Field performance evaluation of low-cost PM sensors for enhancing spatial resolution of PM monitoring: a case study in the smart city of Sejong, Korea.

Due to the adverse health effects of PM (particles with a diameter less than 2.5 μm), the national ambient air quality standards (NAAQS) for PM have been established in many countries. Ambient PM concentrations are monitored to determine compliance with the NAAQS, where beta attenuation monitors (BAMs) are widely used as a reference method. However, the high costs of installation and maintenance of BAMs result in difficulties in enhancing the spatial resolution of PM monitoring. In this context, low-cost PM sensors (LCSs) have been widely deployed for PM measurements. Despite their low cost and ease of installation, concerns regarding the data reliability of LCSs remain unresolved, necessitating further field research under various environmental conditions. In this study, we conducted a data comparability assessment between 125 LCSs and two BAMs over 12 months. Daily average PM concentrations measured by LCSs generally agreed with those from BAMs. However, when comparing hourly PM data, we found that the data comparability of LCSs against BAMs was lower than that of the daily average data, primarily influenced by ambient PM levels. Additionally, we found statistical differences in PM concentrations among six regions within the study area. This indicates that ambient PM levels can vary within a small area, supporting the necessity of monitoring PM on a small scale. Overall, the results of this study suggest that the sensors demonstrate both potential and limitations in PM monitoring. Therefore, to use LCSs for PM monitoring, it is necessary to appropriately select the averaging time and PM concentration ranges, considering local environmental conditions and the inherent characteristics of LCSs.