Characteristics And Source Analysis Of Water-soluble Organic Nitrogen In PM_2.5 In Jiangbei New District, Nanjing

Organic nitrogen plays an important role in the deterioration of environmental quality by changing the buffering capacity and p H value of aerosols.Dissolved organic nitrogen deposition accounts for about 25%of total nitrogen deposition in the world.Organic nitrogen is not only an important component of fine particulate matter,but also an important component of secondary organic aerosol(SOA),which is related to the formation of haze.Through the study of organic nitrogen,it is of great significance to further understand the formation of SOA and haze.This paper analyzes the seasonal and total characteristics of water-soluble organic nitrogen(WSON)in Nanjing Jiang Bei New Area in April,July,November and December2019,discusses the relationship between WSON and water-soluble ions and meteorological conditions,and explores the source of WSON through backward trajectory combined with cluster analysis,potential source analysis and principal component analysis.The results show that:(1)The daily average concentration of WSON in PM_2.5 was 2.04?g·m^-3,accounting for 25%of water-soluble total nitrogen(WSTN).The order of seasonal average concentration was autumn>spring>winter?summer.During the observation period,the highest concentration of WSON was 4.200?g·m^-3,and the lowest concentration was 0.446?g·m^-3.The significant correlation between WSON and WSTN indicates that WSON exists in a relatively stable form in WSTN.There is no significant correlation between WSON and RH and T in PM_2.5 in spring,summer,autumn and winter,but there is a negative correlation between WSON and RH during the whole observation period(R=-0.247,p<0.05).The high concentration of SO₄^2-corresponds to the high concentration of WSON,and the variation trend of WSON is different from that of other ions.(2)The WSON concentration of PM_2.5in haze days in Nanjing Jiang Bei New Area is higher than that in non-haze days,but the contribution to WSTN is decreased,which indicates that the growth rate of WSON concentration is lower than that of WSTN.According to the neutralization degree F<1 and the relationship between acidity and WSON,PM_2.5 in Nanjing Jiang Bei New Area is slightly acidic,and acidity is conducive to the formation of WSON.The coefficient of divergence of Nanjing Jiang Bei New Area is 0.077,which indicates that there is no difference in the concentration of water-soluble ions in PM_2.5between day and night.The trajectory air flow in Nanjing Jiang Bei New Area comes from the sea and land in spring and summer,and from the land in autumn and winter.The results show that the distribution of PSCF in Nanjing Jiang Bei New Area has a significant seasonal change.(3)The distribution of PSCF in Nanjing Jiang Bei New Area has a significant seasonal variation.The four seasons air mass has an impact on WSON in Nanjing Jiang Bei New Area.In spring,WSON is related to the emissions of Shanxi,Henan and Anhui.In summer,South Korea and other regions are important sources of WSON.Sea salt,dust,biomass combustion and fossil fuel combustion are the main sources of WSON.