The long-term influence of a mine spill in soil was studied 12 years after the Aznalcóllar accident. Soils
where the pyritic sludge was not removed, a fenced plot established for research purposes (2000 m2) and
soils where the process of remediation was accomplished successfully were sampled and studied in
detail. Soils were characterized at different depths, down to 100 cm depth, determining chemical
parameters and total concentrations of major and trace elements. Moreover plants colonizing remediated
(RE) and non remediated (NRE) soils were also analysed attending their potential risk for
herbivores. Strong acidification was observed in the NRE soil except in surface (0e10 cm). The
progressive colonization of natural vegetation, more than 90% of the fenced plot covered by plants, could
facilitate this increased pH values in the top soil (pH 6). In the NRE soil, the successive oxidation
and hydrolysis of sulphide in the deposited sludge on the surface after the accident resulted in
a re-dissolution of the most mobile element (Cd, Cu and Zn) and a penetration to deeper layers. Trace
element concentrations in plants growing in the NRE soil showed normal contents for higher plants and
tolerable for livestock. Nitrogen and mineral nutrients were of the same order in both soils, and also
normal for high plants and adequate for animal nutrition. Despite of the natural remediation of the NRE
soil, results demonstrate that the remediation tasks carried out in all the area, the Guadiamar Green
Corridor at present, were necessary to avoid the leaching of the most mobile elements and minimize the
risk of contamination of groundwater sources, many of them close to the Doñana National Park