1 July 2010
Since the Deepwater Horizon oil-drilling platform sank on April 22, millions of gallons of oil and gas have spewed into the Gulf of Mexico. As efforts to staunch the undersea flow continue, scientists (including many AGU members) are working round-the-clock to determine where the oil is going, what’s happening to it, and how it is affecting the environment.
Much is unknown about what the effects will be from a spill of this size. But some of what we do know comes from a 1979 oil spill, also at an offshore oil well in the Gulf of Mexico. That well, called the Ixtoc I, also experienced an explosion, the failure of the blow-out preventer, and the release of oil into the Gulf for months. However, the difference in scale between the two spills is dramatic: the Ixtoc was drilled in waters about 160 feet deep, and released an estimated 10,000 to 30,000 gallons barrels of crude oil a day into the Gulf during the 10 months it took to cap the damaged well head. The Deepwater Horizon well is at depth of about 4,100 5,000 feet below the ocean’s surface, and is estimated to have gushed 1.5 million to 2.5 million gallons of oil and gas each day during the past two months, with months to go before it is expected to be capped.
The Geohazards blog spoke recently with marine geochemist John Farrington, who studied the Ixtoc oil spill as a member of a shipboard research mission 20 years ago. On June 3, 2010, Farrington was one of a group of scientists assembled by the Consortium for Ocean Leadership at Louisiana State University to make recommendations for how scientists can best respond to the Deepwater Horizon spill. He is currently interim dean of the University of Massachusetts at Dartmouth’s School for Marine Science and Technology, an emeritus scientist at the Woods Hole Oceanographic Institution, and AGU’s Ocean Sciences section president.
Farrington spoke by phone with AGU blogger Kathleen O’Neil.
Q: Can you describe where the oil from the Deepwater Horizon spill is going?
JF: The oil seems to be bubbling up from the bottom similar to what one might see from a smokestack. There is both gas and oil coming out under great pressure and at elevated temperature, sometimes as much as 180 degrees Fahrenheit…. The oil is mixing and coming up in little droplets that can be moved by currents. … It’s not a uniform plume of oil droplets, like a big blob; what you have is more like a marble cake mix with filaments at different layers.
It’s a very mixed system, like what you have from a smokestack with a lot of wind – some smoke goes here, some there – and as you get further away you see clouds of it all over in the atmosphere.
Q: Does that early mixing help the environment and organisms break it down?
JF: I think it’s a dual-edged sword, like many things. It’s a problem in the sense that by mixing it and using dispersants, you’re getting more of the more toxic parts of the oil mixed in to the water, so if there are animals nearby that are sensitive to this, they’re being exposed to higher concentrations.
Q: Do you have any sense of how long it will take the oil and gas being released now to break down and become less harmful?
JF: No, I think that’s something that they’re going to have to document with sampling. …We do know that microorganisms, with sufficient oxygen and nutrients, can degrade certain parts of the oil; we know that some parts of the oil will be volatilized to the atmosphere. … What isn’t known is what long-term degradation in the deeper water happens where some of these mixtures of oil droplets and oil compounds might be found.
It was clear from experiments set up on the ship to study the Ixtoc oil spill that although we had oil and oxygen, and plenty of microbes that could degrade the oil, the oil wasn’t going anywhere. But if you added nutrients, like nitrate, to the water, then all sorts of degradation started happening. So that was how we learned that the breakdown of the oil was limited in nutrient-poor conditions. Now, where the oil is coming ashore and in the deeper waters of the Gulf on the U.S. side, people are going to have to make similar assessments to see if microorganisms are present and if they’re degrading the oil.
The good news, if there is any, is that science has advanced tremendously since then, and there are techniques now for using molecular biology to take water samples and find out pretty quickly what types of microbes are there, are they capable of doing oil degradation and what would their requirements be.
Q: Do the organisms that degrade oil exist at all levels of the water column, including where the well is?
JF: Yes, they exist at the depth of the well site, because there are natural oil seeps in the Gulf, and there are organisms that have evolved to use that oil for a source of carbon.
As a National Academies Report called Oil in the Sea III reports, most of the oil that usually enters the ocean comes from run-off from sources on land, discharges from ships during normal operations, and natural undersea oil seeps. [According to the report, an estimated 140,000 tons of oil (or about 3.7 million 41.1 million gallons) released from natural seeps into the Gulf of Mexico each year. By comparison, as of June 25, estimates of the total amount of oil released from the Deepwater Horizon well were 80 million to 150 million gallons]
Q: Have there been any further studies to suggest possibly adding nitrate to the Gulf waters to try to speed up the oil’s degradation?
JF: We simply, in my view, don’t know enough about any of these ecosystems to do that without just complicating things further. There are ways of collecting the oil and putting it in tanks [with microbes and additional nutrients] to degrade it that way. There’s also been research into adding nutrients to wetlands, but that may be detrimental to marshes in the long-term.
Q: What did you do at the Ocean Leadership Conference meeting in the Gulf?
JF: We sat together in a think-tank approach to look at what’s already going on, and what additional things we could suggest, and also offer whatever equipment and sampling gear that they may not have to assess where the oil is and what the impacts might be.
We had an update from NOAA’s [Administrator] Dr. Jane Lubchenco and from [USGS Director] Dr. Marcia McNutt. Several working groups made various recommendations. …You could tell scientists were from the Gulf area, because they looked exhausted. A report is coming out to summarize the findings, but the most important thing is some of our colleagues had already made changes.
Q: What changes have they already made?
JF: They’re bringing new systems to bear, modifying some of the in-situ glider operations, thinking about some of the modeling that they’re doing. In reality, if you compare this system of responses in the scientific and operational sense with what happened with the Ixtoc spill in 1979, we would’ve thought this was science fiction. The ability to do the remote sensing with various sensors from space, the ability to model the circulation of the Gulf in such detail is really quite amazing. It’s not at the level yet that we’d like to see it, and there are various autonomous vehicles that are out there and floats that are feeding back data that are helping to update the models
There’s a tremendous amount of knowledge that has been gained throughout the world from work on oil spills, and in many places they’ve used dispersants in a more regular fashion. Unfortunately, what we don’t have good information on is how deep ocean systems respond, including deep water corals in the Gulf, and there’s some concern how they might be impacted.
More information on the research being done on NOAA’s fleet of research ships
Information about research being done at the Woods Hole Oceanographic Institution in response to the Deepwater Horizon spill
USGS work related to the oil spill cleanup, including satellite imagery
– Kathleen O’Neil, AGU science writer
(*CORRECTION, 3 August: The original post contained some numerical errors that have been corrected. We regret the mistakes.)