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

Poly- and perfluoroalkyl substances (PFAS) are over 4,000 synthetic compounds characterized 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 analyzed PFAS contamination in the Veneto Plain (Northeastern Italy). This was achieved by integrating concentration ratios; ternary diagrams; scatterplots; compositional principal component analysis (PCA); and Red, Green, and Blue (RGB) encoding across 511 groundwater sampling points categorized 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 (perfluorooctanoic acid [PFOA] up to 1,240 ng/L; perfluorooctanesulfonic acid [PFOS] 120 ng/L; perfluorohexane sulfonic acid [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 scatterplot analyses suggested a dual-source influence, from local facility emissions superimposed onto the distal former industrial site plume. Three other groups (downstream, in the eastern and western sector of a tanning district, respectively) exhibited heterogeneous PFAS signatures (PFOS up to 83 ng/L; perfluorobutanesulfonic acid [PFBS] 45 ng/L), reflecting mixed industrial activities including tanning, metal finishing, and concrete production. Principal component analysis dispersion and geochemical fingerprints highlighted a significant groundwater mixing for these groups. Finally, the last well group (near a landfill) showed lower PFAS concentrations (perfluorohexanoic acid [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 analyzed 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.