Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2007
Publication Date: 4/18/2007
Citation: Banuelos, G.S., Lin, Z.Q. 2007. Acceleration of Selenium Volatilization in Seleniferous Agricultural Drainage Sediments Amended With Methionine and Casein. Environmental Pollution, Vol 150 (2007) 306-312, at www.sciencedirect.com Interpretive Summary: Land disposal of selenium-laden drainage sediment accumulated in the San Luis Drain in central California may be an option to consider due to its low cost. To complement this mode of sediment disposal, we have evaluated a remediation strategy using plants and biological volatilization to lower the selenium content within the drainage sediment. Due to the negative effects exerted by high salinity and boron on selenium uptake by the plant, we concentrated our efforts on biological volatilization of Se (i.e. transformation from inorganic selenium to volatile forms of selenium). Our objective in this two-year microplot field study was to accelerate biological volatilization of selenium in vegetated (planted to salado grass) and unvegetated drainage sediment plots amended with methionine and casein. Compared to untreated vegetated and unvegetated plots, we were able to increase selenium volatilization rates at least six-fold 24 hours later with the addition of methionine and casein during the warmest months of the year on irrigated vegetated and unvegetated plots. The addition of methionine was most effective in promoting volatlilization in vegetated plots, while the addition of casein was most effective in the irrigated unvegetated plots. Although rates of selenium volatilization were lower in vegetative plots with casein, our source of casein - milk, may be the preferred organic amendment, due to its low cost and high availability. The management/removal of selenium via biological volatilization can be promoted from drainage sediment disposed of on agricultural soils in central California by amending with either methionine or casein.
Technical Abstract: Phytoremediation is a potential tool for the management of excessive Se in drainage sediment residing in the San Luis Drain in central California via plant extraction or biological volatilization of Se. This two-year field study in 2004/2005 examined the ability of organic amendments-methionine and casein-to enhance Se volatilization from plots containing drainage sediment, either unvegetated or planted in salado grass (Sporoublus airoides). In 2004 methionine and casein treatments were , respectively, added to vegetated and irrigated drainage sediment plots as follows: 1.4, 14.3, and 71.4 mg methionine/kg dry sediment/soil, and 29, 143, 286, and 572 mg casein/kg dry sediment/soil. Selenium volatilization was less than 25 µg/m2/d in all plots without organic amendments. Rates of Se volatilization were as high as 434 µg/m2/d in the irrigated vegetated plot and 289 µg/m2/d in the irrigated bare plot during the first 24 hrs after adding 71.4 mg/methionine kg dry sediment/soil. Seven days later, rates of Se volatilization dropped to 104 and 58 µg/m2/d for the same irrigated vegetated and bare plots, respectively. The average rate of Se volatilization was 346±103 and 114±55 µg/m2/d in the irrigated bare and vegetated plots, respectively, amended with 572 mg casein/kg dry sediment/soil. In 2005 the greatest rates of Se volatilization occurred for both amendments during the warmest time of the year with the continued addition of 71.4 mg methionine and 572 mg and casein/kg soil, respectively, on a regular basis for 210 days to irrigated vegetated and bare plots,. Incorporating organic amendments-methionine or casein-onto Se-contaminated drainage sediment with or without vegetation enhances the efficacy of Se removal via microbiological and plant volatilization.