Extractability and leachability of heavy metals in Technosols prepared from mixtures of unconsolidated wastes |
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Authors: | Camps Arbestain M Madinabeitia Z Anza Hortalà M Macías-García F Virgel S Macías F |
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Institution: | NEIKER, Agroecosistemas y Recursos Naturales, Berreaga 1, 48160 Derio, Bizkaia, Spain. mcamps@neiker.net |
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Abstract: | Mixtures of wastes were prepared to improve on the characteristics of the individual ingredients as Technosols, with special attention given to heavy metal extractability. An anaerobic digested sewage sludge and a CaO-treated aerobic sludge were used. A mixture of the two sludges (50:50 DW basis) was also prepared to provide a third type of sludge. The residues were mixed with other types of waste, such as fly ash, Linz-Donowitz slag, foundry sand, shot blasting machine scrap, fettling and barley straw. Extractability of Cu, Cr, Ni, and Zn by 0.01 M CaCl(2) extraction (Me(CACI(2)) was carried out, and leachability of these elements was estimated by acidification of an aqueous suspension of the mixtures with 0.5 N acetic acid (Me(acetic)). The total concentrations of the metals were also determined (Me(T)). The Me(CACI(2)/Me(T) ratios for Cu and Ni (means: 4.0% and 3.1%) were higher than those for Cr and Zn (means: 0.07% each). The mean Me(acetic)/Me(T) ratios followed the order Ni, Zn, Cu, and Cr (19.5%, 4.1%, 3.7%, and 0.09%, respectively). The results highlight the existence of complex interactions among organic matter solubility, pH and heavy metal extractability. |
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