Cycling of Pt, Pd, and Rh Derived from Catalytic Converters: Potential Pathways and Biogeochemical Processes

Abstract

The present study is an integrated approach to the Pt, Pd, and Rh cycling derived from catalytic converters along highway roadsides of the Athens Basin, including their contents, the dispersed Pt- and Pd-bearing nano- and microparticles in dust and bioaccumulation in plants, aiming to assess the auto-catalyst-derived environmental impact to the large city of Athens and the potential human health risk. The determined mean values of 314 Pt, 510 Pd, and 23 Rh (all in μg/kg) in dust samples are much lower than the 2070 μg/kg Pt and 1985 μg/kg Pd contents in gully pots in the Katechaki peripheral highway and higher than the mean values of 230 Pt, 300 Pd, and 13 Rh (all in μg/kg) in the soil samples. With the exception of two samples from gully pots, from 51% to 70% of the samples (for the Pd and Pt, respectively) fall in the range from 100 to 400 μg/kg. The calculated accumulation factors showed means of 3.88 μg/kg Pd and 2.95 μg/kg Pt for plants and tree leaves, but any significant difference (t-test) is lacking, and they are much lower than those reported for roots of plants (literature data). Although the Pt, Pd, and Rh bioaccumulation factors for shoots of plants/crops are relatively low, the increasing number of cars with catalytic converters in Greece and the relatively high bioaccumulation in the food chain may highlight a potential risk for human health and ecosystems, and the need for special attention on their bioaccumulation and bioaccessibility on a global scale.