Quantifying PM2.5 at two urban sites in Akure, Nigeria using low-cost sensor technology

Particulate matter with aerodynamic diameters smaller than 2.5 µm, PM2.5, is a problem for inhabitants globally. To address this problem, there is a need to know the amount of PM2.5 present in the atmosphere. The quantification of PM2.5 will help to determine the type of remedies for air quality. One of the employed quantification methods is the use of low-cost sensors, which are easy to use, have high temporal resolution, and are small to handle. In this study, we applied low-cost optical sensors to determine PM2.5 during the dry (Harmattan) season at two sites in Akure, Ondo State, Nigeria. The results showed that PM2.5 at one site (Site B) ranged between 14.4 and 590.4 µg/m3, whereas that at the other site (Site C) ranged between 14.5 and 737.2 µg/m3. The mean values (75.7 and 87.5 µg/m3 at Sites B and C, respectively) were significantly beyond the standard limits of World Health Organization and National Environmental Standards and Regulations Enforcement Agency in Nigeria. High daily average PM2.5 concentrations were observed when the air masses coming from the northeast. Shorter timescale peaks within a few hours were frequently observed, especially at Site C during the daytime, attributable to the local emissions of PM2.5 due to combustion activities. Higher-density multi-point observations are highly recommended to understand the sources, behaviors, and health effects of PM2.5 in regional cities in South West Africa.