Raman Spectroscopy in the Deep Ocean:
Successes and Challenges

Jill Dill Pasteris, Brigitte Wopenka & John J. Freeman
Department of Earth and Planetary Sciences
Washington University, Campus Box 1169
St. Louis, MO 63132-4899

Peter G. Brewer, Sheri N. White, Edward T. Peltzer & George E. Malby
Monterey Bay Aquarium Research Institute
7700 Sandholdt Road
Moss Landing, CA 95039-9644

Applied Spectroscopy (2004) 58(7): 195A-208A.

Published: 2004 July.


ABSTRACT

The deep ocean is a demanding environment to the analyst, one that contains fine particles of degraded organic matter and is characterized by high pressures (about 360 atmospheres at 3.6 km depth), low temperatures (down to ~2°C), and a high concentration (3.5 wt %) of corrosive salts. Such conditions make it difficult to analyze in situ interesting and important geologic materials and dynamic processes on the ocean floor, such as the fluids and solids that issue from hydrothermal vents, the rocks that are formed by undersea lava eruptions, the skeletons and shells of calcareous animals such as corals and clams, and ice-like clathrates that form when natural gas seeps upward through the ocean-floor sediments and into the water column above. Because some of the phases of interest are not stable once they are brought to the surface and exposed to ambient pressure, temperature, and high oxygen concentration, only an in situ analytical technique can enable detailed investigation of the ocean environment.

Raman spectroscopy is well suited to meet some of the challenges of analysis on the ocean floor: the technique is very amenable to materials that reside in an aqueous environment (in contrast to infrared spectroscopy); analysis is possible on solids, liquids, gases, and dissolved species; and modern Raman instrumentation has fiber-optically coupled components that can be encapsulated in pressure-resistant housings for operation underwater.

In the present paper we report on the development, modification, calibration, deployment, and first successful applications of the deep ocean Raman in situ spectrometer (DORISS), which is based on a laboratory-model laser Raman spectroscopic system from Kaiser Optical Systems, Inc. (KOSI). This paper documents some of the analytical successes to date and discusses some of the challenges that lie ahead.

© 2004 by Applied Spectroscopy.


Acknowledgements

This research was supported by the David and Lucile Packard Foundation and the United States Department of Energy Ocean Carbon Sequestration Program (grants no. DE-FC26-00NT40929 and DE-FC03-01ER6305). We gratefully acknowledge MBARIís Mark Brown for his engineering and design help and Danelle Cline for her skilled work in implementing the software for system operation. The staff of Kaiser Optical, Inc., are thanked for their willingness to provide information necessary to the reconfiguring of the spectrometer and its software. We thank the following people for providing carbonate samples that were taken to the sea floor: Bob Cradock, Cheryl Seeger, Jere Cadoret, and Larry Nuelle. We thank the officers and crew of the RVs Point Lobos and Western Flyer, and the ROV pilot teams of Ventana and Tiburon, for their skill and support at sea.


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