Trace Metal Distributions among the Humic Acid, the Fulvic Acid, and Precipitable Fractions Extracted with NaOH from Sewage Sludges

Abstract

AbstractThe distribution of Al, Cd, Cu, Fe, Ni, and Zn among the humic acid, fulvic acid, and precipitable (by adjustment of pH) fractions extracted with 0.5N NaOH from four representative sewage sludges was determined by atomic absorption spectrophotometry. It was found that most of the Al and, with one exception, most of the Fe and Zn were precipitable from the extracted solutions by adjustment of pH in unit intervals between 2.5 and 10.5. Almost all of the Cu was associated with the humic acid fraction. Cd and Ni tended to be associated with the precipitable fraction and with the fulvic acid fraction. Data on the amount of each metal remaining in the extracted solutions as a function of pH suggested that Cd, Ni, and Zn would tend to be the more mobile trace metals in soils affected by application of the sludges investigated.