ASSESSMENT/FLUORESCENCE/SPECTROSCOPY: Optical technologies aid oil spill efforts, with boost from NSF

As oil gushed into the Gulf of Mexico this summer, the National Science Foundation (NSF) responded with lightning speed to fund proposals for research related to the spill. Taking advantage of its unique funding mechanism called Rapid Response Research (RAPID), the agency was able to review and award grants in some cases in less than two weeks. The 160 grants issued to date total over $17 million.

"We want to respond to disasters before ephemeral data is lost," says Josh Chamot, NSF media officer for engineering. Getting proposals reviewed and approved involves program officers who set project priorities, an internal review team composed of NSF personnel and a final stamp of approval from the appropriate division director. The money for RAPID and its counterpart Early-concept Grants for Exploratory Research (EAGER) comes from discretionary funds set aside for cutting-edge and/or rapid response research. Each RAPID grant is capped at $200,000 and is judged on merit and budget.

One RAPID grantee turned in a proposal on a Friday and had the money a week later. "NSF has been phenomenal in their response," says Paula Coble, an associate professor of chemical oceanography at the University of South Florida, College of Marine Science. Coble has teamed with WetLabs (Philomath, OR) to develop new optical sensors to track the flow of oil in open water. Corey Koch, a research scientist with WetLabs, which also received a RAPID grant, notes that putting together a three-page proposal rather than the usual 15-pager helped streamline the process.

Discovering oil's fluorescent signature

With the money in hand, Coble and Koch could immediately begin their studies of the spill's optical properties. Using excitation-emission matrix (EEM) spectroscopy, fluorescence lifetimes at multiple excitation wavelengths, absorption, and quantum efficiency, the researchers are studying the fluorescent signatures of oil, weathered oil, and dissolved oil from the spill.

So far, Coble's work in the Gulf has shown that over time, oil's fluorescent signature shifts from shorter wavelengths to longer ones. By characterizing each signature, Coble can distinguish oil fluorescence from naturally occurring fluorescence due to phytoplankton or zooplankton. The ability to separate the oil's fluorescent fingerprint from natural fluorescence is critical to tracking the flow of oil as it dissipates. One of the challenges to mapping the flow of oil in the Gulf this summer was trying to determine where the oil actually was.

The oil spill research has given new life to one of the instruments Coble purchased from WetLabs. The SAFire is a multi-spectral fluorometer that was discontinued in 2006 because of low demand. However, the instrument's wide wavelength range—220-700 nm (25 nm resolution)—six emission wavelengths and 16 excitation wavelengths permit collection of multiple data points. The SAFire can perform up to 1 EEM (96 data points) every 2 s, and is operational to 500 m depth.

Coble is also using WetLabs' next-generation, in situ spectral fluorescence instrument: the XMF. Although the XMF's continuous excitation range is smaller—250-520 nm (10 nm resolution)—the instrument can be deployed to depths below 500 m, and can perform up to two excitation-emission scans per second. This produces an EEM (~3,900 data points) every one to two minutes.

"A lot of single-channel fluorometers used in the Gulf may miss remaining oil because they cannot pick up the oil's spectra. [Because of the range of each instrument] we can tell when the oil has shifted out of range," says Koch.

Monitoring a leaky Gulf

Although the surface oil may be dissipating, "we know that significant quantities of oil remain underwater," says Koch. "This raises new questions of how the degradation will affect the ecosystem." To study these questions, Coble and Koch are collaborating with other scientists to see how oil degrades over time, how its molecular composition changes, and how various conditions contribute to that change.

The optical parameters developed by Coble and Koch will help create new optical sensors to track oil in the event of another oil spill, as well as on a continual basis. Coble notes that oil regularly seeps from previously capped wells and natural weep holes in the Gulf floor. Additional oil comes from land run-off. "The Gulf is leaking," says Coble. "Nobody has ever tried to quantify how much oil is in the Gulf. These instruments may provide some answers."

Using excitation emission matrix spectroscopy, researchers have discovered the unique spectral fingerprints for oil, weathered oil, and dissolved oil from the Deepwater Horizon oil spill in the Gulf of Mexico. Ongoing fluorescence studies will assist in development of new optical sensors to track oil in seawater.

Other optical solutions

Roughly 5% of the RAPID grants issued to date are related to biooptics. Each will provide a unique data set to understanding the impact of the Gulf oil spill. Here are highlights from the other biooptics-related RAPID grants:

  • Development of a submerged oil detector using ultraviolet fluorescence deployable at depths up to 1829 m (James Bonner, Clarkson University)
  • Quantitative assessment of the oil spill's impact on exposed fish populations and coastal ecosystems using a fluorescence-activated cell sorter (Stephen Pruett, Mississippi State University)
  • Use of spectrofluorescence to detect oil, study biomass, and determine photosynthetic capacity of organisms affected by the spill (Alexander Chekalyuk, Columbia University)
  • In situ measurements of oil and vegetation under stress between 350 nm and 2500 nm, as well as assessment of onshore tar balls using spectral un-mixing to support clean-up activities (Daan Liang, Texas Tech University)

Expect a few more additional funding opportunities, as Congress and the White House consider how best to support long-term studies of the effects of the oil spill both on human health and on the environment. NSF will likely get some funding in this area, as will several agencies within the Department of Health and Human Services. In September, the National Institutes of Health announced its own $10 million effort led by the National Institute of Environmental Health Sciences to study of the spill's human health effects. —Susan M. Reiss

 

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