Magnitude and oxidation potential of hydrocarbon gases released from the BP oil well blowout

Journal name:
Nature Geoscience
Volume:
4,
Pages:
160–164
Year published:
DOI:
doi:10.1038/ngeo1067
Received
Accepted
Published online

The deep-sea hydrocarbon discharge resulting from the BP oil well blowout in the northern Gulf of Mexico released large quantities of oil and gaseous hydrocarbons such as methane into the deep ocean. So far, estimates of hydrocarbon discharge have focused on the oil released, and have overlooked the quantity, fate and environmental impact of the gas1. Gaseous hydrocarbons turn over slowly in the deep ocean, and microbial consumption of these gases could have a long-lasting impact on oceanic oxygen levels2. Here, we combine published estimates of the volume of oil released1, 3, together with provisional estimates of the oil to gas ratio of the discharged fluid4, to determine the volume of gaseous hydrocarbons discharged during the spill. We estimate that the spill injected up to 500,000t of gaseous hydrocarbons into the deep ocean and that these gaseous emissions comprised 40% of the total hydrocarbon discharge. Analysis of water around the wellhead revealed discrete layers of dissolved hydrocarbon gases between 1,000 and 1,300m depth; concentrations exceeded background levels by up to 75,000 times. We suggest that microbial consumption of these gases could lead to the extensive and persistent depletion of oxygen in hydrocarbon-enriched waters.

At a glance

Figures

  1. Map of the study domain.
    Figure 1: Map of the study domain.

    a,b, Sites where reservoir alkane composition samples were collected (a) and where plume samples were collected in relation to the position of the wellhead (b).

  2. Depth profiles through the water column.
    Figure 2: Depth profiles through the water column.

    a, Depth distribution of CDOM signal (calibrated to quinone sulphate). b, Beam attenuation. c, Dissolved oxygen. Hot colours (red) denote stations within 5km of the wellhead, whereas cold colours (blue) denote stations more than 5km from the wellhead. The lines identifying stations are given in b.

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Author information

Affiliations

  1. Department of Marine Sciences, University of Georgia, Room 220 Marine Sciences Building, Athens, Georgia 30602-3636, USA

    • Samantha B. Joye
  2. Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, Florida 32306-4320, USA

    • Ian R. MacDonald
  3. Marine Science Institute, University of California, Santa Barbara, California 93106, USA

    • Ira Leifer
  4. Department of Marine Science, University of Southern Mississippi, Stennis Space Center, Mississippi 39406, USA

    • Vernon Asper

Contributions

S.B.J. and V.A. participated in the cruise; S.B.J., I.R.M. and I.L. carried out the gas flux calculations; S.B.J. wrote the paper and other authors provided comments/feedback.

Competing financial interests

The authors declare no competing financial interests.

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