Ramped Pyrolysis - Gas Chromatography - Mass Spectrometry of weathered Deepwater Horizon oil, Grand Isle and Barataria Bay, Louisiana, 2010-2012

We explore the analytical capabilities of ramped pyrolysis – gas chromatography – mass spectrometry (Py-GC-MS) to evaluate environmental samples of petroleum hydrocarbons from the Deepwater Horizon oil spill. Specifically, we use a data set of oil sheen, tars and oiled sediments collected on Grand Isle and within Barataria Bay, LA between 2010-2012. We show that bulk flow Py-GC-MS can quantify overall weathering degree, and that thermal slicing Py-GC-MS can quantify specific petroleum hydrocarbons in the “quantification zone”, as well as qualify changes in non-GC amenable petroleum hydrocarbons in the “cracking zone”. Our data also suggests an increase in thermochemical stability, oxygenated products and complexity of resin and asphaltene components with advanced weathering, particularly in oil sheen. This analysis not only elucidates weathering trends with current samples, but also illustrates the analytical capacity of this method for future petroleum hydrocarbon investigations.