Development and Field Test of a New Laser Induced Fluorescence (LIF) Spectrometer for in Situ Investigation of Oil-Contaminated Soils

For the in situ detection and analysis of oils (petroleum products and vegetable oils) in soils we developed a family of mobile LIF spectrometers (Oil Pollution Transportable Independent Monitoring System, OPTIMOS) designed for field usage. In the full version, the OPTIMOS consists of a Nd:YAG laser (combination with a dye laser optional), an ICCD (intensified charge coupled device) multichannel detection system and flexible waveguide technology (see the contribution by Hengstermann et al. for more experimental details). We have characterized various versions of the OPTIMOS, including simpler configurations with UV light emitting diodes (LED’s) as the light source and photomultiplier tubes (PMT’s) or photodiodes as detectors. Figure 1 shows the LIF spectra of different petroleum products on a German soil (Ahhorizon). The spectra were recorded with a setup consisting of a N₂-laser as the excitation light source, a monochromator / photomultipier combination as the detector and a fibre optical sensor head. Currently, we are improving and expanding the OPTIMOS performance by focusing on: optimized calibration procedures, software-assisted quantification;multi-wavelength excitation (tunable lasers, e.g. dye lasers);improved field performance (ruggedness, reduction in size, weight and electrical power demand);user friendly, ergonomic spectrometer setup.