31 No. 3
Humic-Metal Binding Constants Database
The physicochemical form in which a trace element occurs (i.e., its speciation) determines its mobility, bioavailability, and toxicity in the environment. In natural waters and soils, trace element reactions with natural organic matter (NOM) have been shown to play decisive roles in trace element chemistry. In particular, the fraction of NOM more refractory to degradation, often known as “fulvic” and “humic” compounds, has proven to be particularly important, and a significant amount of research has been devoted to its characterization as well as to the determination of binding constants with trace elements. However, in spite of this effort, the difficulties encountered when trying to compare complexation constants reported in the literature or to find constant values for less-studied elements are well known. This is because our ability to measure and interpret the complexation equilibria of NOM is severely constrained by its complex characteristics that hinder the application of common experimental and interpretation methods. This has led, for instance, to the development of a wide range of interpretation models for the representation and quantification of its binding properties, making it more difficult to apply such data.
Because no systematic compilation of published data exists, this project is gathering data published over the past 40 years. The long-term aim is the critical analysis and interpretation of all data published for complexation of trace elements with NOM in natural water systems. This will provide a robust framework for further research. The first step of the project is to develop a comprehensive database of published values for humic substances. At present, some information is difficult to access, because it has been published in journals or reports not readily available. For this reason, the project initially will be devoted to the collection of all available data. Any scientist willing to collaborate is encouraged to send to the project team copies of articles and reports containing data on binding of trace elements by humic substances.
For more information and comments, contact Task Group Chair Montserrat Filella <[email protected]>.
last modified 24 April 2009.
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