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| 2. |
- Basirat, Farzad, et al.
(author)
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Modeling Gas Transport in the Shallow Subsurface in Maguelone Field Experiment
- 2013
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In: Energy Procedia. - : Elsevier BV. - 1876-6102. ; , s. 337-345
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Journal article (peer-reviewed)abstract
- In this paper, TOUGH2/EOS7CA model is used to simulate the shallow injection-monitoring experiment carried outat Maguelone, France, during 2012 and 2013. The ultimate objective of the work is to improve our understanding ofgas transport in the shallow subsurface as well as to develop and validate the model to monitor it. This workrepresents first results towards modelling the nitrogen and CO2 injection experiments carried out. The pressure datafrom the first injection experiments in summer 2012 is used as basis for comparison. Work is presently going on toincorporate the experimental data into the numerical simulation further.
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| 3. |
- Basirat, Farzad, et al.
(author)
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Modeling gas transport in the shallow subsurface in the Maguelone field experiment
- 2013
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Conference paper (peer-reviewed)abstract
- Developing reliable monitoring techniques to detect and characterize CO2 leakage in shallow subsurface is necessary for the safety of any GCS project. To test different monitoring techniques, shallow injection-monitoring experiment have and are being carried out at the Maguelone, along the Mediterranean lido of the Gulf of Lions, near Montpellier, France. This experimental site was developed in the context of EU FP7 project MUSTANG and is documented in Lofi et al. (2012). Gas injection experiments are being carried out and three techniques of pressure, electrical resistivity and seismic monitoring have been used to detect the nitrogen and CO2 release in the near surface environment. In the present work we use the multiphase and multicomponent TOUGH2/EOS7CA model to simulate the gaseous nitrogen and CO2 transport of the experiments carried out so far. The objective is both to gain understanding of the system performance based on the model analysis as well as to further develop and validate modelling approaches for gas transport in the shallow subsurface, against the well-controlled data sets. Numerical simulation can also be used for the prediction of experimental setup limitations. We expect the simulations to represent the breakthrough time for the different tested injection rates. Based on the hydrogeological formation data beneath the lido, we also expect the vertical heterogeneities in grain size distribution create an effective capillary barrier against upward gas transport in numerical simulations.
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| 5. |
- Goel, Gaurav, et al.
(author)
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Optimal use of surface drains for enhancing ground water recharge
- 2013
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In: Journal of Indian Water Resources Society. ; 33:3, s. 43-52
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Journal article (peer-reviewed)abstract
- Growing demand for the fresh water has resulted in increased exploitation of its limited sources - the foremost of them being the groundwater. Artificial recharge through a network of surface drains can be one of the remedy to this problem. In this paper, Khepar’s model has been used to investigate the effect of drain parameter on the amount of recharge. The parameters which were kept in focus during the investigation were check dam height, number of check dams, bed slope of drain and wetted perimeter of drain. One of the key findings was that the recharge rate is found directly proportional to check dam height, bed slope of drain and wetted perimeter of drain. This formulation can lead to optimization of recharge and consequent raise in water table in addition to effective usage of surface drains.
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| 6. |
- Kocur, Chris, et al.
(author)
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Characterization of nZVI mobility in a field scale test
- 2014
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In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 48:5, s. 2862-2869
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Journal article (peer-reviewed)abstract
- Nanoscale zero valent iron (nZVI) particles were injected into a contaminated sandy subsurface area in Sarnia, Ontario. The nZVI was synthesized on site, creating a slurry of 1 g/L nanoparticles using the chemical precipitation method with sodium borohydride (NaBH4) as the reductant in the presence of 0.8% wt. sodium carboxymethylcellulose (CMC) polymer to form a stable suspension. Individual nZVI particles formed during synthesis had a transmission electron microscopy (TEM) quantified particle size of 86.0 nm and dynamic light scattering (DLS) quantified hydrodynamic diameter for the CMC and nZVI of 624.8 nm. The nZVI was delivered to the subsurface via gravity injection. Peak normalized total Fe breakthrough of 71% was observed 1m from the injection well and remained above 50% for the 24 hour injection period. Samples collected from a monitoring well 1 m from the injection contained nanoparticles with TEM-measured particle diameter of 80.2 nm and hydrodynamic diameter of 562.9 nm. No morphological changes were discernible between the injected nanoparticles and nanoparticles recovered from the monitoring well. Energy dispersive X-ray spectroscopy (EDS) was used to confirm the elemental composition of the iron nanoparticles sampled from the downstream monitoring well, verifying the successful transport of nZVI particles. This study suggests that CMC stabilized nZVI can be transported at least 1 m to the contaminated source zone at significant Fe0 concentrations for reaction with target contaminants.
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| 7. |
- Mekonen, Abenezer, et al.
(author)
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Transport and mobilization of multiwall carbon nanotubes in quartz sand under varying saturation
- 2014
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In: Environmental Earth Sciences. - : Springer Science and Business Media LLC. - 1866-6280 .- 1866-6299. ; 71:8, s. 3751-3760
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Journal article (peer-reviewed)abstract
- In this study, a series of sand packed columnswere used to investigate the mobility of multiwall carbonnanotubes (MWCNTs) in unsaturated porous media underunfavorable conditions for deposition. The flow throughcolumn experiments were designed to assess water content,flow rate, and grain size effect on the mobility ofMWCNTs. It was found that variation in water content hadno significant effect on retention of MWCNTs until it waslowered to 16 % effective saturation. Thick water films,high flow rate, and repulsive forces between MWCNTs andporous media made MWCNTs highly mobile. Differentporous media grain sizes (D50 = 150–300 lm) were usedin this study. The mobility of MWCNTs slightly decreasedin finer grain sands, which was deemed to be an effect ofincrease in surface area and the number of depositionalsites, in combination with low-pore water velocity. However,physical straining was not observed in selected finegrainsands and aspect ratio of MWCNTs had low impacton mobility. Variations in pore-water velocity were producedby both changes in water saturation and in flow rate.At high pore-water velocities, the MWCNTs were generallymobile. However, for the combination of low-porewater velocity with either low water saturation or smallgrain size, some retention of MWCNTs was observed.Hence, low velocity in combination with flow throughsmaller pores increased MWCNT deposition.
