Evaluation of Yakataga Oil Seeps as Regional Background Hydrocarbon Sources in Benthic Sediments of the EXXON VALDEZ Oil Spill Area. EXXON VALDEZ Oil Spill Restoration Project Final Report. (Restoration Project 01599)

摘要

Hydrocarbon distributions among samples of water, suspended particulate matter (SPM), and riparian sediment collected from Yakataga District coastal watersheds were compared with northern Gulf of Alaska benthic sediment geochemistry to determine the fate of petroleum-seep derived hydrocarbons in the fluvio-marine environment. Only the Johnston Creek drainage conveyed a detectable (-4 pg L(sup -1) total PAH) load of seep-derived hydrocarbons to the Gulf of Alaska. The Yakataga District petroleum seeps collectively account for a negligible proportion of the hydrocarbon burden in Gulf of Alaska benthic sediments. Coaly material was separated from Gulf of Alaska sediment samples using a heavy liquid, but this material accounted for only a small portion of the total PAHs (1-6%) and total n-alkanes (0.4-2%) in these samples. The remainder of the hydrocarbon burden in these sediments is associated with the denser siliciclastic material. The major source(s) for these hydrocarbons remains elusive, but the combination of benthic sediment geochemistry and well-documented long-shore sediment transport processes clearly implicates the glaciofluvial drainage system of the Malaspina Glacier as a prominent vector by which this hydrocarbon load is introduced into the Gulf of Alaska.