scholarly journals The Tournemire industrial analogue: reactive-transport modelling of a cement–clay interface

Clay Minerals ◽  
2013 ◽  
Vol 48 (2) ◽  
pp. 167-184 ◽  
Author(s):  
C. Watson ◽  
D. Savage ◽  
J. Wilson ◽  
S. Benbow ◽  
C. Walker ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Reactive Transport ◽  
Transport Model ◽  
Surface Complexation ◽  
General Purpose ◽  
Transport Modelling ◽  
Mineralogical Characterization ◽  
Modelling Techniques ◽  
Materials Used ◽  
Set Up

AbstractIn the post-closure period of a geological disposal facility for radioactive waste, leaching of cement components is likely to give rise to an alkaline plume which will be in chemical disequilibrium with the host rock (which is clay in some concepts) and other engineered barrier system materials used in the facility, such as bentonite. An industrial analogue for cement-clay interaction can be found at Tournemire, southern France, where boreholes filled with concrete and cement remained in contact with the natural mudstone for 15–20 years. The boreholes have been overcored, extracted and mineralogical characterization has been performed. In this study, a reactive-transport model of the Tournemire system has been set up using the general-purpose modelling tool QPAC. Previous modelling work has been built upon by using the most up-to-date data and modelling techniques, and by adding both ion exchange and surface complexation processes in the mudstone. The main features observed at Tournemire were replicated by the model, including porosity variations and precipitation of carbonates, K-feldspar, ettringite and calcite. It was found that ion exchange needed to be included in order for C-S-H minerals to precipitate in the mudstone, providing a better match with the mineralogical characterization. The additional inclusion of surface complexation, however, led to limited calcite growth at the concrete-mudstone interface unlike samples taken from the Tournemire site that have a visible line of crusty carbonates along the interface.

scholarly journals Joint Estimation of Hydraulic and Biochemical Parameters for Reactive Transport Modelling with a Modified ILUES Algorithm

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2161
Author(s):  
Ruicheng Zhang ◽  
Nianqing Zhou ◽  
Xuemin Xia ◽  
Guoxian Zhao ◽  
Simin Jiang
Keyword(s):  
Reactive Transport ◽  
Biochemical Parameters ◽  
Transport Model ◽  
Joint Estimation ◽  
Model Parameters ◽  
Transport Modelling ◽  
Selection Scheme ◽  
Related Model ◽  
Ensemble Smoother ◽  
Iterative Ensemble Smoother

Multicomponent reactive transport modeling is a powerful tool for the comprehensive analysis of coupled hydraulic and biochemical processes. The performance of the simulation model depends on the accuracy of related model parameters whose values are usually difficult to determine from direct measurements. In this situation, estimates of these uncertain parameters can be obtained by solving inverse problems. In this study, an efficient data assimilation method, the iterative local updating ensemble smoother (ILUES), is employed for the joint estimation of hydraulic parameters, biochemical parameters and contaminant source characteristics in the sequential biodegradation process of tetrachloroethene (PCE). In the framework of the ILUES algorithm, parameter estimation is realized by updating local ensemble with the iterative ensemble smoother (IES). To better explore the parameter space, the original ILUES algorithm is modified by determining the local ensemble partly with a linear ranking selection scheme. Numerical case studies based on the sequential biodegradation of PCE are then used to evaluate the performance of the ILUES algorithm. The results show that the ILUES algorithm is able to achieve an accurate joint estimation of related model parameters in the reactive transport model.

scholarly journals Trace element mobility during CO2 storage: application of reactive transport modelling

2019 ◽  
Vol 98 ◽  
pp. 04007
Author(s):  
Dirk Kirste ◽  
Julie K. Pearce ◽  
Sue D. Golding ◽  
Grant K.W. Dawson
Keyword(s):  
Water Quality ◽  
Chemical Composition ◽  
Reactive Transport ◽  
Transport Model ◽  
Co2 Storage ◽  
Chemical Components ◽  
Transport Modelling ◽  
Geochemical Model ◽  
Trace Element Mobility ◽  
The Individual

