The pits and mine ponds from digging small deposits of alluvial gold in the Amazons of Peru has altered the landscapes dramatically and has increased the indigenous communities and wildlife's risk of mercury exposure, a new study revealed.
This particular study is the first to document how mining has greatly altered the landscape and amplified mercury poisoning risks through the creation of ponds and the formation of methylmercury from these hazardous ponds.
The study, led by Simon Topp, a doctoral student at the University of North Carolina, and Jacqueline Gerson, a doctoral student in ecology at Duke University, and their colleagues, was peer-reviewed and published on November 27 Science Advances.
The study methodology in Peru's Amazon
The research team collected water and sediment samples upstream and downstream of artisanal mining sites in Peru's Madre de Dios River. Samples were also taken from its tributaries, surrounding lakes, and mining sites in July and August 2019. Total mercury content and methylmercury content in the samples were also analyzed.
The findings revealed that artificial lakes and ponds are areas mined heavily increased tremendously in 2008, when the price of gold increased. Meanwhile, areas without heavy mining increased by 20 percent only over the entire study period.
The tremendous increase of mine ponds in Amazons of Peru
According to Topp, the heavily mined watersheds in Peru's Amazon had a 670 percent increase of mine ponds since 1985. The mine ponds are almost entirely artificial lakes as the former mining pits become filled with rainwater and groundwater over time.
The study also indicated that the landscapes used to be dominated by forests but are now dotted by small lakes.
Mine ponds with increased mercury risks
The study also revealed that the mine ponds, which have become small lakes, provide low-oxygen conditions, which, aided with microbial activity, cause the submerged mercury to be converted into an even more toxic form of the element, the methylmercury. The mercury on the mine ponds is toxic left-over from the gold mining activities.
Methylmercury bioaccumulates in body tissues as it moves up the food chain, posing high risks for large predators and humans.
Peruvian Amazon has high biodiversity and many indigenous populations; thus, high risks of methylmercury contamination are particularly concerning, Gerson said.
Impact of high mercury risks
Artisanal gold miners commonly use mercury to separate gold ore from soil and sediments. Most often, adequate safety precautions from mercury risks to protect themselves or the environment are ignored.
Mercury is a potent neurotoxin, and exposure can cause several health issues like tremors, muscle weakness, vision and hearing impairment, and loss of coordination and balance. A severe case can lead to congenital disabilities or death.
Previous studies reveal that miners used to burn the mercury into the air or spill it in nearby rivers. These causes greater environmental and health risks to communities and the surrounding wildlife.
Other locations where unregulated artisanal small-scale gold mining occurs like Asia, sub-Saharan Africa, and other parts of South America are also at risk of mercury contamination, she added,
Topp said that as long as gold prices remain high and artisanal small-scale gold mining is a profitable activity, thousands of mining ponds will proliferate in the Amazons on Peru, further altering the landscape once-forested area and amplifying the mercury risk exposure to humans and the wildlife surrounding the area.
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