First detailed oil sample analysis completed from Mauritius oil spill
October 30,2020
| Source:
Woods Hole Oceanographic Institution
When the Japanese bulk carrier MV Wakashio struck a coral reef off the coast of Mauritius on July 25, 2020, and began leaking fuel oil two weeks later, local residents and the international community sprang into action to protect the pristine habitats that fringe the Indian Ocean nation. But they did so without insight from careful chemical analysis, which is customary after spills to help guide short and long-term response plans and protects the health of people facing such a spill.
Now the first ultra-high-resolution analysis of an oil sample from Mauritius shows that the material is a complex and unusual mix of hydrocarbons—and even though some of the components in it may have already degraded or evaporated, what remains still gives it the ability to persist in the environment. That is the conclusion of marine oil spill experts Chris Reddy and Bob Nelson at the Woods Hole Oceanographic Institution (WHOI), who are collaborating with Professor Kliti Grice, Director of the Western Australian Organic Isotope Geochemistry Centre (WA-OIGC) and Associate Professor Monique Gagnon and Alan Scarlett at Curtin University in Perth, Australia. Both teams analyzed a sample of floating residue collected August 16. They subjected it to many of the same analytical techniques used to “fingerprint” samples from other large spills around the world.
The two teams use comprehensive two-dimensional gas chromatography (GC×GC), complemented by compound-specific isotope analyses to identify compounds specific to spilled oils. The analyses performed by the two laboratories provide some of the most highly advanced analytical services and scientific support to oil spill responders. They found their results were consistent with what they would expect from a sample of fuel oil, which is a non-standardized mix of petroleum products that ships often use to run their engines. In recent years, calls to improve air quality around ports has driven the industry to adopt new low-sulfur formulations that reduce emissions. At the same time, however, the potential is rising for spills of this type, but the scientific community has yet to see what happens to these new low-sulfur fuels when they enter the environment.
“Fuel oils, are arguably the most challenging petroleum products to analyze and investigate following marine-based spills,” said Reddy. “There is no single recipe or set of ingredients, and it gets even more complicated with these new low-sulfur fuel oils that require more steps in their manufacture. We don’t know if this was a low-sulfur material, but it’s unlike anything we’ve seen spilled before—that alone demands a closer look.”
Analysis by WA-OIGC at Curtin and also confirmed by WHOI’s Organic Geochemistry Analysis Lab showed that the sample contained relatively low levels of polycyclic aromatic hydrocarbons (PAHs), which are known carcinogens in humans and animals. Although low, the levels of PAHs might accumulate in certain parts of the marine environment. In addition, Reddy found a relatively high concentration and variety of secohopanes and surprisingly low levels of hopanes, both of which are “biomarkers” that will help connect future samples of oil to the Wakashio ship. These substances were present in minute amounts, but still detectable thanks to the technology available in the collaborating laboratories. Only comparison to a “fresh” sample taken from the ship would allow researchers to determine what has already been lost from the oil as a result of evaporation, dilution, photodegradation, and other effects.
“This was just a first step,” said Grice. “Our limited view of what spilled only reinforces the need for long-term monitoring, access to samples from the ship, and a more in-depth analysis that officials can incorporate into detailed plans to help Mauritius and its environment recover from this.”
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