|Wu, L - UC DAVIS|
|Akohoue, S -|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 1996
Publication Date: N/A
Interpretive Summary: Selenium is a naturally-occurring element associated with many soils in the westside of central California. Irrigation drainage water has transported Se to Kesterson Reservoir, where evaporation has led to high concentrations of soil selenium and contributed to the death and deformities in waterfowl frequenting the ponds. As part of a remediation strategy, repeated plantings of canola, kenaf, and tall fescue reduced the levels of Se in Kesterson soils to non-toxic concentrations. Despite slight dry matter reductions under these saline conditions, canola absorbed and concentrated more Se than the two other species. We recommend planting canola as the species for phytoremediation at the measured salinity level. At higher salinity levels tall fescue appears to be more suitable as chosen species. The strategy of using plants to decontaminate Se levels in the soil is a gradual but effective, inexpensive and non-lethal management tool for lowering Se levels in Se-laden sediment at Kesterson Reservoir and other Se-contaminated soils.
Technical Abstract: Elevated levels of selenium (Se) have been measured in sediment at Kesterson Reservoir. High concentrations of Se found in the waterfowl frequenting the Reservoir have contributed to an increased frequency of deformities and reproductive disorders in these birds. Strategies are not readily available for effective reduction of high Se concentrations in soil. We evaluated the use of phytoremediation to lower the soil Se levels. A greenhouse study was condutced to evaluate the ability of canola, kenaf, and tall fescue to absorb Se from sediment collected from Kesterson Reservoir, which contained concentrations of total Se and extractable B as high as 40 mg Se kg/soil and 10 mg B/L, respectively, and a soil salinity of 8 dS/m. Both canola and kenaf experienced dry matter reductions of at least 25% at these salt levels, whereas dry matter production in tall fescue was not affected. Canola accumulated the greatest amount of Se (470 mg Se/kg DM), while kenaf and tall fescue accumulated between 45-50 mg Se/kg DM. After three successive plantings in the same soil, canola reduced soil Se concentrations by 47%; kenaf, reduced soil Se by 23% after two successive plantings, and tall fescue, reduced soil Se by 21% after one planting and 7 multiple cuts. The results show that any of these three plant species, especially canola at these salt levels, lower soil Se concentrations after approximately 1 year of growing under greenhouse conditions. Field trials are presently being conducted with the same species growing in the Se-laden sediment at Kesterson.