南京市冬季PM_(2.5)中水溶性离子污染特征研究

Pollution Characteristics of Water-soluble Ions in PM_(2.5) in Winter in Nanjing

基于城市超级站对2018年12月-2019年2月南京市在线水溶性离子污染特征进行研究。结果表明:监测期间水溶性无机离子(WSIs)质量浓度均值为45.7μg/m^(3),占PM_(2.5)的67.8%,各离子排序为NO_(3)^(-)>SO_(4)^(2-)>NH^(+)_(4)>Cl^(-)>K^(+)>Ca^(2+)>Na^(+)>Mg^(2+)。二次离子(SNA)是PM_(2.5)主要组分,大气气溶胶呈中性。各离子日变化存在差异,SNA变化趋势和WSIs基本一致。南京市冬季存在明显SO_(2)和NO_(2)向SO_(4)^(2-)和NO_(3)^(-)二次转化;NO_(3)^(-)/SO_(4)^(2-)均值为1.96,移动源增量大于固定源。通过相关性和三相聚类分析可知,SNA主要结合方式为(NH_(4))_(2)SO_(4)和NH_(4)NO_(3)。主成分分析表明,南京市冬季PM_(2.5)中水溶性离子主要来源是二次转化,燃煤、生物质燃烧和土壤建筑扬尘也有贡献。

The pollution characteristics of online water-soluble ions in Nanjing from December 2018 to February 2019 were studied based on urban atmospheric supersite.The results showed that the average mass concentration of water-soluble inorganic ions(WSIs)during the monitoring period was 45.7μg/m^(3),accounting for 67.8%of PM_(2.5).The order of ion concentration was NO_(3)^(-)>SO_(4)^(2-)>NH^(+)_(4)>Cl^(-)>K^(+)>Ca^(2+)>Na^(+)>Mg^(2+).Secondary ions(SNA)were the main components of PM_(2.5),and atmospheric aerosol was neutral.The daily variation of each ion concentration was different.The variation trend of SNA was basically consistent with that of WSIs.There was obvious secondary transformation of SO_(2) and NO_(2) to SO_(4)^(2-) and NO_(3)^(-) in Nanjing in winter.The ratio of average concentration of NO_(3)^(-)/SO_(4)^(2-) was 1.96,and the increment of mobile source was greater than that of stationary source.Correlation and three-phase cluster analysis showed that the main combination modes of SNA were(NH_(4))_(2)SO_(4)and NH_(4)NO_(3).Principal component analysis showed that the main source of water-soluble ions in PM_(2.5)in Nanjing in winter was from secondary transformation.In addition,coal combustion,biomass combustion,soil dust and building construction dust also made contribution.