On-Site Laser Probe for the Detection of Petroleum Products in Water and Soil

Time-resolved laser-induced fluorescence spectroscopy and fiber optics are shown to be promising tools for the detection of environmental pollutants in water and soil. Time-integrated data accumulation of fluorescence intensities in an “early” and in a “late” time window with respect to the excitation pulse simplifies the method in such a way that it becomes very attractive for practical applications. Results from field measurements are reported while on-line oil concentrations in an industrial oil separator are monitored for process control. For UV laser excitation at 337 nm and recording LIF signals at 400 nm, typical detection limits of the present setup are 0.5 mg of engine oil/L in water and 5 mg of engine oil/kg in soil. The selectivity of the method can be improved significantly when a multiwavelength laser excitation in the ultraviolet spectral range between 240 and 360 nm is applied. Thus, a separation between different classes of aromatic components in petroleum products is possible.