Decades of widespread use of poly- and perfluoroalkyl substances (PFAS) globally and in Ireland has raised concerns about potential legacy environmental contamination and their impact on human health. PFAS can enter the environment during manufacturing of the substances, the use of the substances themselves and through disposal. The persistence, bioaccumulation, toxicity and long-range transportation of PFAS compounds has meant that it is ubiquitous in the environment and been detected globally in several sample types (soil, air, biota and water). Recent research in Ireland has indicated the presence of PFASs in a variety of media, including surface water. Therefore, the main objective of this work was to characterise exposure risks to the environment and human health, sampling surface water from 20 sites along the river Liffey, between a tributary in County Kildare to the sea. It was found that concentrations of up to 2 µg/L of individual PFAS compounds were detected along the river, with highest concentrations towards the sea. To interpolate the nature and distribution of PFAS compounds along the river and identify potential links to upgradient civil, anthropogenic and industrial sources, a 4-step hierarchical process was used. 1. Geographical proximity - The River Liffey flows through the centre of Dublin, Ireland and is known to have legacy contamination associated with civil, anthropogenic and industry procedures. Known primary and secondary sources of PFASs in the catchment of the river Liffey include civil (airports and fire stations), anthropogenic (wastewater treatment facilities and waste facilities) and industrial pressures (chemical manufacturing plants, paper and wood processing facilities and other industries with emissions licences). 2. Chemical footprint - Nowadays, there are 4700 identifiable PFAS compounds. Individual compounds have unique properties and different combinations are used by industries for specific purposes. By identifying unique compounds and distinguishable compound rations, a specific diffuse PFAS source can be inferred. 3. Dimensional calculation – A solute transport model was employed to predict the spatio-temporal fate of PFAS and infer proximity to industrial sources. 4. Dimensional modelling and cluster analysis was employed to refine the source identification. In conclusion, with the data obtained the occurrence of different PFAS substances were linked to potential civil, anthropogenic and industrial sources in the river Liffey catchment, remarking the effect of the emission not only in the near environment but also in a further one, like river Liffey.