The geologic storage of CO2 carries both physical and chemical risks to the environment. In order to reduce those risks, it is necessary to provide predictive capabilities for impacts so that strategies can be developed to monitor, identify and mitigate potential problems. One area of concern is related to water quality both in the reservoir and in overlying aquifers. In this study we report the critical steps required to develop chemically constrained reactive transport models (RTM) that can be used to address risk assessment associated with water quality. The data required to produce the RTM includes identifying the individual hydrostratigraphic units and defining the mineral and chemical composition to sufficient detail for the modelling. This includes detailed mineralogy, bulk chemical composition, reactive mineral phase chemical composition and the identification of the occurrence and mechanisms of mobilisation of any trace elements of interest. Once the required detail is achieved the next step involves conducting experiments to determine the evolution of water chemistry as reaction proceeds preferably under varying elevated CO2 fugacities with and without impurities. Geochemical modelling of the experiments is then used for characterising the reaction pathways of the different hydrostratigraphic units. The resultant geochemical model inputs can then be used to develop the chemical components of a reactive transport model.

Modelling species fate and porous media effects for landfill leachate flow

2005 ◽  
Vol 42 (4) ◽  
pp. 1116-1132 ◽  
Author(s):  
A J Cooke ◽  
R K Rowe ◽  
B E Rittmann
Keyword(s):  
Porous Media ◽  
Landfill Leachate ◽  
Reactive Transport ◽  
Volatile Fatty Acids ◽  
Transport Model ◽  
Calcium Carbonate Precipitation ◽  
Transport Modelling ◽  
Inorganic Particles ◽  
The Media ◽  
Multiple Species

A numerical, multiple-species, reactive transport model, coupled to models of kinetic biodegradation, precipitation, and particle attachment and detachment for predicting landfill leachate-induced clogging in porous media for one-dimensional flow systems, is described. The finite-element method is used for transport modelling, with reactions incorporated into point-source or sink terms. The species modelled include three volatile fatty acids, active and inert suspended biomass, dissolved calcium, and inorganic particles. The clog matter consists of active biofilm, inert biofilm, and inorganic solids. A biofilm model is used to simulate the growth and decay of active biomass and removal of substrate. Precipitate accumulation and calcium removal are simulated by a model of calcium carbonate precipitation. Interphase movement between clog matter and fluid includes the processes of attachment and detachment. A geometric representation of the porous media allows porosity and specific surface to be estimated from the thickness of the accumulated clog matter. The porosity of the media can thus change spatially and temporally. The behaviour of the model is demonstrated with a hypothetical example.Key words: clogging, landfills, leachate collection systems, modelling, biofilms, mineral precipitation.

scholarly journals Modeling of Ion Exchange Processes to Optimize Metal Removal from Complex Mine Water Matrices

Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3109
Author(s):  
Angela Isabel Pedregal Montes ◽  
Janith Abeywickrama ◽  
Nils Hoth ◽  
Marlies Grimmer ◽  
Carsten Drebenstedt
Keyword(s):  
Ion Exchange ◽  
Mine Water ◽  
Reactive Transport ◽  
Metal Removal ◽  
Transport Model ◽  
Breakthrough Curves ◽  
Exchange Capacity ◽  
Operating Conditions ◽  
Mine Waters ◽  
Exchange Processes

The modeling of ion exchange processes could significantly enhance their applicability in mine water treatment, as the modern synthetic resins give unique advantages for the removal of metals. Accurate modeling improves the predictability of the process, minimizing the time and costs involved in laboratory column testing. However, to date, the development and boundary conditions of such ion exchange systems with complex mine waters are rarely studied and poorly understood. A representative ion exchange model requires the definition of accurate parameters and coefficients. Therefore, theoretical coefficients estimated from natural exchange materials that are available in geochemical databases often need to be modified. A 1D reactive transport model was developed based on PhreeqC code, using three case scenarios of synthetic mine waters and varying the operating conditions. The first approach was defined with default exchange coefficients from the phreeqc.dat database to identify and study the main parameters and coefficients that govern the model: cation exchange capacity, exchange coefficients, and activity coefficients. Then, these values were adjusted through iterative calibration until a good approximation between experimental and simulation breakthrough curves was achieved. This study proposes a suitable methodology and challenges for modeling the removal of metals from complex mine waters using synthetic ion exchange resins.

