The Deepwater Horizon accident discharged a staggering amount of oil (4.9 million barrels, or roughly 780 million litres) into the Gulf of Mexico. What has happened to all that crude? Has it dissolved in the water masses? Has it accumulated in the ocean depths?
Among those seeking answers are Norwegian researchers at the forefront of modelling oil behaviour in water masses.
Problems run deep
The Gulf of Mexico disaster occurred at a depth of 1 500 metres. A major reason for the difficulty of response measures was the problem of predicting how the oil would behave in such deep water.
Much of the spill reached the shoreline or was skimmed from the surface -- but no one knows for certain what has happened to large volumes of the remaining crude.
"Soap" to dissolve oil
One commonly used tactic for managing spilled oil is to apply large amounts of chemical dispersants, which act much like soap to dissolve the oil into fine droplets. In the Gulf of Mexico, this method (along with naturally occurring processes) has dispersed a high proportion of the oil in the water masses.
Great concern about the dispersants' impact on the water column has been expressed by academia and the media alike, as there are fears that these chemicals will worsen the environmental damage already done. The US Senate held a special hearing on this issue in August.
"These agents effectively disperse the oil into the water masses. This increases the oil's bioavailability, which in turn raises the risk of harm to organisms in the water column," explains Research Manager Alf Melbye of SINTEF. The SINTEF Group is the largest independent research organization in Scandinavia and is based in Trondheim.
"In most cases this risk is partially offset due to the accelerated dilution of the oil and the fact that over time the smaller oil droplets are broken down faster by microorganisms. But oil on the surface will not biodegrade as quickly -- so it can harm marine mammals and marine birds, in addition to soiling the shoreline."
Clearly, some critical assessment is called for when using dispersants: Is there a danger that the surface oil can reach the fauna and shoreline? Can the dispersed oil have undesirable impacts on important environmental resources in the water column, particularly fish eggs and larvae?
Research Manager Mark Reed heads a large-scale SINTEF project to develop oil spill trajectory models that is receiving funding under the Research Council's Programme for Optimal Management of Petroleum Resources (PETROMAKS). Such models are valuable to petroleum companies when conducting risk analysis and preparedness planning for an oilfield. One of the best models in use today (OSCAR) was developed by SINTEF.
"SINTEF has provided expertise in the modelling and use of dispersants in the wake of the Gulf of Mexico accident," says Dr Reed. "Personnel from our offices in Trondheim and the USA have also provided advice to BP."
"This project will be able to answer some of the key questions raised by this accident. Our work has already yielded valuable information we can use to further advance the project, particularly when it comes to understanding the process by which oil is biodegraded by microorganisms."
Also highly relevant for Norway
There is heated debate in Norway about the environmental impacts of oil spills, in particular in relation to the fisheries resources off the Lofoten Islands and in the Barents Sea. "The project we are working on now will show what happens to dispersed oil over time," says Dr Reed. "This knowledge will be especially applicable to environmental risk assessments for planned oilfields."
"The modelling tool will also be helpful when determining the best rapid response strategy after a large discharge, and particularly useful when we need to apply dispersants. In addition, it will help us to select sites for measuring and testing water samples in connection with offshore environmental monitoring."
More public funding desired
"In addition to the Research Council's Oceans and Coastal Areas (HAVKYST) and PETROMAKS programmes, the Norwegian petroleum industry has also been an important source of funding for projects of this type. But most of the projects," states Dr Reed, "have been small-scale with a primarily operational angle."
He would like to see the knowledge generated by the Deepwater Horizon episode applied in research to determine which environmental impacts can realistically be expected should a similar incident occur under Norwegian conditions.
"In recent years," points out Senior Adviser Tarjei N. Malme of the PETROMAKS programme, "Norway's petroleum industry has focused heavily on reducing greenhouse gas emissions. The Gulf accident reminds us that we also need to concentrate on secure operations and preparedness systems for containing possible discharges to the sea. The PETROMAKS programme provides funding to a number of excellent projects that address these issues, but is still on the lookout for more."
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