WRF-Chem Simulation Of Air Quality In Spring And Summer In Nanjing

Air pollution is widely concerned by the Chinese government and the public,especially fine particulate matter(PM_2.5)and ozone?O₃?pollutions.With implementations of emission control in recent years,the PM_2.5.5 levels in many Chinese cities have been reduced,but still not meet the national air quality standard II.At the same time,the O₃ problem has been highlighted.Nanjing is an important member of the Yangtze River Delta urban agglomeration,and its air quality issues have received much attention.The O₃ concentration in Nanjing rises to a high level in spring and summer?April-June?,which is much earlier than the arresting O₃pollution normally in summer in the Beijing-Tianjin-Hebei and Pearl River Delta regions.Therefore,it is important to understand the characteristics of O₃ in spring and summer in Nanjing,as well as its correlation with PM_2.5.5 and other air pollutants.We used the WRF-Chem model to simulate O₃,PM_2.5.5 and other air pollutants in spring and summer in Nanjing,and evaluated the potential impacts of emission controls on air quality during a typical pollution control event,focus on PM_2.5.5 concentration changes and the impact of NO_X and VOC_S reduction on O₃ concentration.The main results are as follows:?1?We analyzed the air pollution characteristics and interannual variations in spring and summer in Nanjing from 2014 to 2017,using the observations at nine atmospheric environmental monitoring stations.The results show that the air quality in Nanjing is getting better year by year,and the excellent rate increases from 56%in 2014 to 77%in 2017.The PM_2.5.5 concentration decreases,with the seasonal mean values reduce from 76.7?g/m³ to 36.7?g/m³.PM₁₀,SO₂,and NO₂ also decrease,in a range of 5-15%.O₃ shows an upward trend,and 8h-O₃ concentration increases from 146.7?g/m³ to 150.9?g/m³.?2?Using the WRF-Chem model,we simulated the air pollution in Nanjing from April to June in 2017.The simulated meteorological parameters and air pollutants can capture the magnitude and variation of observations,excepted for CO.The simulated CO,NO₂,SO₂,PM_2.5.5 and PM₁₀0 are concentrated in Nanjing urban area and Jiangbei industrial area;however,for O₃,the concentration in urban surrounding areas is higher than that in urban areas,which is contributed by the high NO₂ in urban Nanjing.?3?Further,we evaluated the impacts of emission reduction measures on air quality in Nanjing during the first Jiangsu Development Conference?May 2017?.During the control period,the reduction of particulate matter was the most significant,with PM_2.5.5 and PM₁₀emissions reduced by 57%and 60%,respectively;and NMVOC,SO₂ and NO_x emissions also reduced by 35%,33%and 26%,respectively.The concentrations of CO,NO₂,SO₂,PM_2.5.5 and PM₁₀0 during the control period decreased by 22.5%,30.1%,30.9%,3.94%and 19.0%respectively compared with those in the pre-control period,while the 8h-O₃ concentration unexpectedly increased by 32.1%.Each pollutant has different sensitivity to the emission reduction measures,as follows:NO₂>PM₁₀>PM_2.5>SO₂>CO>O₃.