南通市PM2.5中水溶性离子季节分布特征

对南通市2016年12月-2018年10月大气污染季节分布特征进行了分析。结果表明,南通市ρ(PM2.5)和ρ(水溶性离子)为冬、春季高,夏、秋季低。春夏秋冬四季ρ(水溶性离子)占ρ(PM2.5)百分比分别为68.2%,70.6%,64.5%和74.5%,其中二次离子SNA(NO3-、SO42-和NH4+)占ρ(PM2.5)的百分比分别为63.1%,67.0%,59.3%和66.8%;ρ(NO3-)/ρ(SO42-)表明,移动源已成为南通市春、秋、冬季的主要污染源,四季均存在不同程度的二次转化,且SO2的转化率均大于NO2,NO2冬季转化率最大、夏季最小,SO2夏季转化率最大、秋季最小。南通市NO2转化为硝酸盐的主要形式是气相均相反应,非均相反应和均相反应对SO2转化为硫酸盐的贡献差异不大。

Seasonal Distribution Characteristics of Water soluble Ions in PM2.5 in Nantong

The seasonal distribution characteristics of atmospheric pollution from December 2016 to October 2018 in Nantong were analyzed.During the study period,the concentrations of PM2.5 and water-soluble ions in Nantong are higher in winter and spring and lower in summer and autumn.In spring,summer,autumn and winter,water-soluble ions contributed 68.2%,70.6%,64.5%,74.5% of PM2.5( mass ratio) respectively,among which SNA( NO3-,SO42- and NH4+) contributed 63.1%,67.0%,59.3%,66.8% respectively.The ρ(NO3-)/ρ(SO42-) ratio implied that mobile source has become the main pollution source in spring,autumn and winter in Nantong.There are different degrees of secondary reactions in the four seasons,and the reaction ratio of SO2 is greater than that of NO2.The reaction ratio of NO2 is the highest in winter and the lowest in summer,and the reaction ratio of SO2 is the highest in summer and the lowest in autumn.The main form of NO2 conversion to nitrate in Nantong is gas homogeneous reaction.Heterogeneous and homogeneous reactions contribute equally to the conversion of SO2 to sulfate.