科研之友
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摘要
The present study investigated the integrated effects of several geochemical processes that control radium-226 (Ra-226) mobility in the aquatic environment and bioaccumulation in in situ caged benthic invertebrates. Radium-226 bioaccumulation from sediment and water was evaluated using caged oligochaetes (Lumbriculus variegatus) deployed for 10d in 6 areas downstream of decommissioned uranium operations in Ontario and Saskatchewan, Canada. Measured Ra-226 radioactivity levels in the retrieved oligochaetes did not relate directly to water and sediment exposure levels. Other environmental factors that may influence Ra-226 bioavailability in sediment and water were investigated. The strongest mitigating influence on Ra-226 bioaccumulation factors was sediment barium concentration, with elevated barium (Ba) levels being related to use of barium chloride in effluent treatment for removing Ra-226 through barite formation. Observations from the present study also indicated that Ra-226 bioavailability was influenced by dissolved organic carbon in water, and by gypsum, carbonate minerals, and iron oxyhydroxides in sediment, suggestive of sorption processes. Environmental factors that appeared to increase Ra-226 bioaccumulation were the presence of other group (II) ions in water (likely competing for binding sites on organic carbon molecules), and the presence of K-feldspars in sediment, which likely act as a dynamic repository for Ra-226 where weak ion exchange can occur. In addition to influencing bioavailability to sediment biota, secondary minerals such as gypsum, carbonate minerals, and iron oxyhydroxides likely help mitigate Ra-226 release into overlying water after the dissolution of sedimentary barite. Environ Toxicol Chem 2015;34:507-517.
- 出版日期2015-3
