Impactos ambientais e dispersão de mercúrio associados à mineração artesanal e de pequena escala (ASGM) no Amazonas, Brasil

Abstract

Artisanal and small-scale gold mining (ASGM) is a complex socioeconomic practice characterized by the absence of technical control, informality, and strong dependence on mercury as an essential input and instrument of economic power, generating severe ecological and social impacts. In the Amazon, this activity has expanded rapidly, driven by the rising value of gold and the socioeconomic vulnerability of riverine populations, who view mining as an alternative means of subsistence. This research aimed to identify, qualify, and quantify the environmental impacts arising from areas affected by ASGM in the state of Amazonas, addressing deforestation, fluvial degradation, and mercury dispersion pathways. The methodology was based on the integration of geotechnologies, geochemical analyses, and field observations, articulating different spatial and temporal scales. Multitemporal remote sensing data and Geographic Information Systems (GIS) were employed to map and quantify deforested areas associated with mining, as well as to detect changes in fluvial morphology and land use patterns. Water and sediment samples were collected from active mining sites, rivers, and amalgamation drums and analyzed using Total Reflection X-Ray Fluorescence (TXRF), a technique that allowed precise quantification of total mercury (HgT) and other trace elements with high sensitivity. The results of Chapter 1 revealed a significant increase in deforestation and geomorphological changes in meandering rivers, especially in alluvial plains, evidencing intensified anthropogenic pressures on fragile ecosystems. In Chapter 2, TXRF analyses showed total mercury concentrations significantly above regulatory limits, particularly in retort wastewater and sediments from mining areas, confirming the existence of a poorly documented direct route of water contamination. It is concluded that artisanal mining is a persistent driver of environmental degradation, whose mitigation requires territorial governance, effective enforcement, and the adoption of clean technologies for the restoration of Amazonian ecosystems. This interdisciplinary approach enabled the understanding of ASGM not only as a point source of degradation but as a diffuse productive system whose effects spread throughout the river basins.