Through-diffusion Experiments Research Articles

How mobile is tritiated water through unsaturated cement-based materials? New insights from two complementary approaches

This work presents two complementary approaches (for low and high desaturation) to study tritiated water (HTO) diffusion through unsaturated cement-based materials. The first approach was based on through-diffusion experiments where suction was controlled by osmosis. In the second approach, diffusion experiments were performed in humidity chambers controlled by under-saturated saline solutions. Results revealed a decrease of effective diffusion coefficient by a factor of 10 from 100% to 23% of saturation degree. Comparison with gaseous H2 suggests that HTO diffuses through unsaturated cement-based materials at rates 4 orders of magnitude lower.

A comparative anion diffusion study on different argillaceous, low permeability sedimentary rocks with various pore waters

Through-diffusion experiments with tritiated water (HTO) and 36Cl− as a function of pore water concentration (0.01–5 M) were performed on two Ordovician-age argillaceous rock samples from the Blue Mountain Fm and Queenston Fm shales of the Paleozoic intracratonic Michigan Basin in Canada. This study reveals that the effect of ionic strength on the anion-transport porosity is similar, and only the minimal anion excluded porosity is higher in the Blue Mountain Fm shale. The differences in rock sample mineralogy cannot explain this effect. It is hypothesized that the structure of the Blue Mountain Fm shale samples has led to pore space openings sufficiently small that they behave as interlayers. Such pores are defined as interlayer equivalent (ILE) pores. These ILE pores, as in the case of interlayer pores, can act to permanently limit the anion-accessible porosity. Pore-size distribution measurements provide further evidence of increased potential for ILE pores within the Blue Mountain Fm samples. A Donnan model, which includes consideration of both ILE and uncharged pores, is shown to describe the effect of molar concentration on the anion-accessible porosity in the argillaceous rocks investigated.

A measurement method for isotope fractionation of 35Cl and 37Cl by a conventional through-diffusion experiment

Chlorine is geochemically stable and is widely used as a groundwater tracer. Stable isotopes of chlorine (35Cl and 37Cl) are fractionated by diffusion and are used to characterize diffusion-dominant systems, understand seawater intrusion and identify the origin of chlorine. However, a method for measuring the fractionation factor by diffusion (α = DCl−35 / DCl−37) has not been established for rock samples. We propose a method for measuring α using a conventional through-diffusion experiment, in which a sample is embanked by a high- to low-concentration tank. This study shows that theoretically, the diffusive flux in a through-diffusion experiment should have mass ratio fractionated by diffusion and that the difference between δ37Cl in the high- to low-concentration tank will approach to 103 ln α with time. The results of the through-diffusion experiment showed a significant difference between δ37Cl in the high- and low-concentration tanks. Measured α ranged from 1.0015–1.0022, which is in good agreement with previous studies. Moreover, the sampling period and correction method are suggested to determine α excluding errors due to an unsteady state. The proposed method is applicable to other isotopes to measure α and will contribute to a more quantitative evaluation of Cl and δ37Cl profiles.

Interplay of molecular size and pore network geometry on the diffusion of dissolved gases and HTO in Boom Clay

Through-diffusion experiments in Boom Clay have been performed with uncharged molecules: tritiated water (HTO) and dissolved gases of different size (He, Ne, H2, Ar, CH4, Xe and C2H6), allowing information to be obtained on the relationship between the diffusion coefficient and the molecular size (characterized by a 'kinetic diameter' of the molecules). Experiments have been performed on both clayey and silty Boom Clay samples, to scope for the changes induced by grain size variations on the diffusion process. Experiments on clay cores taken perpendicular as well as parallel to the bedding plane have also been executed, providing additional information on the anistropy of the diffusion process.Empirical relations are proposed to capture the observed decrease of both the diffusion coefficient in water and the effective diffusion coefficient in the Boom Clay porous medium as a function of molecular size. In the same way, the behaviour of the geometric factor G as a function of size is estimated.Although silty samples have a noticeably higher hydraulic conductivity than clayey samples, the difference in diffusion coefficient is less obvious. The anisotropy factor is roughly the same for all investigated components, with an average value of 1.5.

