Coupled multi-ion electrodiffusion analysis for clay soils

2004 ◽  
Vol 41 (2) ◽  
pp. 287-298 ◽  
Author(s):  
Christian Jungnickel ◽  
David Smith ◽  
Stephen Fityus
Keyword(s):  
Diffusion Coefficients ◽  
Reactive Transport ◽  
Clayey Soil ◽  
Transport Model ◽  
Ion Pairing ◽  
Diffusion Cell ◽  
Coupled Transport ◽  
Exchange Reactions ◽  
Clay Liners ◽  
Ion Species

For a well-engineered compacted clay landfill liner, diffusive transport through the liner is the main mass transport mechanism from the landfill. Therefore, accurate estimates of diffusion coefficients for clay liners are essential for the engineering design of liner systems. A long-standing problem has been the effect of ion pairing on the estimation of diffusion coefficients for multicomponent ionic solutions migrating through clay liners. This paper considers the solution of a fully coupled set of transport equations describing the simultaneous diffusion of several ion species through a clayey soil. The analysis takes into account the diffusion coefficient for each ion species, ion pairing (as required by electroneutrality of the solution), and time-dependent first-order ion and (or) ligand exchange reactions with the clay particles. The behaviour of a double-reservoir diffusion cell, often employed for the estimation of diffusion coefficients in the laboratory, is analyzed using the coupled transport model. A detailed theoretical analysis is made of sodium fluoride transport through saturated kaolinitic clay.Key words: multi-ion diffusion, finite element analysis, reactive transport, kaolinite, double-reservoir diffusion cell.

Contaminant migration from sanitary landfill leachate through soil monoliths

1995 ◽  
Vol 32 (7) ◽  
pp. 215-219 ◽  
Author(s):  
Magdelinka Radenkova-Yaneva ◽  
Emilia Kostakeva ◽  
Dimiter Toshev
Keyword(s):  
Clayey Soil ◽  
Sanitary Landfill ◽  
Potential Danger ◽  
Contaminant Migration ◽  
Clay Liners ◽  
Domestic Waste ◽  
Solid Domestic Waste ◽  
Inorganic Substances ◽  
Sanitary Landfills ◽  
Sanitary Landfill Leachate

It is well known that the leachates from solid domestic waste sanitary landfills are heavily polluted with organic and inorganic substances. As they are of a potential danger for the environment, their uncontrolled seepage is avoided in the modern sanitary landfills by means of suitable insulation. This is mostly made of natural materials with a low filtration coefficient. The present paper considers the results of the filtration characteristics, studying natural clayey soil model liners. The leachate contaminants distribution from the sanitary landfill in Sofia (Suhodol) is traced out in different liner depths. The mechanism of pollutant attenuation in the liners is considered. It is found that a part of the leachate components (Fe, Mn, SO42−, PO43−) stays in clayey liners. Besides, as a result of pore colmatation the permeability of the liners is decreased. It is shown that soil monoliths with a proper thickness might serve as a sufficiently safe barrier against leachate filtration in adjacent aquifers. On the base of the results obtained the thickness of the clay liners in the solid domestic waste sanitary landfills could be optimized.

Modelling uranium leaching from agricultural soils to groundwater as a criterion for comparison with complementary safety indicators

2006 ◽  
Vol 932 ◽  
Author(s):  
D. Jacques ◽  
J. Šimůnek ◽  
D. Mallants ◽  
M.Th. van Genuchten
Keyword(s):  
Soil Profile ◽  
Reactive Transport ◽  
Transport Model ◽  
Agricultural Soils ◽  
Solid Phase ◽  
Water Flux ◽  
Fertilizer Application ◽  
Mineral Fertilizers ◽  
Deep Soil ◽  
Long Time

ABSTRACTNaturally occurring radionuclides can also end up in soils and groundwater due to human practices, such as application of certain fertilizers in agriculture. Many mineral fertilizers, particularly (super)phosphates, contain small amounts of 238U and 230Th which eventually may be leached from agricultural soils to underlying water resources. Field soils that receive P-fertilizers accumulate U and Th and their daughter nuclides, which eventually may leach to groundwater. Our objective was to numerically assess U migration in soils. Calculations were based on a new reactive transport model, HP1, which accounts for interactions between U and organic matter, phosphate, and carbonate. Solid phase interactions were simulated using a surface complexation module. Furthermore, all geochemical processes were coupled with a model accounting for dynamic changes in the soil water content and the water flux. The capabilities of the code in calculating natural U fluxes to groundwater were illustrated using a semi-synthetic 200-year long time series of climatological data for Belgium. Based on an average fertilizer application, the input of phosphate and uranium in the soil was defined. This paper discusses calculated U distributions in the soil profile as well as calculated U fluxes leached from a 100-cm deep soil profile. The calculated long-term leaching rates originating from fertilization are significantly higher after 200 years than estimated release rates from lowlevel nuclear waste repositories.

