Isotopic and Molecular Fingerprinting of Petroleum Hydrocarbon Sources in the Groundwater of Oil-Producing Communities in Akwa Ibom State: An Original Forensic Chemistry Approach

Groundwater contamination in oil-producing communities is often attributed to multiple sources including pipeline leaks, surface spill infiltration, and legacy contamination, yet distinguishing source contributions for legal and remediation purposes requires rigorous forensic chemistry methods. This dissertation develops and applies an original forensic chemistry approach combining compound-specific stable carbon and hydrogen isotope ratio analysis with petroleum molecular fingerprinting for source attribution of groundwater hydrocarbon contamination in six communities in Akwa Ibom State, South South Nigeria. Dissolved hydrocarbons were extracted from groundwater by closed-loop stripping analysis and purge-and-trap methods. A reference library of isotopic and molecular fingerprints was constructed for ten crude oil grades, refined products, and process chemicals used by operating facilities in the study area. Target analytes include resolved and unresolved complex mixtures of alkanes, polycyclic aromatic hydrocarbons, and biomarker compounds including steranes and triterpanes. Isotope ratio mass spectrometry was used for compound-specific delta-13C and delta-D measurements. Multivariate source apportionment combined non-negative matrix factorisation with Bayesian mixing models. Results unambiguously attributed groundwater contamination in four of six communities to crude oil from a single pipeline corridor, while two communities showed contributions from a mixture of crude oil and aged refined product consistent with historical spill legacy. The developed isotopic-molecular fingerprinting protocol provides an original, scientifically defensible forensic chemistry methodology with direct applicability to oil spill litigation and remediation accountability in the Niger Delta context. Keywords: petroleum forensics, isotope fingerprinting, groundwater contamination, Akwa Ibom, source apportionment