上海市道路灰尘中铂族元素(PGEs)富集特征

分析了上海市道路灰尘铂族元素(PGEs)累积水平和分布特征,并探讨了来源变化.样品经王水消解后由ICP-MS测定.研究结果表明,上海市道路灰尘Rh,Pd,Pt浓度分别达到:27.68(61.05-4.50)ng·g~(-1),107.72(12.98-241.4)ng·g~(-1)和34.89(0.36-108.6)ng·g~(-1),分别是参照点的18.33倍、11.12倍和65.83倍,高出地壳丰度值两个数量级以上,与国际其他城市道路灰尘PGEs水平相比,Pt含量较低,Pd和Rh含量处于中间水平;内环-中环区间的道路灰尘PGEs含基最高,从此区域分别往城区内和城区外,PGEs含鼍逐渐降低,至郊区道路,灰尘PGEs含量达到最低,车流量及道路是否限行高污染车辆是主要致因;不同类型道路PGEs浓度水平表现为:快速路(包括环线)>主干道>次干道>高速公路>郊区公路,道路类型会对PGEs分布产生较大的影响,但并没有对其产生决定性作用;PGEs间相关性很好,汽车催化转化器(VECs)排放是道路灰尘PGEs主要来源,Pd含量远高于Pt和Rh,不同于大多数文献的研究结果,VECs类型发生变化是主要原因;同为交通污染排放的元素,Cr与PGEs的相关性很好,Cu与PGEs之间有一定相关性,Zn只与Pt有相关性,而Ph与PGEs没有相关性,Pb和Zn为汽车催化剂毒物是主要原因.

ENRICHMENT FEATURES OF PLATINUM GROUP ELEMENTS IN ROAD DUST OF SHANGHAI

Platinum group elements (PGEs) levels in road dust from Shanghai were measured, and their spatial variation and sources were discussed as well. Road dust samples were analysed by ICP-MS following aqua regia digestion. PGEs levels in all samples were above the average upper crust values, with concentrations of 27.68 (61.05-4.50) ng · g~(-1) Rh , 107.72 (12.98-241.40) ng · g~(-1) Pd and 34.89 (0.36-108.60) ng ·g~(-1) Pt , respectively, Pd and Rh concentrations were in the middle level and Pt concentrations were lower, in comparison with international cities. Highest pollution occurred between inner ring and middle ring, while lowest values were presented from outer ring to suburb. The rank of PGEs levels in different type of roads was: Elevated Road (Including Ring Line) > Trunk Road > Secondary road > Expressway > Suburban road. Levels of the three elements showed strongly positive correlation. Preliminary results for the anthropogenic Rh, Pd and Pt emissions in Shanghai, based on dust samples, indicated a common traffic-related source of these metals. The average Pd concentration was higher than Pt and Rh, which differed from most previous studies. Meanwhile, the average PGEs ratios of road dust samples from Shanghai were inconsistent with Ely's result. These differences were contributed by the change of vehicle exhaust catalyst type. PGEs in these samples were not correlated with Pb and only Pt were correlated with Zn , though positive correlations with Cr and Cu were evident. This lack of statistically significant relationships can be explained by the fact that Pb and Zn are known as poisoning agents for autocatalysts.