Demonstration of a VOC in-situ fiber optic sensor for use with a penetrometer analysis system

Researchers at the Idaho National Engineering Laboratory with their industrial CRADA partner GEO-CENTERS demonstrated a fiber optic based VOC sensor at the Army Environmental Center technology demonstration at Dover Air Force Base. The sensor used during the demonstration was a single fiber optic cable coupled to an in situ sensor element contained in a cone penetrometer tip. The sensor's fluorescence response was measured at the surface using an optical breadboard-based instrument. Results from this demonstration showed that the sensor provided semi-quantitative results for total VOCs comparable to the historical values of VOCs. In addition, the demonstration identified several technical challenges for improvement of the sensor. This paper describes the analytical properties of the reversible sensing materials, construction of an improved sensor system, and the planned demonstration of the modified in- situ VOC sensor system. This sensor system is tentatively scheduled for demonstration at the Army Environmental Center's Aberdeen Proving Ground Test site. Improvements to the VOC sensor system include an optical configuration that will correct for soil matrix interferences and multiple sensing substrates to learn whether VOC selectivity can be achieved.