Perfluoroalkyl substances (PFASs) are stable compounds and commercially desirable. They are widely used, for example, as surfactants in textile and paper products and in aqueous fire fighting foams. PFASs have received increasing public attention due to their persistency and bioaccumulative and toxic potential. The present proposal aims to use neutron reflection to investigate the adsorption of two perfluoroalkyl substances to an alumina/water interface. This interface can be used as a model for mineral soil material. The use of one of these PFASs has been banned, but due to its persistence it will remain an environmental pollutant for many decades to come. Contrary, no regulatory measures are in force for the other one, and it is presently in use in industrial processes.