EVALUATION OF SUBSURFACE OXYGEN SENSORS FOR REMEDIATION MONITORING

Continuous remediation monitoring using sensors is potentially a more effective and inexpensive alternative to current methods of sample col lection and analysis. Gaseous components of a system are the most mobi le and easiest to monitor. Continuous monitoring of soil gases such as oxygen, carbon dioxide, and contaminant vapors can provide important quantitative information regarding the progress of bioremediation effo rts and the area of influence of air sparging or soil venting. Laborat ory and field tests of a commercially available oxygen sensor show tha t the subsurface oxygen sensor provides rapid and accurate data on vap or phase oxygen concentrations. The sensor is well suited for monitori ng gas flow and oxygen consumption in the vadose zone during air sparg ing and bioventing. The sensor performs well in permeable, unsaturated soil environments and recovers completely after being submerged durin g temporary saturated conditions. Calibrations of the in situ oxygen s ensors were found to be stable after one year of continuous subsurface operation. However, application of the sensor in saturated soil condi tions is limited. The three major advantages of this sensor for in sit u monitoring are as follows: (1) it allows data acquisition at any spe cified time interval; (2) it provides potentially more accurate data b y minimizing disturbance of subsurface conditions; and (3) it minimize s the cost of field and laboratory procedures involved in sample retri eval and analysis.