Central-eastern China's chloroform emissions during 2021-2024 inferred from high-frequency in-situ atmospheric...

Chloroform (CHCl₃) is an important ozone-depleting substance and emerging pollutant, with China playing a key role in global CHCl₃ emission variations. Despite the implementation of controls on emerging pollutants since 2021, the most recent CHCl₃ emissions from China remain unclear. This study conducted high-frequency atmospheric measurements of CHCl₃ and comprehensive industrial sampling covered about 300 enterprises, in central-eastern China during 2021-2024. Based on over 20,000 atmospheric samples and inverse modeling techniques, our results indicate a decline in annual CHCl₃ emissions in China, from reported 139 (130-145) gigagrams per year (Gg yr^-1) in 2020 to 83.4 ± 22.3 Gg yr^-1 during 2021-2024 in this study, despite significant increases (p < 0.05) in anthropogenic activities related to CHCl₃. The reduction in CHCl₃ emissions suggests declined emission factors of major CHCl₃ sources due to strict environmental regulations (different from the activity-driven declines during 2017-2020), supported by industrial sample analyses revealing a decrease in average concentrations (from 2.6 ppb in 2021 to 0.3 ppb in 2023). China's share of global CHCl₃ emissions dropped from 42.8±4.0% (2015-2020) to 26.8±6.0 % (2021-2024), indicating the increased importance of other regions, which lack emission estimates currently. This study provides critical data to inform future regulations and highlights the necessity to update CHCl₃ emissions worldwide.