The Department of Defense (DoD) must identify and characterize emissions of trace air toxic compounds from both stationary and mobile sources. Over the past 15 years, the Microsensor Development Program at Argonne National Laboratory has fabricated inexpensive voltammetric microsensors capable of evaluating emissions in near-real time (i.e., within seconds). These microsensors function across a broad range of ambient temperatures and can detect a wide variety of constituents from diesel exhaust. They also have been used to detect xylene, toluene, methylene chloride, formaldehyde, methane, ethanol, isopropanol, and propane in concentrations from part per billion (ppb) to part per million (ppm) based on voltammetric techniques.

This project aimed to (1) develop miniature sensors and portable sensor arrays capable of rapidly detecting and characterizing trace air toxic compounds in near-real time, (2) integrate pollutant data into spatial and temporal emission profile models correlated with specific DoD activities, and (3) produce high-quality emission factors for targeted pollutants released during various activities.

This project used cermet (ceramic-metallic) voltammetric “smart” microsensors to monitor emissions in near-real time. Voltammetric analytical techniques were employed during sensor operation to detect a wide range of gaseous constituents and analyte concentrations from ppb to percent levels. Several chemometric methods, including radial basis neural networks and support vector machines, were used to resolve composite signals from a mixture of gases into individual components. By combining existing and experimental microsensor technologies, more capable and comprehensive microsensor arrays were developed for selected emission constituents.

This project developed new gas voltammetry-based diesel exhaust measurement instrumentation and characterized four target diesel constituents, including acrolein, acetaldehyde, benzene, and 1,3-butadiene. Concentrations of these gases as low as 1-5 ppm were detected in actual diesel exhaust. A new type of titanium dioxide (TiO₂)-based photocatalytic gas sensor was designed, fabricated, and evaluated. While improvements in detection performance are required, its low power consumption and technical simplicity represent a promising new phenomenon.

This project provides DoD with small, portable, and inexpensive micro-sensing systems for detecting and characterizing trace air toxic compounds. Operating from a laptop computer, these new systems provide near-real time analysis and feedback, as well as improved emission characterization profiles associated with DoD activities. (Project Completed - 2005)