The role of natural organic matter in the migration behaviour of americium in the Boom Clay – Part I: Migration experiments

Maes, N.; Wang, Lian; Hicks, Tim; Bennett, D.; Warwick, Peter; Hall, Tony; Walker, G.; Dierckx, A.

doi:10.1016/j.pce.2006.04.006

Cited by 30 publications

(7 citation statements)

References 6 publications

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“…In previous studies [4][5][6][7], experimentally determined solubility values of different radionuclides under Boom Clay geochemical conditions have been coupled to the thermodynamic solubility (solubility product of the stable solid phase, hydrolysis reactions, complexation with inorganic ligands) through a "solubility increasing factor" or "colloid formation factor". This is a conditional constant related to interaction mechanisms between the radionuclide in question and ill-defined phases such as dissolved Boom Clay organic matter.…”

Section: Introductionmentioning

confidence: 99%

The influence of natural organic matter on the speciation and solubility of Eu in Boom Clay porewater

Liu

Bruggeman

Maes³

2008

Radiochimica Acta

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Eu solubility / Organic matter / Boom Clay water / Geochemical modeling Summary. The influence of natural organic matter (NOM) on the speciation and solubility of europium (Eu) was studied under geochemical conditions representative for the Boom Clay. Different organic matter types were used, and analysis was performed both after 0.45 µm microfiltration and after 30 000 MWCO ultrafiltration to distinguish between larger colloids (assumed to be immobile under in situ conditions) and small dissolved species.Equilibrium was approached from undersaturation starting from synthesised Eu(OH) 3 (s), which, during the experiment, transformed into EuOHCO 3 (s), in agreement with thermodynamic considerations. In the absence of NOM, the Eu solution concentrations after 0.45 µm filtration exceeded the thermodynamic solubility of EuOHCO 3 (s) by several orders of magnitude, indicating the presence of inorganic Eu colloids. In the presence of NOM, the Eu solubility increased with increasing NOM concentration as was expected, but, surprisingly, was dependent on the operational size cut-off: at an identical NOM concentration in the filtrate, the Eu solution concentration after 0.45 µm filtration was consistently higher compared to the Eu concentration after 30 000 MWCO filtration. This latter observation necessitates detailed knowledge concerning the pore size cut-off of Boom Clay under in situ conditions in order to use the correct Eu-NOM complexation constant and/or maximum solubility in transport calculations. At higher NOM concentrations (TOC > 30 mg/L) the Eu solubility after 0.45 µm filtration was seemingly independent of the NOM concentration.In contrast, after 30 000 MWCO ultrafiltration, the Eu solution increased linearly with increasing DOC, from the expected thermodynamic solubility (∼ 5 × 10 −7 mol L −1 ) at 0 mg L −1 DOC to ∼ 3 × 10 −5 mol L −1 at 80 mg L −1 DOC. All of the data sets were modelled using the Nagra/PSI database [1] for solubility, hydrolysis and inorganic aqueous complexation reactions, and fitted organic complexation reactions between Eu 3+ and NOM functional groups. Both a free ligand approach (with electrostatic correction) and the humic ion-binding model VI [2], which was for the first time successfully introduced into Phreeqc geochemical code, were tested and provided equally good fits to the data.

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Section: Introductionmentioning

confidence: 99%

The influence of natural organic matter on the speciation and solubility of Eu in Boom Clay porewater

Liu

Bruggeman

Maes³

2008

Radiochimica Acta

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“…Also, a full recovery of the injected quantity was never reached, even for a NOM size fraction < 1 kDa (maximum recovery of ∼ 80%), while for a NOM size fraction > 100 kDa, the recovery was ∼ 20%. Maes et al [4], demonstrated that the recovery of 14 C-labelled NOM molecules in diffusion experiments decreased with increasing travel time which is a clear indication for colloids filtration.…”

Section: Introductionmentioning

confidence: 96%

Modelling of a large-scalein-situmigration experiment with¹⁴C-labelled natural organic matter in Boom Clay

