Field experiments with a portable fiber-Optic sensor system for monitoring hydrocarbons in water
✍ Scribed by J. Bürck; M. Mensch; K. Krämer
- Publisher
- John Wiley and Sons
- Year
- 1998
- Weight
- 409 KB
- Volume
- 2
- Category
- Article
- ISSN
- 1086-900X
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✦ Synopsis
The prototype of a portable fiber-optic sensor system for monitoring apolar hydrocarbons in groundwater or industrial wastewater is presented. This sensor system can be used for quantitative in situ analysis of organic pollutants like chlorinated hydrocarbons, aromatic hydrocarbons, or fuels in a broad concentration range from around up to a few The Ϫ1 Ϫ1 200 g l 100 mg l . sensing principle is based on the reversible enrichment of analyte molecules in a hydrophobic silicone cladding of a quartz glass optical fiber and the direct (spectro)photometric measurement of the extracted species in the polymer through the evanescent wave. The sensing fiber of 12-30-m length is coiled to a compact, cylindrical geometry ( in size) on a stainless steel support 14 ϫ 5 cm and can be connected via all-silica fibers with a length of up to to a low-cost bandpass filter photometer de-100 m veloped at the IFIA, thus allowing even remote analysis. This instrument provides a sum concentration signal of the extracted organic compounds by measuring the integral absorption at the C-H overtone bands in the nearinfrared spectral range. Field measurements with the sensor system have been performed at the research facility for subsurface remediation VEGAS of the Universita ¨t Stuttgart, and at a former chemical landfill in Mu ¨hlacker, Germany. These in situ experiments were carried out in water mainly contaminated with chlorinated hydrocarbon compounds. A comparison of the in situ data and laboratory reference analyses of aqueous samples drawn discontinuously gave rather satisfactory agreement between both data sets with a mean deviation of 9% for the VEGAS experiments and 20% for the Mu ¨hlacker field trials.