Preliminary Testing Results of Sensor for Speciating Benzene, Toluene, and Ethylbenzene/Xylenes in Groundwater

Oral Presentation

Prepared by R. Mohler1, F. Bender2, F. Josse2, A. Ricco3, R. Kolhatkar4
1 - Chevron ETC, 100 Chevron Way, 50-1271, Richmond, CA, 94801, United States
2 - Marquette University, Department of Electrical and Computer Engineering, Marquette University, Milwaukee, WI, 53201-1881, United States
3 - Stanford University, Department of Electrical Engineering, Center for Integrated Systems, Stanford University, Stanford, CA, 94305-4075, United States
4 - Chevron ETC, 3901 Briarpark, Houston, TX, 77042, United States

Contact Information: [email protected]; 510-242-4939


Accidental fuel releases can result in the presence of aromatic hydrocarbons in the groundwater. Once specific hydrocarbons, e.g. benzene, are detected in the groundwater, quarterly, semi-annual, or annual monitoring will commence. These monitoring events can continue for extended periods of time and involve sending people to sites, the collection of groundwater samples, shipment of groundwater samples to the laboratory, analysis of the groundwater at the laboratory and generation of a report for the laboratory in the following weeks. This process can not only be costly, but also result in safety incidents due to personnel traveling to the field. Over the last five years, collaborative research project between Chevron, Marquette University and Stanford University has led to the development of a sensor device that is capable of aqueous phase measurement of hydrocarbons at concentrations down to about one hundred parts per billion in groundwater. This sensor not only detects hydrocarbons, but can also speciate and quantify (within 5 to 10% accuracy) benzene, toluene, and ethylbenzene/xylenes (BTEX) in groundwater (ethylbenzene and xylene, as chemical isomers, are currently indistinguishable by the sensor). The initial phases of the research have demonstrated that the sensor device is capable of quantifying BTEX concentrations in aqueous solutions, and that the device is showing reproducible responses when being repeatedly exposed to BTEX samples dissolved in water over the course of three months. In the current phase of the project, the sensor response to hydrocarbons in groundwater is being evaluated. Systematic sensor measurements in groundwater began in 2014. The performance of the sensor in various environments and early results from the groundwater study will be presented. The BTEX concentrations obtained by the sensor were independently confirmed by a commercial laboratory and a portable gas chromatograph. The progress to date looks promising for future development of a downhole sensor capable of detecting and quantifying dissolved BTEX in groundwater.