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Unraveling the organo-colloidal control on trace element distribution in shallow groundwaters: an experimental contribution

Abstract : Dissolved Organic Matter (DOM) is ubiquitous in aquatic environments and plays a key role in the geochemistry of major and trace elements - acting as a major carrier and transport phase - through complexation, adsorption, dissolution ... reactions. It both does interact with mineral phases modifying the exchange rates with solutions and constrain part of pollutant mobilities such as that of trace metals or hydrophobic organic compounds. Not only does association with DOM influences the mobility of metals through the soil/water system, it also regulates their chemical reactivity, bioavailability and toxicity. In order to study DOM-metal interactions and the role of the colloidal pool in such groundwaters, DOM-rich soil/water interactions were performed (at different pH) through columns. This was coupled with ultrafiltration in a range of molecular weight cut-off - 30, 10, 5 and 2kDalton - to distinguish between organically colloidal complexed metals and 'free' metals. The Dissolved Organic Carbon (DOC) concentrations, the associated aromaticity were determined in the different fractions as well as the trace metal concentrations by ICP-MS. Ascending hierarchical classification was also performed to evidence DOC-trace element relationship. DOC distribution through time follows the same trend whichever was the pH. Three groups can be distinguished based on aromaticity and DOC data whichever can be the pH conditions. While K, Rb, Mg or Ca appear to behave as 'free' ions, Th, U, REE, Fe or Al concentrations are correlated to DOC concentrations, suggesting that the organic colloidal pool dominates the carrying of these latter elements. Further studies dedicated to space- and time-linked variations of the joined colloidal pool and trace element distribution, will be then undertaken in waters recovered from different DOM-rich environments.
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Submitted on : Wednesday, July 25, 2007 - 1:04:33 PM
Last modification on : Tuesday, March 22, 2022 - 11:49:15 AM


  • HAL Id : insu-00165228, version 1



Aline N. Dia, Mathieu Pédrot, Mélanie Davranche, Olivier Pourret, Patrice Petitjean, et al.. Unraveling the organo-colloidal control on trace element distribution in shallow groundwaters: an experimental contribution. American Geophysical Union (AGU) Fall Meeting, Dec 2006, San Francisco,, United States. pp.B32B-08. ⟨insu-00165228⟩



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