Uptake, Metabolism, and Volatilization of Selenium by Terrestrial Plants

Selenium (Se) in irrigation drainage water became a major concern after it was implicated in deaths and deformities of waterfowl at Kesterson Reservoir (Presser and Ohlendorf 1987; Ohlendorf 1989). Subsequently, other areas with irrigationinduced Se problems (or potential problems) have been identified in several western U.S. states (Seiler 1995), reinforcing the status of Se as a U.S. Environmental Protection Agency priority pollutant (Keith and Telliard 1979). Selenium hazards are most often associated with semi-arid climates, geologic sources in proximity to large irrigation projects, and hydrologically-closed basins, all of which lead to significant evapoconcentration of dissolved Se (Seiler 1995). Some 17 % of western US land is found on Cretaceous sediments high in Se. When this land is used for irrigated agriculture, Se concentrations in drainage water can reach mg per L levels. Several measures for mitigating these high levels of Se have been proposed, including phytoremediation and phytoextraction of Se-enriched soils and sediments. Phytoremediation was a newly burgeoning field in the mid-1980s and was being scrutinized as an environmentally benign cleanup technology for a variety of soil contaminants, both inorganic and organic. Researchers affiliated with the UC