南京江北新区冬季PM2.5中化学组分的昼夜变化特征及其来源解析

Diurnal Variations and Source Apportionment of Water-soluble Ions in PM2.5 During Winter in Nanjing Jiangbei New Area

为更好地了解南京江北新区大气气溶胶中水溶性离子的昼夜变化特征,冬季连续采集了2个月的PM2.5样品,研究其水溶性离子昼夜变化特征及来源解析.结果表明,观测期间水溶性离子质量浓度变化范围为17.07~168.43μg·m^-3,均值为(59.01±30.75)μg·m^-3,且白天的水溶性离子平均质量浓度高于夜晚.NO3^-和NH4^+的浓度占离子总浓度的比值在夜晚偏高,而SO4^2-和Cl^-则在白天偏高.SO4^2-、NO3^-和NH4^+(SNA)是南京市PM2.5中最重要的水溶性离子,其质量浓度在污染天要高于清洁天.白天和夜晚的阴阳离子平衡比值(AE/CE)大于1,说明PM2.5呈酸性.相关性分析显示NH4^+与NO3^-、SO4^2-之间具有显著的线性相关性,其在PM2.5中主要是以NH4NO3和(NH4)2SO4结合方式存在.PMF源解析进一步表明南京江北新区冬季大气PM2.5中水溶性离子主要来源于机动车排放、化石燃料燃烧、生物质燃烧和扬尘等.

To gain a better understanding of the day-night variation characteristics of water-soluble ions,PM2.5 samples were continuously collected for two months in the Nanjing Jiangbei New Area during winter.The diurnal variation and sources of watersoluble ions were studied.Results showed that the mass concentration of water-soluble ions ranged from 17.07μg·m^-3 to 168.43μg·m^-3 with a mean value of(59.01±30.75)μg·m^-3.The average mass concentration of water-soluble ions in daytime was higher than that in the nighttime.The concentration ratio of NO3^-and NH4^+to total ion concentrations was higher at night,while SO4^2-and Cl^-were higher during daytime.SO4^2-,NO3^-,and NH4^+(SNA)were the dominant species of water-soluble ions in PM2.5 in Nanjing.The mass concentration of SNA on polluted days was higher than that on clean days.The ratio of the anion-cation balance(AE/CE)was larger than 1,indicating that the PM2.5 was acidic.There was a significant linear correlation between NH4^+with NO3^-and SO4^2-,indicating that it occurred mainly in the form of NH4NO3 and(NH4)2SO4 in PM2.5.The PMF source apportionment indicated that water-soluble ions of PM2.5 were mainly derived from motor vehicle emissions,fossil fuel combustion,biomass burning,and dust in the Nanjing Jiangbei New Area.