The effectiveness of drones in measuring particulate matter

Abstract

The use of low-cost air pollution sensors mounted on drones is an exciting new approach to conduct affordable and highly resolved air quality measurements. However, the air flow around a drone consists of complex, unsteady turbulent structures which interact directly with ambient particulate matter and gases. These interactions influence the transport of fine particulate matter (e.g. PM2.5) and, subsequently, its measurement using on-board PM sensors. In this work, we aim to quantify this effect by conducting wind tunnel and open-air experiments using a quadrotor drone and an array of low-cost sensors and research grade instruments. Sensors and instruments were placed around the drone to assess the effect of mixing, dilution, and particle segregation in the wake generated by the drone. Our results indicate little impact on the shape of the particle size distribution but significant differences (p<0.05) in PM2.5 concentration ranging from -70% to greater than 400% when comparing measurements before and after the drone is turned on. These effects varied greatly with sensor location and across experiments. In the wind tunnel, the sensor least affected was located far upstream from the drone with concentration differences less than 7%. The sensor far downstream from the drone as well as one of the sensors to the side of the drone also showed relatively small concentration differences (<50%) compared to the other sensors. In the open-air tests, the sensor directly under the drone and one of the sensors to the side drone showed the smallest changes after the drone was turned on with concentration differences less than 20%. This study highlights many important factors to consider when working with low-cost sensors mounted on drones. It also lays the groundwork for more in-depth studies into how to effectively take air-quality measurements using drones.