Evaluation Of PM_2.5 Control Effect During Heavy Air Pollution Episode In Shanghai

Heavy ambient PM_2.5 pollution occurred frequently in autumn and winter seasons.In order to evaluate the control effect of short-term emergency and long-term regulated measures for air pollution,the amount of emission reduction was estimated according to Shanghai Air Pollution Emergency Plan and 13^th five-year Plan of Environmental Protection and Ecological Construction.A severe PM_2.5 pollution episode occurred from January 7^th to12^th of 2015.Four emission reduction scenarios were set,they are Shanghai heavy pollution level?emergency scenario,Shanghai 13^th five-year Plan scenario,YRD heavy pollution level?emergency scenario,YRD 13^th five-year Plan scenario,the WRF-CMAQ modeling system was then used to simulate the above four scenarios.The observation datasets were used to revising the simulation results.Finally,a comprehensive assessment of heavy air pollution improvement under the four scenarios is conducted based on the simulation data as well as the corrected data.The simulation results indicate that in case of Shanghai local control,under Emergency Plan and 13^th five-year plan,PM_2.5 mass would be reduced by6%and 14%respectively.For specific PM_2.5 compositions,organic matter gets the maximum reduction ratio 8%and 23%,followed by elemental carbon 5%and 23%,sulfate with 4%and 8%,2%and 8%for nitrate,0%and 4%for ammonium.In case of YRD united control,under Emergency Plan and 13^th five-year plan,PM_2.5 mass would be reduced by 8%and 20%respectively.For specific PM_2.5 compositions,organic matter gets the maximum reduction ratio 9%and 27%,followed by elemental carbon 6%and 27%,sulfate with 6%and 16%,5%and 15%for nitrate,1%and 15%for ammonium.In case of Shanghai local control,the measures conducted in Shanghai alone also have an effect on surrounding areas in a large scale which weakens the improvement of PM_2.5 pollution in Shanghai.In case of YRD united reduction,the reduction of PM_2.5 and its compositions are enhanced compared to Shanghai single reduction scenarios,and the enhancement is bigger in YRD 13^th five-year plan scenario.The PM_2.5 revising method can effectively decrease the simulation bias as well as make the variation trend closer to observation,the corrected results indicate that under the Shanghai heavy pollution level?emergency plan scenario,the PM_2.5 daily concentrations in 9¹1^th of January would be decreased from 151.4,174.8 and 193.3?g/m³ to 140.8,162.8 and181.4?g/m³ respectively,the pollution warning would decline from orange to yellow.Under the Shanghai 13^th five-year Plan scenario,the PM_2.5 daily concentration in 9¹1^th of January would be decreased to 130.0,149.0 and167.4?g/m³ respectively,the pollution warning would decline from orange to blue.Under the YRD heavy pollution level?emergency plan scenario,the PM_2.5 daily concentration in 9¹1^th of January would be decreased to136.9,160.1 and 180.1?g/m³ respectively,the pollution warning would decline from orange to yellow.Under the YRD 13^th five-year Plan scenario,the PM_2.5 daily concentration in 9¹1^th of January would be decreased to119.8,160.1 and 180.1?g/m³ respectively,the pollution warning would decline from orange to blue.Though in the inter-region scenarios,the pollution level didn't change compared to Shanghai single reduction scenarios,the inter-region pollution control can still be assumed as effective according to the PM_2.5 daily concentration values,especially in YRD 13^th five-year plan scenario.In this study,the effect under local and united emission control during a heavy pollution eposide was analyzed for a typical city,the revising method based on observation datasets is expected to be applied in other area.