Physicochemical forms of (90)Sr and (137)Cs in components of Glyboke Lake ecosystem in the Chornobyl exclusion zone.

Lake ecosystems are efficient 'collectors' for a wide range of radionuclides, which are accumulated by abiotic and biotic components after their input to the aquatic environment. Aquatic vegetation accumulates radionuclides, while annual atrophy of vegetative mass for the most species, in the absence of drainage, leads to an increase of radionuclide accumulation in bottom sediments. This leads to the preservation of a rather high level of radionuclides in the components of stagnant water ecosystems. As a result of global fallout and of the Chornobyl disaster, significant areas of Ukraine are contaminated with (90)Sr and (137)Cs, both of which present a significant radiological risk. Therefore, research into the way these radionuclides behave in freshwater ecosystems is of current interest, particularly following the Fukushima disaster. The present paper covers the study of physicochemical forms of radionuclides in the components of Glyboke Lake, located within the Chornobyl exclusion zone and considered to be one of the most contaminated lakes in the area. Physicochemical forms of radionuclides influence their distribution and solubility among the components of aquatic ecosystems, as well as biological availability for aquatic vegetation and intensity of migration processes. The study of chemical forms was conducted in bottom sediments and typical representatives of aquatic vegetation. The ratio of activity concentrations of (90)Sr and (137)Cs in water, aquatic plants and bottom sediments of Glyboke Lake was quantified. A diversity in distribution of physicochemical forms of radionuclides depending on a nutrition type of the studied aquatic plants was observed.