Bioaccumulation of potentially toxic elements from the soils surrounding a legacy uranium mine in Brazil.

It is important to understand the environmental fate and potential risks posed by metals and metalloids around mines and in legacy mining areas. In order to assess the bioavailable concentrations of several potentially toxic elements (PTEs: As, Pb, Cd, Ni, Cu, Cr, Mn, Zn, Ba, U) and rare earth elements (REEs: La to Lu), a multi-method evaluation of their concentrations/fractionation/speciation in soils was related to their biouptake in corn, for a region surrounding a legacy U mine in Brazil. Chemical fractions of the PTE and REE in soils were determined using the BCR (Community Bureau of Reference) sequential extraction procedure; a single extraction with Ca(NO 3) 2 and the diffusion gradient in thin films (DGT) technique. All techniques were better correlated to the metals accumulated by the crops as compared to total metal concentrations. Ba, Cu, Mn and Zn were shown to have high mobility and high bioaccumulation factors in the corn. Concentrations of U, As, Cd, and Pb were above threshold concentrations and strongly correlated, suggesting that they had a similar anthropogenic source. Geospatial modeling agreed with results from principal component analysis, indicating multiple sources for the contamination. Results highlighted the need for multi-method approaches when evaluating the long-term risks posed by PTEs and REEs in agricultural soils. Image 1 • Potentially toxic elements and REE are accumulated by plants in a U mining area. • Chemical extractions and DGT correlated well with the metal bioavailability. • Geospatial modeling, PCA and FA indicated multiple sources of soil contamination. [ABSTRACT FROM AUTHOR]