Abstract:

Since the introduction of Pt as a catalytic element in industrial processes and as an agent in automobile catalytic converters, the emission of the noble metal into the environment has been rising steadily. Consequently, it has been the objective of this thesis to conduct a thorough investigation of introduction of traffic related Pt into rivers and its subsequent distribution in the abiotic and biotic compartments of these systems. In addition the genotoxicological effects of Pt on aquatic organisms have been studied. Initially, the analytic procedures used in this study have been validated with regard to their suitability for analyzing Pt and other traffic related heavy metals in field samples. Furthermore, a passive monitoring study at a representative discharge location of road runoff was performed. It provided evidence about the spatial distribution of Pt in river sediments as well as the Pt accumulation in clams. Highest Pt loads were found in the sand fraction of sediment samples. Pt concentrations in sediments were strongly correlated to concentrations of other traffic related heavy metals. The results also confirm that Pt was accumulated by Corbicula sp. in the field. Due to the fact that no correlation between sediment and clam concentration could be observed, it is assumed that Pt was accumulated in soluble form or ingested with small particles from suspended particulate matter. In comparison to other traffic related heavy metals, Pt concentrations in sediment and clam samples were low. This thesis further aims on the analysis of the accumulation kinetics of Pt in the biota (e.g. bivalves, fish and fish parasites) under laboratory conditions. In exposure studies with Corbicula sp., it could be observed that the accumulation of Pt by the clams is dependent on the ambient Pt concentration. However, due to the accumulation kinetics found for Corbicula sp. it can be concluded that small differences in Pt concentrations of the ambient water (low ng/L range) can not be detected by analyzing clam tissue concentrations. In fish exposure studies, Pt accumulation kinetics for different organs was investigated, along with the influence of endoparasites such as acanthocephalans on the metal metabolism of the fish. In fish, highest Pt concentrations were found in the liver and intestinal tissue of the fish (Squalius cephalus), while concentrations in the muscle tissue were lower. Overall, the highest concentrations were found in the acanthocephalan Pomphorhynchus tereticollis. For chub infected with P. tereticollis, Pt concentrations in liver and intestine were found to be lower compared to Pt concentrations in the respective organs of uninfected fish. As this trend was not observed for fish infected with P. laevis, it can be stated that metal metabolism differs for different host-parasite systems. Pt induced DNA damage was also investigated for fish and clams. Pt as well as the parasites induced the formation of micronuclei in fish erythrocytes. The micronucleus test did not show any induction of micronuclei in the gill cells and hemocytes of the clams. This thesis demonstrates that, due to the relatively low exposure levels in the field, acute lethal or toxic effects of Pt can not be observed for bivalves and fish. Additionally, Pt concentrations are also too low for many of the sublethal effects, observed in laboratory studies. However, Pt can induce DNA damage, as was shown for chub. Therefore, it can be assumed that already low Pt concentrations in the field could possibly endanger individual organism. It can be assumed that Pt does not pose a major threat to freshwater systems, however, it needs to be taken into account as an additional stress factor putting pressure on aquatic organisms.