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• Historical mining/industry highly influences sediment quality of today's rivers. • Historical mining and metal processing superimpose modern pollution sources. • Fluvial morphodynamics force the pollution spreading coming from secondary sources. • Suspendible riverbed sediment represents sediment load of high discharge events. • Neighboring river systems are suitable for the evaluation of pollution sources. 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 km2) 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. [ABSTRACT FROM AUTHOR]

Rivers are a transition system for contaminants, which are adsorbed to fine sediments. (Re-) Mobilization, transport and accumulation are the controlling factors in fluvial systems, which influence the processes of relocation and sedimentation. Contaminants can be stored during a long time in depositional areas such as floodplains or at the riverbed until further remobilization takes place. In this study, pollution profiles of three small rivers – Geul, Wurm, and Inde River – with neighboring catchments are compared. The study area is situated within the International River Basin District Meuse (border triangle between Belgium, the Netherlands and Germany) and is part of the oldest cultural landscapes in Europe, influenced by industry and mining. All three rivers are characterized by similar properties like catchment size (~ 350 km²), length (~ 55 km), altitude difference (210 to 260 m), discharge (~ 3.5 m³ sˉ¹ in the lower course), channel width (~ 10 m), and flow regime (perennial and pluvial). Although similarities concerning the natural settings and the land use exist, there are significant differences. The history of all three catchments is closely connected with the occurrence of coal and ore deposits, and varies due to the geological setting. Even though the mining sector disappeared in the study area, there are still dumps and contaminated sites as their legacy. Modern pollution sources like industries, municipal wastewater, and traffic areas became more relevant over time.A resuspension method after Lambert and Walling (1988) was used to collect "suspendible riverbed sediments" from different river reaches. Those sediments are defined as a mixture of recent riverbed sediments coming from the riverbed itself, from the floodplains, and from the hinterland. The suspendible riverbed sediments can be potentially mobilized during flood events. After sampling, the fine-grained fractions (< 63 µm) were analyzed with an energy dispersive polarized Spectro Xepos X-ray fluorescence (XRF) device. Using the eight trace elements Cr, Ni, Cu, Zn, As, Cd, Sn, and Pb, the variability of pollution profiles and contaminant loads are investigated and compared. The comparison of the three neighboring catchments and the identification of potential pollution sources allow to distinguish between natural geogenic background conditions and human impact. The relevance of pollution sources and the differences between them can be observed evaluating the fingerprint of each river. [ABSTRACT FROM AUTHOR]