Uranium distribution in the solid phases of soils from Cunha Baixa mining site (Portugal)

Abstract

The present study concerns the application of partial chemical extraction, in a parallel procedure, to evaluate the uranium distribution in different solid phases constituents of the soils in the vicinity of Cunha Baixa mining area in order to assess its environmental risk. In the surface horizon of the soils, uranium that reached total concentrations between 9.8 to 362 mg/kg was preferential bound to non-crystalline iron oxides. These phases represent a small environmental risk. The contaminated irrigation water (>100 µg U/L) and the exchangeable complex of the acidic soils (pH <5), are important sources for the available fraction of uranium for crops (up to 30% of total U). The transference of uranium into the soil-water-plant system could be a factor of risk for Cunha Baixa population through the ingestion of vegetal foodstuffs, due to its possible uranium bioaccumulation capacity.