INTERACTION OF SELENATE WITH A WETLAND SEDIMENT

Selenate removal from solution through various biogeochemical processe s occurred in experiments with wetland sediment. The removal of selena te from solution to sediment was rapid and substantial. About 44-80% o f added selenate was accumulated in sediment in a 72-h incubation. Dif ferent biogeochemical processes competed in removing selenate from wat er. Reduction of selenate to elemental Se dominated removal with a red uction rate of 0.147 mu g/g/h. Formation of organically-bound Se (orga nic material Se and adsorbed organic Se) also removed Se from water; t he rate of Se binding to organic material was 0.065 mu g/g/h. In contr ast, selenate adsorption was relatively less important due to a low ad sorption rate, 0.013 mu g/g/h. Volatilization removed little Se from w ater and sediment. These results show that Se reduction to the element al form and binding of Se to organic material are the most important p rocesses removing selenate from water and fixing it in wetland sedimen t. (C) 1997 Elsevier Science Ltd. All rights reserved.