###### Abstract
On German territory, the management of dredged material from reservoirs is of special concern in areas of Saxony. Since this federal state is characterised by the widespread absence of natural lakes, the densely populated and traditionally highly industrialised territory needed the construction of artificial water bodies such as dams, reservoirs and flood retention basins. With approximately 190 of these artificial water bodies, Saxony is the federal state with the most dams in Germany. In most cases, such water bodies were created for a specific purpose but also serve other functions. Drinking water supply, process or industrial water supply, flood protection, electric power generation, wildlife habitat, fishing and recreation are the most common functions (Figure S1) [21]. Since the beginning of the 19 th century, numerous dams have been built in the low mountain ranges of the Ore Mountains, which are characterised by the widespread occurrence of geologic formations with elevated geogenic metal(loid) concentrations [22; 23]. The centre of the Ore Mountains is characterised by highly metamorphic, crystalline and magmatic rocks and is surrounded by an area of weakly metamorphic shale at the outskirts of the mountain range [24; 25] (Figure 1). In this study, metal(loid) concentrations of reservoir sediments were investigated in two reservoirs of the Ore Mountains: the Einsiedel Reservoir, situated south-southeast of the city of Chemnitz, and the Berthelsdorf Smelter Pond (BSP), located approximately 2.5 km south of the city of Freiberg (Table 1). The Einsiedel Reservoir (Figure S2) is a part of the Reservoir Interconnection Middle Ore Mountains (RIMOM) chain, a system of dams [26] that provide drinking water for the city of Chemnitz. No obvious anthropogenic metal(loid) sources were identified in the forested, sloped catchment, either in the literature or during fieldwork. The Berthelsdorf Smelter Pond (BSP) (Figure S3) was built in the 16 th century to provide energy for water wheels operated by the mining industry around Freiberg [27]. Since its construction, the dam has been destroyed, rebuilt and repaired multiple times [28], until it became part of the Freiberg Mining District Water Balance (FMDWB) network in 1882 [29]. The entire area around the BSP is characterised by a flat relief and the former mining industries of both the Freiberg and the Brand mining districts [27; 30]. Mining explorations started during the medieval period, first for silver and later for lead, zinc, tin and copper [27]. In the early years, ore processing usually took place near the local rivers including the Munzbach  
Due to the presence of large amounts of fine-grained, highly sorption capable sediments and a location in rock sections with above-average geogenic background, both reservoirs were used for a status quo analysis of metal(loid) concentrations and for studies of their source and sink functions (Figure S4). The main objectives of this study were:  
1. To record metal(loid) concentrations in the sediments of the reservoirs and to evaluate them exemplarily against legal requirements;
2. To highlight differences between both reservoirs with the help of correlation analyses between physicochemical sediment properties and metal(loid) concentrations and to discuss their causes;
3. To draw conclusions regarding the origin of the measured metal concentrations.