The Pollution Characteristics And Vertical Distribution Of Carbonaceous Aerosols At The Typical Site During Winter In The Yangtze River Delta

The Yangtze River Delta region is one of Chinals "three regions and ten groups" air pollution prevention and control areas,and the atmospheric aerosol pollution is very serious.As an important component of particulates in the Yangtze River Delta region,carbonaceous aerosols are closely to local human activities and are influenced by external transmission.It also have important impacts on the climatic conditions,atmospheric environment,and human health in the Yangtze River Delta region.It is necessary to study the characteristics of carbonaceous aerosol pollution in the delta region.This paper is based on the PM2.5.OC and EC data of 3 sites in Ling'an,Nanjing,and Suzhou in the winter of 2015,and the vertical observations of black carbon at the three stations in Nanjing,Dongshan,and Shou County in the winter of 2016.Carbonaceous aerosols from three typical sites in the Yangtze River Delta region during winter were analyzed for their pollution characteristics and sources,and the vertical distribution characteristics of PM2.5 and BC in Nanjing,Dongshan and Shou counties in winter 2016 were also analyzed.Conclusion:1.The winter PM2.5 average concentrations in Lin'an,Suzhou,and Nanjing in winter were 123.56,144.77,and 156.5 ?g·m-3,both exceeding the "Environmental Quality Standard"second-level daily average(75?g·m-3,GB 3095-2012,published in China in Febraary 2012).Although the Lin'an site as a background point in the Yangtze River Delta region,is also having serious pollution,indicating that the atmospheric pollution in the Yangtze River Delta region in winter is a regional pollution.The mean mass concentrations of ? and EC in three sites were(21.93± 11.69)/(6±3.6),(20.32±10.3)/(5.39±3.07),and(27.08±14.35)/(6.4±4.29)?g·m-3,and is an important part of PM2.5.The backward trajectory pattern shows that when air masses from areas with poor air quality are under control,the air pollution at the three stations increases.At the same time,when controlled by ocean and coastal air masses,the ratio of TCA and OC/EC in PM2.5 also increased.2.The source analysis of winter carbonaceous aerosols at Linan,Suzhou and Nanjing sites in winter 2015 was conducted using the ratio method and principal component analysis.The ratio method showed that the OC/EC averages of the three sites were Lin'an(4.3),Nanjing(4.0),and Suzhou(5.1).In the distribution of OC/EC values of the samples,the OC/EC values of the samples at the three sites are mainly distributed within the range of 2.5 to 6,which is between the vehicle exhaust sources and the coal combustion source,this indicates that during the sampling period,the OC and EC were mainly controlled by vehicle exhaust sources and coal combustion sources during most of the three sampling periods.Principal component analysis was used to analyze the day-night composition of OC and EC.The test found that the vehicle exhaust gas source(gasoline vehicle + diesel vehicle)was used in three sites,and the source of coal combustion and biomass combustion was the main source of winter OC and EC in Linan,Nanjing and Suzhou sites.Using the EC tracer method to estimate the SOC at each site,the average SOC concentrations in Lin'an,Nanjing,and Suzhou were 9.23,6.82,and 12.56 ?g·m-3.Indicate SOC is an important part of the OC in the three sites.3.From the diurnal variation of vertical direction pollutants in 2016 Nanjing,Dongshan and Shou County 3 sites,The Nanjing have the highest concentration of pollution in 8,Shou County and Dongshan have the highest concentration of pollutants in 11 o'clock,this is due to the early peak emission enhancement and weak vertical transportation caused by low temperature in morning.In the vertical direction,BC is more capable of transporting than PM2.5 in the vertical direction.By analysis the haze process from December 29,2016 to January 2nd,2017,found that the increase the boundary layer in haze process,appear,moving down and intensity hindered the surface layer of aerosol particles to high level of transmission in different extent,while the horizontal wind speed decreases,can cause the relative humidity increased,pollutants sustained accumulation causing haze process in the ground layer.