Content of Inorganic and Organic Pollutants and Their Mobility in Bottom Sediment from the Orlík Water Reservoir (Vltava River, Czech Republic)

The content of both inorganic and organic pollutants, in sediment from the Orlík reservoir (Vltava river, Czech Republic), and the main tributaries, was determined to assess the total loads of the pollutants in the upper layer of sediment (0–30 cm), and the potential bioaccessibility and bioavailability of these pollutants. Organic pollutants showed non-hazardous levels of polycyclic aromatic hydrocarbons and polychlorinated biphenyls. Elevated phosphorus content indicated the possible eutrophization potential; however, significant correlation of phosphorus with iron and aluminum suggested a high immobilization rate of this element with iron and aluminum cations. Risk elements in the sediment were separated according to their potential environmental risk: (1) cobalt, nickel, copper, lead, vanadium, and chromium showed both low levels and relatively low mobility, i.e. low environmental risk; (2) the arsenic levels were significantly elevated (exceeding the maximum allowable limits for land application of sediment) but its mobility was low; (3) cadmium and zinc exceeded the limits and showed high mobility and bioaccessibility. These two elements also showed high bioavailability for the bivalves Unio tumidus and Anodonta anatina. The results showed differences in pollutant loads in sediment along the lake, and different input of pollutants via the individual tributaries.