Fracionamento químico e bioacessibilidade de elementos potencialmente tóxicos em área de mineração artesanal de ouro na Amazônia.

Abstract

The Serra Pelada artisanal mine was discovered in the early 1980s, when it attracted workers from around the world to explore gold. Currently, mining waste piles are deposited unprotected on the soil surface, which may put the population's health at risk from exposure to potentially toxic elements (PTEs), especially considering that mineral exploration may have altered the mobility, bioavailability and bioaccessibility of PTEs in the region, which has not yet been studied. The objectives were to perform the chemical fractionation of barium (Ba), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn), and to determine the bioaccessibility of these elements in soils and mining wastes from the influence area of the Serra Pelada mine, Brazil. Twenty-seven samples were collected: 10 in mining areas, 10 in urban areas, 5 in agriculture areas, and 2 in forest areas. Chemical, physical, and mineralogical characterizations of the samples were carried out. Pseudototal concentrations were extracted by acid digestion in a microwave oven. Chemical fractionation was obtained using the BCR (Bureau Community of Reference) protocol for sequential extraction, oral bioaccessibility was obtained using the SBET (Simple Bioaccessibility Extraction Test) method, and lung bioaccessibility was obtained using Gamble’s solution. The concentrations were quantified by flame atomic absorption spectroscopy and subjected to descriptive statistical analysis. The results indicated contamination by Ba, Cu, and Ni, mainly for Ba in the mining area. The chemical fractionation revealed the predominance of the elements in the residual form. However, Ba is in high concentrations in greater mobility forms (exchangeable + reducible + oxidable), ranging from 166.36 to 1379.58 mg kg-1. Regardless of the area, Cr and Cu are more oral bioaccessible in the intestinal phase and Zn in the gastric phase. Ba, Cr, and Zn are not lung bioaccessible, while Cu, Ni, and Pb are bioaccessible by inhalation. The studied elements deserve attention not only due to the high pseudototal concentrations (which indicate potential risk), but also the concentrations in high mobility forms and bioaccessible fractions.