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Fungi: California's answer to selenium?

Fungi: California's answer to selenium?

In 1985, California's Kesterson National Wildlife Refuge was shut down to limit its further contamination with selenium-tainted irrigation-drainage water (SN: 3/30/85, p.206). The toxic selenium pollution has been held responsible fo the poisoning of numerous waterfowl and other animals there. Phased-in measures to clean up the refuge and bury its selenium wastes were due to begin this year at an estimated cost of up to $50 million. But last week soil scientists at the University of California at Riverside unveiled a far less costly alternative--helping fungi convert the pollutant to a nontoxic, gaseous compund that will float away.

William T. Frankenberger Jr. and Ulrich Karlson were not out to solve Kesterson's problem when they began looking for selenium-detoxifying microbes. Says Frankenberger, "We were simply trying to solve an important agricultural problem that is getting more serious all over" -- leaching of the toxic mineral out of soils and into drainage water. In the process, however, the scientists identified three aerobic fungi abundant in crop soils -- Penicillium citrium, Acremonium falciforme and Ulocladium tuberculatum--which will convert selenite (SeO.sub.3.sup.2-.) or selenate (SeO.sub.4.Sup.2-.) salts into harmless volatile compounds through "methylation" (addition of CH.sub.3 groups).

In laboratory tests with Kesterson soil, the scientists got a 300 percent increase in selenium detoxification, or methylation, through the addition of pectin, an inexpensive vegetative carbon source. (Lemon peels, for example, are 75 percent pectin.) Addition of zinc, nickel or cobalt improved methylation three-fold more. In fact, Frankenberger's data indicate "that with further modification we can accelerate this process up to 10-fold." In so doing, their laboratory data suggest, the new process might restore Kesterson to a healthy refuge within a yeat at almost no cost--something the state's plan would not have achieved. Frankenberger will be proposing to field test his enhanced fungi treatment at Kesterson to both federal and state officials.
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Title Annotation:research on selenium-detoxifying microbes
Publication:Science News
Date:Jul 4, 1987
Words:320
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