Internal Research Project I-04

January 2021 - December 2021

Stable water isotopologues can be used to investigate soil-water evaporation as
evaporation leads to an enrichment of heavier isotopologues at the evaporation
surface. This enrichment or fractionation is a function of equilibrium
fractionation and a fractionation that is related to isotope dependent transport
rates, i.e. a kinetic fractionation. Since the isotope concentration profiles in the
soil are sensitive to the kinetic fractionation, an understanding of this fractionation
factor is needed when isotope concentration profiles are used to estimate
evaporation rates.
This projects aims to describe kinetic and equilibrium fractionation with the
help of the involved physical processes by resolving both domains, the porous
medium and the free flow, and coupling them with suitable coupling conditions
to describe the transport of the isotopologues from the soil into the atmosphere.
This is especially helpful when investigating non-planar surface topologies and turbulent transport behaviour, which cannot easily be incorporated into existing models for the kinetic fractionation factor. With this detailed study, the major influences on isotope fractionation can be analysed. This is helpful to develop new formulations for fractionation factors which can be used land surface models.