The United States Environmental Protection Agency (US EPA)1 has published guidelines for managers of hazardous sites on the use of compound specific isotope analysis (CSIA) for source identification and assessment of biodegradation representing the culmination of over a decade of advancements in stable isotope analysis of environmental contaminants, and introduced CSIA has an accepted and necessary approach in environmental forensics. The classical approach to source apportionment in forensic investigation of organic contaminants is a tiered approach using gas chromatography-flame ionisation detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS) for chemical fingerprinting and quantification followed by multivariate or statistical analysis.2 CSIA is used to complement this approach in cases where the chemical fingerprints of samples of different origins appeared very similar because of a limited range of boiling points3 or where the weathering processes such as volatilisation, sorption or biodegradation had affected the chemical fingerprint to such an extent that it limited the relationship with the original contaminant.3"5 In particular, the carbon stable isotopic signature of polyaromatic hydrocarbons (PAHs) and alkanes appeared little affected by weathering and thus have been successfully employed for source apportionment.4"7
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