The past two decades have seen a sharp increase in illegal and informal gold mining in Peru‘s southern Amazon region of Madre de Dios. These small-scale operations typically involve cutting down all of the trees in a particular area, digging a large pit and then using mercury to extract gold from the excavated soil… The mercury binds to any gold in the soil, creating a large chunk that can be easily removed. This chunk is then burned, evaporating and releasing the mercury into the air while leaving behind pure gold
Besides releasing mercury into the atmosphere, miners typically add three to four times more mercury… than is actually needed. While this ensures all of the gold is extracted, it also means there is a large amount of leftover mercury in the slurry that is inevitably dumped back into the excavated pit. And because the whole process started with the clearing of trees, there’s nothing to stop the mercury-laden soil from eroding into nearby rivers.
“This means mining practices can hit people three times with mercury — once from direct contact, once from atmospheric transport and deposition, and once from soil mercury mobilization due to land clearing,” said William Pan,Professor of Population Studies at Duke. “The scenarios we run demonstrate that even if mining were to end today, since vegetation is unlikely to return for several decades, the cleared land will continue to release mercury.”
For more details see Duke University
Excerpts from Deforestation, erosion exacerbate mercury spikes near Peruvian gold mining, Science Daily, Dec. 12, 2019