上海市中心城区大气降水化学组分变化趋势及来源研究

Trend and sources of the chemical components of atmospheric precipitation in Shanghai

对2019年8月-2020年7月共计12个月上海市中心城区的降水样品进行采集并分析,测定了pH、电导率(EC)、主要阴阳离子浓度(SO4^2-、NO3^-、Cl^-、F^-、NH4^+、Ca^2+、Mg^2+、Na^+、K^+)等因子,并对测定结果进行了研究和分析。研究结果表明:2019年8月-2020年7月,上海市中心城区降水的雨量加权平均pH为5.45,低于国内外对酸雨的评判标准(pH=5.6),说明上海仍旧存在酸雨污染,[SO 42-]/[NO 3-]的比值在0.4~1.4之间,说明上海市的SO 2污染下降,NO 2污染仍旧存在。降水中各主要离子雨量加权平均当量浓度的高低顺序为NH4^+>SO4^2->NO3^->Ca^2+>Cl^->Na^+>Mg^2+>K^+>F^-,其中NH4^+、SO^4^2-、NO3^-、Ca^2+是降水中的主要离子,占离子总量的78.01%。富集因子计算结果表明:Mg^2+、K^+大部分来自土壤,Cl^-大部分来自海洋,SO^42-、NO3^-主要来自人为排放。

Precipitation samples were collected from August 2019 to July 2020 in Shanghai.The samples were analyzed for pH and EC and main ionic(SO4^2-、NO3^-、Cl^-、F^-、NH4^+、Ca^2+、Mg^2+、Na^+、K^+)concentrations.Average annual rainfall weighed mean pH of precipitation in downtown Shanghai during August 2019 to July 2020 was 5.45 that was lower than the domestic and foreign standards for acid rain(pH=5.6),indicating that acid rain still exists in Shanghai.The ratio of[SO^42-]/[NO3^-]is between 0.4 and 1.4,indicating that the SO2 pollution in Shanghai has decreased and NO2 pollution still exists.The volume-weighted mean equivalent concentration of precipitation components followed the order NH4^+>SO4^2->NO3^->Ca^2+>Cl^->Na^+>Mg^2+>K^+>F^-Among them,NH4^+,SO4^2-,NO3^-and Ca^2+are the main ions in precipitation,accounting for 78.01%of the total ions.The enrichment factor was used to assess sources of major ions.The most of Mg^2+and K^+come from soil,most of Cl^-comes from the ocean,and SO4^2-and NO3^-mainly come from anthropogenic emissions.