Field performance evaluation of low-cost PM2.5 sensors for enhancing spatial resolution of PM2.5 monitoring: a case study in the smart city of Sejong, Korea

Due to the adverse health effects of PM_2.5 (particles with a diameter less than 2.5 μm), the national ambient air quality standards (NAAQS) for PM_2.5 have been established in many countries. Ambient PM_2.5 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_2.5 monitoring. In this context, low-cost PM_2.5 sensors (LCSs) have been widely deployed for PM_2.5 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_2.5 concentrations measured by LCSs generally agreed with those from BAMs. However, when comparing hourly PM_2.5 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_2.5 levels. Additionally, we found statistical differences in PM_2.5 concentrations among six regions within the study area. This indicates that ambient PM_2.5 levels can vary within a small area, supporting the necessity of monitoring PM_2.5 on a small scale. Overall, the results of this study suggest that the sensors demonstrate both potential and limitations in PM_2.5 monitoring. Therefore, to use LCSs for PM_2.5 monitoring, it is necessary to appropriately select the averaging time and PM_2.5 concentration ranges, considering local environmental conditions and the inherent characteristics of LCSs.