Diffusion of Methane and Chloromethanes in Air

1971 ◽  
Vol 49 (1) ◽  
pp. 74-77 ◽  
Author(s):  
M. Cowie ◽  
Harry Watts
Keyword(s):  
Carbon Tetrachloride ◽  
Diffusion Coefficients ◽  
Methylene Chloride ◽  
Methyl Chloride ◽  
Diffusion Cell ◽  
Infrared Spectrophotometry ◽  
Gaseous Diffusion ◽  
Simple Diffusion ◽  
Concentration Changes

The binary gaseous diffusion coefficients of air with methane, methyl chloride, methylene chloride, chloroform, and carbon tetrachloride at 298.2 °K and 1 atm have been determined. A simple diffusion cell was used, in which concentration changes of the diffusing gas were followed by infrared spectrophotometry.

scholarly journals Reactive Transport Model of Sulfur Cycling as Impacted by Perchlorate and Nitrate Treatments

2016 ◽  
Vol 50 (13) ◽  
pp. 7010-7018 ◽  
Author(s):  
Yiwei Cheng ◽  
Christopher G. Hubbard ◽  
Li Li ◽  
Nicholas Bouskill ◽  
Sergi Molins ◽  
...  
Keyword(s):  
Reactive Transport ◽  
Transport Model ◽  
Sulfur Cycling ◽  
Reactive Transport Model

scholarly journals Mineralogical, numerical and analytical studies of the coupled oxidation of pyrite and coal

2003 ◽  
Vol 67 (2) ◽  
pp. 381-398 ◽  
Author(s):  
K. A. Evans ◽  
C. J. Gandy ◽  
S. A. Banwart
Keyword(s):  
Reactive Transport ◽  
Transport Model ◽  
Pyrite Oxidation ◽  
Spoil Heap ◽  
Reaction Fronts ◽  
Order Of Magnitude ◽  
Magnitude Variation ◽  
Discharge Chemistry ◽  
Analytical Expressions

Mineralogical, bulk and field leachate compositions are used to identify important processes governing the evolution of discharges from a coal spoil heap in County Durham. These processes are incorporated into a numerical one-dimensional advective-kinetic reactive transport model which reproduces field results, including gas compositions, to within an order of magnitude. Variation of input parameters allows the effects of incorrect initial assumptions on elemental profiles and discharge chemistry to be assessed. Analytical expressions for widths and speeds of kinetic reaction fronts are developed and used to predict long-term development of mineralogical distribution within the heap. Results are consistent with observations from the field site. Pyrite oxidation is expected to dominate O2 consumption in spoil heaps on the decadal timescale, although C oxidation may stabilize contaminants in effluents on the centennial scale.

A Numerical Investigation of Low Salinity Polymer Flooding Effects from a Geochemical Perspective

2021 ◽  
Author(s):  
Omar Chaabi ◽  
Emad W. Al-Shalabi ◽  
Waleed Alameri
Keyword(s):  
Aqueous Phase ◽  
Oil Recovery ◽  
Reactive Transport ◽  
History Matching ◽  
Solution Chemistry ◽  
Related Effect ◽  
Exchange Reactions ◽  
Two Phase ◽  
Low Salinity ◽  
Geochemical Reactions

Abstract Low salinity polymer (LSP) flooding is getting more attention due to its potential of enhancing both displacement and sweep efficiencies. Modeling LSP flooding is challenging due to the complicated physical processes and the sensitivity of polymers to brine salinity. In this study, a coupled numerical model has been implemented to allow investigating the polymer-brine-rock geochemical interactions associated with LSP flooding along with the flow dynamics. MRST was coupled with the geochemical software IPhreeqc. The effects of polymer were captured by considering Todd-Longstaff mixing model, inaccessible pore volume, permeability reduction, polymer adsorption as well as salinity and shear rate effects on polymer viscosity. Regarding geochemistry, the presence of polymer in the aqueous phase was considered by adding a new solution specie and related chemical reactions to PHREEQC database files. Thus, allowing for modeling the geochemical interactions related to the presence of polymer. Coupling the two simulators was successfully performed, verified, and validated through several case studies. The coupled MRST-IPhreeqc simulator allows for modeling a wide variety of geochemical reactions including aqueous, mineral precipitation/dissolution, and ion exchange reactions. Capturing these reactions allows for real time tracking of the aqueous phase salinity and its effect on polymer rheological properties. The coupled simulator was verified against PHREEQC for a realistic reactive transport scenario. Furthermore, the coupled simulator was validated through history matching a single-phase LSP coreflood from the literature. This paper provides an insight into the geochemical interactions between partially hydrolyzed polyacrylamide (HPAM) and aqueous solution chemistry (salinity and hardness), and their related effect on polymer viscosity. This work is also considered as a base for future two-phase polymer solution and oil interactions, and their related effect on oil recovery.

Sign in / Sign up

Export Citation Format

Share Document