Modeling Solute and Contaminant Transport in Permafrost Regions

Subarctic and Arctic regions are experiencing rapid warming that is accelerating permafrost thaw and altering groundwater systems, with implications for the transport of solutes, including contaminants. Simulating these processes requires numerical tools that couple water, energy, and solute transport under dynamic freeze–thaw and variably saturated conditions. We present SUTRA-solice, a new version of the USGS SUTRA code developed to simulate variably saturated groundwater flow, advective–conductive heat transport with phase change, and reactive transport of multiple solute species. SUTRA-solice integrates the multi-species solute transport capabilities of SUTRA-MS with the phase-change energy transport framework of SUTRA 4.0, and adds functionality to represent temperature- and saturation-dependent reaction rates. We illustrate the application of SUTRA-solice by exploring contaminant transport in a continuous permafrost setting under warming conditions. Results show that increased seasonal thaw depth and duration enhance groundwater flow and increase solute mobility and transformation, particularly for weakly sorbing species. These results demonstrate the flexibility of SUTRA-solice for investigating solute dynamics in cryohydrogeologic systems. Continued development and testing of the model against field data will lead to improved understanding of climate-driven feedbacks and inform water management in permafrost  environments.