EES Air Pollution Seminar: Characterization and deployment of low-cost air quality sensors

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Jiayu Li, PhD., Assistant Professor, University of Miami

Bio: Dr. Jiayu Li received her BS from Environmental School at Tsinghua University and Ph.D. from the Department of Energy, Environmental, and Chemical Engineering at Washington University in St. Louis. She then continued her research at Carnegie Mellon University. Her research mainly focuses on air quality sensors, including PM sensors and gas sensors. She tries to enhance the accuracy of these sensors through comprehensive calibration and advanced algorithms. These sensors have great potential for pollution mapping with high spatiotemporal resolution.

Abstract: Current instruments measuring air pollutants are still expensive and laborious in operation. These drawbacks limit the number of monitoring stations, which in turn undermines the accuracy of real-time mapping. The new trends of air quality measurement are the networking of a large number of sensors and personalized portable devices. Due to their price advantage and compact size, low-cost air quality sensors have been studied extensively, and they are considered as good supplements of current monitoring techniques for high spatial-temporal air pollution mapping. This talk will introduce my work on the characterization and deployment of various air quality sensors to measure particulate matter (PM) and gaseous pollutants.
Multiple types of low-cost particulate matter sensors were calibrated against reference instruments. A limitation of these sensors is that their outputs depend on particle composition and size. We combined the Mie scattering theory with experimental results to understand how the aerosol physical and chemical properties may lead to biased sensor outputs. After calibration, these sensors were deployed for various indoor and outdoor pollution mapping.
The accuracy and reliability of gas sensors are examined real-time multi-pollutant (RAMP) monitor project. The long-term performance of nitrogen dioxide sensors over four years was characterized. Multiple nitrogen dioxide sensors started generating signals that overestimate nitrogen dioxide concentrations due to the sensor aging caused by O3 scrubber expiration. The criteria for sensor expiration and the method of estimating sensor lifetime will be discussed.