Effects of forage plant and field legume species on soil selenium redistribution, leaching, and bioextraction in soils contaminated by agricultural drain water sediment

Abstract

A study was undertaken to assess the potential of two plant species, tall rescue (Festuca arundinacea Schreb., a forage plant) and yellow sour clover (Melilotus indica L., a naturally occurring legume species) for bioremediation of selenium laden soils. Using soil columns under simulated field soil conditions, the effects of these two species were studied on soil selenium (Se) redistribution, leaching, and Se bioextraction. Both leachate volume and Sc concentration in the leachate were greatly influenced by presence of vegetation. The volume of leachate was considerably lower for columns having either tall fescue or yellow sour clover plantings. Tall fescue had a higher water use rate and greater rooting density than did in yellow sour clover, indicating the tall fescue will be more practical for bioremediation of Se laden soils. Soil Se distribution analysis yielded the following patterns: (1) contamination of the lower soil profile of uncontaminated soil occurred at the first harvest, but Se concentrations at these depths were not at high levels; (2) except for selenite, all forms of water-extractable soil me concentrations showed a clear reduction over time of vegetation harvest; and (3) the reductions of total soil Se were significant, but the difference was relatively small between the forage planting and bare soil treatments. This is due to the fact that only a relatively small fraction of total Se inventory was water soluble and available to plants at any one time. A large reduction may become apparent after a longer period of forage plant management.