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.
This research project involved the study of hydrocarbons released into the ocean environment. The project sought to address fundamental questions as to the fate of hydrocarbons discharged from natural seeps to the Pacific Ocean. The scope of the project was expanded in 2010 following the sinking of the Deepwater Horizon, to include the fate of hydrocarbon discharge from the Macondo Well to the Gulf of Mexico. This project led to ten publications in the peer reviewed literature including five publications with notably high profile – 2 in the journal Science and 3 in the Proceedings of the National Academy of Sciences. Each of these papers describes a new aspect of hydrocarbon fate following discharge to the ocean. These works expand the knowledge base of bacterial preference and timing for the degradation of hydrocarbons, revealing trends among the compounds that make up natural gas that are nearly opposite to the trends that describe biodegradation of liquid crude oil. These works also define the interplay between physical and biological processes in the ocean that modulate hydrocarbon biodegradation and thus control the fate of spilled oil. Results described in the other publications reveal novel molecular transformations within crude oil that contribute to its conversion to tar, and further reveal the rates and patterns for degradation of other hydrocarbons in both seep and spill scenarios. Examples of broader impacts from this project fall into two categories – training and public engagement. Training was conducted at the undergraduate graduate and postdoctoral levels, leading to scientific and technical career paths for several of the participants. Public engagement became a focus of broader impacts following the Deepwater Horizon event. Project personnel engaged with policy makers and the media to provide unbiased scientific information. For example, the lead PI conducted over 200 interviews for major media outlets and appeared on evening network news programs on four occasions.
