Laser Fluorescence EEM Probe for Cone Penetrometer Pollution Analysis

Laser Fluorescence EEM Probe for Cone Penetrometer Pollution AnalysisJie Lin, Sean J. Hart, Todd A. Taylor, and Jonathan E. KennyDepartment of Chemistry, Tufts University, Medford, MA 02155.ABSTRACTA laser-induced fluorescence (LIF) excitation-emission matrix (EEM) probe has been developed in the laboratory,and installed and tested in a cone penetrometer. The laser excitation system uses the fourth harmonic of a flashlamp-pumped Nd:YAG laser (at 266 nm) to pump a Raman shifter. Up to ten laser beams (in the wavelength region of 257 to400 nm) from the Raman shifter are launched into optical fibers that are connected to the optical fibers of the conepenetrometer probe through standard connectors. In the probe head, the laser radiation is focused onto the outer surfaceof sapphire windows that are in contact with the soils. The fluorescence emission is collected by ten collection fibers thattake the fluorescence to a detection system consisting of a spectrograph and a CCD detector.This probe allows real-time collection of LIF-EEMs of pollutants adsorbed on solids or dissolved in groundwater.LIF-EEMs provide a substantial amount of spectral information that can be used to determine the composition and quantityof pollutants in soils. This probe can be used to measure POL (jetroleum, oil, lubricants), PAH (polycyclic aromatichydrocarbons), and other fluorescent pollutants.The LIF-EEM instrument has been developed in the laboratory, and installed in a cone penetrometer truck for a fieldtest at Hill Air Force Base, Utah. The experience of the test will be discussed.Keywords: laser-induced fluorescence, excitation-emission matrix, fiber-optic probe, cone penetrometer, Raman shifter,groundwater pollution, field test.1. INTRODUCTIONCharacterization, remediation, and clean-up of contaminated sites are becoming very important environmental issues.Traditionally, site characterization is done by drilling a well, bailing, and removing samples for conventional laboratory

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