Application of pulsed laser methods to in situ probing of highway originated pollutants

A possibility of a portable field kit for studying traffic originated pollutants based on laser induced fluorescence (LIF) or multi-photon ionization fast-conductivity (MPI-FC) has been addressed. The resulting instrumentation has been successfully tested on soil samples that were collected and classified according to their radial distance, R, from a busy highway. The sampling was done in the near-field range with R varying from 3 to 50 m. Organic material from the samples was transferred into hexane solutions by short-time shaking with pure hexane. These solutions were investigated by simple LIF and MPI-FC instruments, which can be engineered as portable units (e.g., a PC plugged-in spectrometer has been used, in which case both the signal excitation and detection were accessed by means of optical fibers). Detected traces showed a nearly 1R fall-off of the LIF and MPI-FC experimental data as a function of the sample distance from the road. It is estimated that at 50 m from the road the contamination concentrations (about 90% aliphatics and 10% aromatics) are as high as 0.1 μg g−1. Both proposed methods provide good sensitivity at the relevant concentration range and may be applied for fast screening of traffic contamination of soils.