Part I. From the Lab to the Field - Recent Developments in Polymer Coated ATR Sensing for the Determination of Volatile Organic Compounds ; Part II. From the Field to the Lab - Investigating IR Signatures for Remote Sensing Applications

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Karlowatz, Manfred
Mizaikoff, Boris
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Part I: Successful transition of polymer coated, ATR-FTIR sensor devices from a laboratory environment to real world field applications for detecting and quantifying VOCs in water is shown. Simultaneous, quantitative detection of BTX mixtures in water during enrichment into polymer coated ZnSe ATR elements has been performed. The obtained results showed accurate detection and quantification to the low ppb concentration region. Fiber-optic evanescent field measurement campaigns have been conducted at simulated field conditions during which concentration gradients of various VOCs in the mg/L range have been monitored successfully. The first test of an ATR based, polymer coated sensor system under real world field conditions, the chlorobenzene concentration in groundwater at mg/L levels was determined. An interesting aspect of these measurements was the experimental proof for the dependence of analyte extraction dynamics on the flow conditions of the sample matrix surrounding the extractive polymer membrane. The obtained results demonstrate that MIR evanescent field sensors are suitable for in-situ analysis at real world field conditions for environmental monitoring applications. PART II: Recently, measurements of disturbed soils have shown different spectral contrast in comparison to undisturbed soils. In this work first measurements at controlled laboratory conditions have been performed to investigate individual minerals of the soil matrix and their spectral characteristics under various environmental conditions. ATR spectroscopy has been applied to investigate multi-disperse quartz sand and mono-disperse soda lime glass spheres samples. For the investigation of spectral differences between pristine and disturbed quartz sand, a wetting/drying procedure with subsequent sample aerating has been developed. In addition to established differences in spectral contrast of disturbed and undisturbed soil, a strong spectral shift of absorption features was observed. When probed with s- or p-polarized light, both samples showed strong LO-TO mode splitting. The studies also reveal that the main reason for spectral differences of pristine and disturbed soils is caused by water facilitated changes of the particle size distribution in the probed volume. The presented results advance the variety of spectral characteristics useful for the detection of disturbed soils (i.e. possible landmine sites) with MIR imaging systems.
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