Thursday, July 21, 2011

A Novel Solution to Persistent Lead Pollution In Soils

The cost of carting away soils laced with lead is one that can no longer be borne by the EPA and state agencies trying to deal with decades of buildup. Lead, which can cause developmental and mental health issues, was in widespread use until the latter part of the 20th century, which means that communities throughout the country have lead issues, especially in urban areas.

That makes the novel use of fish bone meal all the more appealing. The waste product from processing fish for food can be tilled into top soil with high lead concentrations so as to bind with the lead particles and make them incapable of being absorbed by people.
Today, there is more lead contamination in America’s cities than any federal or state agency could ever afford to clean up and haul away. So scientists and regulators are trying a new strategy, transforming the dangerous metal into a form the human body cannot absorb, thus vastly reducing the risk of lead poisoning.

The principle is straightforward, said Victor R. Johnson, an engineer with Civil & Environmental Consultants Inc. “The fish bones are full of calcium phosphate,” he said. “As they degrade, the phosphates migrate into the soil.” The lead in the soil, deposited by car exhaust from the decades when gasoline contained lead or from lead-based paint residue, binds with the phosphate and transforms into pyromorphite, a crystalline mineral that will not harm anyone even if consumed.

This alchemy has been practiced in university and commercial laboratories for more than 15 years, and more recently has been employed at acid-mine sites and military bases.

But now it is also coming to residential neighborhoods like South Prescott in Oakland, which this month became the first in the country where fishbone meal is being mixed into the soil for lead control under a project organized by the Environmental Protection Agency.

“It’s fair to say, looking forward, that just about every urban residential area probably has a lead problem and we just can’t afford economically and socially to move that amount of dirt any more,” said Steve Calanog, the E.P.A. official in the San Francisco office that is overseeing the project. “Topsoil is a precious resource, and we don’t have enough topsoil to replace it.”

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