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Chemical Dispersant Used To Clean Up America's Largest Deepwater Disaster Leak Probably Didn't Work

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Madison Dapcevich

Staff Writer

clockNov 1 2018, 20:29 UTC

The Deepwater Horizon oil rig explosion released 210 million gallons of crude oil into the Gulf of Mexico for a total of 87 days, making it the largest oil spill in U.S. history. U.S. Coast Guard

On April 20, 2010, an explosion aboard the Deepwater Horizon 41 miles (66 kilometers) off the coast of Louisiana sparked what would later become one of America’s worst environmental disasters. For nearly three months, oil spewed from 1,500 meters (roughly 5,000 feet) below the surface, polluting the Gulf of Mexico and altering the building blocks of oceanic life. We’re still only beginning to understand the long-term consequences of this disaster, and now researchers say the techniques used to mitigate its catastrophic effects probably didn’t even work.

How oil moves through the water column depends on a number of variables, including pressure, turbidity, and the type and behavior of crude oil – all of which can change depending on the depth of the drill site. Following the explosion, responders took a novel approach and injected 3,000 tons of a subsea dispersants injection (SSDI) called Corexit directly at the wellhead, hoping to prevent oil from rapidly rising to the surface. Typically, SSDIs break down oil into smaller droplets that are easily dissolved, but the Deepwater Horizon was different; the turbulent energy and pressure at its depth caused the oil to spread rapidly and continue to the surface, rendering Corexit basically ineffective. What’s more, Corexit could have even added to the ecological damage by stopping the growth of oil-degrading bacteria that occur naturally, making the leaking oil more toxic.

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More than 24,500 water samples from 67 different response studies were tested and analyzed through public data made available by the Gulf of Mexico Research Initiative Information and Data Cooperative.

A satellite image shows the extent of oil pollution in the Gulf of Mexico. NASA/Wikimedia Commons

For 87 days, 210 million gallons of crude oil continued to spew from the well site until workers were able to cap the leak on July 15. The researchers now say the oil industry needs to find new methods to handle major disasters, particularly as drills are heading into deeper and more remote waters. (Just last month, the Trump administration approved plans to drill in Alaska’s federal waters for the first time.) 

Such measures include the “capping stack” – covering a blown-out well with a piece of equipment. This could be the most effective first response in the event of a similar disaster. Biosurfactants, oil-degrading compounds produced by microorganisms, could be a less toxic and more efficient alternative for those that occur in shallower waters.

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Published in Frontiers in Marine Science, the work builds on earlier simulations that suggest the inefficacies of SSDIs.  

"Our earlier work using computer modeling and high-pressure experimental approaches suggested that pumping chemical dispersants at the spewing wellhead may have had little effect on the amount of oil that ultimately surfaced. But empirical evidence was lacking until the release of the BP Gulf Science Data. When completely different approaches converge to the same conclusion, it is time to listen," said researcher Claire Paris in a statement. "There is no real trade-off because there is no upside in using ineffective measures that can worsen environmental disasters."


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