Firing ranges host some of the planet’s most heavily contaminated soils. Toxic lead and copper from spent bullets can leach into the earth, threatening ground water, killing microbes, and poisoning plants. Cleaning this soil is often too costly for the operators of military and private ranges. Now, Korean scientists have created a natural mixture that sops up nearly all the metals: pulverized oyster shells and fly ash, the sooty particles spewed by combustion. Landfills in Korea accumulate more than 250,000 tons of oyster shells each year, while coal-fired power plants churn out just as much fly ash. Combining the two waste products creates a concoction rich in minerals that shackle metal ions within tight molecular bonds, the team reports this month in Environmental Geochemistry and Health. By mixing different ratios of the ingredients with grossly contaminated firing-range soil—holding nearly seven times the amount of lead deemed dangerous by the U.S. Environmental Protection Agency—the researchers identified a unique blend that locked up 98% of leachable lead contamination and 96% of the copper. Other soil-scouring techniques exist, but the shells-and-ashes approach is far cheaper and more sustainable, the scientists claim.

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