Quantifying PM_2.5 at two urban sites in Akure, Nigeria using low-cost sensor technology

Particulate matter with aerodynamic diameters smaller than 2.5 µm, PM_2.5, is a problem for inhabitants globally. To address this problem, there is a need to know the amount of PM_2.5 present in the atmosphere. The quantification of PM_2.5 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 PM_2.5 during the dry (Harmattan) season at two sites in Akure, Ondo State, Nigeria. The results showed that PM_2.5 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 PM_2.5 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 PM_2.5 due to combustion activities. Higher-density multi-point observations are highly recommended to understand the sources, behaviors, and health effects of PM_2.5 in regional cities in South West Africa.