation of aromatics in all cases, the oxidation of DMS was an important contributor to O3 formation in Case I (14