Impacts of Artisanal and Small-Scale Alluvial Gold Mining for Environmental Welfare in Napo, Ecuador

Abstract

Artisanal and small-scale alluvial gold mining (ASGM) is the single largest source of anthropogenic mercury pollution in the world. Gold mining practices involve the use of elemental mercury to purify gold from sediments and ore, leading to the release of mining tailings and increased mercury mobilization. The objective of this study was to analyze the environmental status currently of the Napo Watershed to contribute towards a baseline of data as these efforts expand in the future. The region of Napo, Ecuador is within early development of widespread ASGM activity along the Napo River Watershed, a major tributary of the Amazon. This study seeks to characterize the distribution of mercury in the Napo River and how this relates to potential health risks downstream of ASGM. Water and sediment samples were collected along the Napo River and processed for total mercury, total suspended solids, cations, anions, and methylmercury. Additionally, geographic information systems were used to analyze the spatial distribution of deforestation within watershed delineations. The results indicated total mercury levels in unfiltered water to travel on the particulate level, meaning mercury-bound particles are emitted from mining activity’s dislodgement of sediment. Most samples tested, including cations, anions, and methylmercury, were not as extreme as other ASGM areas in the Amazon with more established gold mining activity. While samples tested do appear low, slight changes can impact human populations that consume riverine fish due to bioaccumulation of methylmercury.