Study On The Characteristics Of Haze Pollution And Atmospheric Extinction In Urban Wuhan

Associated with the rapid economic and social development in Wuhan,air quality and visibility impairment has become serious in recent decades.Combined with on-line observation and field sampling analysis,the characteristics of atmospheric haze pollution in urban Wuhan has been studied,as well as the relationship between chemical species,relative humidity and visibility.In addition,the contribution of each species to light extinction was estimated,which provided a scientific basis to the control policies in haze pollution.In order to study the characteristics of atmospheric extinction in urban Wuhan,online monitoring data during March 2017 to January 2018 was used to evaluate the application of the American IMPROVE formula,compared to the measurement data,the original version of the IMPROVE algorithm underestimates by 30%of the extinction coefficient and the revised version underestimates by 8%.Based on the IMPROVE formula,localized extinction equation was built,and the mass extinction efficiency of three major species,ammonium sulfate,ammonium nitrate and organic matter was calculated and the values were 3.40、4.76、5.41 m²/g,respectively.The contribution of ammonium sulfate,ammonium nitrate and organic matter to light extinction was 23%,32 and 21%,respectively.The main cause of visibility reduction is PM2.5,which contributed 88%to extinction coefficient.In addition,the extinction coefficient of urban Wuhan was in descending order of winter,autumn,spring and summer,whose extinction coefficient was 467,380,341 and287 Mm^-1,respectively.PMF 5.0 model,combined with localized extinction formula was used to the source apportionment of light extinction,and the contribution of six sources,secondary aerosol,vehicle exhaust,biomass burning and waste incineration,coal combustion,metallurgy,fugitive dust to extinction coefficient was 50%,14%,9%,10%,3%,3%,respectively,and their extinction coefficient were 178、50、33、35、9、10Mm^-1,respectively.The extinction coefficient was 865 Mm^-1 in the joint monitoring tests of January2016,the contributions to light extinction by the top three species were ammonium sulfate,ammonium nitrate and organic matter,which contributed about 90%in total,and the contribution of other species were less than 5%.In online observation,the extinction coefficients of ammonium sulfate,ammonium nitrate and organic matter were 258,409 and 177 Mm^-1,respectively,and their contributions to the extinction coefficient were 28%,44%and 19%,respectively.In offline observation,the extinction coefficients of ammonium sulfate,ammonium nitrate and organic matter were 277,388and 164 Mm^-1,respectively,and their contributions to the extinction coefficient were30%,42%and 18%,respectively.The results of online observation and offline observation are similar,and the difference is very small.Considering the tremendous contribution of the secondary source to PM2.5 and extinction coefficient,controlling or treating the gaseous precursors emitted from one source of coal combustion and vehicles would be an effective measure to prevent the haze pollution.