Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America (2012), doi:10.1073/pnas.1110564109.
Detailed airborne, surface, and subsurface chemical measurements, primarily obtained in May and June 2010, are used to quantify initial hydrocarbon compositions along different transport pathways – in deep subsurface plumes, in the initial surface slick, and in the atmosphere – during the Deepwater Horizon (DWH) oil spill. Atmospheric measurements are consistent with a limited area of surfacing oil, with implications for leaked hydrocarbon mass transport and oil drop size distributions. The chemical data further suggest relatively little variation in leaking hydrocarbon composition over time. While readily soluble hydrocarbons made up ~25% of the leaking mixture by mass, subsurface chemical data show these compounds made up ~69% of the deep plume mass; only ~31% of deep plume mass was initially transported in the form of trapped oil droplets. Mass flows along individual transport pathways are also derived from atmospheric and subsurface chemical data. Subsurface hydrocarbon composition, dissolved oxygen, and dispersant data are used to provide a new assessment of release of hydrocarbons from the leaking well. We use the chemical measurements to estimate that (7.8±1.9) x106 kg of hydrocarbons leaked on June 10, 2010, directly accounting for roughly three-quarters of the total leaked mass on that day. The average environmental release rate of (10.1 ± 2.0) x106 kg/day derived using atmospheric and subsurface chemical data agrees within uncertainties with the official average leak rate of (10.2 ± 1.0) x106 kg/day derived using physical and optical methods.
This research was supported by the National Science Foundation through grants to D. Blake (AGS-1049952), J. Kessler (OCE-1042650 and OCE-0849246), D. Valentine (OCE-1042097 and OCE-0961725), E. Kujawinski (OCE-1045811), and R. Camilli (OCE-1043976), by U.S. Coast Guard contract to R. Camilli (Contract HSCG3210CR0020), and by U.S. Department of Energy grant to D. Valentine (DE- NT0005667). The August, September, and October research cruises were funded by NOAA through a contract with Consolidated Safety Services, Incorporated. The NOAA P-3 oil spill survey flights were funded in part by NOAA and in part by a U.S. Coast Guard Pollution Removal Funding Authorization to NOAA.
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