Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: January 29, 1998
Publication Date: N/A
Interpretive Summary: Selenium is a naturally occurring element associated with many soils in the west side of central California. Strategies are not readily available for effective reduction of Se concentrations in field soils. We have evaluated phytoremediation as an alternative plant-based technology that is being considered for managing Se in soils. Growing crops to manage soluble Se by field phytoremediation requires the application of a wide range of knowledge about the chemistry and transformation of Se in soil, Se uptake and its toxicity in plants and animals, and sustainable agronomic practices necessary for long-term crop production. Information is presented from multi-year field trials conducted in Se-containing soils emphasizing selection of crops, crop rotation, irrigation and drainage water management, pest management, biomass use, and economic feasibility. The strategy of using plants to reduce soil Se levels requires time and a long-term commitment.
Field studies are crucial to develop phytoremediation strategies for remediating Se-laden soils and-sediments. Results are presented from multi-year field studies conducted by WMRL on managing levels of naturally-occurring Se in soils of central California. A crop rotation of Indian mustard and tall fescue lowered total soil Se by 60% after 4 years, which was significantly more than losses measured in bare plots or with other crop rotations. In another field study, the production of biomass from Brassica species, a crop used for phytoremediation, was affected by the amount of water applied. Applying excessive water did not result in increases of biomass. Moreover, encouraging deeper root development with planned soil-water moisture deficits may permit Brassica species to access bioavailable Se in the deeper subsoil. Field studies have been conducted with Se-laden effluent used as a source of irrigation water for Brassica. However, unless plant uptake of Se occurs faster than evapotranspiration, the net effect of irrigating land with Se-enriched water may increase the amount of soil Se. Thus, the need to use plants that accumulate Se, e.g., Brassica, is essential in phytoremediation. Another field study has identified the insects frequenting crops used for phytoremediation of Se. Flowering plants attract greater numbers of predators and beneficial insects.