SEPARATION OF SELENIUM SPECIES RELEASED FROM SE-EXPOSED ALGAE

We have assessed a fractionation scheme for selenium species that separates Se-containing amino acids and other organoselenium compounds in aqueous samples. We investigated the retention of standard solutions of selenate (Se+6), selenite (Se+4), and selenomethionine (Se-2) by fractionation media (Sephadex A-25 ion-exchange resin, copper-treated Chelex-100 ligand-exchange resin, and activated charcoal) and by several types of membrane filters. The fractionation method successfully isolated Se from the standard solutions into appropriate fractions for radiometric quantitation of Se-75. However, some filter media retained unacceptably large amounts of selenate and selenite. Mass balance microcosms were inoculated with green algae (Chlamydomonas reinhardtii) previously exposed to inorganic Se-75, and the fractionation scheme was used to examine the release of Se-75 species into water and air. The results of the microcosm exposure indicate that seasonal blooms and crashes of phytoplankton populations may produce increased concentrations of organoselenium species.