Subsurface activities such as carbon storage and oil and gas production has the potential to affect the quality of groundwater supplies by adding contamination from the injection formation or fluids. Therefore, the detection of entrained contaminants that migrate into shallow groundwater aquifers is important to evaluate impacts on water resources. Naturally occurring elements (i.e., Li, Sr) in conjunction with isotope ratios can be used to detect such contamination. We propose the use of laser induced breakdown spectroscopy (LIBS) as an analytical technique to detect a suite of elements in water samples. LIBS has real time monitoring capability and can be applied for elemental and isotopic analysis of solid, liquid, and gas samples. The flexibility of probe design and use of fiber optics make it a suitable technique for real time measurements in harsh conditions and in hard to reach places. The laboratory scale experiments to measure Li, K, Ca, and Sr composition of water samples indicate that the technique produces rapid and reliable data. Included in our study was the effect of high concentration sodium salts on the accuracy of LIBS analysis. This work also outlines the fabrication and application of a miniature ruggedized remotely operated diode pumped solid state passively Q-switched laser system for use as the plasma excitation source for a real-time LIBS analysis. The potential of LIBS as a sensor for continuous measurements of subsurface fluid chemistry over long periods of time without human interaction will be discussed.

Primary Author/Conference Presenter:
Jinesh Jain
R&D Scientist
AECOM/National Energy Technology Laboratory
Pittsburgh, Pennsylvania