Oceanic Applications of Laser Induced Breakdown Spectroscopy: Laboratory Validation

Abstract

New chemical sensors are needed for both present day expeditionary oceanography and an emerging new phase involving long term in situ ocean observations. Over the past four decades, a new spectrochemical technique, laser induced breakdown spectroscopy (LIBS), has been under development for the identification of the elemental constituents of materials. This technique uses a laser to create a spark or plasma on a sample. The plasma emission is then analyzed with a spectrometer to determine its elemental composition. Recently, LIBS has been identified as a viable tool for in situ field measurements because it is able to analyze all forms of matter (solids, liquids, and gases), can operate in a stand-off mode, and is non-invasive and non-destructive. A marine LIBS sensor would be a useful tool for studying many environments in the ocean, especially mid-ocean ridge hydrothermal vents where in situ measurements are difficult due to the presence of high-temperature, corrosive fluids. A feasibility assessment of oceanic LIBS in the laboratory has been initiated. A high pressure chamber was designed and built for investigating the effect of realistic ocean environments on the LIBS signal. Preliminary work shows that LIBS can successfully detect Li, Na, K, Ca, Mn, and Zn in bulk aqueous solutions at pressures up to 272 atm, making LIBS a viable technique for deep ocean chemical sensing.