Project Summary: Once released into the environment, petroleum undergoes physical processes that modify its native composition (water washing and evaporative losses) and chemical processes (largely oxidative, i.e. photo-oxidation and biodegradation) that we and others have shown results in an increase in oxygen-containing chemical functionalities of the predominately hydrocarbon matrix to ketone, hydroxyl, and carboxylic acid functionalities. Efforts to date have documented these weathering trends for Macondo well oil (MWO) from approx. 10 months post-spill to the present. It has been demonstrated that a pool of persistent oxidized petroleum-derived material increased with increasing weathering of MWO in the environment. However, not much is yet known about the molecular structure of the oxygenated transformation products, its environmental fate, or potential effects, as these oxidized products lie largely outside the conventional gas chromatography analytical window. However, there now exists technology to quantitatively track how the various oil-weathering processes (evaporative, water washing, photo-oxidation and biodegradation) change the petroleum composition at a molecular level. For example, it has been demonstrated that ultra-high resolution mass spectrometric analysis allows identification of 1000's of oxidative weathering products.
This project aims to apply these techniques in order to understand how these weathering processes occur, to quantify rate(s) of oxygenated oil weathering product formation and degradation, and characterize toxicological effects on the ecosystem. More specifically, this project aims to answer the questions: (1) How does the molecular composition of MWO oil change over time? (2) Which compositional changes are caused by photo-oxidation? Biodegradation? How does the structural / chemical composition of the oil influence oxidation? (3) How does this compositional change influence toxicity of weathered MWO? (4) What is the overall fate of MWO on a time scale of 8 years?
This project will track the continued weathering of MWO and focus on early sampling dates (0-10 months) immediately after the spill, where a rapid formation of oxygenated products is hypothesized, as well as highly weathered samples (to be collected up to eight years after the spill). The proposed analytical methodologies will capture bulk and molecular level, biotic / abiotic temporal compositional changes in the MWO as it weathers in the environment. The efforts will generate a compositional database of the quantitative and qualitative weathering of MWO. Second, analysis of field samples will be combined with controlled laboratory experiments of MWO photo-oxidation and biodegradation. Third, MWO and other oils, their structurally defined fractions, and all weathering products for each, will be screened for toxicity (narcosis), and observed effects will be linked (correlated) to the molecular compositional change in MWO during weathering. Finally, since the structural dependence of weathering will captured herein, along with each fractions toxicity (and water soluble fractions), a simple model will be constructed based on the quantitative yields of each structural fraction, its associated weathering products, and rate of formation. Thus, simple quantitative fractionation of any future contaminant could potentially be used to predict the rate, mass, and type of weathering products formed. The model will be validated against field data collected from the Deepwater Horizon disaster and other recent oil spills.
Project Research Overview (2016):
An overview of the proposed research activities from the GoMRI 2016 Meeting in Tampa.
Direct link to the Research Overview presentation.