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.

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.

Analog Computation of Forms of Americium Presence in Aqueous Solution

2012 ◽  
Vol 549 ◽  
pp. 500-503
Author(s):  
Jie Hong Lei
Keyword(s):  
Aqueous Solution ◽  
Chemical Composition ◽  
Influencing Factors ◽  
Ph Value ◽  
Safety Evaluation ◽  
Chemical Components ◽  
Migration Behavior ◽  
Analog Computation ◽  
Geological Disposal ◽  
Geochemical Model

In geological disposal of radioactive wastes, the study of Americium migration is very important for the safety evaluation of the repository. The forms of chemical components of Americium presence in aqueous solution that directly affect its migration behavior provide a basis for analog computation of the element. This paper uses PHREEQC, the geochemical model, for analog computation of forms of Americium presence in two types of groundwater, and analyzes the morphologies of the main elements and the influencing factors. The results show that the morphology of Americium is mainly controlled by the characteristics of the chemical composition of groundwater, while the PH value also has a great impact on the forms of Americium presence.

scholarly journals Comparison between simulated and observed chemical composition of fine aerosols in Paris (France) during springtime: contribution of regional versus continental emissions

2010 ◽  
Vol 10 (24) ◽  
pp. 11987-12004 ◽  
Author(s):  
J. Sciare ◽  
O. d'Argouges ◽  
Q. J. Zhang ◽  
R. Sarda-Estève ◽  
C. Gaimoz ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Secondary Organic Aerosols ◽  
Transport Model ◽  
Organic Aerosols ◽  
Carbonaceous Material ◽  
Chemical Components ◽  
Carbonaceous Aerosols ◽  
Time Resolved ◽  
Air Masses ◽  
North Western

Abstract. Hourly concentrations of inorganic salts (ions) and carbonaceous material in fine aerosols (aerodynamic diameter, A.D. <2.5 μm) have been determined experimentally from fast measurements performed for a 3-week period in spring 2007 in Paris (France). The sum of these two chemical components (ions and carbonaceous aerosols) has shown to account for most of the fine aerosol mass (PM2.5). This time-resolved dataset allowed investigating the factors controlling the levels of PM2.5 in Paris and showed that polluted periods with PM2.5 > 15 μg m−3 were characterized by air masses of continental (North-Western Europe) origin and chemical composition made by 75% of ions. By contrast, periods with clean marine air masses have shown the lowest PM2.5 concentrations (typically of about 10 μg m−3); carbonaceous aerosols contributing for most of this mass (typically 75%). In order to better discriminate between local and continental contributions to the observed chemical composition and concentrations of PM2.5 over Paris, a comparative study was performed between this time-resolved dataset and the outputs of a chemistry transport model (CHIMERE), showing a relatively good capability of the model to reproduce the time-limited intense maxima observed in the field for PM2.5 and ion species. Different model scenarios were then investigated switching off local and European (North-Western and Central) emissions. Results of these scenarios have clearly shown that most of the ions observed over Paris during polluted periods, were either transported or formed in-situ from gas precursors transported from Northern Europe. On the opposite, long-range transport from Europe appeared to weakly contribute to the levels of carbonaceous aerosols observed over Paris. The model failed to properly account for the concentration levels and variability of secondary organic aerosols (SOA) determined experimentally by the EC-tracer method. The abundance of SOA (relatively to organic aerosol, OA) was as much as 75%, showing a weak dependence on air masses origin. Elevated SOA/OA ratios were also observed for air masses having residence time above ground of less than 10 h, suggesting intense emissions and/or photochemical processes leading to rapid formation of secondary organic aerosols.

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.

