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Implications of natural organic matter binding heterogeneity on understanding lead(II) complexation in aquatic systems.

Authors
  • Town, Raewyn M
  • Filella, Montserrat
Type
Published Article
Journal
The Science of The Total Environment
Publisher
Elsevier
Publication Date
Dec 02, 2002
Volume
300
Issue
1-3
Pages
143–154
Identifiers
PMID: 12685478
Source
Medline
License
Unknown

Abstract

A critical analysis of data published for complexation (conditional stability constants and complexation capacities) of lead(II) by natural organic matter (NOM) is presented. The same patterns are observed for the different types of NOM, i.e. isolated humic-type substances, isolated algae- and bacteria derived ligands and cell walls, and filtered whole water systems: apparent stronger binding sites are utilised at lower metal ion loadings, progressively weaker sites contribute to metal complexation at higher loadings. Continuous binding functions should thus be used to adequately describe lead-NOM complexation in natural waters. Two important observations arising from our analysis are that: (i) the binding curves (binding affinity as a function of metal ion loading) for whole natural water samples lie between those for compounds representative of the two main NOM types, viz., isolated humic compounds and biota, and (ii) binding constants commonly used in speciation codes probably underestimate the actual extent of lead(II) binding by NOM at natural concentration levels.

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