In the soil environment, organic matter such as humic acid has a strong influence on the behaviour of organic pollutants such as perfluoroalkyl substances (PFASs) and their interactions with other soil constituents such as mineral surfaces. As it is common that mineral surfaces in soils have a coating of organic material, the behaviour of this type of system and its role for sorption of organic contaminants warrants further investigation. Humic acids are one of the main components of organic matter found in soils. In the proposed neutron experiment, we aim to study the behaviour of humic acid at an alumina (Al2O3)/water interface, and investigate how PFASs sorb onto this model soil system.