Speciation of Radium-226 in the Components of Terrestrial and Aqueous Northern Taiga Ecosystems in a Former Radium Production Site

摘要

The paper considers the content and geochemical mobility of(226)Ra in surface waters, bottom sediments, and radioactively contaminated soils (podzolic and alluvial-soddy) of the northern taiga subzone in the area of former radium production site. It is established that the level or radioactive contamination and specific activity of geochemically mobile radium in the podzolic soil is higher, while its migration with surface waters is lower (0.03 Bq/L) than in the alluvial-soddy soil. The drainage waters of the latter are characterized by the maximum radium content (0.55 Bq/L), which is mainly concentrated in the suspended matter (98%) and humic acids (97%) fractions. In the river waters, radium is mainly accumulated in the suspended fraction and fulvic acid compounds. It is shown that under low-temperature and high-water current conditions and a weak sorption capacity of bottom material, the specific activity of the radioactive element in the riverine sediments in the zone of anthropogenic impact is higher than the average background value (0.3-1.8 against 0.2 mBq/g). Sedimentation of radionuclide in the geochemically mobile and weakly mobile species is most intense within contaminated sites. The radium content in the "carbonates", "sesqui-oxides and -hydroxides" and, especially, "exchangeable" fractions extracted from soils was higher than in other fractions. A cumulative fraction of "water soluble", "organic matter", and "amorphous silicates" groups accounts for 0.4-3.7 and 1.6-7.4% of radionuclide content in the podzolic and alluvial-soddy soils, respectively, and was characterized by the predominance of "organic matter" fraction. The fraction of geochemically mobile radium is negatively correlated with its bulk specific activity (r= -0.81), which is noted as trend for bottom sediments. The contribution of insoluble residue in the radionuclide specific activity was 23.5-95.5 and 7.8-69.4% in the podzolic and alluvial-soddy oils, respectively.