We have developed, deployed, and tested a Raman spectroscopic probe for study of the geochemistry of sediment pore waters. The Raman technique has already been used successfully for in situ measurements of targets of scientific interest including gas and hydrothermal vents and complex gas hydrates, but sediment geochemistry has so far been an intractable problem since the sediments themselves are strongly fluorescent and typically only very small sample volumes are obtainable. The 35 cm long probe extracts pore fluids through a 10 micron sintered metallic frit and draws the sample through a 2 mm diameter channel into a sapphire windowed optical cell within which the laser beam is focused and the spectrum recorded. The unique features of this mode of detection include observation of the sulfate gradient in marine pore waters as an indicator of diagenesis, direct measurement of the dissolved sulfide species H2S and HS-, and measurement of dissolved methane; all of which are of primary geochemical interest. This paper outlines the technology and techniques used to accomplish in situ measurements in harsh environments that could possibly be adapted to other applications.

Development and deployment of a deep-sea Raman instrumentation for in situ analysis

245th National Meeting (2013)

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