title: Influence of heteroaggregation processes between intrinsic colloids and carrier colloids on cerium(III) mobility through fractured carbonate rocks.
abstract: Colloid facilitated transport of radionuclides has been implicated as a major transport vector for leaked nuclear waste in the subsurface. Sorption of radionuclides onto mobile carrier colloids such as bentonite and humic acid often accelerates their transport through saturated rock fractures. Here, we employ column studies to investigate the impact of intrinsic, bentonite and humic acid colloids on the transport and recovery of Ce(III) through a fractured chalk core. Ce(III) recovery where either bentonite or humic colloids were added was 7.7-26.9% Ce for all experiments. Greater Ce(III) recovery was observed when both types of carrier colloids were present (25.4-37.4%). When only bentonite colloids were present, Ce(III) appeared to be fractionated between chemical sorption to the bentonite colloid surfaces and heteroaggregation of bentonite colloids with intrinsic carbonate colloids, precipitated naturally in solution. However, scanning electron microscope (SEM) images and colloid stability experiments reveal that in suspensions of humic acid colloids, colloid-facilitated Ce(III) migration results only from the latter attachment mechanism rather than from chemical sorption. This observed heteroaggregation of different colloid types may be an important factor to consider when predicting potential mobility of leaked radionuclides from geological repositories for spent fuel located in carbonate rocks.
authors.affiliation: The Zuckerburg Institute for Water Research, The Jacob Blaustein Institutes for Desert Studies, Ben Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben Gurion, 8499000, Israel.
authors.forename: Emily
authors.initials: E
authors.lastname: Tran
authors.affiliation: Nuclear Research Center of the Negev, Negev, PO Box 9001, Beer Sheva, 84190, Israel.
authors.forename: Ofra
authors.initials: O
authors.lastname: Klein Ben-David
authors.affiliation: Geological Survey of Israel, 30 Malkhe Israel St., Jerusalem, 95501, Israel.
authors.forename: Nadya
authors.initials: N
authors.lastname: Teutch
authors.affiliation: The Zuckerburg Institute for Water Research, The Jacob Blaustein Institutes for Desert Studies, Ben Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben Gurion, 8499000, Israel. Electronic address: weisbrod@bgu.ac.il.
authors.forename: Noam
authors.initials: N
authors.lastname: Weisbrod
mesh_terms: D001546:Bentonite; D002563:Cerium; D003102:Colloids; D011850:Radioactive Waste; D014875:Water Pollutants, Radioactive
chemical_list: D003102:Colloids; D011850:Radioactive Waste; D014875:Water Pollutants, Radioactive; D001546:Bentonite; D002563:Cerium
keywords: Carbonates; Carrier colloids; Colloid-facilitated transport; Fracture networks; Geological repositories; Radionuclides