Applications of a laser-induced fluorescence spectroscopy sensor in aquatic systems

The use of laser-induced fluorescence spectroscopy (LIFS) is fairly accepted as a fast and reliable method for the online detection of contaminations with polycyclic aromatic hydrocarbons (PAHs) and oil in groundwater and soils. Our work was focussed not only on the assessment of those contaminations, but on the use of LIFS as a generic tool to assess subsurface contaminations and aquifer properties. Pattern recognition techniques were successfully applied to map contaminant plumes surrounding waste disposal sites. Remediation activities at a former gas plant site were monitored using a sensor system based on time-resolved fluorescence spectroscopy. Tracer investigations in the saturated and unsaturated zone were enhanced due to the small time intervals between the single measurements. The determination of single analytes (e.g. pyrene, benzo(a)pyrene) out of a complex mixture of fluorescent compounds was possible by taking advantage of the fluorescence decay-times and by applying a site-specific calibration.