Transport in porous media is relevant in many environmental and technical applications. Mass transfer rates in multiphase systems are controlled by the spatial extent and accessibility ofinterfaces and their properties. Using microfluidic channels and advanced experimental techniques, it is now possible to measure the fluid flow and mass transfer rates at these interfacesdirectly. Thus, it is possible to progress from lumped effective mass transfer rates to single interface kinetics. Joining experimental and numerical expertise this proposal quantifies the effect of the Marangoni convection on the mass transfer rates at interfaces between a nonaqueous liquid and water with high temporal and spatial resolution. The results of this project will foster the understanding of subsurface transport, especially in the vadoze zone.