南京江北新区大气颗粒物化学组分的粒径分布特征

Size Distribution of Particulate Chemical Components in Nanjing Jiangbei New Area

为探究南京江北新区大气颗粒物化学组分的污染特征,于2013~2014年进行了分级颗粒物样品的采集,开展了颗粒物化学组分的粒径分布和季节变化研究.结果表明,细粒径段的9种水溶性离子总浓度在秋冬季高于春夏季,而粗粒径段冬季最高.冬季颗粒物中[NO^-3]/[SO4^2-]在粗粒径段最低;春、夏和秋季其粒径分布趋势一致.水溶性离子均呈双峰型分布,4个季节的NO^-3均在0.65~1.1μm出现峰值;夏秋季细粒径段的SO4^2-于0.43~0.65μm出现峰值,冬季峰值位置向更粗粒子的方向移动;而Na+和Cl-主要存在于粗粒子中.由阴阳离子电荷当量表明,大气粗、细粒子分别呈碱性和弱碱性.有机碳(OC)和元素碳(EC)主要存在于细粒径段,均呈双峰型分布;秋冬季细粒径段中的二次有机碳(SOC)远高于春夏季.由比值判断法进一步表明,南京江北新区颗粒物中的碳质组分主要来源于燃煤和生物质燃烧排放、机动车尾气排放等.

In order to explore the pollution characteristics of the chemical components of atmospheric particulate matter in Nanjing Jiangbei New Area,size-resolved samples were collected from 2013 to 2014.The size distribution and seasonal variation of the chemical components of the particles were studied.The results showed that the total concentration of nine water-soluble ions in fine particles was higher in autumn and winter than in spring and summer,while the concentration of coarse particles was highest in winter.The ratio of NO-3/SO4^2-for the fine particles in winter was slightly higher than in the other three seasons,and lowest in the coarse particles.The trend of particle size distribution in spring,summer and autumn was consistent.The distribution of water-soluble ions was bimodal,and NO-3 peaked at 0.65-1.1μm in all four seasons.The peak radius of SO4^2-in the fine particles in summer and autumn was 0.43-0.65μm,and the peak value in winter moved towards the coarser particles,while Na+and Cl-mainly existed in the coarse particles.The charge equivalent of anion and anion indicated that the coarse and fine particles were alkaline and weakly alkaline,respectively.Organic carbon(OC)and elemental carbon(EC)mainly existed in the fine particles,with a bimodal distribution.The secondary organic carbon(SOC)in the fine particles in autumn and winter was significantly higher than in spring and summer.The ratio method further indicated that the carbonaceous component of the particulate matter in Nanjing Jiangbei New Area is mainly from the emissions of coal and biomass combustion,and vehicle exhaust.