Stable water isotopologues tend to fractionate from ordinary water
during evaporation processes resulting in an enrichment of the isotopic
species in the soil. The fractionation process can be split into
equilibrium fractionation and kinetic fractionation. Due to the complex
coupled processes involved in simulating soil-water evaporation
accurately, defining the kinetic fractionation correctly remains an open
research area. In this work, we present a multi-phase multi-component
transport model that resolves flow through both the near surface
atmosphere and the soil, and models transport and fractionation of the
stable water isotopologues using the numerical simulation environment
DuMuX. Using this high resolution coupled model, we simulate transport
and fractionation processes of stable water isotopologues in soils and
the atmosphere without further parameterization of the kinetic
fractionation process as is commonly done. In a series of examples, the
transport and distribution of stable-water isotopologues are evaluated
numerically with varied conditions and assumptions. First, an
unsaturated porous medium connected to constant laminar flow conditions
is introduced. The expected vertical isotope profiles in the soil as
described in literature are reproduced. Further, by examining the
spatial and temporal distribution of the isotopic composition, is
determined the enrichment of the isotopologues in soil is linked with
the different stages of the evaporation process. Building on these
results, the robustness of the isotopic fractionation in our model is
analysed by isolating single fractionation parameters. The effect of
wind velocity and turbulent atmospheric conditions is investigated,
leading to different kinetic fractionation scenarios and varied isotopic
compositions in the soil.