Li, Yan Lei, Lu Sun, Jiaxing Gao, Yueqi Wang, Peng Wang, Siyu Zhang, Zhaolei Du, Aodong Li, Zhijie Wang, Zifa Kim, Jin Young Kim, Hwajin Zhang, Hongliang Sun, Yele 2024-01-19T08:31:24Z 2024-01-19T08:31:24Z 2023-11-17 2023-10 0013-936X https://pubs.kist.re.kr/handle/201004/113174 Air quality in China has continuously improved during the Three-Year Action Plan (2018-2020); however, the changes in aerosol composition, properties, and sources in Beijing summer remain poorly understood. Here, we conducted real-time measurements of aerosol composition in five summers from 2018 to 2022 along with WRF-Community Multiscale Air Quality simulations to characterize the changes in aerosol chemistry and the roles of meteorology and emission reductions. Largely different from winter, secondary inorganic aerosol and photochemical-related secondary organic aerosol (SOA) showed significant decreases by 55-67% in summer, and the most decreases occurred in 2021. Comparatively, the decreases in the primary aerosol species and gaseous precursors were comparably small. While decreased atmospheric oxidation capacity as indicated by ozone changes played an important role in changing SOA composition, the large decrease in aerosol liquid water and small increase in particle acidity were critical for nitrate changes by decreasing gas-particle partitioning substantially (similar to 28%). Analysis of meteorological influences demonstrated clear and similar transitions in aerosol composition and formation mechanisms at a relative humidity of 50-60% in five summers. Model simulations revealed that emission controls played the decisive role in reducing sulfate, primary OA, and anthropogenic SOA during the Three-Year Action Plan, while meteorology affected more nitrate and biogenic SOA. English American Chemical Society Significant Reductions in Secondary Aerosols after the Three-Year Action Plan in Beijing Summer Article 10.1021/acs.est.3c02417 1 Environmental Science & Technology, v.57, no.42, pp.15945 - 15955 Environmental Science & Technology 57 42 15945 15955 N scie scopus 001092747700001 2-s2.0-85175585744 Engineering, Environmental Environmental Sciences Engineering Environmental Sciences & Ecology Article POSITIVE MATRIX FACTORIZATION CHEMICAL SPECIATION MONITOR PM2.5 AIR-QUALITY ANTHROPOGENIC EMISSIONS METEOROLOGICAL MODES SOURCE APPORTIONMENT ORGANIC AEROSOL HAZE POLLUTION CHINA URBAN atmospheric oxidation capacity emissions meteorology three-year action plan secondary aerosol