Lagrangian simulation of mixing and reactions in complex geochemical systems. Issue 4 (24th April 2017)

• Record Type: Journal Article
• Authors: Engdahl, Nicholas B.; Benson, David A.; Bolster, Diogo
• Is Part Of: Water resources research. Volume 53:Issue 4(2017)
• Page Start: 3513
• Page End: 3522
• Publication Date: 2017-04-24
• Subjects: particle tracking -- chemical reactions -- PhreeqcRM -- Lagrangian simulation; Hydrology -- Periodicals; 333.91
• DOI: 10.1002/2017WR020362
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Simulations of detailed geochemical systems have traditionally been restricted to Eulerian reactive transport algorithms. This note introduces a Lagrangian method for modeling multicomponent reaction systems. The approach uses standard random walk‐based methods for the particle motion steps but allows the particles to interact with each other by exchanging mass of their various chemical species. The colocation density of each particle pair is used to calculate the mass transfer rate, which creates a local disequilibrium that is then relaxed back toward equilibrium using the reaction engine PhreeqcRM. The mass exchange is the only step where the particles interact and the remaining transport and reaction steps are entirely independent for each particle. Several validation examples are presented, which reproduce well‐known analytical solutions. These are followed by two demonstration examples of a competitive decay chain and an acid‐mine drainage system. The source code, entitled Complex Reaction on Particles (CRP), and files needed to run these examples are hosted openly on GitHub (https://github.com/nbengdahl/CRP ), so as to enable interested readers to readily apply this approach with minimal modifications. Key Points: A Lagrangian method for simulating complex, multistep reaction systems is introduced The approach couples random walk particle tracking with the PhreeqcRM reaction engine The source code is provided openly on GitHub along with self‐contained examples