Biodegradation of dispersed Macondo oil in seawater at low temperature and different oil droplet sizes

Brakstad, Odd G.; Nordtug, Trond; Throne-Holst, Mimmi

Biodegradation of dispersed Macondo oil in seawater at low temperature and different oil droplet sizes

2015

Brakstad, Odd G. | Nordtug, Trond | Throne-Holst, Mimmi

During the Deepwater Horizon (DWH) accident in 2010 a dispersant (Corexit 9500) was applied at the wellhead to disperse the Macondo oil and reduce the formation of surface slicks. A subsurface plume of small oil droplets was generated near the leaking well at 900–1300m depth. A novel laboratory system was established to investigate biodegradation of small droplet oil dispersions (10μm or 30μm droplet sizes) of the Macondo oil premixed with Corexit 9500, using coastal Norwegian seawater at a temperature similar to the DWH plume (4–5°C). Biotransformation of volatile and semivolatile hydrocarbons and oil compound groups was generally faster in the 10μm than in the 30μm dispersions, showing the importance of oil droplet size for biodegradation. These data therefore indicated that dispersant treatment to reduce the oil droplet size may increase the biodegradation rates of oil compounds in the deepwater oil droplets.

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