The PI requests MRI RAPID funding to purchase three cavity ring-down spectroscopy (CRDS) systems to quantify the isotopic composition and concentration of methane, dissolved inorganic carbon, and dissolved organic carbon in seawater samples. These instruments will be used to characterize the concentration and isotopic signatures of carbon species in the seawater and sediment samples collected in the vicinity of the Deepwater Horizon Oil Spill. These instruments will improve the ability to trace oil and gas derived from the Deepwater Horizon Oil Spill as it is processed and transformed into dissolved inorganic carbon and dissolved organic carbon and microbial biomass. The MRI RAPID investment is timely and critical in light of the recent Gulf of Mexico oil spill.
Broader Impacts: These instruments will substantially improve the PI's ability to analyze the current and future samples collected with current Gulf oil spill RAPID funding. This research has the potential to advance our understanding of oil and gas derived carbon flow in the Gulf of Mexico ecosystem and potentially improving global models of the oceanic carbon cycle.
Quantifying the concentrations and stable isotopic signatures of key climate-active trace gases that are produced and consumed during biological processes remains an analytical challenge in oceanography. Such data are required for understanding basic biogeochemical cycles in the environment as well as for understanding how different biological systems on Earth respond to or generate climate forcing(s). This major research instrumentation grant provided funds to purchase two cavity ring-down spectroscopy instruments manufactured to quantify the isotopic composition and concentration of methane and dissolved inorganic carbon in environmental samples. These instruments were used to analyze seawater and sediment pore fluid samples obtained from areas impacted by the 2010 Deepwater Horizon Oil Spill. The analytical method of cavity ring-down spectroscopy takes advantage of the unique near infrared adsorption spectrum of low molecular weight gases, such as methane or carbon dioxide, etc., to quantify the concentration of a gas as well as the stable isotopic ratio in its carbon atoms. These instruments are among the most sensitive, durable real-time analyzers for quantifying concentration and carbon isotopic composition of methane and carbon dioxide because the effective pathlength within the cavity can exceed 20 kilometers for a 25 cm cavity. The instruments are also easy to maintain, portable, robust and fast compared to other analytical options. Through this award, we have developed new methods and modified existing approaches to make these instruments more useful to the Oceanographic research community. This project has supported one post doctoral researcher, two graduate students, and one technician. The new methods we have developed have been applied to a variety of samples from Gulf of Mexico, including samples collected around the Macondo Wellhead following the BP spill, samples collected from natural hydrocarbon and brine seeps, and samples from the Orca Basin, a large, stable brine-filled basin. The data generated are being used in two graduate student theses and provide a key foundation for our post BP spill monitoring work to describe the long-term ecological and biogeochemical impacts of the discharge.
