乌鲁木齐市米东区大气降水的化学特征及来源分析

为研究乌鲁木齐市米东区大气降水中的化学组分特征及来源,对2017-2019年降水中主要离子浓度及来源进行了分析.研究结果显示,米东区2017-2019年降水的雨量加权pH年均值为7.95,雨量加权平均电导率年均值为16.15 mS·m-1,雨量加权平均总离子浓度为72.75-95.89 μeq·L-1,年均浓度为81....

Chemical characteristics and source apportionment of atmospheric precipitation in Urumqi City

To investigate the characteristics and sources of chemical compositions of precipitation in the Midong district of Urumqi,the concentration and sources of major ions in the precipitation collected during the period from 2017 to 2019 were analyzed.The results showed that the annual weighted mean pH of precipitation was 7.95,and the annual weighted mean conductivity of precipitation was 16.15 mS·m^-1.The variation range of total ion concentrations in precipitation was 72.75—95.89μeq·L^-1,with the annual weighted average concentrations of 81.93μeq·L^-1.The weighted mean concentration of precipitation components followed the order SO₄^2->Ca²⁺>Cl^->Na⁺>NO₃^->NH₄⁺>K⁺>Mg²⁺>F^-,the highest contents of anion and cation was SO₄^2-(29.01μeq·L^-1)and Ca²⁺(21.91μeq·L^-1),the contribution of total ion concentration was 35.41%and 26.74%,respectively.The order of concentration of total ions was winter>summer>autumn>spring.The mean ratio of theSO₄^2-/NO₃^-was 7.51,and the ratio of NO₃^-had increased year by year,which indicated that precipitation of Urumqi City belonged to sulfuric acid,and might gradually evolve from a sulfuric acid to nitric acid type.The significant correlation among Ca²⁺、Mg²⁺、Na⁺、Cl^-、SO₄^2-and NO₃^-indicated their similar sources or the formation of compounds with them.Ca²⁺was preferentially combined with SO₄^2-、NO₃^-in the atmosphere,and the contribution of Ca²⁺to the acid neutralization of rainwater was greater than NH₄⁺,indicated that the chemical compositions of precipitation were mainly existed in the form of CaSO₄ and Ca(NO₃)₂.