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UP: Umweltphysik

UP 13: Zukünftige physikalische Methoden der Meeresforschung

UP 13.2: Hauptvortrag

Mittwoch, 9. März 2005, 10:45–11:15, TU HFT101

Advances in Chemical Physics in the Deep Ocean: NMR and Raman Spectroscopy at 3.5km Depth — •Peter G. Brewer — Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039, USA

For over a century the primary strategy for chemical investigation of the ocean has been to recover samples and return these to ship or shore based laboratories for measurement. Extraordinary advances in laboratory technique have made great progress possible, but the alternative of equally sophisticated work in situ has been largely unexplored. With the advent of remotely operated vehicles for science we now have the power, payload, bandwidth and manipulative ability to carry out deep-sea experiments impossible only a few years ago. For example, we have used proton nuclear magnetic resonance (NMR) at 2MHz to measure changes in the liquid water content of sediment and rock resulting from methane hydrate formation at 1034m depth and 3.8^∘C, and identified the manner in which hydrate forms in pore spaces and alters the hydraulic permeability of sediments. And we have modified and successfully used a laser Raman spectrometer for real time geochemical measurements at 3.6 km depth (1.6^∘C). We have now used this to identify mineral species at hydrothermal vents, the fractionation of gas mixtures at depth from differential solubilities, the geochemical signature of pools of CO2, and the spectral signature of bacterial mats and methane hydrates in the deep sea. For opaque minerals precise laser focusing on the specimen is required and we have successfully developed novel systems for this.