SOIL-MANAGEMENT FACTORS AFFECTING VOLATILIZATION OF SELENIUM FROM DEWATERED SEDIMENTS

Microbial volatilization of selenium (Se) may be an effective bioremed iation technique to remove Se from dewatered sediments. In this labora tory study, soil management parameters (wetting and drying cycles, aer ation, mixing, aggregate size, and water quality) were assessed for th eir influence upon Se volatilization. Selenium volatilization rates we re 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 inventor y, whereas the same sail incubated under wetting and drying cycles had dissipated 7% of the total Se. Incubation under anoxia (N-2 atmospher e) increased evolution of dimethyl selenide (DMSe) 1.4-fold compared w ith aerated conditions. When soil samples were incubated under static versus continuously mixed conditions, the latter treatment enhanced vo latilization 1.8-fold. This was attributed to increased availability o f the Se to the methylating soil microbiota. The optimum aggregate siz e 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 volatiliz ation rates of Se from a highly saline (22 dS m-1) seleniferous dewate red sediment. Each of these parameters should be considered in promoti ng volatilization of Se as a bioremediation approach in the cleanup of seleniferous sediments.