Heavy Metal Concentrations in Pores and Surface Waters during the Emptying of a Small Reservoir

The impact of reservoir emptying on the concentrations of dissolved heavy metals (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in pore and surface waters was studied in the Aar Reservoir, a small reservoir in central Germany, during and after the emptying process. This study was conducted to observe binding changes within pore waters as well as the input of dissolved heavy metals in waters of the Aar Creek, what becomes possible when the reservoirs water table is removed and lake sediments become exposed. In pore waters, no clear shifting tendencies between dissolved and sorbed heavy metal fractions could be found after the completed sediment exposure. These relatively low dynamics in pore waters can be explained by the fine texture of the lake sediments, which are characterized by a high water holding capacity, what led to high remaining water contents and therefore slowed down the redox changes. A few days after the completed emptying, a general increase of dissolved heavy metal concentrations occurred in running waters of the Aar Creek as a result of pore water drainage. Here, element specific differences in mobilization and transportation abilities were found, what can be reconstructed by the ratio of dissolved heavy metals in pore and surface waters.

Catchment soils as a factor of trace metal accumulation in sediments of the reservoir Klingenberg(eastern Ore Mountains, Germany)

The release and accumulation dynamics of trace metals in soils and aquatic sediments were exemplarily investigated in the catchment area of the Reservoir Klingenberg(Germany).Catchment soils were examined for mobilizable and total concentrations of arsenic(As),cadmium(Cd),chrome(Cr),iron(Fe),manganese(Mn),nickel(Ni),lead(Pb),and zinc(Zn)and compared with trace metal quantities accumulated in riverbed and reservoir sediments.The comparison of all samples showed relatively small variations of Cr(7.96–46.0 mg/kg),Fe(7.79–40.4 g/kg),and Ni(6.06–56.5 mg/kg),while stronger differences were found for As(11.2–164 mg/kg),Cd(0.14–30.5 mg/kg),Mn(0.08–1.84 g/kg),Pb(20.7–183 mg/kg),and Zn(69.1–916 mg/kg).The catchment soils were slightly enriched by Cd,Pb,and Zn.Especially Cd and Zn were characterized by large mobilizable proportions.The mean trace metal concentrations in riverbed sediments were higher than in catchment soils,while reservoir sediments accumulated the highest amounts of the analyzed elements.The enrichment of trace metals in reservoir sediments was generally determined by the sedimentation of fine particles,while the distribution of As,Fe,and Mn was additionally impacted by redox conditions.For Cd and Zn,which in comparison were most enriched in riverbed and reservoir sediments,a significant release from soils by leaching processes was observed.The accumulation of As and Pb in reservoir sediments was influenced to a greater extent by soil erosion and by anthropogenic or chalcogen sources in the catchment.