Adsorption and retarded diffusion of EuIII-EDTA− through hard clay rock

Adsorption and diffusion experiments of EuIII were performed in Callovo-Oxfordian (COx) clay rock in the presence of EDTA. The predictive model based on binary system parameters (Eu/COx and EDTA/COx) was in good agreement with the results for the Eu/EDTA/COx ternary system. At low EDTA concentrations, the behaviour of EuIII was mainly driven by Eu3+adsorption and complexation by carbonates and EDTA. At higher EDTA concentrations, the behaviour of EuIII was driven by the adsorption of [EuIII-EDTA]− anions. Europium was then used as a probe to estimate the transport of EDTA. Three through-diffusion experiments of EDTA were compared with 14C, Eu and 152Eu tracers. EuIII-EDTA was not quantitatively dissociated by diffusion through the rock. The effective diffusion coefficients quantified De(EuIII-EDTA)=1.5–1.7·1012m2s−1 were an order of magnitude lower than that of water, evidencing the anionic exclusion of [EuIII-EDTA]− within the clay rock. Break-through curves and diffusion profiles confirmed retardation due to significant adsorption on the clay rock (Rd(EuIII-EDTA)∼6–14Lkg−1) in comparison with inorganic anions. However, the model based on batch adsorption measurements failed to predict the diffusion results. All experiments displayed an early break-through of EDTA complexes. This behaviour contrasted with results on iron oxides rich sediments, which usually led to higher retardation than expected from the batch studies.

Effect of confining pressure on diffusion coefficients in clay-rich, low-permeability sedimentary rocks

The effect of confining pressure (CP) on the diffusion of tritiated-water (HTO) and iodide (I−) tracers through Ordovician rocks from the Michigan Basin, southwestern Ontario, Canada, and Opalinus Clay from Schlattingen, Switzerland was investigated in laboratory experiments. Four samples representing different formations and lithologies in the Michigan Basin were studied: Queenston Formation shale, Georgian Bay Formation shale, Cobourg Formation limestone and Cobourg Formation argillaceous limestone. Estimated in situ vertical stresses at the depths from which the samples were retrieved range from 12.0 to 17.4MPa (Michigan Basin) and from 21 to 23MPa (Opalinus Clay). Effective diffusion coefficients (De) were determined in through-diffusion experiments. With HTO tracer, applying CP resulted in decreases in De of 12.5% for the Queenston Formation shale (CPmax=12MPa), 30% for the Georgian Bay Formation shale (15MPa), 34% for the Cobourg Formation limestone (17.4MPa), 31% for the Cobourg Formation argillaceous limestone (17.4MPa) and 43–46% for the Opalinus Clay (15MPa). Decreases in De were larger for the I− tracer: 13.8% for the Queenston shale, 42% for the Georgian Bay shale, 50% for the Cobourg Formation limestone, 55% for the Cobourg Formation argillaceous limestone and 63–68% for the Opalinus Clay. The tracer-specific nature of the response is attributed to an increasing influence of anion exclusion as the pore size decreases at higher CP.Results from the shales (including Opalinus Clay) indicate that the pressure effect on De can be represented by a linear relationship between De and ln(CP), which provides valuable predictive capability. The nonlinearity results in a relatively small change in De at high CP, suggesting that it is not necessary to apply the exact in situ pressure conditions in order to obtain a good estimate of the in situ diffusion coefficient. Most importantly, the CP effect on shale is reversible (±12%) suggesting that, for argillaceous rocks, it is possible to obtain De values that are representative of the in-situ condition by conducting measurements on re-pressurized samples that were obtained with standard drilling practices. This may not be the case for brittle rock samples as the results from limestone suggest that irreversible damage occurred during the pressure cycling.

Diffusion and Sorption Properties of Some Sorbing Nuclides onto Granodiorite in a Modified Through-Diffusion Setup

Through-diffusion experiments of some sorbing nuclides onto granodiorite have been carried out to understand their diffusion and sorption characteristics. A newly designed experimental setup with compacted structure and dimensions was used for the through-diffusion process. The nuclides used in the experiment were tritiated water (HTO), Sr, Cs, Ni, Nb, and Am. The diffused nuclides were sampled at certain periods of time to estimate the diffusivities. After the diffusion experiment was carried out for 1.5 years, the rock media were recovered. In addition, a sequential chemical extraction was conducted to estimate the sorption types of the nuclides for the recovered rock disks. The relationship between diffusion and sorption was investigated from the viewpoint of sorption reversibility. The measured diffusivity was compared to the other experimental results.

