Residual pollution load of soils impacted by the Aznalcóllar (Spain) mining spill after clean-up operations.

By comparing total concentrations of potentially toxic elements in soils affected by the Aznalcóllar mining spill with those of the adjacent unaffected soils, it can be inferred that after the sludge removal, there still exists a considerable amount of residual pollution. This exceeds the suitable levels for cultivation, especially in the case of arsenic for which total concentrations are in the range of values above which eco-toxicity is considered to be possible. Elemental distribution in the soil seems to be determined by two distinctive associations (As-Pb-Hg-Sb and Cu-Zn-Cd) with different geochemical behaviours.