EDAFOLOGIA, Vol. 10 (2), pp. 177-183, 2003
EFECTO DEL ENCALADO EN SUELOS CONTAMINADOS POR LODOS PIRÍTICOS
F. MARTÍN1, M. SIMÓN2, I. GARCÍA2, P. BOUZA3, C. DORRONSORO1, J. AGUILAR1
1Departamento de Edafología y Química Agrícola, Facultad de Ciencias, Universidad de Granada, Granada.
2Departamento de Edafología y Química Agrícola, Escuela Politécnica Superior, Universidad de Almería, Almería.
3CONICET. Centro Nacional Patagónico. Puerto Madryn. Argentina. e-mail: fjmartin@ugr.es
To analyse the effect of calcium carbonate on the soil pollution caused by the oxidation of pyrite tailings, we added 10 different quantities of CaC03 (between 1% and 25%) to a non-carbonated soil. In each case, for each 10 g of soil, we added 100 cm3 of a contaminated solution from the tailings oxidized with H2O2. The liming raised the soil pH, favouring the precipitation of the dissolved elements in the contaminating solution. At soil pH<2.6, Fe precipitated as sulphates and hydroxysulphates (molar ratio Fe/S<2), adsorbing As; however, neither Cu nor Zn precipitated. At pH=2.6-6.0, the hydroxysulp- hates were far richer in Fe (molar ratio=2-6), and Cu and also Zn precipitated. At pH=6, As and Cu pre- cipitated almost completely, and Zn roughly 85%. At pH>6, in addition to Fe hydroxysulphates, Fe hydro- xides also precipitated (the Fe/S molar ratio reaching 14 at pH 6.5), and Zn adsorption rose to 95%. Consequently, a rise in soil pH to 6.5 would ensure the precipitation of Cu, As and Zn, thereby preven- ting the spread of these contaminants to the groundwater and surrounding ecosystems.
Key words: Pyrite tailings, liming, heavy metals, adsorption.