Long-term Fate and Persistence of Oil from theExxon ValdezOil Spill: Lessons Learned or History Repeated 2011 International Oil Spill Conference, Portland, Oregon

Abstract

Abstract As a continuation of the extensive shoreline studies undertaken since 1989, we conducted systematic surveys in 2007 and 2008 to evaluate the form, chemical composition, accessibility, and location of remaining subsurface oil (SSO) residues of Exxon Valdez oil on shorelines in Prince William Sound. We found SSO residues only in isolated patches, buried in low-permeability sediments protected from water-washing and erosion by surface boulder and cobble armoring. These SSO residues are sequestered and largely isolated from natural weathering processes that would result in their complete and rapid removal. SSO residues are not accessible or bioavailable to wildlife that forage on the shore. These findings confirm the lessons learned from all previous crude oil spills: 1) SSO residues can be sequestered for decades in intertidal sediments at locations where the subsurface water flow required for erosion, dissolution, and biodegradation of the oil is low. 2) Sequestration limits the exposure of biota t...