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The Use of Zonal Centrifugation in Delineating Trace Element Distributions in Sewage Sludges from the Dayton, Ohio, Area¹

ABSTRACT

Density gradient zonal cenfrifugation, using tetrabromoethane-ethanol solutions as density gradients, was used to fractionate two sewage sludges. The distributions of Cd, Cu, Pb, Ni, and Zn in the sludge fractions were determined using atomic absorption spectrophotometry. Trace element concentrations are related to density in a simple pattern. Seventy-five weight percent of the total trace elements in the sludges are contained in low-density (1.60 to Z.10 g/cm³), organic-rich fractions. A small portion of the total trace elements in sludge is also associated with minerals such as sulfides and sulfates in high-density fractions.

Because organic-rich fractions of sludge contain the highest absolute amount of trace elements, it is concluded that most of the trace elements are located in organic compounds in the sludges studied. Furthermore, it is suggested that particular organic compounds, within a limited density range, contain the greatest concentrations of trace elements.

Key Words: cadmium • tetrabromoethane • heavy metals

¹ This project was supported by grants from the Office of Water Resour. Res. and Technol. of the Dep. of the Interior (Grant no. B-065-OHIO), and the Univ. of Dayton Res. Council.

² Dep. of Geological and Geophysical Sciences, Princeton Univ., Princeton, NJ 08540.

³ Geology Dep., Biology Dep., and Physics Dep., respectively, Univ. of Dayton, Dayton, OH 45469.

Received for publication May 12, 1978.