Soil pollution by a pyrite mine spill in Spain: evolution in time

Soil pollution was studied after the spill of the Aznalcóllar pyrite mine between 1998 and 2001, analyzing As, Zn, Cd, Cu and Pb both in total concentrations as well as in soluble and bioavailable forms. The main remediation measures were: clean-up of the tailings and polluted soils, plus application of amendment materials (liming). The results indicate that, after three years, 50–70% of the acidic soils and 25–30% of the basic soils are still highly polluted in total arsenic. The limit of 0.04 mg kg−1 for water-soluble arsenic is exceeded in 15–20% of all soils. The EDTA-extractable arsenic (bioavailable) exceeds the limit of 2 mg kg−1 only in the acidic sectors. After clean-up, the homogenization of the upper 20–25 cm of the soils appears to be the most recommended measure in the reduction of pollution.