The explosion at the Deepwater Horizon in 2010 and the subsequent events released ~5 million barrels of oil to the Gulf of Mexico.  An appreciable proportion of this has oiled the wetlands and shorelines of the nearby states.  This influx of organic matter to the wetlands was expected to act as an oxygen donor to the system and thereby change the redox conditions and the cycling of metals between porewaters, surface waters, and sediments. Ten field sites along the Alabama, Missippi, and Louisiana coastlines were visited, sediment cores obtained, and porewaters extracted from these cores.  Measurements of sulfide in the porewaters show that oiled sites contained  sulfide at concentrations several orders of magnitude higher than pristine sites.  In this context, the toxic metals arsenic and mercury were of particular interest.  Under strong sulfide-producing conditions arsenic may be reduced to its more mobile form, As(III), or stabilized at high concentrations as an As-S compound.  Activity of sulfate reducing bacteria may methylate mercury which can then bioaccumulate. However, initial data indicate that porewater metal concentrations remain low and evidence of altered metal cycling is limited. Explanations for this will be explored using both aqueous and solid phase analyses.

Effects of oil contamination on metal cycling in pore waters and sediments of wetlands

243rd National Meeting (2012)

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