新乡市秋季大气细颗粒物PM2.5中水溶性离子特征及其来源解析

Characterization and source analysis of the water-soluble inorganic ions in PM_(2.5) of Xinxiang during autumn

为探究新乡市秋季PM_(2.5)污染水平及水溶性离子特征,于2016年9—11月期间,利用TH-150C中流量大气采样器分别在新乡市城市和郊区设立的两个采样点采集了大气PM_(2.5)样品,并分别用重量法和离子色谱法测得PM_(2.5)的浓度值和水溶性离子的组分,分析了大气PM_(2.5)的组成特征、变化规律及污染来源.结果表明,采样期间,城市站PM_(2.5)浓度为122.65~223.56μg·m-3,平均值为164.17μg·m-3,郊区站PM_(2.5)浓度为92.99~217.40μg·m-3,平均值为144.75μg·m-3,均超过国家二级标准浓度限值(75μg·m-3).采样期间,城市站7种水溶性无机离子(NH+4、NO-3、SO2-4、K+、Mg2+、Ca2+、Cl-)的平均质量浓度分别为9.98、22.05、13.41、0.65、0.04、0.30、2.19μg·m-3,郊区站分别为7.49、17.95、10.34、0.38、0.03、0.57、1.35μg·m-3;其中,NO-3、SO2-4、NH+4是大气PM_(2.5)中水溶性离子最主要的二次污染成分,而硝酸盐则是新乡市大气灰霾污染的关键组分.对PM_(2.5)中阴、阳离子进行相关性分析,结果发现,新乡市大气颗粒物PM_(2.5)总体呈酸性.PM_(2.5)中水溶性离子来源主要有二次转化,以及工业源、燃烧源及土壤建筑尘等,移动源(汽车尾气)对新乡市秋季大气污染的贡献较大.

PM2.5 samples were collected at urban and suburban sites from September to November of 2016 by TH-150C. Mass concentration of PM2.5 was analyzed gravimetrically and water-soluble inorganic ions were determined by ion chromatography. The characteristics and variations of PM2.s and its main components of water-soluble inorganic ions as well as source were discussed. The result showed that the variation range of mass concentration of PM2.5 was 122.65-223.56 μg·m^-3 with average mass concentration of 164.17 μg·m^-3, during the sampling period in the urban site of Xinxiang. While in the suburban site, the variation range of mass concentration of PM2.5 was 92.99-217.40 p^g＂ m-3 with average mass concentration of 144.75 μg·m^-3. All of the samples over the limit（ 75 μg·m^-3）. During the sampling period in the urban site, the average mass concentrations of water-soluble ions including NH ,NO3 ,SO2- ,K＊ ,Mgz＋ ,Ca2＋ and C1- were 9.98,22.05,13.41,0.65,0.04,0.30,2.19 μg· m-3 and the water-soluble ions of suburban site were 7.49, 17.95,10.34,0.38,0.03,0.57,1.35 μg·m^-3. The secondary inorganic species, including NO3 ,SOZ4- ,NH~ （SNA） were the major components of the water-soluble ions in PM2.5 , of which nitrate was the most important key components. It was acidic basically according to the ionic equilibrium analysis in PM2.5. It was also detected through source analysis that the PM2.5 mainly from secondary reaction, industrial sources, burning, soil and building dusts and the traffic emission in Xinxiang.