Temporal and spatial studies of autocatalyst-derived platinum, rhodium. and palladium and selected vehicle derived trace elements in the environment

The distribution of platinum; rhodium, and palladium (platinum-group elemen ts; PGEs) adjacent to two major U.K. roads shows a rapid decrease (more tha n 1 order of magnitude) away from the road and reflects patterns shown by o ther traffic-derived trace elements such as Ph and Zn. However, ratios of P t:Rh remain relatively constant from Oto 10 m distance, suggesting that at least some of the PGEs are transported away from the source. A temporal stu dy over a 12-month period, of;road dust and surface samples, reveals elevat ed concentrations above background levels, with maximum values of Pt >500 n g g(-1), Rh 70 ng g(-1), and Pd 70 ng g(-1). Concentrations vary considerab ly throughout the year and show some tentative correlation with rainfall. E lement speciation, an essential control on mobility and hence distribution, was investigated, and the results of solubility experiments show that up t o 30% of the Pd present dissolves in acid solutions. This indicates that at east some of the Ed is present in a soluble-term and is therefore potentia lly highly mobile.