太原市采暖季清洁天与灰霾天PM2.5中水溶性无机离子组成及来源分析

Composition and source analysis of water-soluble inorganic ions of PM2.5 in clean and haze days during heating season in Taiyuan City

为探究太原市采暖季PM2.5水溶性无机离子组成及其来源,于2017年11月至2018年3月在太原城区连续采集大气颗粒物PM2.5样品共151个,并于离子色谱仪中分析样品的9种水溶性无机离子(F^-、Cl^-、NO3^-、SO4^2-、K^+、Na^+、Ca^2+、Mg^2+、NH4^+).结果表明,太原市采暖季PM2.5质量浓度的平均值为77.89±47.16μg·m^-3,总水溶性无机离子质量浓度平均值为53.21±29.76μg·m^-3,占PM2.5的68.3%±23.3%,其中SO4^2-、NO3^-和NH4^+是PM2.5中最主要的离子成分,NH4^+在PM2.5中主要以NH4NO3、(NH4)2SO4与NH4Cl等形式存在,NH4^+、NO3^-、K^+、SO4^2-和Cl^-等5种离子的爆发性增长对灰霾天污染贡献最大.随着气温回升,硫氧化率和氮氧化率均有一定程度的升高,大气中存在明显的气溶胶二次转化过程.主成分分析表明,燃煤源和二次污染源是太原市采暖季灰霾期间的主要污染源,土壤扬尘为清洁天的首要污染源,大气污染以固定污染源为主,移动污染源为辅.后向轨迹模型显示,采暖季期间气团基本上来自本地和西北方向的内陆排放源.

To research the composition and source of water-soluble inorganic ions of PM2.5 in the heating season of Taiyuan city,a total of 151 samples of PM2.5 were continuously collected from November 2017 to March 2018 in Taiyuan city,and nine water-soluble inorganic species(F^-,Cl^-,NO3^-,SO4^2-,K^+,Na^+,Ca^2+,Mg^2+,NH4^+) in these samples were analyzed by using an ion chromatograph.The results showed that the mass concentrations of PM2.5 and of total water-soluble inorganic ions were 77.89±47.16 μg·m^-3 and 53.21±29.76 μg·m^-3,respectively,and those ions accounted for 68.3%±23.3% of PM2.5,among them,SO4^2-,NO3^- and NH4^+ were the most important ionic components in PM2.5.NH4+ exists mainly in the form of NH4NO3,(NH4)2SO4 and NH4Cl in PM2.5.The explosive growth of the five ions(i.e.,NH4^+,NO3^-,K^+,SO4^2- and Cl^-) were main contributors in haze days.,As the temperature went up,the sulfur and nitrogen oxidation rate had a certain degree of elevation,demonstrating a significant aerosol secondary conversion processes in the atmosphere.The principal component analysis indicated that the coal source and the secondary pollution source were the main pollution sources in haze days,while the soil dust was the major pollution source in clean days.Air pollution of Taiyuan city were dominated by fixed pollution sources,supplemented by mobile pollution sources.The backward trajectory model showed that during the heating period air mass came mainly from inland emission sources of the local and of northwest directions.