Interaction of selenate with a wetland sediment

Selenate removal from solution through various biogeochemical processes occurred in experiments with wetland sediment. The removal of selenate from solution to sediment was rapid and substantial. About 44–80% of added selenate was accumulated in sediment in a 72-h incubation. Different biogeochemical processes competed in removing selenate from water. Reduction of selenate to elemental Se dominated removal with a reduction rate of 0.147 μg/g/h. Formation of organically-bound Se (organic material Se and adsorbed organic Se) also removed Se from water; the rate of Se binding to organic material was 0.065 μg/g/h. In contrast, selenate adsorption was relatively less important due to a low adsorption rate, 0.013 μg/g/h. Volatilization removed little Se from water and sediment. These results show that Se reduction to the elemental form and binding of Se to organic material are the most important processes removing selenate from water and fixing it in wetland sediment.