Geochemistry of potentially toxic elements in gold mining areas in the paraense Amazon
Contamination. Heavy Metals. Pollution rates. Mining.
The Amazon is an important source of water and mineral resources and biodiversity. It provides ecological services essential to life on earth, such as storing fresh water and minimizing the effects of global warming. Studies that demonstrate the dynamics of potentially toxic elements (ETSs) and rare earth elements (ETRs) in the soil are of great relevance, especially in mineral exploration areas. The identification and knowledge of these pollutants are necessary for control and decision making in relation to the most appropriate management to avoid negative environmental impacts. The objective was to determine the concentration of EPTs and ETRs in areas of influence of garimpos in Cachoeira do Piriá. Samples were collected in different garimpos and native forest to characterize the chemical and granulometric attributes, for which the pH, organic matter, CEC, clay, sand and silt content and the concentrations of EPTs and ETRs in soils and residues were analyzed. With this information, the enrichment factor (FE), geoacumulation index (Igeo) and pollution load index (PLI) were determined to determine the level of contamination in the study areas. The spatial variability of EPTs and ETRs was expressed through dispersion maps of contaminants. High levels of EPTs and ETRs were determined, surpassing the reference values of soil quality (VRQs) for the state of Pará and values of prevention (PV) and values of investigation (VI) determined by CONAMA. Of the 35 evaluated elements only Ag, Cd and If are in natural levels in the soil, the others are in high concentrations. The total concentrations of EPTs are very high relative to the VRQs of Pará soils and the abundance per sampled site follows the order G1 - reject and sterile> 10 years: As> Ni> Mo> Cr> Co> Mn> Fe> Zn> Cu> Hg> Pb = Ba> Al = V, the Cd is below VRQ, in G2 - tail and sterile <10 years: As> Ni> Mo> Co> Mn> Cr = Hg> Zn> Fe> Pb The elements Cd, Cu, Hg, and V are below the VRQs, in GC. - reject and sterile after cyanidation: As Ni, Mo> Cr> Fe = Co> Mn> Cu = Zn> Hg = Pb> Ba> V> Al, element Cd is below VRQ and in AM - native vegetation area Where Cd, Co, Cr, Co, Hg, Pb and V are at lower levels than the VRQs. In view of the results we can affirm that artisanal gold mining in Cachoeira do Piriá is contributing to the enrichment of EPTs on the soil surface, which can cause pollution of the environment and health risks to the population.