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(W/MF193) Remediation of an area affected by a spill of pyritic tailings in Aznalcollar (Sevilla, Spain). Martín, Francisco1, Ortiz, Irene1, Simón, Mariano1, Fernández, Emilia1, Fernández, Juan1, García, Inés1, Belver, Rafael2, Aguilar, José1, Dorronsoro, Carlos1, 1 2 ABSTRACT- We analyse the pollution produced by a toxic spill of tailings and water (4,5 hm3) along the Agrio and Guadiamar river basin (southern Spain), affecting 44 km2. The principal pollutants were Zn, Pb, Cu, As, Cd and Tl and there was an intense acidification when the sulphides oxidized to sulphates. The layer of tailings that covered the soils was removed and carbonates were added to the affected soils (2 kg m-2). All soils were asigned to 5 different categories by a cluster analysis via the k-means method and the progress of the contamination was analysed in each group. pH of the soils hardly changes before and after the addition of the carbonates, indicating that the addition of carbonates was insufficient in the acid soils to increase substantially the pH and to ensure the immobilisation of the contaminants, whereas it was not necessary to add a limestone amendment to the carbonated soils. Electric conductivity clearly decreases, mainly in the most contaminated soils, which could be the result of the clean-up, or a consequence of an insolubilization process of the soluble metals over time. Total content of the different pollutant elements tends to decrease over time. The decrease mainly occurred in the most contaminated soils, which could be attributed to the clean-up work. In general, concentrations of soluble and EDTA extractable metals tend to decrease over time, which indicates that they are changing to non-bioavailable forms. Key words: pirityc tailing, remediation, heavy metals, pollution |