A comparative study on sorption and diffusion of Cs in crushed argillite and granite investigated in batch and through-diffusion experiment

The batch and through-diffusion experiments in this study were conducted and compared in order to investigate the sorption and diffusion of cesium (Cs) for two potential host rocks in Taiwan: argillite from Taitung and granite from Kinmen Island, with the purpose of establishing a reliable safety-performance assessment methodology for the final disposal of low level radioactive waste. The results of Cs mapping by scanning electron microscope equipping by energy dispersive spectrometer (SEM–EDS) showed that the distribution of Cs on argillite and granite were enriched in illite and biotite, respectively. In addition, it showed that higher sorption capacities were found for argillite than granite; due to the clay mineral content (illite) in the argillite. Experiments for diffusion of Cs is agreement to the values estimated for the diffusive results (Da) of Cs in argillite were revealed to be lower than those of granite.

Determination of sorption and diffusion parameters of 99Tc in crushed granite using through-diffusion experiments

Diffusion and sorption are important processes associated with radionuclides migration in crystalline rock. These processes are studied in the laboratory using borehole core samples. In this study, we obtained distribution coefficients (K d), apparent diffusion coefficients (D a) and retardation factor (R f) using batch and through-diffusion experiments. The $$ R_{\text{f}}^{\text{H/Tc}} $$ and $$ K_{\text{d}}^{\text{H/Tc}} $$ values obtained using the accumulative concentration method were lower than those derived in the batch experiments. These findings demonstrate that reliable R f and K d values of 99Tc can be obtained using through-diffusion experiments with a non-reactive radiotracer, thereby bolstering confidence in the assessment of the long-term performance of disposal repositories.

Sorption and diffusion of selenium oxyanions in granitic rock

The processes controlling diffusion and sorption of radionuclides have been studied extensively in the laboratory, whereas, only a few in-situ experiments have been carried out in order to study in-situ diffusion over the long-term (several years). This is largely due to the fact that in-situ experiments are typically time consuming and cost intensive, and it is commonly accepted that laboratory scale tests are well-established approaches to characterizing the properties of geological media. In order to assess the relevance of laboratory experiments, the Swiss National Cooperative for Disposal of Radioactive Waste (Nagra) have been conducting extensive experiments in the Underground Rock Laboratory (URL) at the Grimsel Test Site (GTS) in order to study radionuclide transport and retention in-situ. One of the elements used in these experiments is non-radioactive selenium, as an analog for the radiotoxic isotope Se-79, which is present in radioactive waste.In this work, two laboratory through-diffusion experiments using selenium as a tracer were carried out in block (decimeter) scale rock specimens to support one of the ongoing radionuclide transport and retention in-situ experiment at the GTS mentioned above. The though-diffusion tests of selenium were performed under atmospheric conditions in both Kuru grey granite (KGG) and Grimsel granodiorite (GG). The decrease of selenium concentration in an inlet hole drilled into each of the rock samples and the breakthrough of selenium into sampling holes drilled around the inlet were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The effective diffusion (De) and distribution coefficients (Kd) of selenium were then determined from the changes of selenium concentration in the inlet and sampling holes using a Time-Domain Diffusion (TDD) simulations. In addition, Kd of selenium was measured by batch sorption experiments as a function of pH and Se concentration in atmospheric conditions and nitrogen atmosphere. The speciation of selenium was studied by HPLC-ICP-MS in simulated ground waters of each of the rock types.The Kd of selenium was found to be in the range of (6.2–7.0±2.0)×10−3m3/kg in crushed rock whereas the Kd obtained from block scale through diffusion experiment varied between (1.5±0.3)×10−3m3/kg and (1.0±0.6)×10−4m3/kg. The De of selenium was significantly higher for GG; De=(2.5±1.5)×10−12m2/s than for KGG; De=(7±2)×10−13m2/s due to the higher permeability of GG compared with KGG.

