HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Sposito, G. Articles by Inouye, C. A. Search for Related Content PubMed Articles by Sposito, G. Articles by Inouye, C. A. Agricola Articles by Sposito, G. Articles by Inouye, C. A.

Trace Metal Complexation by Fulvic Acid Extracted from Sewage Sludge: II. Development of Chemical Models¹

ABSTRACT

Two recent chemical models of trace metal complexation by fulvic acid extracted from sewage sludge were incorporated into the computer program GEOCHEM and were compared in illustrative speciation calculations. These calculations were performed for 21 saturation extracts obtained from three acid soils that had been amended with sewage sludge. One of the models studied, the Mixture Model, consisted of a set of nine organic acids whose metal-complexing functional groups were expected to simulate closely the distribution and complexation behavior of the groups in the ligands of the fulvic acid fraction of sewage sludge. The other model, the Fulvate Model, comprised 18 metal-fulvic acid complexes whose stability constants had been either measured in the laboratory or estimated by linear correlation analysis.

The speciation calculations that incorporated the Fulvate Model were used as a basis for evaluation of those involving the Mixture Model. The two calculations disagreed in their estimates of the extent of organic complexation of Cu(II) and Cd(II), but were in general accord on the overall speciation of Cd(II). The reasons for the differences could be understood in terms of competition effects and the values of the stability constants employed in each calculation. The good general correspondence in the case of Cd(II) speciation suggested that a direct comparison with experiment of the two computer estimates of Cd²⁺ concentration would be worthwhile. The two sets of predictions for the concentration of the species Cd²⁺ in the 21 saturation extracts were found to be in good agreement with measured values obtained with a Cd electrode. These results indicated that the Mixture Model could be used in conjunction with computer estimates of Cd(II) speciation in soil solutions, but should not be applied to help speciate metals, such as Cu(II), which are expected to form strong fulvic acid complexes, but evidently do not.

Key Words: chemistry of trace metals in soils • computer models of trace metal speciation

¹ Contribution from the Dep. of Soil and Environmental Sciences, Univ. of Calif., Riverside, CA 92521.

² Professors of Soil Science, Fulbright Research Scholar, and Graduate Laboratory Helper, respectively. Present address of Dr. Yadav: Haryana Agricultural University, Hissar-125004, India.

Received for publication January 17, 1980. Accepted for publication August 3, 1981.

This article has been cited by other articles:

				R. Vulkan, U. Mingelgrin, J. Ben-Asher, and H. Frenkel Copper and Zinc Speciation in the Solution of a Soil-Sludge Mixture J. Environ. Qual., January 1, 2002; 31(1): 193 - 203. [Abstract] [Full Text] [PDF]