Effect of flood with mine wastes on metal extractability of some soils of the Guadiamar river basin SW Spain/

The availability of metals in soils affected by the accidental flood of mining wastes in the Guadiamar river SW Spain. is studied at three sites by sequential extraction and by extraction with CaCl2 and EDTA solutions. Significant increases in the available fractions of some potentially toxic metals like Pb and Zn, and in some cases Cu, were found by sequential extraction in the first 5 cm of the soils studied. However, beyond this depth, the pattern was variable along the river. At two of the sites the metals in soluble form did not penetrate further than 5 cm into the soil, while at the site closest to the mineworks, the soluble forms of some potentially toxic metals such as Pb, Zn and, to a lesser extent, Cu, were significantly more abundant at depths )5 cm of the affected soils than those of analogous unaffected soils. The results indicate that the environmental hazard of metal availability for plants penetrating further than 10 cm is not likely to be significant, although it varies along the river. Further studies are needed to assess the long-term environmental damage to the area after removal of the wastes.