| 摘 要： | China promulgated the Air Pollution Prevention and Control Action Plan(the Action Plan) in 2013 and developed stringent control measures to mitigate fine particulate matter(PM_(2.5) pollution.Here,we investigated the PM_(2.5) chemical composition changes over eastern China associated with the Action Plan during 2013-2017 using satellite-based PM_(2.5) chemical composition data derived using CMAQ simulations and satellite inputs.The PM_(2.5) concentrations decreased considerably during this time as a result of the reductions in all chemical species in PM_(2.5).The population-weighted mean concentrations over eastern China decreased from 11.1 to 6.7μgm~(-3) for SO_4~(2-),13.8-13.1μgm~(-3) for NO_3~-,7.4-5.8μgm~(-3) for NH_4~+,9.9-8.4μgm~(-3) for OM,4.6-3.8 μg m~(-3) for BC and 12.9-9.6 μg m~(-3) for other species in PM_(2.5).SO_4~(2-) had the largest reduction of 40%,while NO_3~-had the lowest reduction of 5%,resulting in a greater fraction of NO_3~-and a smaller fraction of SO_4~(2-) in PM_(2.5).Among the three key regions,Beijing-Tianjin-Hebei had the largest reduction in PM_(2.5) and its chemical compositions.The decrease in SO_4~(2-) concentrations was in line with the reduction of SO_2 emissions,and the major driver of the SO_2 emission reductions was the industrial sector.The decrease in NO_3 concentrations was limited because the decrease in SO_2 emissions and the stable NH_3 emissions facilitated the formation of NO_3~- from HNO_3,which partiall_y offset the reduction in NO_x emissions driven by the power sector.To mitigate PM_(2.5) pollution more effectively,future efforts are needed to reduce NH_3 emissions.
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