Potentially toxic elements in soils and contamination indices at the serra pelada gold mine, Para, Brazil / Elementos potencialmente tóxicos em solos e índices de contaminação na área de mineração de ouro de serra pelada, Pará, Brasil

The large surface stacking volume of waste and tailings at the Serra Pelada gold mine, with a high content of potentially toxic elements (PTEs), has led to environmental damage in the area, which continues to this day and is yet to be measured. Total and available Cu, Mo, Pb, and Zn and an indicator index was formulated for soil contamination in the artisanal mining area of Serra Pelada, Amazônia, Brazil. To obtain these data, six soil samples were collected surrounding the lake formed from the mining trenches and one from a forest area outside the influence of mining activities. Metal solubilization and partial extraction were conducted by aqua regia and 0.5 mol L-1 HCl, respectively, followed by detection using argon plasma optical emission spectrometry. All PTEs showed total contents above the quality reference values for soils in the state of Para. The available fractions of Cu, Pb, and Zn were higher than the concentrations expected for Para in forest soils. The total Cu contents were above the value of prevention defined by the National Council of Environment. In general, there was Mo enrichment (41.0) > Cu (3.5) > Pb (1.4), indicating that the areas had been contaminated by PTEs a resulting from human activity.

O empilhamento superficial de volume expressivo de rejeito e estéril, com alto teor de elementos potencialmente tóxicos causou danos ambientais até hoje não mensurados. Neste contexto, constituiu-se objetivo deste trabalho, avaliar os teores totais e disponíveis de Cu, Mo, Pb e Zn e determinar índices indicadores de contaminação em solos na área de exploração artesanal de Au em Serra Pelada -Amazônia, Brasil. Para tanto, foram coletados seis pontos amostrais no entorno do lago formado a partir da cava e um ponto em área de mata sem influência do garimpo. Os teores totais e disponíveis dos metais foram extraídos com água régia e solução 0,5 mol L-1 HCl respectivamente, seguidos das determinações através da espectrometria de emissão ótica com plasma de argônio acoplado indutivamente (ICP-OES). Todos os PTEs apresentaram teores totais acima dos valores de referência de qualidade para solos do estado do Pará. Os teores disponíveis de Cu, Pb e Zn foram superiores aos observados em solos de área de floresta do estado do Pará. Os teores de Cu total estão acima do valor de prevenção definido pelo Conselho Nacional de Meio Ambiente. Em média houve enriquecimento de Mo (41,0) > Cu (3,5) > Pb (1,4), o que indica que as áreas foram contaminadas por PTEs a partir das atividades antrópicas.

Serra Pelada: the first Amazonian Meteorite fall is a Eucrite (basalt) from Asteroid 4-Vesta

ABSTRACT Serra Pelada is the newest Brazilian eucrite and the first recovered fall from Amazonia (State of Pará, Brazil, June 29th 2017). In this paper, we report on its petrography, chemistry, mineralogy and its magnetic properties. Study of four thin sections reveals that the meteorite is brecciated, containing basaltic and gabbroic clasts, as well of recrystallized impact melt, embedded into a fine-medium grained matrix. Chemical analyses suggest that Serra Pelada is a monomict basaltic eucritic breccia, and that the meteorite is a normal member of the HED suite. Our results provide additional geological and compositional information on the lithological diversity of its parent body. The mineralogy of Serra Pelada consists basically of low-Ca pyroxene and high-Ca plagioclase with accessory minerals such as quartz, sulphide (troilite), chromite - ulvöspinel and ilmenite. These data are consistent with the meteorite being an eucrite, a basaltic achondrite and a member of the howardite-eucrite-diogenite (HED) clan of meteorites which most likely are from the crust asteroid 4 Vesta.