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Characterization of copper(II) binding by molecular weight fractions of a soil fulvic acid
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The University of Arizona.Rights
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.Abstract
Cu(II) binding characteristics of bulk, <30,000, <10,000, <5,000, <1,000, and <500 dalton molecular weight (MW) fractions of soil fulvic acid were determined from Cu(II)/dissolved organic matter interactions. Manual complexometric and potentiometric titrations measured Cu(II) MW fraction binding capacities and acidities. Ionic strength, temperature, and pH were varied. Cu averaged 7.3 x 10⁻⁴ micromoles per liter and carbon ranged between 0.5 and 3.5 ppm. Total Cu(II) binding capacity differed among all but bulk and <30,000 fractions due to site concentration differences; binding was insignificant for the <500 fraction. A three-site discrete ligand model determined conditional stability constants 10⁷˙⁰ 10¹¹˙⁰ and 10¹³˙⁸ and site concentrations 1.8 x 10⁻⁶ 8.5 x 10⁻⁶ and 7.6 x 10⁻⁵ M L⁻¹ for the bulk and 30,000 fractions (pH 6.2, 0.01 M, 22°C). Similar stability constants were determined for lower MW fractions. Cu(II) complexation capacity was pH-dependent; Ionic strength effects were significant at pH 7.0, not at 6.2. Temperature effects were insignificant.Type
textThesis-Reproduction (electronic)