Evaporation and condensation in bare soils govern water and energy fluxes between the land and atmosphere. Phase change between liquid water and water vapor is commonly evaluated in soil hydrology using an assumption of instantaneous phase change (i.e., chemical equilibrium). Past experimental studies have shown that finite volatilization and condensation times can be observed under certain environmental conditions, thereby questioning the validity of this assumption. A comparison between equilibrium and nonequilibrium phase change modeling approaches showed that the latter is able to provide better estimates of evaporation, justifying the need for more research on this topic. Several formulations based on irreversible thermodynamics, first-order reaction kinetics, or the kinetic theory of gases have been employed to describe nonequilibrium phase change at the continuum scale. In this study, results from a fully coupled nonisothermal heat and mass transfer model applying four different nonequilibrium phase change formulations were compared with experimental data generated under different initial and boundary conditions. Results from a modified Hertz-Knudsen formulation based on kinetic theory of gases, proposed herein, were consistently in best agreement in terms of preserving both magnitude and trends of experimental data under all environmental conditions analyzed. Simulation results showed that temperature-dependent formulations generally better predict evaporation than formulations independent of temperature. Analysis of vapor concentrations within the porous media showed that conditions were not at equilibrium under the experimental conditions tested.

Natural fissures/faults or pressure‐induced fractures in the caprock confining injected CO2 have been identified as a potential leakage pathways of far‐field native brine contaminating underground sources of drinking water. Developing models to simulate brine propagation through the overlaying formations and aquifers is essential to conduct reliable pre‐ and post‐risk assessments for site selection and operation, respectively. One of the primary challenges of performing such simulations is lack of adequate information about source conditions, such as hydro‐structural properties of caprock fracture/fault zone and the permeability field of the storage formation. This research investigates the impact of source condition uncertainties on the accuracy of leaking brine plume predictions. Prediction models should be able to simulate brine leakage and transport in complex multilayered geologic systems with interacting regional natural and leakage flows. As field datasets are not readily available for model testing and validation, three comprehensive intermediate‐scale laboratory experiments were used to generate high‐resolution spatiotemporal data on brine plume development under different leakage scenarios. Experimental data were used to validate a flow and transport model developed using existing code FEFLOW to simulate brine plume under varying source conditions. Spatial moment analysis was conducted to evaluate how uncertainty in source conditions impacts brine migration predictions. Results showed that inaccurately prescribing the permeability field of storage formation and caprock fractures in models can cause errors in leakage pathway and spread predictions up to ∼19% and ∼100%, respectively. These findings will help in selecting and characterizing storage sites by factoring in potential risks to shallow groundwater resources.

At the fundamental process level, many of the concepts that form the foundation of our understanding of bare‐soil evaporation dynamics have advanced little since their initial formation. This investigation explores experimental scaling issues that should be considered during the study of bare‐soil evaporation dynamics under conditions of sustained above‐ground airflow. Results are presented from a series of large‐scale laboratory experiments conducted for various soil conditions (i.e., heterogeneity and surface roughness). Fundamental experimental research of this nature is not feasible in the field or small laboratory columns that are limited by system control and scale. All experimentation was therefore conducted in a test facility that couples a climate‐controlled, low‐speed wind tunnel with a 7.15‐m‐long soil tank—allowing for control over soil properties and initial and boundary conditions. Measured flow phenomena supported, and agreed well with, existing wind tunnel and field study literature. These data were in turn, used to explain observed evaporative water loss and soil moisture distribution spatiotemporal trends and patterns. Results demonstrated that relatively large length scales are required for the impacts of atmospheric feedbacks on the subsurface hydrodynamics to manifest themselves and become quantifiable. Airflow had the greatest impact in the case of a flat homogeneous soil; the strength of this feedback was significantly weaker in the presence of soil heterogeneities and surface undulations that were dominated by other transport phenomena. Comparison of these results with those of past studies furthermore cautions against the use of column scale data to make generalizations about bare‐soil evaporation dynamic upscaling.