喀斯特城市大气颗粒物及其稀有金属、铂族元素的来源解析与示踪

The contents of rare heavy metals such as Ge, Mo, In, Tl, Bi, Re and the paltinum group metals (PGM) in the fly ash released by power plants, smelteries and automobil catalyst converters，which are major components of PM10 and PM2.5, are 1-3 orders of magnitude higher than those in the normal dust. Compared to conventional metals,these metals are significant parameters in investigating the components and souces of atmospheric particulates due to their obvious characteristics. However, there have been few reports on the effects of rare heavy metals and PGE on airborne particulate matter. In this project, we will investigate the features of rare heavy metals and PGE contained in atmospheric particulates in the karst city Guiyang based on its unique geographic conditions and its particular human activities. A receptor model and tracer technique CMB for regional atmospheric particulates will be established using PGM and rare metals as indicator for particulates released by automobiles and smelteries. The model is capable to conduct sources apportionment on rare heavy metals and PGM contained in atmospheric particulates of different functional regions of Guiyang city, help us more accurately quantize the contribution rate of emission sources such as automobiles and smelteries to the receptor, provide a scientific basis for us to find out new indicators and to conduct sources apportionment on atmospheric particulates based on optimized tracer technique, and guarantee an acurate and complete sources apportionment result on atmospheric particulates in Guiyang City.

稀有金属如Ge、Mo、In、Tl、Bi、Re及铂族元素在对PM10和PM2.5贡献极大的火电厂、冶炼厂及汽车尾气排放的粉尘中含量是一般尘土的1-3个数量级，与常规重金属比较特征明显，是研究大气颗粒物成份及来源的重要参数，但以往的研究对这些元素很少涉及。本申请针对喀斯特城市独特的地域特性及人类活动的特殊性，开展PM10、PM2.5中稀有金属、铂族元素含量特征及源区特征研究，将铂族元素、稀有金属分别作为量化一次颗粒物汽车尾气尘、冶金尘排放的示踪物，建立区域大气颗粒物注入新示踪物的CMB受体模型及示踪方法；运用该模型对喀斯特城市不同功能区大气颗粒物进行来源解析，更准确的量化冶金尘、汽车尾气尘排放源对受体的贡献率，为寻找新的化合物种示踪物、利用并优化示踪技术进行大气颗粒物源解析提供科学依据，并将对提高城市大气颗粒物源解析结果的准确性和完整性具有积极意义。

铂族元素（PGE）及稀有金属是大气中不易被生物降解且具有生物蓄积性的组分之一，能以颗粒物为载体迁移转化。本研究建立了颗粒物样品中铂族元素及稀有金属的检测分析方法，同时，采用同位素法示踪大气细颗粒物中铂族元素的来源与迁移途径；研究了受体及污染源PM2.5中PGE的含量水平、分布特征及同位素组成特征；测定了PM2.5中铂族元素、稀有金属、无机元素、黑碳及水溶性阴离子等的含量，构建了贵阳市受体及污染源PM2.5成分谱，并运用PMF模型和比值特征法分别对贵阳市大气PM2.5及其中Pt、Pd、Rh和重金属等来源进行解析。结果表明：石英滤膜采样前经王水处理可有效的降低铂族元素及微量元素空白值；贵阳市PM2.5中Pd、Pt和Rh浓度均值分别为16.04±4.15、5.84±1.91和1.46±0.37 pg/m3，同位素组成特征和线性分析表明PM2.5中PGE主要来源于汽车尾气；贵阳市七类污染源中金属冶炼尘、燃煤尘和汽车尾气尘的PGE浓度占比达97.09%，是大气PGE污染的主要来源；对市区和郊区大气PM2.5贡献值最大的均为汽车尾气尘，其中市区PM2.5主要来源于汽车尾气尘源、金属冶炼尘与燃煤尘混合源、锅炉排放源、二次源与垃圾焚烧复合源、土壤与建筑尘复合源，贡献率分别为32.4%、29.5%、18.7%、15.2%、4.2%；交通污染、燃煤和工业冶金是PM2.5中10种金属的主要来源，贡献率分别为39%、37%、14%，其中As、Cr和Cd的致癌风险值介于4.3×10-6和4.4×10-5之间，对人群可能存在致癌风险；PM2.5中24 h的黑碳质量浓度分别为1.48-8.49 μg/m3，后向轨迹分析结果表明，贵州省本地及重庆东南部气流对贵阳市秋、冬季黑碳贡献更大。本研究对提高城市大气颗粒物源解析结果的准确性和完整性具有积极意义。