Anthropogenic emission of platinum-group elements (Pt, Pd and Rh) into the environment: concentration, distribution and geochemical behaviour in soils

Abstract

The introduction of catalytic converters on cars in order to meet emission standards initiated the beginning of a sometimes controversial discussion on the probable immission of platinum-group elements (PGE) into, and their possible effects on the environment. The used PGE (platinum, palladium and rhodium) reduce by catalytic reactions hazardous components in engine emissions. However, the complex and often adverse working conditions (temperature changes, variations in gas composition and flow rate, and mechanical abrasion by vibrations) lead to a chemical and mechanical treatment of the catalytic converters, resulting in a loss and emission of PGE. In consequence, even only 15 years after the introduction of catalytic converters in Germany, one finds significantly elevated PGE contents in environmental compartments along roadsides. The geogenic background PGE concentrations are estimated to lie in untreated soil at ca. 1 µg/kg (Zereini et al. 1997a), whereas contaminated soils along roadsides show contents up to several hundred µg/kg (e.g. Cubelic et al. 1997; Claus et al. 1999; Beyer at al. 1999; Dirksen 1998; Helmers and Mergel 1997; Laschka et al. 1996; Zereini 1997; Zereini and Alt 1999). Whereas this trend is well proven, the environmental effects are still not understood and await further investigation.