Several methods for Pu speciation study are compared using the same sample of bottom sediment. Data on Pu distribution among different soil fractions (water-soluble, exchangeable and readily soluble, mobile, associated with organic matter, including humic and fulvic acids, and also with amorphous hydroxides, primarily of iron and manganese) are reported. The major fraction of plutonium is associated with the organic matter. The experimental results on the Pu speciation, obtained by different methods, show satisfactory agreement.To predict of the radiation situation and develop measures aimed at rehabilitation of contaminated territories, knowledge is required not only of the contamination levels, but also of the radionuclide speciation in the biosphere, since the partitioning of radionuclides to components of environmental objects controls the direction and rate of their migration in the systems water3bottom sediment, soil3plant, and groundwater3rock.Study of the speciation of radionuclides and stable elements is a challenging problem. Soils and bottom sediments are multiphase systems in which diverse physicochemical, chemical, and biological processes occur. Furthermore, sequential extraction (SE) methods (successive leaching of a sediment using increasingly aggressive treatments) commonly used in such studies have such limitations as nonselectivity of the extractants for the individual target phases and incomplete extraction of these phases. The sediment phase dissolved by a given treatment is operationally defined. This phase is considered as a totality of chemically similar compounds. Generally the SE methods are based on different solubility of the target phases. Despite the indicated limitations, these methods are widely used in geochemistry, soil science, and radioecology, in studying the speciation of radionuclides and stable elements, and the results obtained provide valuable information on their environmental fate.In this study we compare several SE methods for Pu speciation, used in Russia and abroad, with the goal of their further improvement. As a subject matter we used bottom sediment collected from Pond V-10 (horizon 20 323 cm) at the Mayak Production Association. This pond was designed for storage of low-level liquid radioactive wastes and natural remediation through sorption of radionuclides on bottom sediments and also by radioactive decay of short-lived radionuclides. The sample used was a light loam, dun in color, peat-mineralized.The contents of stable elements in the sample were as follows: K 5.1, Na 5.6, Sr 0.2, Ca 23.0, Mg 8.2, Fe 20.0, Al 26.0, and Mn 0.8 mg per gram air-dry sample; C 14.4, H 2.4, and N 2.1%. The contents of radionuclides (Bq/g air-dry sample): 238!240 Pu 13.4 + 1.0 ( 238 Pu 6.1 + 0.7 and 239, 240 Pu 7.3 + 0.2), 60 Co 1.4 + 0.2, 90 Sr 185 + 6, 137 Cs 304 + 3, and 241 Am 2.0 + 0.2. In all cases, 1-g samples were taken for analysis.
