川南四座城市PM_(2.5)化学组分污染特征及其源解析

Pollution characteristics and source apportionment of PM_(2.5) in four urban environment of Southern Sichuan

为探究川南地区大气气溶胶中化学组分与来源特征,于2015年9月—2016年8月在四川盆地南部4个典型代表城市(泸州、内江、宜宾、自贡)采集了226个PM_(2.5)样品,对PM_(2.5)的质量浓度和主要化学组分(水溶性离子和碳质组分)进行测定,并利用颗粒物源解析受体模型对PM_(2.5)来源进行解析.结果表明:川南地区PM_(2.5)日均浓度为46.4—68.0μg·m^(-3),均高于国家环境空气质量标准年均PM_(2.5)限值(35.0μg·m^(-3)).OC、EC和水溶性二次离子(SO_(4)^(2-)、NO_(3)-和NH_(4)+)分别占PM_(2.5)质量的15.7%—22.8%、4.2%—6.4%和28.6%—55.8%.PM_(2.5)及其主要化学组分浓度有显著的季节变化,即冬季浓度显著高于其他季节,夏季浓度最低.泸州除夏季外,其他季节SO_(4)2-、NO_(3)-同源性较好;其他城市在冬季,SO_(4)2-、NO_(3)-同源性较好.NH_(4)+主要存在形式为NH_(4)NO_(3)、(NH_(4))2SO_(4)、NH_(4)HSO_(4).OC、EC来源复杂,主要为机动车源、煤燃烧源和生物质燃烧源.川南地区PM_(2.5)的来源主要受8种因子影响,按总体贡献排序依次为:二次硫酸盐、生物质燃烧、工业源、二次硝酸盐、机动车源、煤燃烧、道路尘埃和建筑尘埃.此外,相比较而言,机动车源贡献在泸州市较凸显,煤燃烧源贡献在宜宾市较凸显.

To investigate the chemical compositions and determine the sources of PM_(2.5) in southern Sichuan Basin,226 PM_(2.5) samples were collected from four representative cities:Luzhou,Neijiang,Yibin,and Zigong,from September 2015 to August 2016.The mass concentration of PM_(2.5) and major chemical compositions,including water-soluble inorganic ions and carbonaceous species,were determined,and the contributory factors to the mass of PM_(2.5) were analyzed by a receptor model on source apportionment.The results showed that the PM_(2.5) mass concentration during sampling periods in southern Sichuan were 46.4—68.0μg·m^(-3),which were higher than the annual PM2.5 National Ambient Air Quality Standard of China(35.0μg·m^(-3)).The mass fraction of OC,EC and total secondary inorganic ions(SO_(4)2-,NO_(3)-and NH_(4)+)in PM_(2.5) were 15.7%—22.8%,4.2%—6.4%and 28.6%—55.8%,respectively.Higher mass concentration of PM_(2.5) and major chemical compositions were observed in winter compared to other seasons,while the lowest mass concentration of PM_(2.5) were observed in summer.High homology had been found between SO_(4)2-and NO3-in Luzhou across the sampling periods except for summer,and higher homology had been found in the other three cities during winter.The dominant forms of NH_(4)+in PM_(2.5) were NH_(4)NO3,(NH_(4))2SO_(4)and NH_(4)HSO_(4).The sources of OC and EC showed great diversity,and the analysis of correlation and ratio between OC and EC revealed that the sources for the two carbonaceous species were:vehicle exhaust,coal combustion and biomass burning.In addition,the results of source apportionment indicated that PM_(2.5) in southern Sichuan was mainly attributed to eight factors:secondary sulphate,biomass burning,industrial emission,secondary nitrate,vehicle exhaust,coal combustion,road dust,construction dust.In terms of the different factors in different cities,the contribution of vehicle exhaust was more prominent in Luzhou,and the contribution of coal combustion was more prominent in Yibin.