Martens

Maes²,

Weetjens

et al. 2010

Ract

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For the assessment of the long-term safety of a geological disposal of high-and intermediate-level radioactive waste and/or spent fuel in the Boom Clay, a better understanding of the migration behaviour of Natural Organic Matter (NOM) is needed because it can act as a carrier molecule for radionuclides. Therefore, an in-situ migration experiment with 14 C-labelled NOM was performed to study the NOM migration behaviour on a large scale (m), on the long-term (> 10 a) and in directions parallel and perpendicular to the bedding plane (transport anisotropy). The numerical modelling tool HYDRUS2D/3D was used to interpret the results. The model was built stepwise, testing the influence of advection, (non-)linear equilibrium sorption, colloid attachment/detachment and anisotropy. The up scaling of previously determined parameters from small scale lab tests was also tested. A classic diffusion-advection-retardation description, using parameter values in the range of those obtained in the lab tests, provided already reasonable results. Inclusion of a colloid filtration term in the model significantly improved the simulation. Finally, the model was successfully tested against a second dataset and the anisotropy of the Boom clay was brought into account.

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“…Batlle-Aguilar et al (2011)). Dissolved organic matter (DOM) plays also an important role in many soil processes including contaminant transport (e.g., Maes et al (2006), Paradelo et al (2012)). For example, Leterme and Jacques (2015) showed that DOM concentrations are among the most sensitive factors in simulating Hg fate in soil systems.…”

Section: Introductionmentioning

confidence: 99%

The HPx software for multicomponent reactive transport during variably-saturated flow: Recent developments and applications

Jacques

Šimůnek

Mallants

et al. 2018

Journal of Hydrology and Hydromechanics

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HPx is a multicomponent reactive transport model which uses HYDRUS as the flow and transport solver and PHREEQC-3 as the biogeochemical solver. Some recent adaptations have significantly increased the flexibility of the software for different environmental and engineering applications. This paper gives an overview of the most significant changes of HPx, such as coupling transport properties to geochemical state variables, gas diffusion, and transport in two and three dimensions. OpenMP allows for parallel computing using shared memory. Enhancements for scripting may eventually simplify input definitions and create possibilities for defining templates for generic (sub)problems. We included a discussion of root solute uptake and colloid-affected solute transport to show that most or all of the comprehensive features of HYDRUS can be extended with geochemical information. Finally, an example is used to demonstrate how HPx, and similar reactive transport models, can be helpful in implementing different factors relevant for soil organic matter dynamics in soils. HPx offers a unique framework to couple spatial-temporal variations in water contents, temperatures, and water fluxes, with dissolved organic matter and CO 2 transport, as well as bioturbation processes.

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The role of natural organic matter in the migration behaviour of americium in the Boom Clay – Part I: Migration experiments

Cited by 30 publications

References 6 publications

The influence of natural organic matter on the speciation and solubility of Eu in Boom Clay porewater

The influence of natural organic matter on the speciation and solubility of Eu in Boom Clay porewater

Modelling of a large-scalein-situmigration experiment with¹⁴C-labelled natural organic matter in Boom Clay

The HPx software for multicomponent reactive transport during variably-saturated flow: Recent developments and applications

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The role of natural organic matter in the migration behaviour of americium in the Boom Clay – Part I: Migration experiments

Cited by 30 publications

References 6 publications

The influence of natural organic matter on the speciation and solubility of Eu in Boom Clay porewater

The influence of natural organic matter on the speciation and solubility of Eu in Boom Clay porewater

Modelling of a large-scalein-situmigration experiment with14C-labelled natural organic matter in Boom Clay

The HPx software for multicomponent reactive transport during variably-saturated flow: Recent developments and applications

Contact Info

Product

Resources

About

Modelling of a large-scalein-situmigration experiment with¹⁴C-labelled natural organic matter in Boom Clay