Good for more than barbecuing, charcoal may be the key to improving the health of mercury-laden soils and sediments. In the most polluted areas—Superfund sites and other contaminated hotspots—mercury cleanup has traditionally meant dredging, a disruptive and costly endeavor. But activated carbon, a granulated form of charcoal, can trap mercury in place, which may allow for cheaper, simpler remediation efforts.
“Instead of digging up contaminated sediments or soil, we hoped to add something to the sediments that will keep the mercury from getting into the food web,” says Cynthia Gilmour of the Smithsonian Environmental Research Center. In a recent study, she and her colleagues tested how well activated carbon locked up methylmercury, the form of mercury that tends to rise up the food chain and that can cause neurological problems, to prevent it from accumulating in living tissue.
Using sediments from four mercury hotspots, the scientists measured the amount of the toxic substance taken up by sediment-dwelling worms. Activated carbon reduced the bioaccumulation of methylmercury by 30 to 90 percent, the researchers reported last October in a study published online in Environmental Science & Technology.
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The charcoal idea came from study co-author Upal Ghosh of the University of Maryland, Baltimore County, who had been using activated carbon as a remediation tool for polychlorinated biphenyls (PCBs), another pollutant that lingers stubbornly in sediments and then climbs the food chain. Ghosh suggested trying the same approach to deal with methylmercury. “These two chemicals have probably the highest bioaccumulation rates that we know of,” Gilmour notes.