Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have devised a way to combine chemical treatment with "pollutant-busting" bacteria to remove cadmium from contaminated soil. They will present their latest data at the 220th national meeting of the American Chemical Society in Washington, D.C., on Thursday, August 24, 2000, at 10:10 a.m., in the Grand Hyatt Independence Ballroom D-E.
"Environmental contamination by heavy metals such as cadmium is a serious and growing concern," says environmental chemist Murthy A. Vairavamurthy, who leads the research at Brookhaven. Cadmium is a highly toxic and carcinogenic metal used in metal plating, nickel-cadmium batteries, pigments, plastic stabilizers, pesticides and more. It is most toxic in its free (ionic) form, which easily dissolves and moves through water, threatening groundwater supplies.
There are two basic ways to deal with soil contaminated with such toxic heavy metals, Vairavamurthy says. One is to mobilize the metals so they can be extracted from the soil and treated. The other is to convert the metals to a stable form that will not migrate into groundwater. To find ways to accomplish one or the other, the Brookhaven team looked for clues from nature.
"Many organisms use thiols - organic sulfhydryl compounds - to detoxify metals in the body," Vairavamurthy says. Many thiols form soluble complexes with toxic metals, which can then be excreted. "We thought these might work in soil as well," he says.
The team was also intrigued by the natural ability of many microbes to detoxify contaminants. "Bacteria have versatile biochemical mechanisms, which we thought we might be able to exploit intelligently," Vairavamurthy explains.
In the end, the team has proposed a method that combines both approaches:
First, thiosulfate, an inorganic compound with a sulfhydryl group, is injected into the subsurface soil. Thiosulfate has an affinity for and forms highly soluble comp
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Contact: Karen McNulty
kmcnulty@bnl.gov
631-344-8350
DOE/Brookhaven National Laboratory
23-Aug-2000