title: Effects of ionic strength and fulvic acid on adsorption of Tb(III) and Eu(III) onto clay.
abstract: High salinity and natural organic matter are both known to facilitate migration of toxic or radioactive metals in geochemical systems, but little is known on their combined effect. We investigated complexation of Tb(III) and Eu(III) (as analogues for trivalent actinides) with fulvic acid and their adsorption onto a natural clay in the presence of NaCl, MgCl2 and CaCl2 up to very high ionic strengths. (160)Tb, (152)Eu and (14)C-labelled fulvic acid were employed as radiotracers, allowing investigations at very low concentrations according to probable conditions in far-field scenarios of nuclear waste repositories. A combined Kd approach (Linear Additive Model) was tested for suitability in predicting solid-liquid distribution of metals in the presence of organic matter based on the interactions in the constituent subsystems. In this analysis, it could be shown that high ionic strength does not further enhance the mobilizing potential of humic matter. A quantitative reproduction of the influence of fulvic acid failed for most systems under study. Assumptions and limitations of the model are discussed.
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Permoserstraße 15, 04318 Leipzig, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Poetsch
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Permoserstraße 15, 04318 Leipzig, Germany. Electronic address: h.lippold@hzdr.de.
authors.forename: Holger
authors.initials: H
authors.lastname: Lippold
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D001578:Benzopyrans / Q000737:chemistry*; D002122:Calcium Chloride / Q000737:chemistry; D000077215:Clay; D005063:Europium / Q000737:chemistry*; D006812:Humic Substances; D015636:Magnesium Chloride / Q000737:chemistry; D008962:Models, Theoretical; D009994:Osmolar Concentration; D011850:Radioactive Waste; D012965:Sodium Chloride / Q000737:chemistry; D013725:Terbium / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D001578:Benzopyrans; D006812:Humic Substances; D011850:Radioactive Waste; D015636:Magnesium Chloride; D013725:Terbium; D005063:Europium; D012965:Sodium Chloride; D002122:Calcium Chloride; D000077215:Clay; C005023:fulvic acid
keywords: Adsorption; Fulvic acid; Ionic strength; Linear Additive Model; Metal binding