Fingerprinting of dissolved constituents in groundwater at an operating refinery

In traditional petroleum forensic investigations, source identification primarily relies on chemical fingerprinting of oil, whereas groundwater fingerprinting, which focuses on dissolved constituents, remains rarely used despite its potential as an important forensic tool. This study collected 10 floating oil samples, 10 groundwater samples beneath the floating oil, and 11 pure groundwater samples for chemical fingerprint analysis. The results indicated that the chemical compositions of the groundwater beneath the floating oil were predominantly influenced by the high-solubility chemicals present in the floating oil. Notably, even when floating oil samples had significantly different compositions of low-solubility components but similar compositions in high-solubility components, the groundwater samples beneath the floating oil showed similar chemical compositions. This similarity in groundwater composition reflected the resemblance in the soluble fraction of the floating oils and didn't necessarily indicate identical oil sources. Groundwater beneath the floating oil was dominated by aromatics, whereas pure groundwater was dominated by naphthenes and isoparaffins. Correlation analysis revealed a positive correlation in molecular composition between floating oil and the groundwater beneath it. However, no significant correlation was observed between the groundwater beneath the floating oil and the pure groundwater samples. This study demonstrated that fingerprinting of groundwater beneath the floating oil provided useful information for source identification, while the performance of pure groundwater fingerprinting depended on the distance between the sampling location and the source. Only a "nearby" sampling location retained consistent characteristics with the oil source, rendering it suitable for forensic investigations. However, the definition of "nearby" was highly site-specific.