ABSTRACT

Laser-induced fluorescence (LIF) provides considerable sensitivity in the detection of fluorescent analytes, based upon laboratory experiments of single-molecule detection limits. In the realm of geophysical testing of soils and subsurface environments, cone penetrometer testing (CPT) has proven its effectiveness. LIF-CPT has proven to be a rapid, cost-effective approach to environmental site characterization and monitoring. It provides real-time data collection for mapping contaminant distribution in the subsurface, which surpasses conventional data collection methods. The LIF probe uses simultaneous multiple-wavelength excitation and emission detection and processes the data as an excitation–emission matrix. To improve capabilities of the US Environmental Protection Agency-funded tool, a second-generation LIF system was constructed. The probe was redesigned to allow all 10 excitation–emission fiber pairs to send and receive signals through one 1-cm-diameter sapphire window. This modification was made to eliminate the need for depth correction of fluorescence data collected from separate windows.