###### Abstract  
Since reservoirs can act as sinks for potential contaminants, such as metal(loid)s, sediment management is a challenge for reservoir operators. To exemplify the variability of concentrations of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), vanadium (V) and zinc (Zn), the sediments of two differently constituted reservoirs located in the Ore Mountains (Saxony, Germany) were comparatively investigated. In the sediments of the Einsiedel Reservoir, which has a catchment area dominated by forestry, the median values showed an enrichment of Cd (6.7 mg/kg), Co (31.4 mg/kg), Hg (0.57 mg/kg), Ni (39.0 mg/kg) and Zn (283 mg/kg), mainly due to an elevated geogenic background and a preferential input of these elements from the soils of the catchment area. Sediments of the Berthesdorf Smelter Pond, which has a predominantly agricultural catchment, had relatively high median concentrations of As (62.9 mg/kg), Cd (10.3 mg/kg), Cr (43.1 mg/kg), Cu (50.2 mg/kg), Hg (0.51 mg/kg), Pb (204 mg/kg), V (57.0 mg/kg) and Zn (626 mg/kg), which was due to an elevated geogenic background and heavy anthropogenic metal(loid) inputs over the past. Statistical analyses indicated that site-specific differences (e.g., in the content of organic matter or in the physicochemical properties of sediments) may influence the sink and source functions of the reservoirs for metal(loid)s. In this context, a strong influence of the specific catchment characteristics on the sediment composition of the reservoirs was concluded. Based on the German Federal Soil Protection Ordinance, the status quo of the metal(loid) contamination of the two reservoirs was evaluated and recommendations for further management and investigations were derived. water pollution; soil and sediment contamination; metals and metalloids; field sampling; sink and source functions; status quo evaluation +
Footnote †: journal: Applied Soft  
sediments into the water phase. This allows trace elements to pass into the food chain, where sufficiently high concentrations can have toxic effects on organisms [5; 6; 7; 8; 9; 10; 11; 12]. For this reason, reservoirs and their sediments are often studied for metal(loid) contamination [6; 7; 10; 12]. Reservoir sediments often exhibit differences in the spatial distribution of metal(loid) concentrations [13], in the temporal tendencies of contaminant accumulation [14; 15], or in the release of metal(loid)s into the water phase [16; 17; 18]. Therefore, in order to estimate the sink and source functions of a reservoir, it is important to know the extent to which the sediment quality in reservoirs may differ within a large geologic unit due to the differences in land-use history, catchment characteristics and relief conditions. Recognising the key determinants of metal(loid) accumulation provides the opportunity to identify causes of sediment contamination, apply these to similar study sites and derive future measures to improve sediment quality. Further questions often arise with the use of dredged sediments as soil material, which is regulated in Germany by the Soil Protection Ordinance [19]. For use on arable land, the Soil Protection Ordinance requires compliance with existing precautionary values. Furthermore, the presence of a \"harmful changed soil\" or a \"contaminated site\", respectively, can be assessed by the exceeding of examination values, while action values determine the need for a case-by-case assessment or remediation measures [20]. The specific limits of examination and action values are adapted to the respective use of a soil. However, reservoir sediments from regions with a naturally elevated geogenic background frequently exceed the precautionary values, which largely limits their potential for reuse. Unlike soils, no examination or action values apply to reservoir sediments, which means that almost the only option for them after dredging is backfilling excavations.