北京市延庆区PM2.5中主要水溶性无机离子特征及来源解析

Characteristics and source analysis of water-soluble inorganic ions in PM2.5 in Yanqing District,Beijing

对2017年6月—2018年5月北京市延庆区大气PM2.5样本进行采集,分析了PM2.5中9种水溶性无机离子的污染特征,并利用SPSS软件进行来源解析。结果表明:延庆区大气PM2.5中总水溶性无机离子平均浓度为28.0μg/m^3,其中,SO^2-4、NO^-3和NH^+4是最主要的水溶性无机离子,合计占比为82.1%。受天气影响,NO^-3和SO^2-4浓度均表现为秋高冬低,NH^+4浓度为秋高夏低;受冬季气象条件和施工影响,Ca^2+、Mg^2+、Na^+浓度冬季最高。根据电荷平衡分析,春季PM2.5中阴、阳离子基本达到平衡状态,夏、秋季呈弱酸性,冬季呈弱碱性;PM2.5中硫氧化率(SOR)、氮氧化率(NOR)的均值分别为0.53和0.27,大气中存在明显的二次转化过程;NO^-3/SO^2-4为1.66,说明机动车尾气排放源对PM2.5中水溶性无机离子贡献较大;根据NH^+4与SO^2-4、NO^-3、Cl^-的相关性分析,PM2.5中NO^-3和SO^2-4以(NH4)2SO4、NH4HSO4、NH4NO3以及HNO3形式存在。利用SPSS软件进行皮尔森相关性分析,PM2.5中NO^-3、SO^2-4、NH^+4两两相关性强,说明二次反应显著;Ca^2+、Mg^2+、Na^+两两相关性强,说明其污染来源可能相同;Cl^-与K^+相关性强,说明大气中Cl^-主要以KCl的形式存在。利用因子分析模块进行主成分分析,发现延庆区主要污染源为生物质燃烧、扬尘污染和机动车尾气排放。

The atmospheric PM2.5 samples were collected from June 2017 to May 2018 in Yanqing District,Beijing.The pollution characteristics of nine water-soluble inorganic ions in PM2.5 were analyzed,and the sources were analyzed by SPSS software.The results showed that the average concentration of total water-soluble inorganic ions in PM2.5 in Yanqing District was 28.0μg/m^3,of which SO^2-4,NO^-3and NH^+4 were the main water-soluble inorganic ions,accounting for 82.1%.Influenced by weather,the concentration of NO^-3and SO^2-4 was high in autumn and low in winter,while the concentration of NH^+4 was high in autumn and low in summer.Influenced by meteorological conditions and construction activities in winter,the concentration of Ca^2+,Mg^2+,Na^+was the highest in winter.According to the charge balance analysis,the anions and cations in PM2.5 basically reached equilibrium in spring,with weak acidity in summer and autumn,and weak alkalinity in winter.The mean values of SOR and NOR in PM2.5 were 0.53 and 0.27,respectively,and there were obvious secondary transformation processes in the atmosphere.The ratio of NO^-3/SO^2-4 was 1.66,which indicated that vehicle exhaust contributed a lot to water-soluble inorganic ions in PM2.5.According to the correlation analysis between NH^+4 and SO^2-4,NO^-3,Cl^-in PM2.5 in Yanqing District,NO^-3and SO^2-4 existed in the form of(NH4)2SO4,NH4HSO4,NH4NO3 and HNO3.Pearson correlation analysis using SPSS software showed that the correlations between any two of NO^-3,SO^2-4,NH^+4 in PM2.5 in Yanqing District were strong,indicating that the secondary reaction was significant;the correlations between any two of Ca^2+,Mg^2+,Na^+were strong,indicating that the sources of pollution may be the same;Cl^-was strongly correlated with K^+,and Cl^-mainly existed in the form of KCl in the atmosphere.Using factor analysis module to analyze the main components,it was found that the main pollution sources in Yanqing District were biomass combustion,dust pollution and motor vehicle exhaust emissions.