Quantification of Fine Particulate Matter (PM2.5) and Its Correlation with Meteorological Parameters Within the Ambient Air of Automobile Workshops in Benin City

Abstract

This study explores the quantification of PM_2.5 (particles with an aerodynamic diameter of less than or equal to 2.5 µm) and how it is impacted by meteorological parameters. The study was conducted in Benin City between January and December 2019. The city was divided into four zones, namely, North West (NW), North East (NE), South East (SE), and South West (SW). A total of 180 representative samples for PM_2.5 were collected from artisans’ workshops in both wet and dry seasons, using an Apex2IS Casella standard pump fitted with a conical inhalable sampling (CIS) head at a flow rate of 3.5 L/min for 8 h. Meteorological parameters were collected simultaneously with PM_2.5. The PM_2.5 levels range from 37.9 to 735.1 (µg/m³) and 60.6 to 313.9 (µg/m³) during the dry and wet seasons, respectively. The estimated PM_2.5 concentration exceeded the World Health Organization (WHO) and National Ambient Air Quality Standard (NAAQS) of 25 and 250 ug/m³, respectively. The meteorological parameters were estimated to be 27.9–33.4 (°C), 59.8–78.9 (%), 748.4–754.3 (mmHg), 2.8–6.9 (km/h), 154.9–205.4 (^o), 425.1–1,073.4 (W/m²), and 717.3–1,133.7 (µW/m²) for temperature, relative humidity, pressure, wind speed, wind direction, solar radiation, and ultra-violet radiation, respectively. A significant positive correlation was observed between PM_2.5, temperature, solar radiation, and ultra-violet radiation. However, a negative correlation was observed for pressure. This positive correlation may influence the poor dispersion of PM_2.5, particularly in the wet season when we experience low temperatures and low wind speeds, and consequently impact negatively on human health.