Metal-Associated Forms and Speciation in Biosolid-Amended Oxisols

• Published in: Communications in soil science and plant analysis 2007-04, Vol.38 (7-8), p.851-859
• Main Authors: Silveira, M.L, Chang, A.C, Alleoni, L.R.F, O'Connor, G.A, Berton, R
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Biosolids; cadmium; chemical speciation; copper; fractionation; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; heavy metals; ionic strength; Other nutrients. Amendments. Solid and liquid wastes. Sludges and slurries; Oxisols; sequential fractionation; soil amendments; Soil and water pollution; soil pH; soil pollution; Soil science; Soil-plant relationships. Soil fertility. Fertilization. Amendments; solubility; solutions; spatial distribution; zinc
• ISSN: 0010-3624; 1532-2416
• DOI: 10.1080/00103620701263700

The objective of this study was to determine the effects of pH and ionic strength on the distribution and speciation of zinc (Zn), copper (Cu), and cadmium (Cd) in surface soil samples from two Brazilian Oxisols amended with biosolids. Soils and biosolids were equilibrated in an experimental dual-chamber diffusion apparatus that permits the soils and biosolids to react through a solution phase via diffusion across a membrane. After equilibrium was reached, soil and biosolids samples were sequentially fractionated to identify various solid forms of Zn, Cu, and Cd. Metal concentrations in the solution phase were determined and mass balance calculated. Equilibrating pH had no major effect on Cu solubility from biosolids and, at pH range from 4 to 7, most Cu remained in the biosolids. Soluble Zn and Cd concentration increased with decreasing pH because of the increased solubility of the biosolids. Copper and Zn were primarily associated with the residual fraction and Fe oxides in one soil, but were primarily associated with chemically unstable fractions, or adsorbed to the surface of oxides, in the other soil. In both soils, Cd was primarily associated with readily bioavailable fractions. The effect of pH on the metal distribution was more evident than the ionic strength effect. Free ions were the predominant metal species in solution, especially at lower pH values.