Ethylene, xylene, toluene and hexane are major contributors of atmospheric ozone in Hangzhou, China, prior to the 2022 Asian Games

The occurrence of volatile organic compounds (VOCs) in the atmosphere is a major health issue, notably in China, because those compounds are the precursors of tropospheric ozone and sources of secondary organic aerosols. Also, some compounds are carcinogenic. Atmospheric nitrogen oxides (NOx) are also a source of tropospheric ozone, thus creating diseases in human respiratory systems. Therefore, controlling VOCs and NOx is essential for the welfare of local citizens and incoming 2022 Asian Games in Hangzhou. Here, we recorded daily average concentrations for 55 different VOCs species and NOx in 2017. For each VOC, we calculated the ozone formation potential, the propene equivalent concentration and the secondary organic aerosol formation potential. We used the Weather Research and Forecast coupled with Community Multi-scale Air Quality models to assess the regional transport and local sector contributions for VOCs and NOx. Results show that ethylene contributed over 16% of total ozone generated from VOCs, followed by M/P-xylene and toluene. M/P-Xylene, toluene and n-hexane were the top 3 VOCs species that generated ozone fastest. Benzene, toluene and ethylbenzene generated most secondary organic aerosols. The annual regional transport rate is 45% for VOCs and 22% for NOx. Local industry produced 28% VOCs, while local traffic contributed 64% NOx. Overall, ground-level ozone could be reduced by controlling VOCs emissions first and then controlling NOx emissions.