A long-term air quality and meteorological coupling dynamics in Abeokuta, Nigeria

Abstract

This study examines the dynamics of ambient air pollutants and their meteorological determinants in Abeokuta, Nigeria. This study averaged 12 years of hourly data (2012–2023) for PM 2 . 5 , PM₁₀, NO 2 , SO 2 , CO, and O 3 , alongside six meteorological variables: temperature, relative humidity, pressure, wind speed, wind direction, and rainfall. Specifically, Particulate matter (PM 2.5 and PM 10 ) were the most dominant pollutants, consistently surpassing World Health Organisation (WHO) standards and reaching their highest concentrations during the Harmattan dry season, typically occurring between December and March. Regression analysis demonstrated moderate to strong positive correlations with temperature (R² = 0.48–0.52), while also indicating negative relationships with rainfall and humidity, thereby validating the impacts of thermal stagnation and wet scavenging processes. Furthermore, fluctuations in atmospheric pressure contributed to the buildup of pollutants during periods of stagnant air. Gaseous pollutants showed relatively weaker sensitivity; however, levels of NO 2 and CO increased during the hot, arid months, while O 3 levels rose in the late dry season. The Aggregate Air Quality Index (AAQI) values fluctuated between 39 and 51, thereby designating the air quality as “moderate.” Furthermore, the Health-Risk Adjusted AQI (HAQI) revealed heightened relative risks, especially concerning PM 2 . 5 exposure, with seasonal maxima exceeding 90. These findings highlight the cumulative health impacts of particulate matter, even when gaseous pollutants remain within permissible thresholds. The results highlight the necessity for seasonally adjusted mitigation measures, including dust suppression, emission controls, and cleaner combustion technologies. Furthermore, they advocate for the incorporation of Health-Adjusted Quality Index (HAQI) metrics within air quality management systems.