Extinction Contribution Of PM_2.5in The Northern Suburbs Of Nanjing

The atmospheric extinction coefficient is related to the aerosol physicochemical properties,and the aerosol chemical composition is very complex,different chemical components also have different effects on extinction coefficient.In order to explore the characteristics of Nanjing aerosol pollution and the contribution of each component extinction,this article analyzed the online data of PM_2.5,PM₁₀,SO₂,NO₂,O₃,and CO in Nanjing from 2015 to 2018,and compared it with Shanghai and Suzhou in the YRD region,Beijing and Tianjin in the BTH region,Guangzhou and Shenzhen in the PRD region,Chengdu in the SB region,and Linfen in FP area.The samples were collected from March 15 to April 15,July,and October in Nanjing to investigate the pollution characteristics of carbonaceous particles and water-soluble ions.Based on this,the change of extinction coefficient during the 2017 sampling period was studied.（1）From 2015 to 2018,PM_2.5,PM₁₀,SO₂,NO₂,and CO all showed a downward trend,while O₃ showed an upward trend.Except for O₃,it was low in summer and high in winter.O₃was high in summer and low in winter.The haze rate was lowest in summer and highest in winter.（2）Water-soluble ions and carbonaceous particles were the main components of Nanjing PM_2.5.The composition of water-soluble ions in descending order was:NO₃^->SO₄^2->NH₄⁺>（3）The secondary transformation in the northern suburbs of Nanjing was serious,and the contribution of mobile sources was large.（4）In spring,summer and autumn in Nanjing,NH₄⁺,NO₃^-and SO₄^2-all appeared as（NH₄）₂SO₄ and NH₄NO₃.Pollutants in autumn and winter were mainly affected by air masses from the land,while in summer they were mainly ocean air masses.（5）The extinction contribution of SNA was the largest in spring and the smallest in summer.Unlike autumn and spring,summer（NH₄）₂SO₄ had the largest extinction contribution.The rising contribution of NH₄NO₃ extinction was one of the main reasons for the formation of haze.