Relating biomolecular data to denitrification rates in infiltrating river water – insights from enzyme-based reactive transport modelling

2021 ◽  
Author(s):  
Anna Störiko ◽  
Holger Pagel ◽  
Adrian Mellage ◽  
Olaf A. Cirpka
Keyword(s):  
Reactive Transport ◽  
Transport Model ◽  
Reaction Rates ◽  
Poor Correlation ◽  
Gene Transcript ◽  
Single Event ◽  
Reactive Transport Modelling ◽  
Transport Modelling ◽  
Temporal And Spatial ◽  
Denitrification Genes

<p>Biomolecular quantities like gene, transcript or enzyme concentrations related to a specific reaction promise to provide information about the turnover of nutrients or contaminants in the environment. Particularly transcript-to-gene ratios have been suggested to provide a measure for reaction rates but a relationship with rates currently lacks validation.<br>We applied an enzyme-based reactive transport model for denitrification and aerobic respiration at the river-groundwater interface to simulate the temporal and spatial patterns of transcripts, enzymes and biomass under diurnal dissolved oxygen fluctuations.<br>Our analysis showed that transcript concentrations of denitrification genes exhibit considerable diurnal fluctuations, whereas enzyme concentrations and biomass are stable over time. The daily fluctuations in denitrification rates yielded a poor correlation between rates and transcript and enzyme concentrations. Daily averaged reaction rates, however, show a close-to-linear relationship with enzyme concentrations and mean transcript concentrations.<br>Our findings suggest that, under dynamic environmental conditions, single-event sampling may result in the misinterpretation of biomelucular quantities as these relate to reaction rates. A better representation of rates can be achieved via sampling that captures the temporal variability of a particular system.</p>

Growth and yield of okra (Abelmoschus esculentus (L.) Moench) grown in the marginal upland area of Sta. Rita, Samar as influenced by different planting densities and mulching materials

2017 ◽  
pp. 44-54
Author(s):  
Zenaida Gonzaga ◽  
Warren Obeda ◽  
Ana Linda Gorme ◽  
Jessie Rom ◽  
Oscar Abrantes ◽  
...  
Keyword(s):  
Bare Soil ◽  
Abelmoschus Esculentus ◽  
Growth And Yield ◽  
Planting Density ◽  
Rice Hull ◽  
Plastic Mulch ◽  
Lady’S Finger ◽  
Materials Used ◽  
Set Up ◽  
A Minor

Okra or Lady’s finger, botanically known as Abelmoschus esculentus (L.) Moench, is a tropical and sub-tropical indigenous vegetable crop commonly grown for its fibrous, slimy, and nutritious fruits and consumed by all classes of population. It has also several medicinal and economic values. Despite its many uses and potential value, its importance is under estimated, under-utilized, and considered a minor crop and little attention was paid to its improvement. The study was conducted to evaluate the effects of different planting densities and mulching materials on the growth and yield of okra grown in slightly sloping area in the marginal uplands in Sta. Rita, Samar, Philippines. A split-plot experiment was set up with planting density as main plot and the different mulching materials as the sub-plot which were: unmulched or bare soil, rice straw, rice hull, hagonoy and plastic mulch. Planting density did not significantly affect the growth and yield of okra. Regardless ofthe mulching materials used, mulched plants were taller and yielded higher compared to unmulched plants. Moreover, the use of plastic mulch resulted to the highest total fruit yield. The results indicate the potential of mulching in increasing yield and thus profitability of okra production under marginal upland conditions.

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