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Assessment of radium‐226 bioavailability and bioaccumulation downstream of decommissioned uranium operations, using the caged oligochaete ( Lumbriculus variegatus )
Author(s) -
Wiramanaden Cheryl I.E.,
Orr Patricia L.,
Russel Cynthia K.
Publication year - 2015
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.2852
Subject(s) - bioaccumulation , environmental chemistry , sediment , bioavailability , chemistry , barium , radium , benthic zone , total organic carbon , carbonate , radiochemistry , geology , oceanography , inorganic chemistry , paleontology , bioinformatics , biology , organic chemistry
The present study investigated the integrated effects of several geochemical processes that control radium‐226 ( 226 Ra) 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 10 d in 6 areas downstream of decommissioned uranium operations in Ontario and Saskatchewan, Canada. Measured 226 Ra radioactivity levels in the retrieved oligochaetes did not relate directly to water and sediment exposure levels. Other environmental factors that may influence 226 Ra bioavailability in sediment and water were investigated. The strongest mitigating influence on 226 Ra bioaccumulation factors was sediment barium concentration, with elevated barium (Ba) levels being related to use of barium chloride in effluent treatment for removing 226 Ra through barite formation. Observations from the present study also indicated that 226 Ra 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 226 Ra 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 226 Ra 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 226 Ra release into overlying water after the dissolution of sedimentary barite. Environ Toxicol Chem 2015;34:507–517. © 2014 SETAC