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Environment

Dispersants one of many oil cleanup tools, panel says

by Jeff Johnson, special to C&EN
April 10, 2019 | A version of this story appeared in Volume 97, Issue 15

 

Photo of a plane spraying a substance over oil on the ocean.
Credit: SIPA USA/SIPA/Newscom
An airplane sprayed dispersant on oil in the Gulf of Mexico released from the Macondo after the Deepwater Horizon rig sank.

In the chaos of a major marine oil spill, emergency responders and oil companies often have released a flood of chemical dispersants to break up the oil. Dispersants promote the formation and diffusion of small oil droplets that may biodegrade more readily, limiting the impact of hydrocarbon slicks on response workers and ecosystems.

Trying to mitigate the 2010 Deepwater Horizon oil leak, for instance, some 7 million L of dispersant were dropped on the ocean surface and injected to the sea at the gushing well head.

But dispersants have their own detrimental effects, an issue that has greatly troubled shoreline residents and ocean advocates.

A recent report by the US National Academies of Sciences, Engineering, and Medicine examines the effects and efficacy of using dispersants to reduce oil at the water’s surface.

The report finds few clear answers and poses a host of unknowns and variables that cloud dispersants’ use. For example, exposure and toxicity can vary greatly in the ocean environment, and predicting impact and contamination is difficult, said Dominic Di Toro, one of the National Academies’ panel members and an engineering professor at the University of Delaware, at a National Academies webinar April 9.

Nevertheless, the report stresses that field and modeling studies show that dispersants can limit the amount of surface oil, reducing response personnel’s potential exposure to hazardous compounds and lessening the extent of surface oil encountered by marine species.

Every oil spill presents unique circumstances and challenges, and dispersants are one of several response options, including mechanical recovery of oil using skimmers and booms, as well as burning the oil, the report says.

“In our report, what we have are a series of tools to enable responders to make decisions,” said David Valentine, another panel member and a University of California, Santa Barbara earth science professor, at the webinar.

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