Identifying PFAS sources using groundwater fingerprints in the Veneto Plain (Italy)

Poly- and perfluoroalkyl substances (PFAS) are over 4,000 synthetic compounds characterised by high chemical stability and environmental persistence. Building on data from the Forever Pollution Project, which mapped the extent of PFAS contamination across Europe, this study analysed PFAS contamination in the Veneto Plain (NE Italy). This was achieved by integrating concentration ratios, ternary diagrams, scatter plots, compositional principal component analysis (PCA), and RGB encoding across 511 groundwater sampling points categorised into seven distinct well groups. One group (contamination plume from a former industrial site near Vicenza that produced PFAS until 2018), exhibited the highest PFAS concentrations (PFOA up to 1,240 ng/L; PFOS 120 ng/L; PFHxS 84 ng/L), with tight clustering in PCA score space, indicating a dominant single-source industrial release. Two additional groups (250-300 meters east and immediately adjacent to a chemical-pharmaceutical facility, respectively) recorded intermediate PFOA concentrations (80-320 ng/L). Combined ternary and scatter plot analyses suggested a dual-source influence, from local facility emissions superimposed onto the distal former industrial site plume. Other three groups (downstream, in the eastern and western sector of a tanning district, respectively) exhibited heterogeneous PFAS signatures (PFOS up to 83 ng/L; PFBS 45 ng/L), reflecting mixed industrial activities including tanning, metal finishing, and concrete production. PCA dispersion and geochemical fingerprints highlighted a significant groundwater mixing for these groups. Finally, the last well group (near a landfill) showed lower PFAS concentrations (PFHxA up to 56 ng/L) and a distinct PFAS signature linked to leaching of aged municipal waste. The integrated forensic methodology distinguished discrete and mixed contamination sources, highlighting the value of compositional and spatial representation of analysed PFAS in groundwater. By enabling more precise identification of contamination sources, this approach supports the application of the 'Polluter Pays Principle', informs policy decisions and guides land management strategies for the remediation of affected areas.