Modeling multicomponent ionic transport in groundwater with IPhreeqc coupling: Electrostatic interactions and geochemical reactions in homogeneous and heterogeneous domains

Abstract

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Mixing and Reactive Fronts in the Subsurface

“…Reactive transport simulators (Steefel et al 2015) are instrumental to study mixing processes in the subsurface. Advanced multiscale modeling tools (Molins 20XX,this volume) are needed to integrate the effects of physical, chemical, biological and electrostatic interactions (e.g., Thullner et al 2005;Appelo and Rolle 2010;Tournassat and Steefel 2015;Rasouli et al 2015;Muniruzzaman and Rolle 2016), to quantify mixing and mixing-controlled reactions at different scales using pore, continuum and hybrid approaches (e.g., Battiato and Tartakovsky 2011;Scheibe et al 2015), and to describe reactive transport processes across different environmental compartments and critical zones (e.g., Li et al 2017).…”

Quantifying Geochemical Processes of Arsenic Mobility in Groundwater From an Inland Basin Using a Reactive Transport Model

“…Individual SCMs were developed to model As (III) and As(V) adsorption, separately, with adsorption sites of Surf_a for As (III) adsorption onto gray sediments and Surf_b for As(V) adsorption onto brown sediments. The models were developed using the geochemical codes of PHREEQC-3 (Parkhurst & Appelo, 2013), coupled with MATLAB software using the Iphreeqc module (Charlton & Parkhurst, 2011;Muniruzzaman & Rolle, 2016;Stolze et al, 2019) and the wateq4f.dat database (Ball & Nordstrom, 1991). A genetic algorithm calibration code was linked with Iphreeqc by MATLAB to estimate the parameters of the SCMs, including the equilibrium constants of each surface complexation reaction (log K) and the number of surface sites (m).…”

Multicomponent Ionic Transport Modeling in Physically and Electrostatically Heterogeneous Porous Media With PhreeqcRM Coupling for Geochemical Reactions

“…where θ (−) is the total porosity, f FW , f DL , and f IL (−) represent the fractions of the total porosity occupied by the free, Donnan and IL water respectively, t (s) is time, q (m/s) is the specific discharge vector, (mol/m 2 /s) is the vector of total fluxes in all porosities, R r (mol/m 2 /s) is the reactive source/sink term, and υ ir (−) is the stoichiometric coefficient of species i for r‐ th reaction. In presence of advection in free porosity, the entries of are derived following the approach formally equivalent to equations , , and – but replacing the self‐diffusion coefficients by the hydrodynamic dispersion coefficients for free porewater and pore‐diffusion coefficients for Donnan and interlayer porosities (e.g., Appelo et al, ; Muniruzzaman & Rolle, ; Rolle et al, ). Furthermore, these flux components can also be expressed only in terms of FW concentrations ( c i ) by using the constitutive relationships in equations and .…”