Deep-C Scientists Study the Fate of Oil in the Gulf of Mexico
April 2012 - Two years ago, in the wake of an explosion on the Deepwater Horizon drilling rig, thousands of barrels of crude oil were flowing into the ocean daily from a damaged well about 40 miles southeast of the Louisiana coast. The flow of oil would continue for nearly three months while scientists and engineers worked to cap the Macondo well, and the disaster would eventually become the largest accidental marine oil spill in history.
As the Deepwater Horizon accident was unfolding, Deep-C scientists were among those who worked feverishly to determine how much oil was being discharged into the environment and where it was going. In the immediate aftermath of the blowout, experts from Woods Hole Oceanographic Institution (WHOI) and other Deep-C institutions worked to collect urgently needed samples and data. This data would assist investigators, other scientists, and engineers in their oil spill response efforts.
Today, the process of gathering and analyzing information about the fate of the Deepwater Horizon oil carries on. Deep-C researchers continue to work in the areas affected by the spill studying the long-term fate and effects of petroleum hydrocarbons in the Gulf.
Over the past two years, marine chemist Chris Reddy and other members of the WHOI lab have visited and revisited sites along the Gulf Coast that were affected by the spill. Reddy looks for samples of Deepwater Horizon oil that have mixed with sand to create what he refers to as "sand patties" on the beaches.
"Grand Isle, Louisiana was one of the areas heavily oiled after the blowout." Reddy explains. "And despite an excellent clean-up effort, we can still find small samples on the beaches there."So in a recent visit, Reddy collected samples on the beaches of Grand Isle to determine if they contained oil from the Deepwater Horizon spill. Reddy notes that oil from the Macondo well has an orange tint to it that you can still see if you look for it. And his lab confirmed that the samples collected at Grand Isle in April 2012 did, in fact, contain Macondo well oil.
Understanding what happens to oil discharged in the oceans helps scientists anticipate what crude oil will do when it is spilled and where it will go.
Tracking oil from a spill like the Deepwater Horizon oil spill over a long period of time helps researchers determine a “mass balance.” We can then account for how much of the oil broke down and where the remaining material still resides. Lastly, if we study the long-term fate of oil, we identify areas where it has the greatest likelihood to last, which in turn, can be used in the next spill when setting priorities on what to “protect” or what to clean-up first.
One of the ways the fate of the oil can be determined is to study an effect called weathering — that is, how oil that is discharged into the environment changes over time. Weathering affects the properties of spilled oil. In part, Reddy's research provides insights into the natural weathering of oil.
"All chemicals have a different personality towards biodegradation, photochemical breakdown, etc., "Reddy explains. So Reddy is interested in knowing which chemicals are the most susceptible to each weathering processes.
Oil is a mixture of compounds, and hydrocarbons are the most abundant compounds found in crude oils. "So, Reddy says, “the goal is to study what happens to the hydrocarbons in oil. And, of course, when does the weathering stop so we can identify the 'toughest compounds? Also, if we know more about the compounds that resist weathering then we use that knowledge in clean-up strategies.” This all goes back to the idea of “how clean is clean,” said Reddy, regarding when efforts to clean up should be stopped.
Researchers at the National High Magnetic Field Laboratory at Florida State University are using incredibly precise analytical tools housed at the lab to analyze petroleum samples collected at Grand Isle and other locations along the Gulf Coast. Amy M. McKenna is an assistant scholar scientist in the magnet lab’s Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry facility. McKenna and her colleagues, including lab director Alan Marshall and scholar scientist Ryan P. Rodgers, have been analyzing samples of raw crude oil, ocean surface samples and tar balls collected by the WHOI researchers at various distances from the Deepwater Horizon site. Results of those analyses help determine whether or not the samples originated from the Deepwater Horizon oil spill.
Results from the WHOI/FSU collaboration include a series of gas chromatograms or “images” of the Macondo well oil and the hydrocarbons that were mixed with sand patties collected in Grand Isle, LA and Perdido Beach, FL (in July and November 2011, respectively). What is evidenced by these images is that the oil in the sands has very different chromatograms compared to what flowed from the Macondo well. These differences are a result of, at least, evaporation, microbial degradation, and photochemical degradation. And the compounds left in the sand patties are the toughest compounds to weathering despite being at trace levels in the Macondo oil.
"An oil spill changes its chemical composition due to evaporation and dissolution over time,” McKenna said. “The incorporation of oxygen into the components makes it difficult for other analytical techniques to characterize the molecules of spilled oil. FT-ICR mass spectrometry is the only technique that can look at these changes at the molecular level without prior, tedious sample preparation.”
Reddy plans to continue to collect these types of samples to better understand how the oil breaks down over time. “The results shed light on the fate and behavior of the oil,” says Reddy, “and that information will help to prepare us for future spills and learn how nature responds to uninvited guests.”
The Woods Hole Oceanographic Institution is a Deep-C partner institution. WHOI is a private, independent, non-profit organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment. Chris Reddy is a senior scientist in WHOI's Department of marine chemistry and geochemistry. Since April 2010, he has devoted most of his research efforts to studying the Deepwater Horizon oil spill in the Gulf. He has studied numerous other oil spills including oil leaking from a Japanese warship sunk in 1945.
The National High Magnetic Laboratory, also part of the Deep-C Consortium, is the largest and highest-powered magnet laboratory in the world, headquartered in a sprawling 370,000-square-foot complex near Florida State University in Tallahassee. Established by the National Science Foundation in 1990, the lab is a national resource open to both curious visitors and world-renowned scientists. Professor Alan G. Marshall, the director of the magnet lab’s Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry facility. Amy McKenna and Ryan P. Rodgers are scientists in the magnet laboratory's FT-ICR mass spectrometry facility.