渭南市大气降水的化学特征及来源解析

Chemical characteristics and source apportionment of precipitation in Weinan City

基于2017-2021年间对渭南市大气降水的pH、电导率及离子浓度(F^(-)、Cl^(-)、NO_(3)^(-)、SO_(4)^(2-)、Na^(+)、NH_(4)^(+)、K^(+)、Mg^(2+)、Ca^(2+))的监测分析,运用相关性分析和PMF模型进行离子组分来源解析。结果表明,城区和乡村两个站点降水量加权pH和电导率5年均值分别为6.14和6.12,141.4μS/cm和137.9μS/cm,虽无酸化现象,但降水污染程度较严重;城区站主要离子Ca^(2+)、SO_(4)^(2-)、NH_(4)^(+)、NO_(3)^(-)分别占总离子浓度的26.0%、24.9%、15.0%和10.1%,乡村站主要离子Ca^(2+)、NH_(4)^(+)、SO_(4)^(2-)、NO_(3)^(-)分别占总离子浓度的26.6%、23.3%、22.1%、15.1%;总离子浓度城市站高于乡村站;5年间的SO_(4)^(2-)/NO_(3)^(-)均在0.5与3.0之间,污染物排放类型为硫酸-硝酸混合型。相关性分析表明SO_(4)^(2-)与NO_(3)^(-),Ca^(2+)与Mg^(2+),Cl-与Na+相关系数较高,其有相关来源;Ca^(2+)与SO_(4)^(2-)、NO_(3)^(-)相关性大于NH_(4)^(+)与其相关性,表明Ca^(2+)对致酸阴离子SO_(4)^(2-)和NO_(3)^(-)的中和作用大于NH_(4)^(+)。PMF源解析效果较好,解析结果显示大气降水离子主要来源于海盐、农业排放、机动车排放和生物质燃烧、扬尘、工业排放和化石燃料燃烧;Ca^(2+)主要来自扬尘源(51.10%),NH_(4)^(+)主要来自农业活动源(68.60%),SO_(4)^(2-)主要来自工业排放和化石燃料燃烧源(44.00%),NO_(3)^(-)主要来自机动车排放源(67.00%)。

Based on the monitoring and analysis of pH,conductivity,and ion concentration(F^(-),Cl^(-),NO_(3)^(-),SO_(4)^(2-),Na^(+),NH_(4)^(+),K^(+),Mg^(2+),Ca^(2+))of precipitation in Weinan City from 2017 to 2021,correlation analysis and PMF model were used to analyze the source of ion components.The results showed that the 5-year average weighted pH and conductivity of precipitation at urban and rural stations were 6.14 and 6.12,141.4μS/cm and 137.9μS/cm,respectively.Although there was no acidification phenomenon,the degree of precipitation pollution was relatively severe.The main ions Ca^(2+),SO_(4)^(2-),NH_(4)^(+),and NO_(3)^(-)in urban stations account for 26.0%,24.9%,15.0%,and 10.1%of the total ion concentration,respectively.In rural stations,the main ions Ca^(2+),NH_(4)^(+),SO_(4)^(2-),and NO_(3)^(-)account for 26.6%,23.3%,22.1%,and 15.1%of the total ion concentration,respectively.The total ion concentration in urban stations is higher than that in rural stations.Over the past 5 years,the SO_(4)^(2-)/NO_(3)^(-)levels were between 0.5 and 3.0,and the pollutant emissions were classified as a mixture of sulfuric acid and nitric acid.Correlation analysis shows that the correlation coefficients between SO_(4)^(2-)and NO_(3)^(-),Ca^(2+)and Mg^(2+),Cl-and Na+are relatively high,indicating they have related sources.The correlation of Ca^(2+)with SO_(4)^(2-)and NO_(3)^(-)is greater than that of NH_(4)^(+)with them,indicating that Ca^(2+)has a greater neutralizing effect on acidogenic anions SO_(4)^(2-)and NO_(3)^(-)than NH_(4)^(+).The PMF source apportionment effect is good,and the apportionment results show that atmospheric precipitation ions mainly come from sea salt,agricultural emissions,motor vehicle emissions,biomass combustion,dust,industrial emissions,and fossil fuel combustion;Ca^(2+)mainly comes from dust(51.10%),NH_(4)^(+)mainly comes from agricultural activity(68.60%),SO_(4)^(2-)mainly comes from industrial emissions and fossil fuel combustion(44.00%),and mainly comes from motor vehicle emissions(67.00%).