Gas Phase Measurements of Matrix Diffusion in Rock Samples from Olkiluoto Bedrock, Finland

The Finnish plan for the final deposition of nuclear waste is deposition deep in the crystalline bedrock. In the safety case of the final deposition, matrix diffusion, along with sorption, is considered the most important retarding factor for radionuclide transport in the geosphere. We set out to measure matrix diffusion in the gas phase for two 80 cm long drill-core samples from Olkiluoto, Finland. One sample consisted of veined gneiss and the other of pegmatitic granite. The measurements were taken in the laboratory with an advection–diffusion measurement setup that uses nitrogen as the carrier gas and helium as the tracer. The measured breakthrough curve for the veined gneiss sample could be interpreted with a homogeneous mathematical model, and the result for the effective diffusion coefficient (\(D_{\mathrm{e}}\)), \(4.2 \pm 0.9 \times 10^{-10}\,\frac{\mathrm {m}^2}{\mathrm {s}}\), agreed with previous results for veined gneiss from through-diffusion experiments in the gas phase. The breakthrough curve for the pegmatitic granite sample required a three-component model because of high variations in the local transport parameters (porosity, diffusion coefficient). The spatial distributions of porosities were characterized with the \(^{14}\)C-polymethylmethacrylate-autoradiography technique. The result, \(D_{\mathrm{e}} = \left( 32 \pm 7\right) \times 10^{-10}\,\frac{\mathrm {m}^2}{\mathrm {s}}\), for the most abundant component was also in accordance with the previous through-diffusion results. Comparison of the two measurements showed that diffusion phenomena can be very sensitive to the microstructure of rock even when macroscopic properties such as porosity remain the same. The retarding effect of matrix diffusion from flow was clearly observed for both samples, and knowledge of the sample structure, rock types, and mineralogy were concluded to be vital in analyzing and interpreting the results.

An improved model for through-diffusion experiments: application to strontium and tritiated water (HTO) diffusion in Boom Clay and compacted illite

Abstract Through-diffusion experiments are conventional experiments to measure the transport parameters of radionuclides in clays. Typically, a regular replacement of the outlet volume by a tracer-free volume is performed. In the classical approach, this type of through-diffusion experiment is modelled by assuming a zero concentration in the outlet volume. Nonetheless, this assumption is not always correct, usually because the outlet volume is insufficiently large or the time between two consecutive replacements of the outlet volume is too long. Therefore, a model was developed disregarding this assumption and, instead, considers the tracer concentration in the outlet volume to evolve, as in the experiments: the flux into the outlet volume increases the tracer concentration and, at each replacement, the tracer concentration in the outlet volume is set to zero. The model was used to reproduce the diffusion of strontium (Sr) and tritiated water (HTO) in illite and Boom Clay. Model results yielded good matches with the tracer evolution in the inlet and the outlet, and the tracer profile in the core at the end of the experiment.

Diffusion and retention behaviour of Cs in illite-added compacted montmorillonite

AbstractCompacted bentonite is to be used as a component of an engineered barrier system to retard the migration of radionuclides in the geological disposal of radioactive waste. In such an environment, montmorillonite in compacted bentonite might be altered to illite due to the hydrothermal reactions caused by the decay heat of radionuclides. In the present study, the diffusion and retention behaviour of Cs in compacted montmorillonite containing illitewas investigated using through-diffusion experiments. The experimental results showed that the flux of Cs attributed to the surface diffusion was independent of the sorption of Cs on illite, indicating that the Cs sorbed on illite was immobile or considerably less mobile than the Cs sorbed on montmorillonite. Consequently, the illite content in compacted bentonite is expected to enhance the sorption capacity of Cs without causing surface diffusion.

Experimental and molecular dynamics study on anion diffusion in organically modified bentonite

The work presents experimental and molecular modeling study of the anion diffusion with nitrate as a model probe in the organically modified bentonite. Organoclay samples with different loadings of the two cations Hexadecyltrimethylammonium (HDTMA+) and Hexadecylpyridinium (HDPy+) were prepared. The diffusivity of NO3− in the interfacial area of the organo-bentonite is strongly affected by the packing density of the organic coating. Through-diffusion experiments verified that the retardation capacity of the organoclays increases with the increasing amount of both organic cations on the clay surface. Observed NO3− diffusion in HDTMA+- and HDPy+-bentonite is in a similar range. Further, classical molecular dynamics studies, performed on sets of HDTMA+- and HDPy+-montmorillonite models, explained a molecular mechanism of the diffusion process of the nitrate anion at the organoclay–water interface. The molecular simulations showed comparable trends of the dependence of the NO3− diffusion coefficient on the content of organic cations on the surface as observed in experiment. Calculations explained how the organic cations are arranged on the surface and revealed that the positively charged head groups of the organic cations play a key role in the decreasing of the diffusivity of nitrate ions.

