Technique May Cure Kesterson’s Woes

Two soil microbiologists at the University of California, Riverside, reported the discovery Tuesday of a way to accelerate a natural process for detoxifying selenium, a substance that has killed or deformed hundreds of migratory birds at Kesterson National Wildlife Refuge in Merced County.

William T. Frankenberger Jr. and Ulrich Karlson said their technique, in laboratory experiments, reduced selenium concentrations by as much as 35% in 30 days.

If the process is proven in field tests, they said, it could lead to ways to cope with a buildup of selenium not only at Kesterson but in major agricultural regions throughout the United States that are threatened by toxic levels of the substance.

Selenium is a natural mineral found in soil. In minute amounts, it is necessary for human and animal nutrition. In high concentrations, it is toxic. Its levels have been elevated in ponds at Kesterson because the ponds became the the final holding area for agricultural waste water heavily laden with selenium from ranches in the western San Joaquin Valley. The Kesterson is no longer used for agricultural waste water.

Frankenberger and Karlson estimated that selenium concentrations in ponds at the 5,900-acre Kesterson wildlife preserve could be reduced to acceptable levels within a year, at a cost of $1 million; other approaches have been estimated to cost between $25 million and $50 million.

“I think we’ve established clear evidence that this particular process can remove selenium from soil,” Frankenberger said.

The UC Riverside announcement was greeted cautiously, however, by a researcher at UC Berkeley and by the U.S. Bureau of Reclamation, which is in charge of the Kesterson cleanup.

Larry Waldron, chairman of the plant and soil biology department at Berkeley, said of Frankenberger, “He may very well have some real startling and wonderful things. I hope he does.” Waldron cautioned, however, that the findings are “very preliminary.”

He also took issue with a claim in the UC Riverside press release that said scientists at Lawrence Berkeley Laboratory had verified Frankenberger’s and Karlson’s experiments.

Edwin Lee, head of the Bureau of Reclamation’s technical development branch of the San Joaquin Valley Draining Program, said the government is viewing the UC Riverside work “rather favorably.” He also said more work is required to verify results, a statement repeated by an official spokesman for the bureau.

Nonetheless, the Riverside findings are of considerable interest to the Bureau of Reclamation and others who are wrestling with how to clean up Kesterson and develop manageable ways of preventing a recurrence of the problem on a larger scale elsewhere in the San Joaquin Valley and in other agricultural areas of the country where selenium threatens to reduce crop yields and contaminate water supplies.

The natural process of detoxifying selenium described by the Riverside scientists has been recognized for at least 30 years, according to Waldron. He said the real issue is whether the natural process can significantly reduce selenium levels within a reasonable time.

Frankenberger and Karlson reported that they discovered the optimum conditions for doing just that. They said that if contaminated ponds at Kesterson were drained and harmless fungi in the soil were exposed to air, the fungi would absorb the toxic forms of selenium known as selenate and selenite and convert them to nontoxic forms of selenium known as dimethylselenide and dimethyldiselenide. The nontoxic forms are volatile and quickly evaporate.

The Riverside scientists said this process can be accelerated by 300% by adding straw or animal manure to the mix. It can be speeded by 300% more by adding zinc, cobalt or nickel, they said.