Identify the likely sources of polycyclic aromatic hydrocarbon (PAH) contamination in soil samples using diagnostic isomer ratios. The tool generates three double ratio plots based on the widely cited framework from Yunker et al. (2002) and Costa & Sauer (2005), helping distinguish between petrogenic (petroleum-derived) and pyrogenic (combustion-derived) sources.
Each plot shows source attribution zones so you can visually assess whether your data clusters in petrogenic, petroleum combustion, or grass/coal/wood combustion regions.
Enter PAH concentrations — input concentrations (mg/kg) for the eight required PAH compounds: Fluoranthene, Pyrene, Anthracene, Phenanthrene, Indeno[1,2,3-cd]pyrene, Benzo[ghi]perylene, Benz[a]anthracene, and Chrysene. Add more samples with the + button.Review calculated ratios — four diagnostic ratios are calculated automatically and shown in a summary table.Interpret the plots — data points appear on three double ratio charts with colour-coded source zones. Hover over any point for details.Export or share — download a plot as SVG for reports, or share the ratio summary.Diagnostic ratios and threshold values follow Yunker et al. (2002) as summarised by Tobiszewski & Namiesnik (2012).
Diagnostic ratios
Fl/(Fl+Py) — <0.4 petrogenic, 0.4–0.5 petroleum combustion, >0.5 grass/coal/wood combustion.An/(An+Phe) — <0.1 petrogenic, >0.1 pyrogenic.IP/(IP+BghiP) — <0.2 petrogenic, 0.2–0.5 petroleum combustion, >0.5 grass/coal/wood combustion.BaA/(BaA+Chr) — <0.2 petrogenic, 0.2–0.35 mixed, >0.35 pyrogenic/combustion.Important caveats
The An/(An+Phe) and BaA/(BaA+Chr) ratios are more sensitive to weathering, biodegradation, and photolysis and may shift over time in the environment. The Fl/(Fl+Py) and IP/(IP+BghiP) ratios are more conservative and less affected by environmental alteration (Tobiszewski & Namiesnik 2012). Multiple ratios should always be used together rather than relying on a single ratio. Contradictory results may indicate mixed contamination from different sources. PAH ratio analysis is an indicative screening tool only. Results should be interpreted alongside site history, conceptual site model, and professional judgement. Limitations Diagnostic ratios are empirical indicators, not definitive source identifiers. Mixed sources, weathering, and biodegradation can shift ratios and make interpretation ambiguous.
The Yunker et al. (2002) thresholds were derived primarily from sediment and atmospheric samples. Applicability to heavily contaminated brownfield soils should be considered with caution.
PAH ratios require concentrations above the limit of detection for both isomers in each pair. Ratios calculated from near-LOD values are unreliable.
Revision history 27 October 2026: Content update and publish
Disclaimer This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.
Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.
All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.
By using this tool, you accept full responsibility for how you interpret and apply the information provided.
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