J. Phys. IV France
Volume 104, March 2003
Page(s) 409 - 412

J. Phys. IV France
104 (2003) 409
DOI: 10.1051/jp4:20030110

Functional group analysis of natural organic colloids and clay association kinetics using C(1s) spectromicroscopy

T. Schäfer1, N. Hertkorn2, R. Artinger1, F. Claret1 and A. Bauer1

1  Forschungszentrum Karlsruhe, Institut für Nukleare Entsorgung, INE, P.O. Box 3640, 76021 Karlsruhe, Germany
2  GSF-Forschungszenfrum für Umwelt und Gesundheit, Institut für Ökologische Chemie, P.O. Box 1129, 85758 Neuherberg, Germany

The quantification of natural humic colloid functional group content and chemical association of humic substances with clay minerals exerts a crucial role in the colloid-borne mobility of actinides due to the functional group dependent strong interaction with multivalent metal ions. Functional group quantification in isolated fulvic acids of the Gorleben groundwater (Lower Saxony, NW Germany) by comparison of high resolution C(1s) NEXAFS spectra deconvolution with 13C-NMR measurements showed good correlation ( r2> 0.9) and gives a potential quantification tool in complex natural groundwater Systems. Time resolved soft X-ray spectromicroscopy on dissolved organic carbon stabilized SWy-2 smectite colloids revealed an enrichment of carboxyl groups on broken edges (silanol/aluminol groups) at short contact times (1h). With longer contact times (7d, 6 months) the clay associated organic carbon increases and significantly higher aromatic content associated with basal surfaces were detected. The enhanced sorption of aromatic compounds can be related to an increase in mineral surface hydrophobicity and/or preferential sorption on charged siloxane surfaces.

© EDP Sciences 2003