Bio-availability of PGE-emissions

Over the past 20 years the determination of platinum group elements (PGE) has received special interest in order to evaluate possible risks for human health and living organisms. This interest is motivated by the increased use of Pt, Pd and Rh as catalysts in car exhaust systems, the medical application of platinum containing drugs in anti-cancer chemotherapy, and the use of different PGE as catalyst metals during the synthesis of pharmaceuticals. All these applications contribute to the increase of the concentration of PGE in environmentally relevant matrices, especially in roadside dusts, soils and plants, which consequently may affect the health of human beings and other living organisms. Although a lot of work has been dedicated to the determination of PGE in environmental, biological and clinical samples information about the environmental pathways of PGE - from automobile emission to biological accumulation - is still very sparse. The purpose of this project is to extend the current knowledge on environmental transformation, mobility, speciation and bioavailability of anthropogenic Pt, Pd and Rh emissions. The proposed research covers the following innovative aspects: A major goal of the present project is to assess the fraction of Pt, Pd and Rh in solid environmental matrices which can be mobilised under environmental conditions. A novel dynamic extraction procedure will be developed for time-resolved investigation of the mobilization process - providing insight into leaching kinetics. Partitioning between organically complexed and labile Pt, Pd and Rh species in aqueous extracts of aerosol, road dust and soil samples will be investigated for assessment of the environmental and biological significance of mobilised species. Pt, Pd and Rh uptake potential of Ni hyperaccumulator plants and Ni excluder species will be studied to explore the uptake of traffic related Pt, Pd and Rh emissions by the terrestrial biosphere. In a model study the mobilisation and bioaccessibility of Pt, Pd and Rh inhaled via urban particulate matter will be investigated to provide information about the mobility of inhaled metals. Automation and further enhancement of existing procedures for sample preparation and analysis to allow an accurate detection of Pd, Rh and Pt in environmental, biological and medical samples. The project will be performed in collaboration with the University of Natural Resources and Applied Life Sciences BOKU - Vienna (Department of Chemistry and Department of Forest and Soil Sciences) and the University of Munich (Institute and Outpatient Clinic for Occupational and Environmental Medicine).

Since the introduction of three-way-catalysts for combustion engines, automobiles have become a main source for the emission of the platinum group elements (PGE) Pt, Pd and Rh, especially in the vicinity of motorways and in urban areas. Generally, PGEs are known to behave in an inert manner and to be immobile in the environment. However, there is evidence of spread and bioaccumulation of these elements. The purpose of this project was to extend the current knowledge on environmental transformation, speciation, bioavailability and mobility of anthropogenic Pt, Pd and Rh emissions. Up to now, the bio-accessibility of Pd and Pt has been determined by using ground catalyst material or road dust only. Within this project, the physiologically soluble fraction of Pd and Pt in airborne particulate matter has been investigated for the first time. The results indicate a distinctly improved bio-accessibility of these elements (approximately one order of magnitude higher) and could be explained with aging processes of the emitted PGE containing particles in the atmosphere, which transform the initially metallic PGE into more soluble and thus bio- accessible species. Therefore, the potential toxicological impact of inhaled PGE has been underestimated in the past. Based on the findings derived from soil sorption experiments, sorption isotherms for Pt, Pd and Rh on Austrian soils were determined for the first time. These data are a prerequisite to assess the risk of PGE-transfer into the food chain and to evaluate their potential to leach into the groundwater. For Pd, an almost quantitative sorption was observed in all soils, whereas Rh and Pt are adsorbed to a much lesser extent, suggesting a higher leachability for these elements. Furthermore, within this project a systematic investigation of PGE uptake by the terrestrial biosphere has been conducted using Brassica napus and Alyssum serpyllifolium. For all investigated plants a significant uptake of PGEs has been observed, the degree of uptake was found to be dependent on the buffer system (MES versus BES) used in the nutrient solutions. The spatial PGE-distribution inside the plants showed significant differences between the leaves, stem, coarse and fine roots. Moreover, the results showed that rhodium is the element with the highest impact on plant toxicity, while platinum is the preferred element transferred into the upper parts of the plants.