caa a22 4500 378927019 CHVBK 20180305123620.0 cr unu---uuuuu 161128e20041101xx s 000 0 eng 10.1524/ract.92.9.731.54975 doi (NATIONALLICENCE)gruyter-10.1524/ract.92.9.731.54975 U, Th, Eu and colloid mobility in a granite fracture under near-natural flow conditions [Elektronische Daten] [Thorsten Schäfer, Horst Geckeis, Muriel Bouby, Thomas Fanghänel] Laboratory core migration experiments were performed in a granite fracture from the Grimsel Test Site (GTS, central Swiss Alps). The flow velocity was varied (46m yr-1, 94m yr-1, 187m yr-1) and solutions with 10-6mol L-1 U(VI), 10-8mol L-1 Th(IV) and 10-8mol L-1 Eu(III) without (cocktail I) and with addition of 2mgL-1 bentonite colloids (cocktail II) have been injected. Results are compared with those obtained in a field study at the GTS. Flow field-flow fractionation and ultrafiltration measurements show that U(VI) is not colloid borne, different from Th(IV) and Eu(III) which are associated with colloids in both spiked natural groundwaters with and without bentonite colloid addition. The partly unretarded U(VI) migration observed at short contact times (1-2h) diminished under near-natural groundwater velocities (∼46m yr-1) and only a weak retardation (Rf=19.5) could be observed. Furthermore, the U(VI) mass recovery decreased with increasing contact time and was as expected unaffected by bentonite colloid addition. A groundwater colloid mediated Th(IV)/Eu(III) migration without bentonite colloid addition could be confirmed in the core experiments but only at fast groundwater flow rates. Experiments at a water flow rate of 94m yr-1 with cocktail II demonstrated a partially bentonite colloid facilitated transport of Th(IV) and Eu(III) with 27% and 37% mass recovery, respectively. At long tracer residence times in the flow field, no breakthrough of colloidal Th(IV)/Eu(III) could be observed in both runs, indicating the strong dependence of reaction kinetics on their mobility. Reference colloid experiments using fluorescence dye labeled carboxylated polystyrene microspheres (25nm, 50nm and 100nm) revealed in general a higher recovery of smaller colloid size classes increasing with groundwater velocity. Additionally, an earlier peak arrival time of colloids and colloid-associated Th(IV) and Eu(III) was observed with respect to the conservative tracer 3H in all experiments due to pore-size or charge exclusion effects. In general, the colloid recoveries found in the laboratory core experiments are lower than those obtained in the field studies. The decrease of colloid mobility with increasing residence time suggests the occurrence of colloid attachment to the rock surfaces even under the colloid stabilizing groundwater conditions. © 2004 Oldenbourg Wissenschaftsverlag GmbH Laboratory techniques, experiments nationallicence Analytical chemistry nationallicence Inorganic chemistry nationallicence Schäfer Thorsten aut Geckeis Horst aut Bouby Muriel aut Fanghänel Thomas aut Radiochimica Acta/International journal for chemical aspects of nuclear science and technology Oldenbourg Wissenschaftsverlag GmbH 92/9-11/2004(2004-11-01), 731-737 0033-8230 92:9-11/2004<731 2004 92 ract https://doi.org/10.1524/ract.92.9.731.54975 text/html Onlinezugriff via DOI 1 research article jats NATIONALLICENCE 856 40 https://doi.org/10.1524/ract.92.9.731.54975 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Schäfer Thorsten aut NATIONALLICENCE 700 1- Geckeis Horst aut NATIONALLICENCE 700 1- Bouby Muriel aut NATIONALLICENCE 700 1- Fanghänel Thomas aut NATIONALLICENCE 773 0- Radiochimica Acta/International journal for chemical aspects of nuclear science and technology Oldenbourg Wissenschaftsverlag GmbH 92/9-11/2004(2004-11-01), 731-737 0033-8230 92:9-11/2004<731 2004 92 ract CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-gruyter