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Revista Brasileira de Ciência do Solo

On-line version ISSN 1806-9657

Abstract

CARDOSO, Gildevan Viana; AMARAL SOBRINHO, Nelson Moura Brasil do; WASSERMAN, Maria Angélica Vergara  and  MAZUR, Nelson. Geochemistry of natural radionuclide in soils surrounding a Mining and Plant Uranium Concentration. Rev. Bras. Ciênc. Solo [online]. 2009, vol.33, n.6, pp.1909-1917. ISSN 1806-9657.  http://dx.doi.org/10.1590/S0100-06832009000600040.

The environmental impacts resulting from uranium exploration and processing are to a great extent identical to those caused by extractive mining activities in general. This study aimed to determine the geochemical partitioning of the natural radionuclides 238U, 226Ra and 210Pb in areas surrounding the Uranium Mining and Concentration Plant (URA) of the Brazilian Nuclear Industries S.A., in the uranium deposit region of Lagoa Real, in Caetité, southwestern Bahia state. Representative soil samples of the main regional soil classes were collected from the layer 0-20 cm, in five areas around the URA. The level of total activity and geochemical fractionation (F1slightly acidic, F2 reducible, F3 oxidisable, F4 alkaline, and F5 residual) were determined for the five areas. The average total radioactivity levels were, in Bq kg-1 soil: 50 for 238U, 51 for 226Ra, and 159 for 210Pb. During the potentially bioavailable phase (F1) 11 % were extracted for 238U, 13 % for 226Ra and 3 % for 210Pb. The bioavailability of 238U was higher in more acidic soils and the affinity for iron oxides was greater, unlike in the case of 226Ra, with the greatest bioavailability. 210Pb was predominantly associated with F5. The high percentage of 238U, 226Ra and 210Pb in the geochemical fraction F5 indicates that the concentrations observed in the five soils are predominantly associated to the parent material of these soils, rather than to an artificial contamination caused by the URA activity.

Keywords : radio; uranium; lead; geochemical partitioning.

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