Distribution Characteristics And Source Analysis Of PM_2.5 Components In Haze Weather In Winter In Yangtze River Delta Region

As an important component of particulates in the Yangtze River Delta region,water soluble ions and carbonaceous aerosols are closely to local human activities and are influenced by external transmission.It also have important impacts on the climatic conditions of 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.Therefore,this paper analyzes the temporal and spatial distribution characteristics and sources of atmospheric PM_2.5.5 components through regional joint observations,which is of great significance for understanding the air quality status of the Yangtze River Delta region and assessing the climatic effects of atmospheric aerosols.This study was conducted from December 13,2016 to January 5,2017 in the Yangtze River Delta region including Dongshan,Nanjing,Shouxian and Xuzhou through the use of KC-120H intelligent medium flow sampler,ion chromatography?Wantong 850 professional?IC)and heat/light carbon analyzer?DRI2001A?.The mass concentration of PM_2.5,water-soluble ions,OC and EC were obtained by external field and laboratory experiments,and then the temporal and spatial distribution characteristics and sources of the PM_2.5components of different sites in the Yangtze River Delta are analyzed.The results showed that the concentration of water-soluble ions and organic carbon in Xuzhou was much larger than that of the other three sites during the observation period.The most important ion components of the four sites were NO₃^-,SO₄^2–,NH₄⁺,Cl^-and Ca²⁺,and both water-soluble ions and carbonaceous aerosols were important parts of the PM_2.5,the winter carbonaceous aerosol in the Yangtze River Delta contributes less to PM_2.5.5 than to water-soluble ions,and even less than the contribution of one of the major ions.During the observation period,the PM_2.5,water-soluble ions,OC and EC mass concentrations of the four sites were consistent with the change of time.The cold air played a significant role in the removal of water-soluble ions,but the removal of carbonaceous aerosols was not significant.The importance of the source and fixed source contribution to PM_2.5.5 during the process of the Yangtze River Delta before and after the cold airwas quite different.Under the influence of the same weather system,the concentration of pollutants in the large-scale area of??the Yangtze River Delta are basically the same.In the case of haze weather without large area transportation,the ion concentration of each station are mainly affected by the local source,and the Xuzhou station was affected by coal combustion.The Nanjing station was affected by the chemical industry source.The Dongshan station was surrounded by the lake on three sides,and the Cl^-was relatively high.The Shouxian station was affected by the ammonia emissions from the local agricultural activities,and the NH₄⁺has risen sharply compared with the non-stationary weather.Secondary organic carbon is prevalent during the observation of the four sites.The haze days were conducive to the accumulation of components of carbonaceous aerosols and the increase of organic carbon was dominated by the accumulation of primary carbon emissions.In ion source analysis,Principal Component Analysis found that the four sites had the largest variance contribution to water-soluble ions.The Shouxian and Dongshan K⁺loads were high,representing the combustion of biomass,which was related to the observation period.The sites were related to straw burning.In the analysis of carbonaceous aerosol sources,both the correlation analysis and the OCEC ratio method found that the source of carbonaceous aerosol components in the Xuzhou site was more complex than the other three sites,while the OCEC ratio method and the carbon component analysis method showed that the most important source of carbonaceous aerosol in the Yangtze River Delta in winter was the vehicle exhaust and coal-burning source.The PMF source analytical model is used to analyze the water-soluble ions and carbonaceous aerosol as a whole,and PM_2.5.5 in the Yangtze River Delta during winter was mainly from secondary conversion,soil dust,coal burning,automobile exhaust and biomass burning,the secondary conversion contribution rate was the highest,followed by coal burning.