Local Interpolation of Some Chemical Parameters After the Removal of the Aznalcóllar Mine Spill Sludge (South-West Spain)

On April, 25th 1998, the retaining wall of a tailings reservoir collapsed at the Aznalcollar pyrite mine, south-west Spain, releasing approximately 6 Hm3 of acid sludge into the adjacent river catchments, causing a huge flood and posterior deposition of the toxic sludge on the river bed and banks. Consecutively a cleaning program was set up to remove the toxic residue from the river bed and banks and to amend the cleaned zone. Remaining sludge forms an important source of concern since it constitutes a potential source of contamination and a threat for successful revegetation. Data from periodically taken soil samplings in the area were merged after normal score transformation. Simple kriging with local varying means was used to make maps of the remaining sludge in terms of different chemical parameters.