Spatial And Temporal Distribution And Source Characteristics Of Nitrogen Deposition In The Yangtze River Delta

The monitoring distribution of atmospheric nitrogen deposition in China is uneven.To supplement the research on nitrogen deposition in eastern China,this paper analyzes the aerosol,precipitation and atmospheric chemical characteristics of four monitoring points in the Yangtze River Delta from April 2018 to March 2019,including Quanjiao,Hangzhou,Nanjing and Pudong.Combined with the characteristics of nitrogen stable isotopes,the paper uses the backward trajectory model and the multi-source syntagmatic mixture model to analyze the nitrogen source,and analyzes the different types of nitrogen concentration and nitrogen deposition in the Yangtze River Delta By analyzing the temporal and spatial variation of the depression,the main conclusions are as follows:(1)The aerosol in the Yangtze River Delta region is generally acidic,the annual average mass concentration of ions in Quanjiao,Hangzhou,Nanjing and Pudong are 17.39?g·m^-3,14.51?g·m^-3,28.84?g·m^-3and 8.14 g·m^-3,respectively.The maximum annual precipitation of the four monitoring points all occurred in August,and the average concentration of ions in precipitation is 19.32 mg·L^-1,14.96 mg·L^-1,14.61 mg·L^-1and 17.44mg·L^-1,respectively;The average mass concentrations of ammonia in the atmosphere at the four monitoring points is 2.13 mg·L^-1,1.73 mg·L^-1,0.67 mg·L^-1,0.64 mg·L^-1,respectively.The overall performance is spring and summer>autumn and winter.(2)The annual?¹⁵N-NH₃content in the atmosphere of Quanjiao and Pudong is-46.81‰and-39.18‰,respectively.The contaminated air masses transferred to Quanjiao area basically come from the short-distance transmission of nitrogen formed by the application of nitrogen fertilizer volatilization in Shandong and other agricultural provinces;the contaminated air masses transferred to Pudong area mainly come from areas with serious industrial pollution in the northwest.The contribution of agricultural nitrogen sources in Quanjiao exceeded 70%,mainly including chemical fertilizers and biomass burning.In Pudong,the contribution of the nitrogen combustion source is close to 70%,mainly including motor vehicle emissions and coal combustion.(3)The monthly weighted average concentration of different types of nitrogen and the wet deposition of nitrogen are positively correlated with precipitation in Quanjiao,Hangzhou,Nanjing and Pudong.The annual wet deposition of nitrogen at the four monitoring points is22.68 kg N ha^-1,18.48 kg N ha^-1,14.98 kg N ha^-1and 12.55 kg N ha^-1,respectively.The annual dry deposition of nitrogen is 34.39 kg N ha^-1?22.07 kg N ha^-1?32.11 kg N ha^-1?11.61kg N ha^-1,respectively.