CHEMICAL-FRACTIONS OF COPPER AND ZINC IN ORGANIC-RICH PARTICLES FROM AQUEOUS EXTRACTS OF A METAL-CONTAMINATED GRANITE SOIL

Chemical fractions of copper (Cu) and zinc (Zn) in the organic-rich pa rticles collected from filtered aqueous extracts (< 20 mu m) of an aci d soil were determined. A sequential extraction procedure was used to partition the particulate Cu and Zn into four operationally defined ch emical fractions: adsorbed (ADS), iron (Fe) and manganese (Mn) oxides bound (FeMnOX), organic matter bound (OM) and residual (RESD). Total e xtractable concentrations of Cu and Zn in the fine particles were high er than their total concentrations in the original bulk soil. The conc entration of particulate Cu was usually much higher than that of parti culate Zn. Addition of lime stabilized sewage sludge cake and/or inorg anic metal salts markedly increased the concentrations of particulate Cu and Zn in aqueous extracts, especially from limed soil. The proport ional distributions of particulate Cu and Zn were quite similar. The t wo particulate metals were present predominantly in the ADS and FeMnOX fractions, with less (about 20%) in the OM and RESD fractions. Some o f the ADS metal fraction was associated with dissolved organic substan ces. The concentrations of particulate Cu and Zn in the various extrac table fractions were significantly affected by the application of lime , lime stabilized sewage sludge cake, or inorganic metal salts.