AROMATIC HYDROCARBON OPTRODES FOR GROUNDWATER MONITORING APPLICATIONS

AROMATIC HYDROCARBONS SPILLED OR LEAKING FROM UNDERGROUND STORAGE FACILITIES POSE A MAJOR THREAT TO GROUNDWATER RESOURCES. IN RESPONSE TO AIR FORCE REQUIREMENTS, GEO-CENTER, INC. PROPOSE TO DESIGN, DEVELOP, AND TEST FIBER OPTIC OPTRODES SUITABLE FOR LONG TERM IN-SITU MONITORING OF GROUNDWATER AND EARTH MATERIAL FOR THE PRESENCE OF AROMATIC HYDROCARBONS. GEO-CENTERS, INC. WILL CONSTRUCT AROMATIC HYDROCARBON SENSORS USING TWO ALTERNATE FIBER OPTIC APPROACHES AND EVALUATE THEM ON AN EQUAL BASIS TO DETERMINE THEIR PERFORMANCE AND RECOMMEND THE MOST SUITABLE APPROACH FOR USE AT AIR FORCE SITES. THE TWO FIBER OPTIC APPROACHES ARE: 1. A POROUS WAVEGUIDE SENSOR: A POROUS SECTION OF FIBER IS IMPREGNATED WITH A CHEMICAL INDICATOR. THE OPTICAL TRANSMISSION OF THE INDICATOR WILL CHANGE WITH CONCENTRATION OF AROMATICS AND AN OPTICAL MEASUREMENT IS MADE. 2. AN INFRARED PROBE SENSOR: IR FIBER OPTICS ARE COUPLED TO A PROBE TIP WHERE EVANESCENT ABSORPTION SPECTROSCOPY IS USED TO MEASURE CONCENTRATION OF AROMATICS. AN ANALYSIS OF SYSTEM FUNCTION AND MULTIPLEXING METHODS WILL ALSO BE CONDUCTED.