Contribution for tier 1 of the ecological risk assessment of Cunha Baixa uranium mine (Central Portugal): I soil chemical characterization

Within the tier 1 of a site specific risk assessment, the pseudo-total concentrations (extracted with aqua regia) and the potential mobile fractions of metals were determined to perform a preliminary evaluation of risks posed by contaminated soils from an abandoned uranium mine (Mangualde, Central Portugal). Considering the mobile fractions of metals, extracted with artificial rain water, aluminium and uranium were the most concerning elements, since their concentrations were above soil quality criteria values (SQGVs) established for both elements. However, according to the evaluation based on potential mobile fractions of elements, rather than on pseudo-total metal concentrations the risks were limited to sites within the exploitation area, where contamination derives mainly from past in-situ leaching activities of pore ore as well as from the deposition of sludge from the effluent pond. The exclusion of other sites under evaluation, from the risk assessment process, requires additional data provided by soil screening ecotoxicological assays.