Collaborative Research: Chemical Changes Accompanying Petroleum Weathering in the Coastal Ocean

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The weathering of petroleum hydrocarbons in the coastal ocean is a phenomenon that marine chemists and environmental chemists have been interested in for more than three decades. While there have been countless studies on this topic, advances have stalled due to the narrow analytical windows provided by traditional analytical techniques, leaving fundamental questions unanswered. In this project, researchers at the University of California at Santa Barbara and the Woods Hole Oceanographic Institution will look at this problem in a new way through a concerted application of two advanced approaches: comprehensive, two-dimensional gas chromatography and Fourier transform ion cyclotron resonance mass spectrometry, to provide an unprecedented level of detail on the weathering of hundreds to thousands of petroleum hydrocarbons. Specifically, this research will identify and apportion the role of photolysis, evaporation, dissolution, and biodegradation associated with oil weathering at the natural oil seeps off Santa Barbara, CA, where more than 5 million liters of oil seep annually into the ocean. This effort directly addresses recommendations by the US National Research Council's 2003 report Oil in the Sea III, and will be driven by two overarching hypotheses: (1) Hydrocarbon mass loss in chronic oil slicks is dominated by evaporation biodegradation dissolution photo-oxidation; and (2) High-molecular-weight and polar compounds in petroleum are transformed primarily in shallow sediments by microbiological processes, yielding high molecular weight dissolved organic molecules and a residual tar. These hypotheses will be addressed by collecting and analyzing oil samples from the Santa Barbara seeps. Changes in the distribution of molecules within each sample will be assessed as a function of environmental exposure to provide tests of the hypotheses. New data analysis tools will also be developed and validated. Broader Impacts: Results from this research will contribute broadly to an understanding of petroleum weathering and carbon cycling in the Earth system, and will be broadly disseminated through popular outlets. Knowledge gained from this research will also be translated directly to federal agencies including the National Oceanic and Atmospheric Administration's Assessment and Restoration Division where such information is critical for short and long-term decision making following oil spills. Direct educational impacts of this research include the training and education of undergraduate and graduate students.