Artisanal and small-scale gold mining (ASGM) is one of the largest anthropogenic sources of mercury to the global atmosphere and contributes to local mercury contamination and exposure, often disproportionately affecting disadvantaged communities. We studied the impact of ASGM on water quality and human mercury exposure in the Madre de Dios region of the Peruvian Amazon. This region has experienced tremendous growth in ASGM activity over the last 15 years that has led to significant migration to the region, deforestation, and associated ecosystem alterations. Our work included sampling river water and sediment to delineate the extent of mercury contamination, geospatial modeling to understand the links between deforestation and mercury mobilization, and epidemiological risk assessments of mercury exposure and disease vulnerability. The results demonstrate that total Hg contents in river sediments and in fish were greater downstream of ASGM activity than upstream. However, Hg concentrations in river sediments were surprisingly low (~0.02 mg kg<sup>-1</sup>) given the large number of mines located throughout the watershed. Moreover, families living in indigenous communities, who were identified as most vulnerable to methylmercury exposure, were often living hundreds of kilometers (both upstream and downstream) from the mining, outside the government designated mining regions. We employed a watershed-scale soil erosion and transport model to demonstrate that observed differences in Hg loadings in subcatchments of the Madre de Dios watershed were consistent with soil transport as predicted by the extent of deforestation in the subcatchments. Altogether, this work highlights how small scale mining activities collectively can have broader regional impacts on landscapes, mercury release to the environment, and exposure to residents who are likely to be especially vulnerable to the negative effects of mercury exposure.

Mobilization, methylation and exposure of mercury from artisanal and small-scale gold mining in Madre de Dios, Peru

2019 Spring National Meeting

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