An Updated Anthropogenic Emission Inventory of Reactive Chlorine Precursors in China

The chlorine radical (Cl-center dot) plays an important role in the formation of secondary pollutants such as ozone and secondary organic aerosols. However, primary emissions of reactive chlorine species are not well known. Here, we develop an up-to-date emission inventory of major primary reactive chlorine precursors, including chlorine gas (Cl-2), hypochlorous acid (HOCl), hydrogen chloride (HCl), and particulate chloride (pCl) in mainland China for the year 2019 with a spatial resolution of 0.1 degrees x 0.1 degrees. The anthropogenic sources considered in this study include six major source categories (coal combustion, industrial processes, municipal solid waste incineration, biomass burning, cooking, and chlorine-containing disinfectants) and 22 sub-categories. The Cl-2, HOCl, HCl, and pCl emissions in mainland China in the year 2019 are estimated to be 7.8, 27.6, 270.3, and 183.5 Gg, respectively, with the major source contributors being use of chlorine-containing disinfectant (46%), use of chlorine-containing disinfectant (100%), biomass burning (36.1%), biomass burning (78.0%), respectively. The emission intensity of Cl-2, HOCl, HCl, and pCl for most provinces range from 0 to 3 tons.year(-1).km(-2). Emissions are highest in Eastern China, especially in the Beijing-Tianjin-Hebei and surrounding area, and the Yangtze River Delta region. The temporal distribution varies in different regions due to different human activities, industrial structures, and climatic conditions. The Monte Carlo method was applied to quantify the uncertainty of this emission inventory. The ranges of uncertainty in the emission of Cl-2, HOCl, HCl, and pCl were estimated to be 4.4-14.2, 9.7-51.6, 207.2-422.7, and 106.4-321.1 Gg.yr(-1), respectively. This study provides an updated chlorine emission inventory with improved spatial and temporal resolution, enabling better quantification of chlorine production and its impact on the air quality in China.

Automated summary

This study estimates the emissions of chlorine gas in mainland China in 2019 and identifies the major sources and regions. The study finds that the use of chlorine-containing disinfectants and biomass burning are the main contributors to chlorine gas emissions. The emission intensity varies among provinces, with the highest emissions in the eastern region. The findings of this study provide insights into chlorine production and its impact on air quality in mainland China.