Within hours of discovering a capsized ship off the coast of Tobago, leaking what appeared to be a thick, black oil-like substance, samples were sent from Tobago to the Institute of Marine Affairs in Trinidad for “fingerprinting.” This integral process may hold the clues needed to identify the origins of a vessel that, for a large part, still remains shrouded in mystery.
What is fingerprinting?
Because many different types of oil exist, officials may need to tell one oil from another during a spill. The chemical composition of oil found in the environment yields important clues about its origin. This process of determining where a sample of oil (or hydrocarbon residue) originated is what we call “fingerprinting.”
According to the U.S.-based Office of Response and Restoration within the National Oceanic and Atmospheric Administration, fingerprinting oil to discover its source is a complex procedure that has both qualitative and quantitative components. Virtually all oils contain the same hydrocarbon structures, but the relative quantities of these structures depend on the source of the oil.
As a result, oil fingerprinting relies on the expertise and experience of an analytical chemist, who compares the relative quantities of hydrocarbons unique to petroleum in the spilt oil versus the source oil.
How does fingerprinting oil work?
Like human “fingerprints”, in which the differences in patterns of our fingers can be used to distinguish one person from another, the differences in the pattern of oil composition can distinguish one oil from another.
This is done by first collecting a sample and separating it into various fractions. Each fraction is analysed using instruments to give “printouts” of their chemical compositions. The “printouts” are in the form of graphs called “chromatograms,” which are then interpreted by chemists. One technique that is used to create the chromatograms is called Gas Chromatography-Mass Spectrometry (GC-MS). GC-MS is the most reliable method to fingerprint an oil sample since it uses a multi-parameter approach in which individual compounds present in a sample are identified.
This process also has to take into consideration the effect of weathering on these relative quantities; therefore, chemists refer most often to hydrocarbon ratios resistant to the changes that occur during weathering.
Similar to the literal uses of fingerprinting, experienced chemists can analyze the evidence left at a “crime scene” (site of an oil spill) to make a reasonable determination of “whodunit”—that is, if a hydrocarbon residue is, in fact, oil, where it might have originated, and, hopefully, who spilt it.
In cases where the source is of an unknown origin, it is important that Trinidad and Tobago build an extensive database of oils that are either produced locally or crude oils that may be imported or shipped through our waters to assist in determining the identification of oils when spills occur.
Institute of Marine Affairs, March 2012
The “lead investigator” – T&T’s Institute of Marine Affairs
The Institute of Marine Affairs’s (IMA) Marine Chemistry Department has conducted several oil fingerprinting exercises over the last two decades. However, fingerprinting alone isn’t a silver bullet in finding the culprits who pollute T&T’s land and water.
At the IMA, a fingerprinting database is maintained, with some components still to be developed as of December 2020. The database is a centralized national archive used in oil comparisons for matching purposes and in identifying the Responsible Party (Polluter) for probable prosecution. When the source is still unknown, unlike the Tobago Oil Spill, fingerprinting is used with other techniques like aerial surveillance and oil trajectory modelling.
In the case of the Tobago Oil Spill, fingerprinting may give clues into whether the thick, black oily substance is, in fact, crude oil and clues to the origin of the oil and the mystery boat. The samples were collected on the first day of the spill and, according to the Tobago House of Assembly Chief Secretary Farley Augustine, were sent to Trinidad for testing within the first 24 hours of the oil-like substance reaching Tobago’s shores.
