The PIs have requested a RAPID award to continue development their prototype in-situ instrumentation capable of measuring spectral fluorescence (the excitation emission fluorometer (XMF) and the spectral fluorescence sensor (SAFire)) to aid in the tracking of the Deepwater Horizon oil spill in the Gulf of Mexico.
The Deepwater Horizon oil spill has generated a demonstrable and urgent need for in-situ verification of crude oil presence at all depths in seawater, the effect of dispersants, and an in-situ methodology to study the molecular transformations crude oil undergoes as it weathers, is dispersed, and is acted upon by biota. The results from this project will be used to develop an upgrade path to transform current, low-cost, in-situ sensors developed for other parameters into effective crude oil tracking instruments. These advanced sensors could be used to track changes in the Gulf spill over the long term, would be appropriate for various autonomous observational platforms, provide real-time field affirmation of crude oil presence, and be readily available for future crude oil sensing applications.
Broader Impact:
The proposed work will identify optimal fluorescence pairs needed to provide refined and low-cost multi-spectral UV/VIS sensors for studying the fate and impacts of crude oil in the environment. This, and the study results, will directly improve our ability to accurately track oil in the natural ocean environment, providing for a better assessment of the impacts of the current spill and thereby improve response if needed in the future. The conclusions drawn from this study may have far reaching impacts in that they will add to the body of knowledge society can draw upon to manage natural resources. Additionally, this work will provide valuable research experience for the PI, a Post- Doctoral scientist, as a beginning young investigator.
" was intended to help us learn more about tracking subsurface oil and understanding the chemical changes oil undergoes in the environment. Fluorescence is a sensitive optical phenomenon that can be made compact and robust for submerged use in the water column (in-situ) and at significant depth. Generally, light of a shorter wavelength (e.g., UV light) is shown onto a sample and, if fluorescent, light of a longer wavelength is emitted (e.g., visible light); this is akin to what one sees when a black light shines on white fabric. Fluorescence sensors were used in response to the Deepwater Horizon oil spill to track oil and identify the deep-water oil plumes, but the utility of the measurements was not well understood. In RAPID Deepwater Horizon Oil Spill: In-situ tracking of oil in seawater and the aging process using spectral fluorescence, we used a more comprehensive form of fluorescence by looking at oil fluorescence behavior over a larger range of wavelengths than typical fluorometers, which may only have a single channel representing a short range of wavelengths. This results in something akin to a fluorescence fingerprint for a sample. Further we wanted to better understand how changes in the fluorescence fingerprint can help us understand how oil is weathering or what the oil source could be. The RAPID grant allowed researchers to quickly mobilize and optimize several "SAFire" spectral fluoromters to aid in the oil spill response. In-situ spectral fluorometers capable of generating coarse fingerprints were deployed in the deepwater Horizon response and in wave tank studies with oil. In addition to this, controlled laboratory experiments were performed with various oils from around the globe to understand how oil-type, time, photodegradation, and biodegradation affect fluorescence response and the chemical makeup of the oil sample. In the lab studies, chemical analysis (via Gas Chromatography Mass Spectrometry or GC-MS) was performed to better understand how fluorescence signatures are related to specific compounds. Several results have come from the study. One example is key optical parameters that can track oil of numerous types, help determine oil type, dispersant efficiency, and maintain sensitivity as optical signals are bleached by sunlight. This information will help sensor manufacturers design oil tracking fluorometers that are much more effective. Additionally, understanding how the fingerprints change with environmental weathering combined with wave tank experiments with other fluorometers used in the oil spill response is helping us better interpret data from deep measurements made with different sensors. Toxic polycyclic aromatic hydrocarbons (PAHs) identified in chemical analysis have been tied to specific regions of the fluorescence fingerprint and can thus be traced with fluorescence to help understand how the public and fisheries are impacted. Additional outcomes include methods for controlled simulation of oil spill samples and better understanding the chemicals that contribute to the fluorescence fingerprint of oil. Finally, results also suggest that fluorescence could be a useful tool to understand how PAHs dissolve from dispersed oil droplets into the water column. This will help us better understand the impact using disperants can have. Images included show a photo of the SAFire in-situ spectral fluorometer (WET Labs), a schematic of the Water Accommodated Fraction (WAF; just the dissolved part) of oil, a comparison of an oil spectral fluorescence fingerprint from the SAFire in-situ fluorometer and a water sample taken back to the lab and analyzed with a benchtop fluorometer, and some results from the GC-MS chemical analysis.
