An In-Situ Ion Mobility Spectrometer Sensor System for Detecting Gaseous VOCs in Unsaturated Soils

Existing methods for the detection and measurement of volatile organic compounds (VOCs) in the vadose zone are often hampered by issues associated with ease of use, accuracy, and cost. As a result, there remains a need for inexpensive, minimally invasive, real-time instrumentation and sensor systems that can be used for characterizing or long-term monitoring of contaminated sites. A new sensor system to meet this need is under development at Boise State University, in collaboration with Washington State University. A miniature Ion Mobility Spectrometer (IMS) has been fabricated from a machinable ceramic material and has been shown to have a resolving power comparable to a commercial IMS. The IMS system will be packaged in a probe housing for deployment using direct push methods and will be ultimately equipped with water content, temperature, and pressure sensors. The proposed system is designed for use in multi-probe arrays and features wireless transmission of data directly to the user. To our knowledge, an in-situ IMS for detection of subsurface gaseous VOCs has not been previously developed.