Solubility constraints affecting the migration of selenium through the cementitious backfill of a geological disposal facility

This work presents the study of the solubility of selenium under cementitious conditions and its diffusion, as SeO32−, through monolithic cement samples. The solubility studies were carried out under alkaline conditions similar to those anticipated in the near-field of a cement-based repository for low- and intermediate-level radioactive waste. Experiments were conducted in NaOH solution, 95%-saturated Ca(OH)2, water equilibrated with a potential backfill material (Nirex reference vault backfill, NRVB) and in solutions containing cellulose degradation products, with and without reducing agents. The highest selenium concentrations were found in NaOH solution. In the calcium-containing solutions, analysis of the precipitates suggests that the solubility controlling phase is Ca2SeO3(OH)2·2H2O, which appears as euhedral rhombic crystals. The presence of cellulose degradation products caused an increase in selenium concentration, possibly due to competitive complexation, thereby, limiting the amount of calcium available for precipitation. Iron coupons had a minor effect on selenium solubility in contrast to Na2S2O4, suggesting that effective reduction of Se(IV) occurs only at Eh values below −300mV. Radial through-diffusion experiments on NRVB and in a fly ash cement showed no evidence of selenium breakthrough after one year. However, autoradiography of the exposed surfaces indicated that some migration had occurred and that selenium was more mobile in the higher porosity backfill than in the fly ash cement.

Mineral precipitation-induced porosity reduction and its effect on transport parameters in diffusion-controlled porous media.

BackgroundIn geochemically perturbed systems where porewater and mineral assemblages are unequilibrated the processes of mineral precipitation and dissolution may change important transport properties such as porosity and pore diffusion coefficients. These reactions might alter the sealing capabilities of the rock by complete pore-scale precipitation (cementation) of the system or by opening new migration pathways through mineral dissolution. In actual 1D continuum reactive transport codes the coupling of transport and porosity is generally accomplished through the empirical Archie’s law. There is very little reported data on systems with changing porosity under well controlled conditions to constrain model input parameters. In this study celestite (SrSO4) was precipitated in the pore space of a compacted sand column under diffusion controlled conditions and the effect on the fluid migration properties was investigated by means of three complementary experimental approaches: (1) tritiated water (HTO) tracer through diffusion, (2) computed micro-tomography (µ-CT) imaging and (3) post-mortem analysis of the precipitate (selective dissolution, SEM/EDX).ResultsThe through-diffusion experiments reached steady state after 15 days, at which point celestite precipitation ceased and the non-reactive HTO flux became constant. The pore space in the precipitation zone remained fully connected using a 6 µm µ-CT spatial resolution with 25 % porosity reduction in the approx. 0.35 mm thick dense precipitation zone. The porosity and transport parameters prior to pore-scale precipitation were in good agreement with a porosity of 0.42 ± 0.09 (HTO) and 0.40 ± 0.03 (µ-CT), as was the mass of SrSO4 precipitate estimated by µ-CT at 25 ± 5 mg and selective dissolution 21.7 ± 0.4 mg, respectively. However, using this data as input parameters the 1D single continuum reactive transport model was not able to accurately reproduce both the celestite precipitation front and the remaining connected porosity. The model assumed there was a direct linkage of porosity to the effective diffusivity using only one cementation value over the whole porosity range of the system investigated.ConclusionsThe 1D single continuous model either underestimated the remaining connected porosity in the precipitation zone, or overestimated the amount of precipitate. These findings support the need to implement a modified, extended Archie’s law to the reactive transport model and show that pore-scale precipitation transforms a system (following Archie’s simple power law with only micropores present) towards a system similar to clays with micro- and nanoporosity.Graphical abstract:Electronic supplementary materialThe online version of this article (doi:10.1186/s12932-015-0027-z) contains supplementary material, which is available to authorized users.

