ACEIC: a comprehensive anthropogenic chlorine emission inventory for China

Abstract. Reactive chlorine species play a crucial role as precursors to Cl radicals, which can significantly impact the atmospheric oxidation capacity and influence the levels of trace gases related to climate and air quality. However, their anthropogenic sources remain uncertain and require further investigation. In previous studies, we developed the Anthropogenic Chlorine Emission Inventory for China (ACEIC) for the years 2012 and 2014. This inventory focused solely on the emissions of hydrogen chloride (HCl) and chlorine gas (Cl₂) from coal combustion and prescribed waste incineration. In the present study, we updated this inventory to include data from a more recent year (2018) and expanded the range of species considered (HCl, fine particulate Cl^-, Cl₂, and hypochlorous acid (HOCl)) as well as the number of anthropogenic sources (41 specific sources). The emission factors used in this updated inventory were primarily based on localized survey data. The total emissions of HCl, fine particulate Cl^-, Cl₂, and HOCl in mainland China for the year 2018 were estimated to be 454 (-48 %~45 %), 238 (-59 %~89 %), 17 (-44 %~58 %), and 73 (-44 %~79 %) Gg, respectively. To facilitate analysis, we aggregated the chlorine emissions from various sources into five economic sectors: power, industry, residential, agriculture, and biomass burning. HCl emissions were primarily derived from biomass burning (45 %), industry (35 %), and residential (15 %) sectors. The biomass burning and industry sectors accounted for 78 % and 14 % of the fine particulate Cl^- emissions, respectively. Residential and industry sectors contributed 59 % and 31 % of the total Cl₂ emissions. HOCl emissions were predominantly from the residential sector, constituting 90 % of the total emissions. Notably, the usage of chlorine-containing disinfectants was identified as the most significant source of Cl₂ and HOCl emissions in the residential sector. Geographically, regions with high HCl and fine particulate Cl^- emissions were found in northeast China, the North China Plain, and the Sichuan Basin, whereas the Pearl River Delta, Yangtze River Delta, and Beijing-Tianjin-Hebei regions exhibited elevated levels of Cl₂ and HOCl emissions. Regarding monthly variation, emissions of HCl and fine particulate Cl^- were relatively higher during early summer (June–July) and October due to intensified agricultural activities, while Cl₂ and HOCl emissions were higher in the summer months due to increased demand for water disinfection. This updated inventory contributes to a better understanding of anthropogenic sources of reactive chlorine species and can aid in the formulation of emission control strategies to mitigate secondary pollution in China.