[Temporal variation characteristics of PGEs concentrations in road dust]

In order to study temporal variation characteristics and influencing mechanism of platinum group elements (PGEs) in road dust, 24 seasonal samples and 18 inter annual samples of road dust were collected from roads in Shanghai, and were analysed by ICP-MS following aqua regia digestion. The results are as following: average concentrations of PGEs in spring, summer, autumn, winter were 10.40 (6.06-17.28) ng/g, 11.60 (5.52-20.11) ng/g, 32.91(18.53-61.05) ng/g, 32.33 (16.29-47.89) ng/g with Rh, 52.99 (27.48-100.2) ng/g, 53.77 (20.42-72.31) ng/g, 125.50 (75.41-247.8) ng/g, 132.59 (78.45-199.9) ng/g with Pd, 13.58 (7.96-30.97) ng/g, 13.24 (6.40-17.96) ng/g, 48.20 (25.07-122.9) ng/g, 53.63 (22.11-107.7) ng/g with Pt. PGEs concentrations had obvious seasonal change that were lower in spring and summer, higher in autumn and winter, and rainfall were main effect factors. The comparison of levels of PGEs between 2003 and 2007 showed that PGEs concentrations in road dust had increased over the period of 4 years with 11% - 19% of average annual growth rate because of the rapid increase in the number of vehicles in Shanghai. 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 VECs type.