Distribution of platinum group elements in urban soils, comparison of historically different large cities Prague and Ostrava, Czech Republic

The distribution of platinum group elements (PGE) was studied in the soils of municipal parks in two large industrial cities with different histories, Prague and Ostrava in the Czech Republic. Soil samples were taken from depths of 0–10, 10–20 and 20–30 cm and the Pd, Pt, Rh and Ir contents were studied in the individual samples following dokimastic separation into NiS using ICP MS. Higher PGE contents were determined in Prague; the highest contents were found in the centres of both cities because of the slower, stop-and-go movement of automobiles during which more PGE's are emitted. The maximum PGE contents found were for Pt in Prague (160 μg kg− 1), with lower contents of Pd (49 μg kg− 1), followed by Rh (3.9 μg kg− 1). Elevated PGE concentrations are observable in the topmost layers of most soils. At some locations, the maximum PGE concentrations were observed in deeper parts of the profile. On the basis of the maximum numbers of registered vehicles (1997) and assumption that new vehicles emit the highest amounts of PGE, the calculated velocity of migration of metals through the profile corresponded to 1.1–2.2 cm year− 1. The statistically lower PGE contents in areas under the tree crowns compared to open sites can be explained by the annual collection and removal of fallen biomass containing the captured catalyst particles.

► The distribution of PGE was studied in the soils of municipal parks.
► The maximum contents decreased in the order Pt, Pd and Rh.
► Open sites contain higher PGE compared with those under tree crowns.
► The rate of migration of PGE in the soil varies between 1.1 and 2.2 cm year- 1.