SOIL-MANAGEMENT FACTORS AFFECTING VOLATILIZATION OF SELENIUM FROM DEWATERED SEDIMENTS

Microbial volatilization of selenium (Se) may be an effective bioremediation technique to remove Se from dewatered sediments. In this laboratory study, soil management parameters (wetting and drying cycles, aeration, mixing, aggregate size, and water quality) were assessed for their influence upon Se volatilization. Selenium volatilization rates were higher under continuously moist conditions (-33 kPa) compared with wetting and drying cycles. After 6 months of incubation a continuously moist seleniferous soil had lost approximately 21% of the Se inventory, whereas the same sail incubated under wetting and drying cycles had dissipated 7% of the total Se. Incubation under anoxia (N-2 atmosphere) increased evolution of dimethyl selenide (DMSe) 1.4-fold compared with aerated conditions. When soil samples were incubated under static versus continuously mixed conditions, the latter treatment enhanced volatilization 1.8-fold. This was attributed to increased availability of the Se to the methylating soil microbiota. The optimum aggregate size to promote volatilization of Se was 0.53 mm when compared to 0.15, 1, and 2 mm. The application of saline well water (7.5 dS m(-1)) over 6 months, compared with deionized water, had little effect on volatilization rates of Se from a highly saline (22 dS m-1) seleniferous dewatered sediment. Each of these parameters should be considered in promoting volatilization of Se as a bioremediation approach in the cleanup of seleniferous sediments.