|Wu, L - UC DAVIS|
|Guo, X - UC DAVIS|
Submitted to: International Journal of Phytoremediation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2003
Publication Date: August 1, 2003
Citation: Wu, L. X. Guo, G.S. Banuelos. International Journal of Phytoremediation. 5:25-40. 2003 Interpretive Summary: Soils at the Kesterson Wildlife Refuge have been contaminated by agricultural drainage sediment rich in both selenium and sulfur. Natural phytoremediation of sediment selenium with Se non-accumulator plant species such as forage plants and natural grassland plant species is desirable for restoration of Se-contaminated ecological habitat because they minimize the possibility of Se poisoning of wildlife and selenium's bioaccumulation in the food chain. The objective of this column study is to determine the natural efficiency of four perennial herbaceous plant species(a forage grass, a forage legume, a wetland species, and an alkaline soil grass) to accumulate selenium and sulfur and lower selenium levels in soil collected from Kesterson National Wildlife Refuge. After 8 months of growth, losses of total soil selenium did occur, however, the lost selenium was not accounted for in the plant tissue or in the leachate. Moreover, selenium accumulation and selenium dissipation from the soil were not impaired by the high level of soil sulfur. We assume that losses of soil selenium were primarily dependent on biological volatilization. The tested selenium nonaccumulator plant species may be favorable candidates for restoring the natural grassland habitat at Kesterson Wildlife Refuge.
Technical Abstract: Kesterson Reservoir in the San Joaquin Valley, CA was constructed to store drain water and to be used as part of the Kesterson Wildlife Refuge. Following the discovery of detrimental effects of selenium (Se) on the waterfowl, Kesterson Reservoir was closed to the input of drainwater and the wetland was transformed into an upland grassland. In this study, drainage sediment was collected from Kesterson Reservoir, and placed into 17 x 25 cm high columns. Four different Se nonaccumulator plant species; tall fescue, alfalfa, rush, and saltgrass were grown for 6 months in the Se and sulfur (S)rich sediment. Plants were harvested 5 times in 4-week intervals and analyzed for Se and S accumulation. Plant tissue Se and S concentrations ranged from 8.3 to 23.0 mg/Kg and from 3239 to 7034 mg/Kg, respectively. Percent losses of total soil Se ranged from 12 to 17% at final harvest. Because plant accumulations of Se and S were small compared to total soil Se and S losses and leaching was minimized, over 90% of the soil Se losses were unidentified. We can only presume that losses of Se volatilization were attributed to volatilization, since rates of Se volatilization were not measured. Hence, Se nonaccumulator plant species may be favorable for safely restoring Kesterson Wildlife Refuge to its natural habitat, despite the long time required for this biological process.