Emission reduction measures for typical PM2.5and O3 co-pollution event based on the adjoint model
To investigate PM2.5 and O3 co-pollution and its effective control measures,the"source-concentration"sensitivity analysis of a typical co-pollution event in Beijing from April 19 to 25,2019 was conducted by GRAPES-CUACE adjoint model in this paper.The contribution of local and surrounding precursor emissions to the peak concentrations of 24h average PM2.5(24-hr PM2.5)and MDA8O3 in Beijing was quantitatively assessed,and corresponding emission reduction experiments were conducted using the adjoint model.The results of the adjoint sensitivity analysis indicated that the peak concentrations of 24-hr PM2.5 and MDA8O3 in Beijing were jointly influenced by the precursor emissions from both local and surrounding areas.The peak 24-hr PM2.5 concentrations were mainly contributed by primary PM2.5(PPM2.5)emission sources within the preceding 48h,with the largest contribution from Hebei(49.7％),followed by Shandong(24.4％)and Beijing(20.1％).The formation of O3 was controlled by VOCs.The primary contribution periods were within the first 30h for NOx and the first 38h for VOCs.Hebei made the largest contributions,with NOx and VOCs contributing 27.0％and 23.8％,respectively,followed by Beijing(20.9％and 4.9％).The results of the emission reduction experiments for co-pollution event showed that when the peak 24-hr PM2.5 concentrations in Beijing met the standard,the reduction percentages of NOx,VOCs and PPM2.5 were similar,with the reduction percentages for each province as follows:Hebei(55.8％,59.1％,and 61.3％),Beijing(60.0％,47.4％,and 60.4％),Shandong(44.0％,51.2％,and 61.3％),Tianjin(42.7％,42.7％,and 42.7％),and Shanxi(44.0％,40.9％,and 42.7％).The peak MDA8O3 concentrations initially increased and then decreased during the iterative process,and more NOx and VOCs needed to be reduced when reaching the standard.The emission reduction percentages for local and surrounding areas were as follows:Hebei(67.8％and 67.1％),Beijing(66.0％and 56.3％),Shandong(57.3％and 59.5％),Tianjin(50.9％and 52.4％),and Shanxi(55.4％and 46.0％).
adjoint modelingPM2.5 and O3 co-pollutionsensitivity analysispollution controlBeijing
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