Deposition Characteristics of Water-soluble Inorganic Nitrogen and Organic Nitrogen in Atmospheric Precipitation in the Northern Suburbs of Nanjing

Abstract

Based on atmospheric precipitation collected in the northern suburbs of Nanjing from 2019 to 2020, the pH, conductivity, and chemical components of precipitation were analyzed. The seasonal variation in pH and conductivity of atmospheric precipitation in the northern suburbs of Nanjing were studied. The pollution levels and deposition characteristics of water-soluble inorganic nitrogen (WSIN) and organic nitrogen (WSON) in precipitation were also analyzed. The frequency of acid rain (pH<5.6) in atmospheric precipitation in the northern suburbs of Nanjing reached 37.18% during the observation period. Precipitation acidification was more serious in autumn and winter, and the pH value showed a variation trend of spring>summer>autumn>winter. The average conductivity of precipitation was 29.49 μS·cm-1; high pH and conductivity in spring were related to the high dust content in the atmosphere. The seasonal difference between WSIN and WSON in precipitation was significant. The highest and lowest concentrations of NO3--N and NH4+-N appeared in spring and summer, respectively. The concentration of WSON was the highest in autumn (2.63 mg·L-1). The average concentration ratio of WSON to water-soluble total nitrogen (WSTN) in precipitation was approximately 0.47, indicating that WSON played an important role in the study of total nitrogen. The average wet deposition fluxes of WSIN and WSON were 12.10 kg·(hm2·a)-1 and 11.13 kg·(hm2·a)-1, respectively, in which the inorganic nitrogen deposition was mainly NH4+-N.