贵阳公路周边尘土和土壤铂族元素特征分析

Characteristics of Platinum-group Elements in the Road Dust and Roadside Soil of Guiyang,Guizhou,China

为降低温室效应气体一氧化碳、氮氧化物及碳氢化合物的排放,全球自上世纪80年代末期开始在汽车中引入铂族元素（PGE）催化剂,其释放的Pt、Pd和Rh等元素在城市道路尘土和路边土壤中聚积,对自然环境及人体健康产生危害。本文在贵州省贵阳市的主要交通路段采集了尘土和土壤样品,对样品中的铂族元素进行了同位素稀释-等离子体质谱法测定。结果表明,所有样品的铂族元素均高于未被污染土壤的背景值,而尘土样品中铂族元素含量明显高于土壤样品。其中Pt、Pd和Rh含量明显高于其它铂族元素（Ru和Ir等）,并与Ru和Ir呈一定的正相关关系,表明汽车尾气催化剂的主要组成为Pt、Pd和Rh;高含量的Os具有低的187Os/188Os比值,表明Ru、Ir和Os也源于汽车尾气催化剂,可能是以杂质的形式存在于汽车尾气催化剂中。

Platinum group elements（ PGEs） were used as automobile catalytic converters to reduce greenhouse gases,such as carbon monoxide,nitrogen oxides（ NOx） and hydrocarbons in the late 1980 s. However,the increasing utility of PGEs as catalytic converters had led high concentrations of PGEs in road dusts and roadside soils of urban areas,which is harmful to ecological environment and human health. This paper evaluated contaminations of PGEs in road dusts and roadside soils around the Guiyang city,Guizhou,China.PGEs were analyzed using the isotope dilution method on ICP-MS. Results indicated that all samples showed raised PGE concentrations relative to the background uncontaminated soil,the PGEs concentrations of road rusts were much higher than those of roadside soils,and Pt,Pd and Rh contents were higher than other PGEs（ i.e. Ru and Ir）. In addition,clear positive correlations among Pt,Pd and Rh were observed in all samples,indicating that automobile catalysts are composed mainly by Pt,Pd and Rh. The concentrations of Ir,Ru and Os were higher in all samples than in the background uncontaminated soil,and the higher was the Os concentration the lower was 187Os/188Os ratios,suggesting that Ir Ru and Os elements also derived from automobile catalytic converters as impurities of the automobile catalysts.