Laser fluorescence excitation-emission matrix (EEM) probe for cone penetrometer pollution analysis

摘要

Abstract: A 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 to 400 nm) from the Raman shifter are launched into optical fibers that are connected to the optical fibers of the cone penetrometer probe through standard connectors. In the probe head, the laser radiation is focused onto the outer surface of sapphire windows that are in contact with the soils. The fluorescence emission is collected by ten collection fibers that take 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 quantity of pollutants in soils. This probe can be used to measure POL (petroleum, oil, lubricants), PAH (polycyclic aromatic hydrocarbons), and other fluorescent pollutants. The LIF-EEM instrument has been developed in the laboratory, and installed in a cone penetrometer truck for a field test at Hill Air Force Base, Utah. The experience of the test is discussed. !15