Characteristics and source apportionment of some halocarbons in Hangzhou, eastern China during 2021.

In recent years, eastern China has been identified as an important contributor to national and global emissions of halocarbons, some of which are ozone depletion substances (ODSs) that delay the recovery of the stratospheric ozone layer. However, the most recent characteristics and sources of halocarbons in eastern China remain unclear. Thus, hourly atmospheric observations of halocarbons were conducted in Hangzhou throughout 2021. The results showed that methylene chloride (CH2Cl2) was the most abundant halocarbon (2207 (25 %-75 % quantile: 1116-2848) ppt; parts per trillion) followed by chloromethane (CH3Cl) (912 (683-1043) ppt), and 1,2-dichloroethane (CH2ClCH2Cl) (596 (292-763) ppt). Then, backward trajectory and potential source contribution function (PSCF) analysis show that the emission hot spots of halocarbons were concentrated in adjacent cities in Zhejiang and neighboring provinces in eastern China. Moreover, based on positive matrix factorization (PMF) analysis, industrial emission (38.7 %), solvent usage (32.6 %), and the refrigeration sector and biomass burning (23.7 %) were the main sources of halocarbons (observed in this study). This study reveals high concentrations and potential sources of halocarbons in eastern China, which are important for studying the recovery of the ozone layer.