Effects of Soil Moisture, Depth, and Organic Amendments on Selenium Volatilization

Effects of soil moisture, depth, and organic amendments on selenium (Se) volatilization in a Se‐contaminated soil were studied in three different experiments. Results showed that the volatilization rate of Se as dimethylselenide (DMSe) was increased during a transition from air‐dry soil (<2 µg/m2 per day) to a wetted soil (185 µg/m2 per day), and was also much higher after rewetting an air‐dried soil than keeping the soil continuously moist. Although more DMSe was produced with increasing soil mass, DMSe was trapped in the subsoil layers. DMSe emission to the air was related to the moisture content. After 10 d, 96 and 14% of injected DMSe was volatilized to the air from an air‐dried soil and a water‐saturated soil, respectively. Both insoluble (casein) and soluble (Casamino acids) organic amendments enhanced DMSe production and removal from soil through volatilization. This study suggests that organic amendments and frequent tillage are needed to increase Se volatilization from soil by enhancing production of DMSe and increasing soil porosity in facilitating the diffusion of trapped DMSe to the atmosphere.