Coupling soil/atmosphere interactions and geochemical reactions

    Activity: Talks and presentationsConference presentations


    The exchange of mass, momentum and energy across the subsurface/atmosphere interface influences a wide range of biogeochemical processes that are critical for water quality in the subsurface and for greenhouse gas emissions to the atmosphere. Soil water evaporation under dynamic forcing (e.g., wind flow) in the atmospheric compartment is an important example of such interchange processes [1]. Evaporation from soil surface influences the migration of important gas components (e.g., O2 and CO2) and can impact geochemical reactions (e.g., dissolution of minerals) in the subsurface porous media by controlling fluid phase distribution in the pore space. Dynamic atmospheric forcing results in a number of intertwined phenomena such as fluid(s) phase flow, heat transport, multicomponent transport within and across the fluid(s) phases, and geochemical reactions in coupled atmosphere/subsurface systems.
    We developed a new modeling tool capable of simulating non-isothermal multiphase flow and multicomponent reactive transport in porous media and to explicitly incorporate the effects of exchange processes at the soil/atmosphere interface on the dynamics of physical and reactive processes in porous media. The modeling approach is based on a coupled porous medium/free flow domain in which Navier-Stokes equation is used to describe single-phase (gaseous) flow in the free-flow subdomain and Darcy’s law is applied for two-phase flow in the porous medium subdomain (i.e., two-domain approach). In the proposed modeling tool, the simulation of the interplay between multi-physical processes (i.e., flow, mass and heat transport) in the coupled compartments and geochemical reactions in the porous medium is performed by coupling the PDE solver COMSOL Multiphysics and the geochemical code PhreeqcRM [2].
    We tested the key features of the proposed model in a set of benchmark examples by comparing the simulation outcomes with the geochemical code MIN3P and with the solution of a non-isothermal multiphase and multicomponent problem [3, 4]. We successively presented two application examples to explore conservative and reactive transport of gas components in a coupled porous medium/free flow domain in the absence and presence of geochemical reactions. The results show that the exchange processes between the compartments control the gas migration behaviour, the location of reactive zones and the extent of mineral reactions (i.e., pyrite oxidation and calcite dissolution) by changing the spatiotemporal distribution of fluid phases and enhancing the interphase mass transfer of key gas components such as oxygen and carbon dioxide.
    Period21 Jun 2022
    Event titleXXIV International Conference on Computational Methods in Water Resources
    Event typeConference
    Conference number24
    LocationGdansk, PolandShow on map
    Degree of RecognitionInternational