Physicochemical forms of 90 Sr and 137 Cs in components of Glyboke Lake ecosystem in the Chornobyl exclusion zone Ch. Ganzha a, * , D. Gudkov a , D. Ganzha b , V. Klenus a , A. Nazarov c a Department of Freshwater Radioecology, Institute of Hydrobiology of the National Academy of Sciences of Ukraine, Geroyev Stalingrada Ave.12, 04210 Kyiv, Ukraine b Centralized Enterprise for the Management of Radioactive Waste, Kirova Str. 52, 07270 Chornobyl, Ukraine c Chornobyl Specialized Enterprise, Radyanska Str. 70, 07270 Chornobyl, Ukraine article info Article history: Received 16 June 2011 Received in revised form 25 February 2013 Accepted 29 March 2013 Available online xxx Keywords: Water Bottom sediments Aquatic vegetation Radionuclides Chornobyl exclusion zone Lake ecosystem abstract 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 accu- mulates 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 dis- tribution 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 concentra- tions 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. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The main characteristics of the initial contamination of the environment with radionuclides from the Chornobyl disaster are the data about the physicochemical condition of the emission and the peculiarities of geochemical migration of the emitted matter (Sobotovych, 1992). A unique feature of radioactive emissions following the Chornobyl disaster, is that the release was in two main forms: fine-dispersed products of irradiated fuel and condensation products of volatile radionuclides. As a rule, water- soluble compounds are available for vegetation and are able to migrate in soil cover, and the exchangeable form is referred to as a reserve of the water-soluble one. If in May 1986, in the initial radioactive emissions, water-soluble forms made up one tenth to one hundredth part of one percent, then by the end of the same year, the content of ion forms of 90 Sr had reached several percents in the Chornobyl exclusion zone (Sobotovych and Dolin, 1994). The content of 137 Cs water-soluble forms in the upper layers of soils did not exceed one percent. In the first post-disaster period, the general content of water-soluble, exchange and acid-soluble forms of 90 Sr made up 80e99% of the total quantity of this radionuclide for various soils, and 137 Cs these forms were in the range 1 up to 10e 20% (Bondarenko and Kononenko, 1995). By the end of the first decade post-disaster, the share of mobile forms of 137 Cs remained almost at the same level, while for the fixed forms it has increased to 75% (Voytsehovych et al., 1996). During the post-disaster period, radionuclides in the Chornobyl exclusion zone became involved in the process of biogeochemical migration. In water ecosystems, a secondary contamination took place as a result of accumulation and transformation of physico- chemical forms of radionuclides by aquatic biota. The study of physicochemical forms allows a conclusion to be made about the redistribution of radionuclides among basic components of aquatic ecosystems, which occurs under the influence of deposition * Corresponding author. Tel. þ380 (0)66 3704330. E-mail address: krisgan@rambler.ru (Ch. Ganzha). Contents lists available at SciVerse ScienceDirect Journal of Environmental Radioactivity journal homepage: www.elsevier.com/locate/jenvrad 0265-931X/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jenvrad.2013.03.013 Journal of Environmental Radioactivity xxx (2013) 1e6 Please cite this article in press as: Ganzha, C., et al., Physicochemical forms of 90 Sr and 137 Cs in components of Glyboke Lake ecosystem in the Chornobyl exclusion zone, Journal of Environmental Radioactivity (2013), http://dx.doi.org/10.1016/j.jenvrad.2013.03.013