基于在线观测的太原市冬季PM_(2.5)中金属元素污染水平及来源解析

On-line Measurement of Trace Elements in PM_(2.5)in Winter in Urban Taiyuan,China:Levels and Source Apportionment

为更好地识别太原市PM_(2.5)的来源,于2022年1月采用在线多金属监测仪对太原市区PM_(2.5)中13种金属元素(K、Ca、Ba、Cr、Mn、Fe、Cu、Ni、Zn、As、Se、Pb和Sr)小时浓度进行了监测,分析了其污染特征,采用正定矩阵因子分解(PMF)模型解析了其来源.结果表明,13种金属元素浓度之和均值为(3901.6±2611.2)ng·m^(-3),在PM_(2.5)中平均占比为(7.1±7.7)%.Fe、Ca和K是3种主要的金属元素,浓度平均值分别为(1319.5±1003.5)、(1181.0±1241.6)和(883.3±357.3)ng·m^(-3).ρ[Cr(Ⅵ)](4.6ng·m^(-3))和ρ(As)(11.2 ng·m^(-3))平均值高于国家环境空气质量(GB 3095-2012)和世界卫生组织的标准值.PMF源解析结果显示:扬尘、机动车排放、不锈钢制造、生物质燃烧与垃圾焚烧、散煤燃烧和工业燃煤是PM_(2.5)中金属元素的主要来源,分别贡献了45.5%、1.4%、15.8%、23.7%、5.5%和8.1%.在PM_(2.5)污染事件中,相比于污染发展和消散阶段,污染维持阶段工业燃煤、散煤燃烧、生物质燃烧与垃圾焚烧对金属元素的贡献率上升明显,分别贡献了11.8%、7.1%和28.1%.研究结果可为其他区域开展精细化PM_(2.5)来源解析工作提供一定的科学参考.

In order to better identify the sources of PM_(2.5)in Taiyuan,hourly concentrations of 13 trace elements(K,Ca,Ba,Cr,Mn,Fe,Cu,Ni,Zn,As,Se,Pb,and Sr)in PM_(2.5)were monitored at an urban site in Taiyuan from January 1 to 29,2022.The pollution characteristics of trace elements were analyzed and sources were apportioned using positive matrix factorization(PMF).The results showed that the average concentration of 13 total trace elements was(3901.6±2611.2)ng·m^(-3),which accounted for(7.1±7.7)%of PM_(2.5).The three dominant elements were Fe[(1319.5±1003.5 ng·m^(-3))],Ca[(1181.0±1241.6 ng·m^(-3))],and K[(883.3±357.3 ng·m^(-3))].The average concentrations of Cr(Ⅵ)(4.6 ng·m^(-3))and As(11.2 ng·m^(-3))exceeded the guideline values of the Chinese National Ambient Air Quality Standard(GB 3095-2012)and the World Health Organization.Fugitive dust,vehicle emissions,industry,stainless-steel production,biomass burning and waste incineration,residential coal combustion,and industrial coal combustion were identified by the PMF model,which accounted for 45.5%,1.4%,15.8%,23.7%,5.5%,and 8.1%,respectively,of the total elements.Compared with those during the stages of pollution development and dissipation,the contributions of industrial coal combustion,residential coal combustion,and biomass burning and waste incineration to the total elements during the pollution maintenance stage of the PM_(2.5)pollution episode increased significantly,contributing 11.8%,7.1%,and 28.1%,respectively,of the total elements.These results could provide scientific references for the refined source apportionment of PM_(2.5)in other areas.