REDUCTION POTENTIAL OF SELENATE IN WETLAND SEDIMENT

Laboratory and field experiments were conducted to examine the reducti on potential of dissolved selenate in wetland sediment at Benton Lake, Montana. Results showed that selenate reduction in wetland sediment w as a microbially mediated process. This process proceeded rapidly and removed more than 50% of added selenate from solution to the sediment during the first day of the experiment. The reduction potential of sel enate in sediment was positively correlated to Se concentrations in se diment, but not to sediment organic C content. This process occurred a t the sediment surface because the depth of diffusion of selenate was limited, resulting in most Se accumulating in the top 2 cm of the sedi ment. The results from this study indicate that selenate reduction in sediment dominates selenate removal from water.