Impacts Of Emission Control Strategies On PM_2.5and O₃ Concentrations Over The Yangtze River Delta Investigated By The Two-Way Coupled WRF-CMAQ Model

Due to rapid urbanization and industrialization,the Yangtze River Delta has suffered severe air pollution over the past few decades.In order to prevent and control air pollution,the State Council issued the "Action Plan for Air Pollution Prevention and Control" in September 2013,which required the Yangtze River Delta region to achieve a 20%reduction in average annual PM2.5 level by 2017 relative to those of 2013.This paper created the emission inventory by integrating high-resolution local emissions with the national emission inventory using the GIS technology with the the Yangtze River Delta region as the studying area.In this study,we present a computational evaluation of the predicted effectiveness of different emission control strategies on the PM2.5 and O3 concentrations over the YRD region using the two-way coupled Weather Research and Forecasting(WRF)-Community Multi-scale Air Quality(CMAQ)model.The results indicate that the predicted annual mean percentage reductions for PM2.5 concentrations over the YRD region for the four emission control strategies for industry,power plants and transportation are the highest in Hangzhou(ranging from-9.7%to-20.1%),followed by Nanjing(ranging from-8.2%to-18.7%),Shanghai(ranging from-7.4%to-15.8%),and Hefei(ranging from-6.1%to-13.8%).By implementing these emission control strategies,only Hangzhou with the strictest emission controls can meet the 20%reduction goals of PM2 5 concentration set in the 12th Five-Year Plan.Sensitivity tests show that residential emissions have the highest contributions to the PM2.5 concentrations in January in all four cities(Hangzhou,Hefei,Nanjing,Shanghai),followed by agriculture,industry,transportation and power plants.On the other hand,the results of O3 indicate that the predicted annual mean percentage reductions for O3 concentration over the YRD region for the different emission control strategies for industry,power plants and transportation are different for different seasons and different cities because of non-linear and complex responses of O3 to the NOx and VOCs reductions.For example,the four emission control strategies for industry,power plants and transportation decreased O3 concentrations in July(summer time)but increased O3 concentrations in other seasons(Jannuary,April and October)in most of locations over the YRD region.The similar results can be obtained from the sensitivity tests.The more studies about the effects of the different emission control strategies on O3 are needed in the future.The results also indicate the importance of implementing emission controls for all surrounding areas,in order to accomplish the PM2.5 and O3 reduction goals of the 12th Five-Year Plan.