The BP oil spill clean-up has been virtually useless, because chemical dispersants didn’t actually succeed in removing the contaminants, a recent study conducted by experts at the University of Georgia has shown.
On April 20, 2010, the Deepwater Horizon oil rig exploded and sank in the Gulf of Mexico, causing 11 crew members to go missing, never to be found again.
It also triggered the most significant accidental marine oil spill ever reported, by leaking approximately 210 million gallons of liquid petroleum hydrocarbon into the water, for a period of 87 days.
Authorities managed to contain the spill only by July 15, 2010, although according to reports issued at the beginning of 2012 some leaking had still remained at the accident site.
In order to limit damage incurred by marine wildlife, beaches and salt marshes, approximately 1.84 million gallons of Corexit oil dispersant were sprayed from planes, but it appears that this substance wasn’t as effective as previously thought.
The chemical agent, which was supposed to break the pollutant into smaller clusters that could be biodegradable, only managed to remove oil from the water’s surface. At greater depths it actually hampered the activity of bacteria, which could’ve naturally broken down the contaminant.
This theory launched by researchers was proven by reconstructing the circumstances of the accident in a lab experiment. Corexit 9500 was employed as a dispersant against a somewhat radioactive oil leak, and its impact on the activity of microorganisms was examined.
It was revealed that colwellia bacteria, which digested these chemicals intended to clean the area, were the ones that thrived, their number initially representing 1% of the total microbe population, and reaching 43%.
On the other hand, marinobacters, which function as much more beneficial agents when it comes to decomposing oil, dropped in numbers, although in the absence of dispersants they would’ve increased from 2% to 42%.
Samples collected below water surface at the time of the oil spill had also indicated the presence of useful marinobacters was greatly diminished, most likely due to artificial agents.
As a result, the natural process of breaking down oil was perturbed and slowed down, which was especially damaging since chemical substances were powerless anyway.
It was also determined that a large heterogeneous population of microbes could’ve been actually much more useful in curbing the oil spill, in comparison with chemical substances that were eventually used.
According to Samantha Joye, lead study author and science professor at the University of Georgia, it was extremely surprising to discover that Corexit had actually hindered oil biodegradation.
The scientific paper, which has been published in the journal PNAS, shows that in fact the contaminants weren’t actually cleaned, but they simply sank to the bottom of the Gulf of Mexico.
Prior studies had also estimated that microbes removed between 43 to 61% of the oil spill, while around 2 to 15% remained on the ocean floor, which left between 24 and 55% of the leak unaccounted for.
As researchers point out, officials who supervised the clean-up efforts should’ve studied the potential impact that dispersants might have on oil degradation carried out by bacteria.
These findings come just a few months after BP accepted it would pay $18.7 billion across a period of 18 years, in order to settle economic and environmental damage claims made by 4 states and over 400 local governments, after breaching the Clean Water Act.
In September 2014, a federal judge came to the conclusion that the British oil giant had been overly preoccupied with profit-making and had shown “gross negligence”, being at least 67% to blame for the oil spill.
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