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The BP Deepwater Horizon oil spill began on April 20, 2010 and lasted 87 days, releasing about 4.9 million barrels of oil into the ocean from a mile deep well.In response to the largest oil spill in US history more than 1 million gallons of oil dispersant was added to the sea surface and over 770 thousand gallons to the sub sea.
Almost two years later, we still do not know the full impact this catastrophe has had on marine life, human life, and the environment.
A special feature of articles on the Deepwater Horizon Oil Spill appearing in the Proceedings of the National Academy of Sciences, today, Dec. 3, examines the physical and environmental science and engineering that guided the response to the spill — if it was successful and how it could be improved.
The clean-up was a collaborative effort between government, academic and industry scientists, and engineers.
“The coordination within and across agencies was impressive, but so too was the engagement of academic scientists in a joint effort to respond to the disaster,” said Steve Murawski, co-author on both PNAS papers, said in a press release. Murawski was chief scientist at NOAA Fisheries during the response effort, and is now a professor at the University of South Florida.
“Through these partnerships, new scientific discoveries were made such as estimating flow rate from atmospheric measurements, testing for dispersant in seafood, understanding the behaviour of the loop current, and discovering novel microbial communities in the Gulf.”
The introductory article, Science in Support of the Deepwater Horizon Response, was written by Murawski and other researchers at NOAA, the EPA, and others to address the important questions below:
Where did all the oil go?
Only about one half of the oil released during the spill reached the surface, and this oil was so spread out that common skimming and burning techniques were not very effective.
Only about a quarter of the oil was removed using different methods which include three per cent from skimming, five per cent from burning, and 17 per cent recovered directly through a pipe. About five per cent evaporated into the atmosphere and 10 per cent contributed to the surface slick.
So, what remains of the spill?
Oil that was not removed through the techniques above was broken down by dispersants and consumed by bacteria, or settled into the sediment on the ocean floor around the site of the spill, as well as coastal areas, marshes, and beaches. The settled oil has impacted deep coral communities more than 12 miles from the site.
Samples of offshore waters indicated that by August 3, 2010 — 19 days after the well was finally shut off — the level of oil in the water went down to normal background levels.
Should we use the dispersant in the future?
The purpose of the oil dispersants is to accelerate the breakdown of hydrocarbons, and keep the oil away from the coastline. Dispersants have been used before, but not in this great amount and this is the first time they were added under the surface of the sea. Testing and monitoring was required to make sure it was safe and did not add to the toxicity cause by the oil.
Tests performed on microscopic animals, called marine rotifers, did not indicate any significant impacts to ocean life at the time, although a new study suggests that once the dispersants mix with oil, the mixture is more toxic.
Teams also had to develop new techniques to test for chemicals in the dispersant. Thousands of sediment and water samples showed detectable levels of these chemicals, but none that exceeded the limits set by the EPA.
Mysid shrimp and the silverside fish, which are commonly found in the Gulf of Mexico were also tested, and there was no effects on the hormone system of these animals. More long term tests are required to fully understand the impact of these chemicals, but as of now they look safe and useful for future oil spills.
Was seafood contaminated?
No contaminated seafood reached consumers. The NOAA and FDA took great measures to protect consumers by closing about 88,500 square miles of federal fishing water in the Gulf of Mexico, where about one-fifth of American seafood is caught commercially.
In order to be reopened three criteria had to be met: the area had to be clean of oil for 30 days, free of any expected oil for 72 hours, and pass tests that detected oil and dispersant. Overall more than 8,000 seafood species were tested and found to be safe for consumers.
What did we learn?
The catastrophe has accelerated the science of deep spill decontamination and we’ve learned more about the environmental impacts of oil spills.
New methods on determining the flow rate of spills were developed and quicker methods to test for contamination in marine animals were developed and validated by the FDA. These areas are still heavily monitored, because no one knows how long the oil and dispersants will impact marine life, the environment, and humans.
“While the federal family was well versed in oil response and remediation, and we brought many resources to bear, the scale and complexity of Deepwater Horizon taxed our organisations in unprecedented ways,” first author Jane Lubchenco, under secretary of commerce for oceans and atmosphere and NOAA administrator, in a statement.
“We learned much during this extraordinary disaster and we hope the lessons learned will be implemented before and used during any future events.”
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