http://dspace.nitrkl.ac.in:8080/dspace/bitstream/2080/134/1/tksen5.pdf

Review on subsurface colloids and colloid-associated contaminant transport in saturated porous media.

Many potentially toxic trace metals and radionuclides are strongly adsorbed onto surfaces of mineral and organic compounds in soils and sediments, limiting their mobility in the environment. However, recent studies have shown that trace metals in soils, groundwater, rivers, and lakes can be carried by mobile colloidal particles. Understanding the release, transport, aggregation, and deposition of natural colloidal particles is therefore of utmost importance for developing quantitative models of contaminant transport and the biogeochemical cycling of trace metals.

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Metal Retention and Transport on Colloidal Particles in the Environment

Sorption of Eu(III)/Cm(III) on Ca-montmorillonite and Na-illite. Part 1: Batch sorption and time-resolved laser fluorescence spectroscopy experiments

The colloid and radionuclide retardation experiment at the Grimsel Test Site: influence of bentonite colloids on radionuclide migration in a fractured rock

Kinetics and irreversibility of cesium and uranium sorption onto bentonite colloids in a deep granitic environment

The influence of smectite colloids on the migration behaviour of U(VI), Th(IV), Pu([V), Am(III), Np(V), Sr(II) and Cs(I) is investigated within the Colloid and Radionuclide Retardation experiment (CRR). Two in situ experiments in a well-characterized granitic fracture zone are carried out in presence and absence of bentonite colloids. Radionuclide retardation observed in the field studies increases in the sequence Np(V) ∼ U(VI) < Sr(II) < Cs(I), where a small fraction of colloid borne breakthrough is only stated for Cs(I) in presence of bentonite colloids. Arn(III) and Th/Pu(IV) mainly migrate as colloids without retardation in the presence and absence of smectitic colloids. The radionuclide migration behaviour is discussed on the basis of results obtained in laboratory batch sorption experiments and spectroscopic studies. Consistent with the field observation, laboratory derived K d values increase in the order Np(V) ∼ U(VI) < Sr(II) < Cs(I). Significant kinetic hindrance for the sorption to fault gauge minerals is observed for Sr(II) and Cs(I), but notably for Am(III) and Pu(IV). The slow sorption reaction of tri-and tetravalent actinide ions is explained by their kinetically hindered dissociation from colloidal species. In order to explain the colloidal behaviour of tri- and tetravalent actinides even in absence of bentonite colloids, ultracentrifugation and spectroscopic experiments are performed. It is found that up to 60% of Pu(IV) and Am(III) species can be centrifuged off. Adding Cm(III) (5 x 10 - 8 molL - 1 ) into both injection solutions instead of Am(III) allows for a spectroscopic study by using the time resolved laser fluorescence spectroscopy (TRLFS). Peak position and fluorescence lifetimes (λ = 604 nm, T = 110-114 μs) together with the fact that Cm(III) can be widely separated by ultracentrifugation, suggest the existence of inner-sphere surface complexes on groundwater and bentonite colloids. Carbon K-edge XANES analysis of the bentonite colloids reveal the presence of natural organic constituents. They are mainly of aliphatic nature containing high fractions of carboxylate groups. A contribution of these organic species towards the bentonite colloid stability and sorption of actinides is assumed to be likely.

Results of the colloid and radionuclide retention experiment (crr) at the grimsel test site (gts), switzerland - impact of reaction kinetics and speciation on radionuclide migration

A mobile laser-induced breakdown detection system and its application for the in situ-monitoring of colloid migration

Full excavation of a water-conducting shear zone used for radionuclide migration experiments is part of a comprehensive study to physically determine the sites of in-situ radionuclide retardation. Prior to the excavation, multi-tracer solutions containing strongly sorbing y - and αemitting nuclides were injected into the shear zone and the water extracted was analyzed on-line using in situ , high-resolution y-spectrometry. In addition, water samples were collected to compare quantitatively the on-line data with subsequent laboratory measurements α- and γ- spectrometry) and also to analyze samples with activities below the detection limits of the in-situ analysis. The breakthrough curves indicate that Se had passed through the fracture with a velocity comparable to a conservatively behaving dye (uranine), but very strong retardation of Co. Eu and Sn was observed. The recoveries of these nuclides were found to be in the order of only a few percent when the dipole flow-field was interrupted about one month after radionuclide injection and the fracture was sealed off for excavation. Significant retardation was also obtained for the oxemitters U, Np and Pa. Almost identical breakthrough curves for these actinides were measured, suggesting a similar spatial distribution in the fracture at any given time.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400249233

The Excavation Project in the Grimsel Test Site: In Situ High-Resolution Gamma and Alpha Spectrometry of 60Co, 75Se, 113Sn, 152Eu, 235U, and 237Np/233Pa

Th. Fierz

Papers

The colloid and radionuclide retardation experiment at the Grimsel Test Site: influence of bentonite colloids on radionuclide migration in a fractured rock

Results of the colloid and radionuclide retention experiment (crr) at the grimsel test site (gts), switzerland - impact of reaction kinetics and speciation on radionuclide migration

A mobile laser-induced breakdown detection system and its application for the in situ-monitoring of colloid migration

The Excavation Project in the Grimsel Test Site: In Situ High-Resolution Gamma and Alpha Spectrometry of 60Co, 75Se, 113Sn, 152Eu, 235U, and 237Np/233Pa