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Trace concentration – Huge impact: Nitrate in the calcite/Eu(III) system

Hofmann, S.; Voïtchovsky, K.; Schmidt, M.; Stumpf, T.


S. Hofmann

M. Schmidt

T. Stumpf


The interactions of trivalent lanthanides and actinides with secondary mineral phases such as calcite is of high importance for the safety assessment of deep geological repositories for high level nuclear waste (HLW). Due to similar ionic radii, calcium-bearing mineral phases are suitable host minerals for Ln(III) and An(III) ions. Especially calcite has been proven to retain these metal ions effectively by both surface complexation and bulk incorporation. Since anionic ligands (e.g., nitrate) are omnipresent in the geological environment and due to their coordinating properties, their influence on retentive processes should not be underestimated. Nitrate is a common contaminant in most HLW forms as a result of using nitric acid in fuel reprocessing. It is also formed by microbial activity under aerobic conditions. In this study, atomic force microscopy investigations revealed a major influence of nitrate upon the surface of calcite crystals. NaNO3 causes serious modifications even in trace amounts (<10−7 M) and forms a soft surface layer of low crystallinity on top of the calcite crystal. Time-resolved laser fluorescence spectroscopy of Eu(III) showed that, within this layer, Eu(III) ions are incorporated, while losing most of their hydration shell. The results show that solid solution modelling for actinides in calcite must take into account the presence of nitrate in pore and ground waters.


Hofmann, S., Voïtchovsky, K., Schmidt, M., & Stumpf, T. (2014). Trace concentration – Huge impact: Nitrate in the calcite/Eu(III) system. Geochimica et Cosmochimica Acta, 125, 528-538.

Journal Article Type Article
Publication Date Jan 15, 2014
Deposit Date Aug 15, 2014
Journal Geochimica et Cosmochimica Acta
Print ISSN 0016-7037
Publisher Meteoritical Society
Peer Reviewed Peer Reviewed
Volume 125
Pages 528-538