Characteristics, source apportionment and health risks of ambient VOCs during high ozone period at an urban site in central plain, China

On 3rd to May 24, 2018, volatile organic compound (VOC) samples were collected four times a day by using stainless steel canisters at an urban site in Zhengzhou, China. The concentrations, compositions, sources, ozone (O3) formation potential (OFP), and health risk assessment of VOCs were discussed based on the measurements of 103 VOC species. Results show that the average mixing ratio of VOCs was 29.11 ± 15.33 ppbv, and the dominant components comprised oxygenated VOCs (OVOCs) and alkanes, followed by halocarbons, alkenes, aromatics, and a sulfide. Various groups of VOCs had typical diurnal variation characteristics. Alkenes, alkanes, and aromatics contributed most to the OFP. Five sources identified by the positive matrix factorization model revealed solvent utilization as the largest contributor, followed by industrial production, long-lived and secondary species, vehicular emission, and biogenic emission. Solvent utilization and vehicular emission were important sources to OFP. During O3 episode days, the mixing ratios of alkanes, alkenes, halocarbons, OVOCs, aromatics, and TVOCs decreased to varying degrees; the source contribution of solvent utilization decreased significantly while industrial production showed the opposite trend. VOC species and sources posed no non-carcinogenic risk while five species and all sources except for biogenic emission had carcinogenic risks to exposed population. Industrial emission was the largest contributor to both non-carcinogenic and carcinogenic risks. These results will help to provide some references for O3 pollution research and prevention and control of pollution sources.