Middle Distillate Fuel Fingerprinting Using Drimane-Based Bicyclic Sesquiterpanes

Petroleum biomarkers are ubiquitous hydrocarbons that occur in crude oils and are derived from formerly living organisms whose organic materials gave rise to the crude oil over geologic time. Biomarkers' specificity and resistance to weathering renders them useful in chemical fingerprinting of petroleum contamination in the environment. The biomarkers most commonly used in forensic issues, viz., tri- and penta-cyclic triterpanes and regular or rearranged steranes, are too high boiling for use in fingerprinting middle distillate petroleum products. The present article describes a suite of “low boiling” biomarkers (i.e., drimane-based bicyclic sesquiterpanes) that boil within the distillate fuel range (n-C13 to n-C16; ∼ 240°C to 285°C). GC/MS analysis of 24 dispensed (fresh) distillate fuels (Jet A, JP-5, and diesel fuel/fuel oil #2) demonstrate the specificity of sesquiterpane patterns in fuels of different origins. Analysis of fresh diesel fuel #2 and its associated, variably weathered NAPLs demonstrate the stability of the sesquiterpane despite complete biodegradation of n-alkanes. Finally, a case study of a forensic investigation is presented in which the sesquiterpanes are used to further unravel the sources of weathered diesel fuel/fuel oil #2 impacting soils on adjacent properties. Sesquiterpanes were used to demonstrate that the soils from the plaintiff's and defendant's properties contained distinct diesel fuel/fuel oil #2, which implied distinct sources and thereby led to a rapid settlement of the case.