The contamintation level of sediments from water reservoir Orlík by organic and inorganic pollutants

Due to sorption processes, sediments can retain a wide range of toxic substances, which are transported together with the sediment over long distances from the place of their origin. Dam reservoirs are significant sinks of such sediments and they can be indicative of the overall burden level in surface water of the basin. This thesis works with the assumption that sediments of a valley reservoir can help to estimate the sources and extent of water pollution in the area of interest. The aim of this thesis was to assess i) the level of contamination of bottom sediments in the Orlík reservoir with organic and inorganic pollutants, and ii) the potential impact of individual tributaries on the overall level of contamination of the sediments. In the literature review, the current level of knowledge in the topic of the total contents and speciation of toxic elements and specificities of the behavior of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in water, sediments and aquatic organisms was evaluated. The biological activity and eutrophication potential of sediments were discussed, as well. A total of 34 composite samples of bottom sediment collected in different parts of the Orlík reservoir and its major tributaries were evaluated. Bioavailability of major pollutants was also observed in individual tributaries based on their content in the tissues of mollusks. Atomic spectrometry revealed increased concentrations of As, Cd and Zn in sediments of the Orlík reservoir. Arsenic concentration limits were significantly exceeded at the bottom part of the reservoir from the confluence of the Otava and Vltava rivers toward the body of the dam. Higher level of cadmium and zinc were detected in sediments of the Otava River. The analysis of tissues of bivalves in tributary areas confirmed significant bioaccumulation ability of cadmium. Among others, significant dependence of phosphorus level on the total content of iron and aluminum in sediments was detected