Soil pollution in copper sulphide mining areas in Galicia (N.W. Spain)

We have analyzed runoff waters from spoil heaps and scalped land surface in a sulphide mining area in Galicia (N.W. Spain). In comparison with uncontaminated waters, there are marked increases in H⁺ (up to 10⁻³ M), SO₄²⁻, Al, Mn, Zn, Cu and Ni, to levels strongly toxic to fish (up to 2500, 100, 80, 7, 2 and 2 mg L⁻¹, respectively). Not only Me-sulphate species, but also simple ions increase in concentration, the latter being considered as more toxic than the complexed forms. The solution extracted from soil affected by acid waters differs little from such waters, while the solid fractions shows a total increase of these elements, principally in forms more or less easily extractable (which we take to be exchangeable, organically complexed and barely crystalline minerals). Plant material collected on these soils reflect the extent of existing contamination, their concentration of these elements increasing many times with respect to reference samples.