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| 8. |
- Poulsen, Tjalfe, et al.
(author)
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Apparent porous media gas dispersion in response to rapid pressure fluctuations
- 2011
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In: Soil science. - 0038-075X .- 1538-9243. ; 176:12, s. 635-641
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Journal article (peer-reviewed)abstract
- The impact of rapid pressure fluctuations (frequency >0.02 min−1) on gas transport in two filter sands with different gas permeability (kg) was investigated. Pressure fluctuation–induced gas transport characterized as a dispersion process governed by a pressure fluctuation–induced dispersion coefficient (Dp) was measured using a column containing the sand, connected to a membrane pump for generating pressure fluctuations. Measurements ofDp in both sands were carried out for different combinations of pressure-fluctuation amplitude (A) and frequency (f). To assess if Dp is affected by the presence of a background steady gas flux in addition to the gas movement induced by the pressure fluctuations, Dpmeasurements were carried out for different constant pore gas velocities (u). Measurements of Dp corresponding to a total of 102 combinations of u, A, f, and kg were carried out. The results showed that the value of Dp increases with increasing A, f, and kg but is independent of u. Relations between Dp and A, f, and kg were generally strong.
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| 9. |
- Sharma, Prabhakar, 1976-, et al.
(author)
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Deposition and mobilization of functionalized multiwall carbon nanotubes in saturated porous media : effect of grain size, flow velocity and solution chemistry
- 2014
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In: Environmental Earth Sciences. - : Springer Science and Business Media LLC. - 1866-6280 .- 1866-6299. ; 72:8, s. 3025-3035
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Journal article (peer-reviewed)abstract
- Carbon nanotubes (CNTs) are widely manufactured nanoparticles which are utilized in a number of consumer products, such as sporting goods, electronics and biomedical applications. Due to their accelerating production and use, CNTs constitute a potential environmental risk if they are released to soil and groundwater systems. It is therefore essential to improve the current understanding of environmental fate and transport of CNTs. The current study systematically investigated the effect of solution chemistry (pH and ionic strength) and physical conditions (collector grain size and flow rate) on the deposition and mobilization of functionalized multiwall carbon nanotubes (MWCNTs) using a series of column experiments under fully saturated conditions. A 1-dimensional convection-dispersion model including collector efficiency for cylindrical nanoparticles was used to simulate the transport of MWCNTs in porous media. It was observed that an increase in pH resulted in increased mobility of MWCNTs. However, the transport of MWCNTs was strongly dependent on ionic strength of the background solution and a critical deposition concentration (CDC) was observed between 3 and 4 mM NaCl concentration, with more than 99% filtration of MWCNTs at 4 mM. The finer sand grains were able to filter a significant amount of MWCNTs (15% more than coarse sand) from the inflow solution; this was likely caused by grain-to-grain straining mechanisms in the finer sand. A decrease in pore-water velocity also led to more deposition of MWCNTs due to lowering of the kinetic energy of the particles. The results from this study indicated that a weak secondary minimum existed under unfavorable conditions for deposition, but the particles were trapped at both primary and secondary minimum.
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| 10. |
- Sharma, Prabhakar, 1976-, et al.
(author)
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Detachment of colloids from a solid surface by a moving air–water interface
- 2008
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In: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 326:1, s. 143-150
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Journal article (peer-reviewed)abstract
- Colloid attachment to liquid–gas interfaces is an important process used in industrial applications toseparate suspended colloids from the fluid phase. Moving gas bubbles can also be used to removecolloidal dust from surfaces. Similarly, moving liquid–gas interfaces lead to colloid mobilization in thenatural subsurface environment, such as in soils and sediments. The objective of this study was toquantify the effect of moving air–water interfaces on the detachment of colloids deposited on an airdriedglass surface, as a function of colloidal properties and interface velocity. We selected four typesof polystyrene colloids (positive and negative surface charge, hydrophilic and hydrophobic). The colloidswere deposited on clean microscope glass slides using a flow-through deposition chamber. Air–waterinterfaces were passed over the colloid-deposited glass slides, and we varied the number of passagesand the interface velocity. The amounts of colloids deposited on the glass slides were visualized usingconfocal laser scanning microscopy and quantified by image analysis. Our results showed that colloidsattached under unfavorable conditions were removed in significantly greater amounts than those attachedunder favorable conditions. Hydrophobic colloids were detached more than hydrophilic colloids. Theeffect of the air–water interface on colloid removal was most pronounced for the first two passagesof the air–water interface. Subsequent passages of air–water interfaces over the colloid-deposited glassslides did not cause significant additional colloid removal. Increasing interface velocity led to decreasedcolloid removal. The force balances, calculated from theory, supported the experimental findings, andhighlight the dominance of detachment forces (surface tension forces) over the attachment forces (DLVOforces).
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