title: Colloidal transport of uranium in soil: Size fractionation and characterization by field-flow fractionation-multi-detection.
abstract: The aim of this study was to characterize colloids associated with uranium by using an on-line fractionation/multi-detection technique based on asymmetrical flow field-flow fractionation (As-Fl-FFF) hyphenated with UV detector, multi angle laser light scattering (MALLS) and inductively coupling plasma-mass spectrometry (ICP-MS). Moreover, thanks to the As-Fl-FFF, the different colloidal fractions were collected and characterized by a total organic carbon analyzer (TOC). Thus it is possible to determine the nature (organic or inorganic colloids), molar mass, size (gyration and hydrodynamic radii) and quantitative uranium distribution over the whole colloidal phase. In the case of the site studied, two populations are highlighted. The first population corresponds to humic-like substances with a molar mass of (1500+/-300)gmol(-1) and a hydrodynamic diameter of (2.0+/-0.2)nm. The second one has been identified as a mix of carbonated nanoparticles or clays with organic particles (aggregates and/or coating of the inorganic particles) with a size range hydrodynamic diameter between 30 and 450nm. Each population is implied in the colloidal transport of uranium: maximum 1% of the uranium content in soil leachate is transported by the colloids in the site studied, according to the depth in the soil. Indeed, humic substances are the main responsible of this transport in sub-surface conditions whereas nanoparticles drive the phenomenon in depth conditions.
authors.affiliation: Université de Pau et des Pays de l'Adour-CNRS, LCABIE, UMR 5254, IPREM, 2 avenue P. Angot, 64000 Pau, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Claveranne-Lamolère
authors.forename: Gaëtane
authors.initials: G
authors.lastname: Lespes
authors.forename: Stéphane
authors.initials: S
authors.lastname: Dubascoux
authors.forename: Jean
authors.initials: J
authors.lastname: Aupiais
authors.forename: Fabien
authors.initials: F
authors.lastname: Pointurier
authors.forename: Martine
authors.initials: M
authors.lastname: Potin-Gautier
mesh_terms: D003102:Colloids / Q000737:chemistry; D031521:Fractionation, Field Flow / Q000295:instrumentation / Q000379:methods*; D010316:Particle Size; D012990:Soil Pollutants, Radioactive / Q000737:chemistry*; D014501:Uranium / Q000737:chemistry*
chemical_list: D003102:Colloids; D012990:Soil Pollutants, Radioactive; D014501:Uranium