CHEMICAL COMPOSITION AND SENSORY QUALITY OF SWEETPOTATO CRISPS AS AFFECTED BY VARIETY AND FRYING CONDITIONS

2017 ◽  
Vol 15 (1) ◽  
pp. 108-121
Author(s):  
G O OLATUNDE ◽  
B O OGUNYINKA ◽  
M E ASHIMI ◽  
A G TAIWO
Keyword(s):  
Chemical Composition ◽  
Sensory Quality ◽  
Total Sugar ◽  
Chemical Components ◽  
Frying Time ◽  
Standard Methods ◽  
Overall Acceptability ◽  
Peroxide Values ◽  
The Individual

The effect of frying temperatures ranging from 150-180 °C and frying time of 3-12 mins on the compo-sition and sensory quality of sweetpotato crisps from white-fleshed and yellow-fleshed varieties were investigated in this study. Chemical composition, sensory properties and overall acceptability of the crisps were determined using standard methods. Results obtained showed moisture content (2.37-7.50%), fat (9.77-16.22%), total sugar (1.52-4.44%), carotenoids (31.65-55.29 μg/100 g), free fatty acid (0.11-0.44%) and peroxide values (2.95-12.30 mEq/kg). Each of the chemical components and sensory attributes of the crisps were significantly (p<0.001) affected by the individual and combined effects of variety, frying temperatures and frying duration (time) in minutes. The highest overall accept-ability scores were 8.46 for yellow-fleshed crisps fried at 170 °C/5 min and 7.84 for white-fleshed crisps fried at 180 °C/5 min.

Analog Computation of Forms of Uranium Presence in Aqueous Solution

2012 ◽  
Vol 463-464 ◽  
pp. 12-15
Author(s):  
Jie Hong Lei
Keyword(s):  
Aqueous Solution ◽  
Chemical Composition ◽  
Ph Value ◽  
Safety Evaluation ◽  
Chemical Components ◽  
Migration Behavior ◽  
Analog Computation ◽  
Geological Disposal ◽  
Geochemical Model ◽  
Uranium Migration

In geological disposal of radioactive wastes, the study of uranium migration is very important for the safety evaluation of the repository. The forms of chemical components of uranium presence in aqueous solution that directly affect its migration behavior provide a basis for analog computation of the element. This paper uses PHREEQC, the geochemical model, for analog computation of forms of uranium presence in two types of groundwater, and analyzes the morphologies of the main elements and the influencing factors. The results show that the morphology of uranium is mainly controlled by the characteristics of the chemical composition of groundwater, while the PH value also has a great impact on the forms of uranium presence.

scholarly journals Reactive transport of chemicals in unsaturated soils: numerical model development and verification

2016 ◽  
Vol 53 (1) ◽  
pp. 162-172 ◽  
Author(s):  
Majid Sedighi ◽  
Hywel R. Thomas ◽  
Philip J. Vardon
Keyword(s):  
Numerical Model ◽  
Unsaturated Soils ◽  
Reactive Transport ◽  
Transport Model ◽  
Model Development ◽  
Chemical Diffusion ◽  
New Developments ◽  
Geochemical Model ◽  
Porosity Evolution ◽  
Gas Phases

This paper presents the development of a numerical model for reactive transport of multicomponent chemicals in unsaturated soils. The model has been developed based on a coupled thermal, hydraulic, chemical, and mechanical (THCM) formulation, and extended by the inclusion of geochemical processes under mixed equilibrium and kinetically controlled reactions in–between the solid, aqueous, and gas phases in soil. This has been achieved by coupling the transport model, COMPASS, with the geochemical model, PHREEQC. Key coupling between the geochemical modelling and the flow of chemicals has been established via the inclusion of porosity modification from mineral precipitation–dissolution reactions and the consequential effects on flow processes. Verification of the developed model is addressed via a series of benchmark simulations with a focus on testing the coupling between the transport model and geochemical model. Good results have been achieved for the verification of the theoretical and numerical implementation of the new developments in the model. A simulation is presented to demonstrate the effects of mineral reactions on porosity evolution and chemical diffusion in a low porosity soil. The model developed is an advanced tool for studying the hydrogeochemical processes in unsaturated soils under variable THCM conditions.

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