南通市冬季PM2.5中水溶性离子污染特征

Pollution Characteristics of Water-soluble Ions in PM2.5 in Winter in Nantong

根据南通市2016和2017年冬季大气多参数站自动监测PM2.5数据和在线离子色谱分析仪Marga监测的PM2.5中水溶性离子数据,分析了南通市冬季PM2.5中水溶性离子污染特征。结果表明,南通市2016和2017年冬季,ρ(PM2.5)分别为58和54μg/m 3,均高出其年均值(14μg/m^3);ρ(水溶性离子)总占ρ(PM2.5)百分比分别为74.5%和74.3%;二次离子ρ(NO3^-、SO4^2-和NH4^+)占ρ(PM2.5)百分比分别为66.8%和66.6%;各水溶性离子占比大小依次为:NO3^-、SO4^2-、NH4^+、Cl^-、K^+、Na^+、Ca^2+、Mg^2+。对ρ(NO3^-)/ρ(SO 4^2-)分析表明,移动源已经成为南通市冬季的主要污染源,且呈逐年增强趋势。对氯氧化率和硫氧化率的分析表明,南通市冬季存在较明显的二次污染,SO2的转化程度大于NO2。除Na^+和Mg^2+外,其他离子与PM2.5均呈显著相关性,NO3^-、SO4^2-与NH4^+之间的相关系数最高,Cl^-与除Na^+外的所有阳离子均呈显著相关性。

The pollution characteristics of water-soluble ions in PM2.5 in winter in Nantong were analyzed based on the ion compositions monitored by Marga and PM2.5 measured by Nantong atmospheric multi-parameter automatic monitoring in winter,2016 and 2017.Results showed that the concentrations of PM2.5 was 58 and 54μg/m^3 respectively in winter of 2016 and 2017 in Nantong,both were 14μg/m^3 higher than their average annual concentration.In the winter of 2016 and 2017,water-soluble ions contributed 74.5% and 74.3% of PM2.5(mass ratio)respectively,among which SNA(NO3^-、SO4^2- and NH^+)contributed 66.8% and 66.6% respectively.The proportions of water-soluble ions in PM 2.5 follow the trend,NO3^->SO 4^2->NH4^+>Cl^->K^+>Na^+>Ca^2+>Mg^2+.Theρ(NO3^-3)/ρ(SO 4^2-)ratio implied that mobile sourcehas become the main pollution source in winter,and the trend is increasing.NOR and SOR showed that there is obvious secondary pollution in winter,and the reaction ratio of SO2 is greater than that of NO2.Water-soluble ions are significantly correlated with PM2.5 except Na^+ and Mg^2+.The correlation coefficients between NO3^-,SO4^2-and NH4^+ are the largest.Cl-is significantly correlated with cations except Na+.