2015—2019年昆明市大气降水变化趋势及离子特征研究

Study on the Change Trend and Ion Characteristics of Atmospheric Precipitation in Kunming from 2015 to 2019

根据2015—2019年昆明市5个大气降水监测点的数据,从降水pH、降雨量、电导率、离子浓度年际变化及离子间的相关性等方面研究了昆明市大气降水变化趋势及离子特征,分析结果表明:2015—2019年昆明市尚未出现酸雨;除2019年外,其余4年的电导率呈下降趋势;降水无机离子中,SO_(4)^(2-)和Ca^(2+)浓度占比最大,SO_(4)^(2-)/NO_(3)^(-)呈下降趋势,表明昆明市的降雨类型由硫酸型逐渐演变为硫酸+硝酸的混合型;2019年昆明市降雨中的SO_(4)^(2-)和NO_(3)^(-)的相关性较好,说明二者的前体物(SO_(2)和NO_(x))有着共同的来源及在降水过程中有着相似的化学行为。

According to the data of 5 atmospheric precipitation monitoring sites in Kunming from 2015 to 2019,from the aspects of precipitation pH,rainfall,conductivity,inter-annual variation of ion concentration and the correlation between ions,the trend of atmospheric precipitation change and ion characteristics in Kunming are studied.The analysis results showed that the pH value of the precipitation in Kunming from 2015 to 2019 fluctuated slightly,all above 5.6,and acid rain has not occurred.Except for 2019,the conductivity of the remaining 4 years showed a downward trend.In terms of the inorganic ions in precipitation,the concentrations of SO_(4)^(2-) and Ca^(2+)accounted for the largest proportions,respectively 34.5%and 29.3%;SO_(4)^(2-)/NO_(3)^(-) showed a downward trend,indicating that the rainfall type in Kunming gradually evolved from sulfuric acid to mixed sulfuric acid&nitric acid.The Pearson correlation analysis of the ions in the rainfall in 2019 showed that the correlation between SO_(4)^(2-) and NO_(3)^(-) is good,indicating that the precursors(SO_(2) and NO_(x))of these two had a common source and a similar chemical behavior in the precipitation process.