Fachdokumente Online der Landesanstalt für Umwelt Baden-Württemberg

zur LUBW   zum Ministerium für Umwelt, Klima und Energiewirtschaft   zum Ministerium für Ländlichen Raum und Verbraucherschutz   zum Ministerium für Verkehr und Infrastruktur  

Summary

The noble metals Rh, Pd and Pt are used in catalytic converters since the mideighties to reduce emissions of pollutants. The application of these platinum group elements (PGE) has lead to a drastic increase of the PGE-concentration in the environment, especially in urban particulate matter and along roads with high traffic density. Most emitted particles are smaller than 10 µm.

Despite the considerable efforts during the last 10 years to trace the fate of PGE emitted by car exhausters into the environment, the possible toxic and ecotoxic consequences of high concentrations of PGE in different environmental compartments health are still unknown. This lack of knowledge is due to the heterogeneous distribution and overall low concentration of PGE-containing particles in environmental and biological samples. The assessment of the chemical and mineralogical speciation of these elements is of fundamental importance to estimate the mobility of PGE and their impact on human health. This topic was the main focus of this joint research project processed by the Institut für Lebensmittelchemie und Toxikologie (ILT) and the Institut für Mineralogie und Geochemie (IMG).

The toxicological investigations of ILT focussed on the genotoxic capability of Pt-and Pd-compounds in A549 human lung-cells.

The IMG stressed on 1. development and carrying out reliable analyses of PGEconcentration in the samples of the toxicological experiments; 2. characterization of PGE-bearing particles and investigation of the PGE-speciation in road-side sampled materials.

During this project, high-resolution ICP-MS has turned out to be a reliable and efficient method for measuring Pt und Pd in DNA-adducts and intracellular proteins. The analytical procedure was ensured by quality assurance. The PGE-data of the toxicological investigations are presented in report part B of this joint project.

A specific sampling strategy was conceived to collect car-emitted particles at an engine test stand with respect to the particle diameter. Furthermore, air dust samples were taken, which represent different heights of exposure to human beings (0 – 2.5 m), at a road with a great volume of traffic. In addition, road dust was collected and classified in several particle size fractions.

To characterize the PGE bearing particles (form, mineralogical and chemical composition) and speciation of the PGE in deposition (road/tunnel dust, exhaust gas, atmosphere, run-off) a combination of different sampling devices/techniques (exhaust sampler, Bergerhof-sampler, different impactors and devices) and analytical methods (HR-ICP-MS ±HPLC, ±laser ablation, µ-Synchrotron-EDX, ESEM, XPS, XRD) were used. Despite the high spatial resolution and sensitivity of some of these methods and due to the heterogeneous distribution and the particle size it was not possible to spot and sufficiently characterize PGE bearing grains in dust samples.

Not only the overall concentration in road dust, but also the particle size distribution with the total PGE concentration increasing with decreasing particle size, underlines the potential toxic effect of emitted PGE particles. By carrying out shaking experiments it was found that the solubility of elemental PGE (catalyst material) is enhanced by the interaction with complexing agents, in this case by natural organic matter.

Indirect characterisation of the mineralogical speciation of PGE were carried out by sequential extractions and column experiments. The sequential extraction experiments were performed on tunnel dust and on gully sediments using a dissolution method specially developed for small sample amount and a matrix specific for such kind of environmental materials. The sequential extraction experiments showed, that a high portion (up to 40 %) of Pt is emitted in a mobile or easily mobilised form. The remaining part of Pt showed to be immobile in both, tunnel dust and gully sediments. Column experiments aimed to fill out the gap of the adsorbing behaviour of different environmentally relevant materials on PGE. So far the experiments were carried out with two different kinds of materials (Mn-/Fe-Oxides, Quartz), showing that PGE behaves very similar to heavy metals. These results were underlined by adsorption-experiments.

Within part B of the projects it was investigated whether or no platinum and/or palladium is bioavailable and genotoxic in cultured human lung cells. It was shown that after incubation with particulate platinum compounds platinum was bound to cytoplasmic and nuclear proteins, showing a time-dependent accumulation in the nucleus. Furthermore, platinum-induced DNA adducts were detected, most pronounced after incubation with Al2O3-Pt-particles, which closely resemble those emitted from automobile catalysts. Nevertheless, no mutagenic potential and no increase in micronuclei formation was observed; it cannot be excluded, however, that these test systems may not be sensitive enough towards particulate compounds. Taken together, our results point towards a bioavailability also of particulate platinum compounds, demonstrating that they are not inert towards biological systems.

 


Weitere Themenbereiche
Weitere Fachsysteme
 
Seitenanfang Seite drucken

Fachdokumente Online