Signatures of recent pollution profiles in comparable central European rivers - Examples from the international River Basin District Meuse

Rivers are strongly influenced by humans. As the natural occurrence of trace elements (TEs) is controlled by the geological setting, elevated contents of TEs are caused by anthropogenic activities. TEs can be adsorbed at fine sediments and (re-)mobilized, transported and accumulated at the riverbed and as overbank deposits on the floodplains. Thus, rivers are the transition system for pollutants between their source areas and the depositional areas. To investigate the recent distribution of TEs related to different impact factors, suspendible riverbed sediments of three rivers with neighboring catchments (catchment size each +/- 350 km(2)) within the International River Basin District Meuse (border triangle between Belgium, the Netherlands and Germany) were analyzed. The aim is to compare the variability of pollution profiles (longitudinal TE distribution of sediment samples along the river) of three rivers, that are representative for central European foothills to lowland rivers, with both similar natural settings and disparate human impact factors, and to identify and analyze the 'fingerprint' of each river. Hence, a characterization of the individual pollution characteristics of the rivers, with past and recent TE sources, is achieved, which is applicable to other rivers with a similar land use history. The suspendible riverbed sediments of all three rivers show high contents of Cr (71.3-846.7 mg kg(-1)), Ni (15.2-61.9 mg kg(-1)), Cu (10.7-357.8 mg kg(-1)), Zn (186.35-6,571 mg kg(-1)), As (3.05-25.25 mg kg(-1)), Cd (1.1-22.8 mg kg(-1)), Sn (0.325-36.1 mg kg(-1)), and Pb (16.6-1,116 mg kg(-1)). Most of the concentration values exceed European supraregional background levels. The three catchments are characterized by high geogenic background contents due to the occurrence of ore and coal deposits and urban sources. However, each river shows different characteristics, driven by the natural setting and the individual anthropogenic activities. The pollution profiles show heterogeneous patterns along the river, with both, increasing and decreasing TE values and pollution hotspots. The used sampling method after Lambert and Walling (1988) is very well suitable for comparable rivers with a heterogeneous riverbed composition and enables to analyze characteristics of longitudinal pollution profiles in different river catchments. The TEs contents of the suspendible riverbed sediments of the three catchments are anthropogenically elevated. While urbanization causes heterogeneous patterns and moderately elevated contents of TEs, concentrations caused by past exploitation and processing of ore and coal and other related industries exceed other possible pollution sources. Today, the historical pollution sources stored in the sediments still have a major impact on the river systems, while modern pollution sources contribute to a minor extent.