[Characteristics and Source Apportionment of Atmospheric Ion Deposition During Winter and Spring in the Core Area of...

In recent years, the Ministry of Ecology and Environment and the Beijing Municipal Government have continuously strengthened the control indicators of dustfall. In order to grasp the characteristics and sources of ion deposition in dustfall, the filtration method and ion chromatography were used to determine the dustfall and ion deposition during winter and spring in the core area of Beijing, and the PMF model was carried out to analyze the sources of ion deposition. The results indicated:① the average values of ion deposition and its proportion in dustfall were 0.87 t·(km²·30 d)^-1 and 14.2%, respectively. The dustfall and ion deposition on working days were 1.3 times and 0.7 times that on rest days, respectively. ② The coefficient of determination in the linear equations between ion deposition and precipitation, relative humidity, temperature, and average wind speed were 0.54, 0.16, 0.15, and 0.02, respectively. In addition, the coefficient of determination in the linear equations between ion deposition and PM_2.5 concentration and dustfall were 0.26 and 0.17, respectively. Therefore, controlling the concentration of PM_2.5 was crucial to treating ion deposition. ③ Anions and cations accounted for 61.6% and 38.4%, respectively, in the ion deposition, and SO₄^2-, NO₃^-, and NH₄⁺ accounted for 60.6% in total. The ratio of anion and cation charge deposition was 0.70, and the dustfall was alkaline. The ρ(NO₃^-)/ρ(SO₄^2-) in the ion deposition was 0.66, which was higher than that of 15 years ago. ④ The contribution rates of secondary sources, fugitive dust sources, combustion sources, snow-melting agent sources, and other sources were 51.7%, 17.7%, 13.5%, 13.5%, and 3.6%, respectively.