Laser-Induced Breakdown Spectroscopy for In Situ Chemical Analysis at Sea

Spectroscopy is emerging as a technique that can expand the envelop of modern oceanographic sensors. The selectivity of spectroscopic techniques enables a single instrument to measure multiple components of the marine environment, and can form the bases of versatile tools to perform in situ geochemical analysis. This work investigates emission spectroscopy using laser-induced plasmas to perform multi-element chemical analysis of liquids and solids at sea. In situ measurements of both liquids and solids have been successfully performed at sea using the 3000 m depth rated prototype I-SEA (In situ Seafloor Element Analyser). Techniques aimed at optimising the signals observed from plasmas generated at high pressure are described and their mechanisms discussed. I-SEA is just an example of a new generation of chemical cameras (ChemiCam) that can probe different aspects of the environment. It is hoped that through integration with platforms such as underwater vehicles, drilling systems and subsea observatories, this technology will contribute to more efficient scientific surveys, and serve as a tool to facilitate both spatially and temporally continuous study of the ocean.