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(W/FF243) Retention of copper and zinc by a soil amended with organic residues. Madrid, Luis1, Maqueda, Celia1, Diaz-Barrientos, Encarnacịn1, Morillo, Esmeralda1, 1 ABSTRACT- The disposal of many organic wastes on agricultural lands is a widely used practice, as they frequently contain substances which improve soil fertility, although other components can have undesired consequences for crops. The purpose of this study was to evaluate the effect of the addition of two residues used as amendment on the retention of copper and zinc on a sandy soil, affecting the availability of these metals, both as micronutrient and as contaminant. The soil was sampled from the surface horizon of a soil classified as Hydromorfic Regosol. The soil had been amended with urban waste compost (USR)or a compost obtained from olive mill wastewater and other plant residues (OI). The results of the present study showed that the addition of the residues increases the retention of both heavy metals, being greater for copper than for zinc. The amount of Cu and Zn adsorbed on the soils varied according to the amendments in the order USR> OI > untreated. The addition of the waste amendments increases the pH and organic matter content of the soil. The results for Cu strongly support tha pH is the main driving "force" for retention of the metal, while Zn data, at least in the concentration range tested here, are no conclusive enough. The application of composted wastes to soils must be studied carefully because in same cases can immobilise metal, but sometimes the solubles components can increase the DOM and contribute to mobilise metals though formation of soluble complexes. Key words: Waste amendments, trace metals, metal immobilisation |
