Sedimentary Evolution of Deepwater Horizon/Macondo Oil on Sand Beaches of the Northern Gulf of Mexico, USA

TitleSedimentary Evolution of Deepwater Horizon/Macondo Oil on Sand Beaches of the Northern Gulf of Mexico, USA
Publication TypeJournal Article
Year of Publication2015
AuthorsParham PR, Gundlach E
JournalOpen Journal of Ocean and Coastal Sciences
Date Published01/2015
Observations of sedimentary evolution of oil along northern Gulf of Mexico sand beaches, made in conjunction with Shoreline Cleanup Assessment Technique (SCAT) surveys for the Deepwater Horizon/Macondo (DWH/M) spill, can assist oil spill managers and responders, and provide further insight into sedimentary processes in this and similar environments. Helicopter over-flights during active oiling gave a broad perspective of distributional patterns from Mississippi to western Florida while ground surveys provided details of the oils sedimentary behavior within the coastal system over a 20-month period. During active oiling, June/July 2010, floating emulsified oil (mousse patties) stranded onshore in appreciable quantities. High wave and tide conditions resulted in overwash and backshore flooding, deposition of oil well into the supratidal zone and burial to depths of as much as one meter. Once stranded, adherence of sand to mousse patties increased their density, promoted burial and began their transformation into oil/sand aggregates. Beachface wave action generally reduced the size of oil/sand aggregates. Under heavy accumulations, oil coalesced into subtidal oil/sediment mats in surf zone depressions. Oil stranded in supratidal pools was remobilized by the suns heat, floated to the surface, and was re-deposited in concentric rings around the pools as water levels decreased. Post-active oiling processes influencing stranded oil had definite seasonal components including eolian, wave energy/overwash, cleanup-related activities and weathering. Higher summer water levels and wave energy/overwash associated with storms reworked stranded oil. Strong northerly fall/winter winds resulted in lower water levels and exposed previously buried supratidal oil as concentrated surface lag deposits. In situ weathering/breakdown occurred under surface, subsurface and subtidal conditions. Continued wave energy/overwash and weathering processes will likely prove effective in removal and the long-term breakdown of remaining oil.