Complexation of Lead in Model Solutions of Humic Acid: Heterogeneity and Effects of Competition with Copper, Nickel, and Zinc

Ismail I. Fasfous; C. L. Chakrabarti; John Murimboh; Tahir Yapici

doi:10.1071/EN06022

RESEARCH ARTICLE

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Complexation of Lead in Model Solutions of Humic Acid: Heterogeneity and Effects of Competition with Copper, Nickel, and Zinc

Ismail I. Fasfous ^A , C. L. Chakrabarti ^A ^C , John Murimboh ^B and Tahir Yapici ^A

+ Author Affiliations

- Author Affiliations

^A Department of Chemistry, Carleton University, Ottawa, Ontario K1S 5B6, Canada.

^B Department of Chemistry, Acadia University, Wolfville, Nova Scotia B4P 2R6, Canada.

^C Corresponding author. Email: chuni_chakrabarti@carleton.ca

Environmental Chemistry 3(4) 276-285 https://doi.org/10.1071/EN06022
Submitted: 18 March 2006 Accepted: 31 July 2006 Published: 5 September 2006

Environmental Context. Metal bioavailability and toxicity are often related to free metal concentration rather than total metal concentration. Humic substances are chemically and physically heterogeneous complexants for metals in natural waters, and play an important role in trace metal transport, fate, and bioavailability. Metal bioavailability, which depends on chemical speciation of metals, is greatly influenced by the presence of other trace metals and major cations in natural waters. In this work, the effects of heterogeneity of humic substances, and of competition of trace metals on lead speciation in model solutions have been studied to gain a better understanding of these effects on complexation of trace metal lead and its bioavailability.

Abstract. Physicochemical heterogeneity of a well characterized humic acid (HA) in its complexation with a trace metal lead in model solutions was investigated using pseudo-polarography at a stationary mercury drop electrode, and the differential equilibrium function (DEF) of Pb(ii)–HA complexes was determined. The complexation of Pb(ii) by HA was determined by taking into account the dependence of the strength of the binding on the metal (Pb) loading. Also investigated were the effects of competition of the trace metals copper, nickel, and zinc on the DEF of Pb(ii)–HA complexes in model solutions. The results showed that these trace metals competed with trace metal lead for binding by HA even when present at the same concentrations as that of lead.

Keywords. : competition — humic substances — pseudo-polarography — speciation — trace elements

Acknowledgements

Thanks to Dr L. Evans, University of Guelph, Ontario, Canada, for characterization and supply of HA. A research grant from the Natural Sciences and Engineering Research Council of Canada (NSERC) is gratefully acknowledged. I.I.F. received a graduate scholarship from the Hashemite University, Jordan.

References

Complexation of Lead in Model Solutions of Humic Acid: Heterogeneity and Effects of Competition with Copper, Nickel, and Zinc

Acknowledgements

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