Matrix diffusion and sorption of Cs+, Na+, I– and HTO in granodiorite: Laboratory-scale results and their extrapolation to the in situ condition

Matrix diffusion and sorption are important processes controlling radionuclide transport in crystalline rocks. Such processes are typically studied in the laboratory using borehole core samples however there is still much uncertainty on the changes to rock transport properties during coring and decompression. It is therefore important to show how such laboratory-based results compare with in situ conditions. This paper focuses on laboratory-scale mechanistic understanding and how this can be extrapolated to in situ conditions as part of the Long Term Diffusion (LTD) project at the Grimsel Test Site, Switzerland. Diffusion and sorption of 137Cs+, 22Na+, 125I– and tritiated water (HTO) in Grimsel granodiorite were studied using through-diffusion and batch sorption experiments. Effective diffusivities (De) of these tracers showed typical cation excess and anion exclusion effects and their salinity dependence, although the extent of these effects varied due to the heterogeneous pore networks in the crystalline rock samples. Rock capacity factors (α) and distribution coefficients (Kd) for Cs+ and Na+ were found to be sensitive to porewater salinity. Through-diffusion experiments indicated dual depth profiles for Cs+ and Na+ which could be explained by a near-surface Kd increment. A microscopic analysis indicated that this is caused by high porosity and sorption capacities in disturbed biotite minerals on the surface of the samples. The Kd values derived from the dual profiles are likely to correspond to Kd dependence on the grain sizes of crushed samples in the batch sorption experiments. The results of the in situ LTD experiments were interpreted reasonably well by using transport parameters derived from laboratory data and extrapolating them to in situ conditions. These comparative experimental and modelling studies provided a way to extrapolate from laboratory scale to in situ condition. It is well known that the difference in porosity between laboratory and in situ conditions is a key factor to scale laboratory-derived De to in situ conditions. We also show that cation excess diffusion is likely to be a key mechanism in crystalline rocks and that high Kd in the disturbed surfaces is critically important to evaluate transport in both laboratory and in situ tests.

Study on sorption and diffusion of Sr in crushed and intact basalt and granite investigated in through-diffusion experiments

This study investigates sorption and diffusion of strontium (Sr) in two potential host rocks (granite from Kingman Island and basalt from Penghu Island) by using batch and column methods. According to solid-phase analysis, the sorption component primarily contained iron–magnesium (Fe–Mg) minerals in basalt and granite. Moreover, the distribution coefficient (K d) of Sr in various concentrations obtained from batch tests indicated a higher sorption capacity in basalt than that in granite because of the 10 % Fe–Mg mineral content. According to the diffusive results in crushed and intact rocks, it showed that major retardation of Sr depended on the micro-porous structure of tested media, such as decreases of constrictivity and increases of tortuosity.

Analytical model for 1-D contaminant diffusion through clay barriers

Studies on diffusion transport of contaminants through clays are vitally important for performance assessment of waste disposal facilities. Laboratory through-diffusion (double-reservoir) experiment represents a well-established and routinely used technique for the determination of design mass transport parameters in a single test. Availability of accurate and simple theoretical models is valuable for simulating diffusion transport of contaminants through clays for the design and evaluation processes of many waste disposal facilities. The theoretical solutions for this problem are commonly obtained by numerically solving the governing diffusion equation in combination with finite mass boundary conditions. The lack of analytical solutions to this problem encouraged the development of numerical solutions. However, a high computational cost is associated with such time-marching numerical solutions. Closed-form analytical solutions are proposed, in this work, for one-dimensional (1D) transient through diffusion transport of sorptive contaminants through homogeneous clays. Proposed analytical solutions are compared with the solution obtained using existing methods on experimental data. The proposed analytical solutions are simple and accurate for theoretically estimating transient diffusion transport of sorptive contaminants through clays. The proposed model has ready application for analysing routine laboratory through-diffusion experimental data.

Determination of sorption and diffusion parameters of Se(IV) on crushed granite

Sorption and diffusion are important processes for the transport of radionuclides through geomedia from a radioactive disposal facility. In this study, batch tests and through-diffusion experiments were performed to investigate the sorption and diffusion of Se(IV) in crushed granite. Different column lengths of 2, 4 and 8, were employed in the through-diffusion experiments to study the effect of the column length on the apparent diffusion coefficients. Synthetic groundwater (GW) and synthetic seawater (SW) were the liquid phases in these experiments. A two-site kinetic linear model and the Freundlich isotherm were applied to match the sorption/desorption batch data quite closely for both of GW and SW conditions. The retardation factors (Rf) were estimated by comparing the breakthrough curve of Se(IV) with that of HTO. Experimental results indicated that whether in GM or SW solution, the column lengths did not significantly affected Da or Rf of Se in crushed granite.