EVALUATING AIR QUALITY DIFFERENCES: PM POLLUTION IN PORT HARCOURT VS. ILORIN VIA LOW-COST SENSORS

Abstract

Air pollution, particularly particulate matter (PM) pollution, poses significant dangers to public health and the environment. Port Harcourt and Ilorin, two major Nigerian cities, exhibit varying levels of industrial development, traffic density, and climate conditions, which may influence PM concentrations. However, limited studies have compared air quality between these cities using low-cost sensors, which offer an affordable alternative to conventional monitoring systems. Therefore, this study presents a comparative analysis of PM concentrations (PM₁.₀, PM₂.₅, and PM₁₀) in Port Harcourt and Ilorin, Nigeria, using high-frequency measurements from Clarity Node-S sensors deployed at River State University, Port Harcourt and the University of Ilorin ,Ilorin. The data, obtained at 60-minute intervals from January 2022 to February 2023, were calibrated to measure particle mass concentrations (µg/m³) across six size bins (0.3–10 µm).  The results of the analyses show high pollution levels in both cities, with Port Harcourt having significantly higher concentrations across all PM sizes. Mean PM₁.₀  (35.87 µg/m³), PM₂.₅ (64.06 µg/m³) and PM₁₀ (65.19 µg/m³) levels in Port Harcourt far exceeded WHO annual guidelines (5 µg/m³ and 15 µg/m³, respectively). the PM concentration was observed to be higher in the dry-season (December–February); this is probably linked to Harmattan winds and dusts. Statistical analysis emphasized right-skewed distributions (skewness: PM₂.₅ = 1.05, PM₁₀ = 1.29) and high kurtosis (PM₁₀ = 2.37), confirming frequent extreme events.  Ilorin’s PM levels, though lower, also exceeded WHO standards, with mean PM₁.₀ (27.41 µg/m³), PM₂.₅  (39.89 µg/m³) and PM₁₀ (47.63 µg/m³). In the Statistical analysis a kurtosis of −0.67 to −0.98 was obtained, which suggests less excesses than Port Harcourt. The maximum values of PM₂.₅ (155.05 µg/m³) in Port Harcourt is about 2.7 times higher than the Ilorin’s peak (57.51 µg/m³) and about six times higher than the WHO 24-hour limit (25 µg/m³).  This result shows that both cities exhibited unsafe AQI levels during its maximum, which demands an urgent intervention. The findings reveal the contributions of traffic, industry, and climate to urban PM pollution and the associated health implications. Therefore, an expanded low-cost sensor networks, strict emission regulation in Port Harcourt is advised, to safeguard public health.