Friday, July 22, 2011

Fighting Lead with Fish Meal

Lead has been one of the worst ecological catastrophes of the industrial age, and the amount of lead in the soil of many old urban neighborhoods is still dangerous. Fortunately, scientists may have hit on an affordable way of dealing with the problem:

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.”

The project in South Prescott, expected to cover a six-block area and cost $4 million over two years, will train up to 75 workers, many previously unemployed, in toxic cleanup methods. In this 100-year-old neighborhood of west Oakland, the average contamination levels in the soil are twice the federal limit of 400 parts per million, and some hot spots have lead levels five or six times greater, Mr. Calanog said. South Prescott was built on landfills holding the detritus of the 1906 San Francisco earthquake. . . .

When it came to fixing the problem, local E.P.A. officials consulted with community leaders. The fishbone approach appealed to everyone involved because no one liked the idea of the heavy construction associated with soil removal, or the idea of taking and dumping the toxic soil on another community, Mr. Calanog said.

1 comment:

Erich J. Knight said...

Manure based Biochars that are high in P are proving very cost effective for in situ remediation of toxic agents

USDA is looking at heavy metals; ARS Research Turns Poultry Waste into Toxin-grabbing Char
The in situ remediation of a vast variety of toxic agents in soils and sediments.
Biochar Sorption of Contaminants;

The International Biochar Intuitive now has 33 biochar affiliates around the world.
Note also the Japan Biochar Association have a very long tradition of biochar use and have been developing "modern methods" over the last thirty years. A governmental act officially acknowledged charcoal as a "soil ameliorator" back in 1988 and have completed work using Biochar as an in situ sorbent of Cd, and starting work on heavy metal radionuclides.