•what is oil? •dispersed oil? Deepwater Horizon Oil Edward B. Overton, Ph.D. Professor Emeritus Dept of Environmental Sciences School of Coast and Environment Louisiana State University Baton Rouge LA 70803 •what happens to oil in the environment? Exxon Valdez Oil Rules of Thumb: •Oil contains many thousands of compounds, •All oils, regardless of source, contain the same molecular structures, •It is the quantity of specific hydrocarbons that separated oils from different sources, •It is the quantity of specific hydrocarbons that determines the chemical and physical properties of oils •Light oils contain relatively more of the low molecular weight compounds •Heavy oils contains relatively more of the higher molecular weight compounds •Aromatic compounds in oils are predominately the alkyl homologs of the parent polycyclic compound •Photo-oxidation can enhance aromatic toxicities GCMS Analyses •Modified 8270 GCMS Method •Alkyl homologs of PAHs •Hopane/stearane Biomarkers TLV Aliphatic Hydrocarbons: Butane 1000ppm Pentane 600 Hexane 50 Heptane 400 Octane 300 Quantitative Analysis Fresh of oil in the environment is problematic because of oil’s heterogeneous distribution weathered Photo-enhanced toxicity? weeks days months Surface oil weathering Toxic & sticky floating Sticky Floating Sinking? Gunky Floating Sinking Tarball nuisance Loss of Light Ends Saturates and Aromatics Degraded Asphaltenes Bon Secour National Wildlife Refuge Ben Raines/Press Register Dispersed micro-droplets Subsurface oil weathering Toxic BOD ? (biomass) large high MW small low MW Evaporative Losses light moderate heavy Time Source oil •oil at depth •oil on surface •dispersed oil at depth •dispersed oil on surface Weathered oils •dissolved and modified oils at depth •dispersed weathered oils on surface •dispersed dissolved and modified oil at depth •dispersed weathered oil on surface source dispersed Impacts •Ecological •Geological •Economic •Sociological Why use dispersants? In deep water, dispersants dissolve concentrated surface oil into the water column so that natural bacteria can more rapidly degrade the oil Fuel Products from Crude Oil gasoline kerosene diesel plastics in cars, and almost everything else heavy fuel oil lube oil asphalt
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