The idea: Use common crops to soak up contaminants in soil from gold-mining sites and return the areas to productive agriculture. The gold harvested from the process pays for the cleanup – with money left over for training in sustainable agriculture.

“We get the plants to do the hard work, and then we basically harvest the plants and extract the metal,” says Christopher Anderson, an environmental geologist from Massey University in Palmerston North, New Zealand. “So we farm mercury and gold.”

Aimed at small-scale mines, such a program could prove especially beneficial to Latin America, where some 1 million artisanal miners ply their trade, according to estimates by the International Labor Organization. The bulk of them are in Brazil.

Dr. Anderson has already run successful field tests last year in an Amazonian gold mine near Bahía, Brazil. In a few months, he plans to begin a larger project, most likely in Serra Pelada, about 1,800 miles northwest of Bahía.

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