Assessing the spatiotemporal dynamics of PM2.5 concentrations during the Harmattan season in Sokoto State, Nigeria, 1980-2024

Abstract

The Harmattan season, characterised by dry and dusty north-easterly trade winds, significantly impacts air quality across West Africa. This paper assessed the spatiotemporal dynamics of PM_2.5 concentrations during the Harmattan season in Sokoto State, Nigeria, from 1980 to 2024, and evaluates the climatic factors influencing these variations. The PM_2.5 of MERRA-2 data was downloaded from NASA Giovanni, a web-based data portal Goddard Space Flight Centre developed. The data were analyzed using image thresholding technique, anomaly analysis and stepwise regression. The results revealed significant internal fluctuations and spatial disparity. The year 2016 recorded the highest PM_2.5 concentration (163.68 ± 7.02 µg/m³), followed by 2007, 1992, and 2020, while 2013 had the lowest concentration (77.39 ± 4.03 µg/m³). Stepwise regression analysis identified wind as the primary climatic driver of PM_2.5 variability (r = 0.596, p < 0.001), with a positive coefficient (27.442), indicating its strong influence on particulate matter transport. Other factors, including precipitation, humidity, temperature, and pressure, had less but notable impacts. The findings underscore the significant role of Harmattan winds in transporting Saharan dust across the region, elevating PM_2.5 levels to hazardous thresholds. These elevated concentrations pose substantial public health risks, particularly respiratory and cardiovascular issues, affecting vulnerable populations. The study highlights the need for enhanced air quality monitoring, public awareness campaigns, and targeted health interventions during the Harmattan season to mitigate exposure risks. Additionally, it calls for future research to integrate longterm observational data and advanced climate modelling to better understand PM_2.5 dynamics under changing climatic conditions.