NICKEL AND ZINC SORPTION IN SLUDGE-AMENDED SOILS

Publisher Website
Google Scholar
Abstract
The sorption was examined of Ni and Zn in 3 soils that were unamended, freshly amended or preconditioned with gamma-irradiated sewage sludge. Metal sorption was also studied in the same soils treated with a 0.01 N CaCl2-extract of the sludge. Adsorption of both metals was greatest in the unamended soils, less in soils preconditioned with sludge, and least in the freshly amended soils and sludge-extract-treated soils. Treatment effects were explained on the basis of reduced metal activity as a result of increased soil solution ionic strength, reduced metal activity as a result of inorganic-metal complexes, increased competition for sorbing sites, and reduced metal activity as a result of organic-metal complexation. None of the hypotheses completely explained the observed treatment effects, although the data suggested that organic-metal complexes play a significant role in reduced free metal activity, particularly for Ni. Despite the reduction in metal retention effected by various sludge treatments, little Ni or Zn leaching is expected in these sludge-amended soils, for sorption of both metals is very high.