Novel Optical Detection Schemes for In-Situ Mapping of Volatile Organochlorides in The Vadose Zone

Angel, S. Michael

University of South Carolina (United States)

关键词: Hydrocarbons;    Lawrence Livermore National Laboratory;    Cones;    Electrostatics;    Fluorescence;   

DOI  :  10.2172/823367
RP-ID  :  DOE/ER/62881
RP-ID  :  FG07-99ER62881
RP-ID  :  823367

美国|英语

来源: UNT Digital Library

【 摘 要 】

The long-term objective of this research is to develop a system for measuring and identifying a wide rang of volatile organic hydrocarbons, including organochlorides, at ppb levels in-situ in the subsurface (''at-dept'') using a fiber-optic REMPI probe. In this renewal proposal we would also like to expand the range of analytes to include contaminated soil and certain metal pollutants such as Hg and Pb. And, to do this in a ruggedized system that is compatible with existing fiber-optic sensors, Raman and fluorescence probes and image guides. The specific focus of much of the proposed work is to identify and optimize those experimental parameters which effect the in-situ determination of organic molecules using resonance-enhanced multi-photon ionization (REMPI). To accomplish this goal we will systematically investigate the dependence of REMPI on laser wavelength, power and other experimental parameters for a variety of high-priority groundwater and vadose zone contaminants to determine optimal measurement conditions. Emphasis will be placed on visible or fiber-optic compatible wavelengths of excitation so that the high transmission of fiberoptics can be fully utilized. A fiber-optic REMPI system is being designed that is suitable for integration into an existing cone penetrometer system being delivered by LLNL. Fiber-optic probe designs that we tested in the first studies will be refined by LLNL. Probe performance will be predicted using previously developed optical techniques and also using electrostatic field models.