Beneficiation of Two Different Low-Grade Nigerian Manganese Ore Deposits to Improve its Quantitative Composition | Applied Science, Computing, and Energy

Abstract

Air pollution has become one of the most significant environmental and public health challenges confronting Nigeria, with increasing urbanization, industrialization, biomass burning, transportation emissions, gas flaring, and desert dust contributing to deteriorating atmospheric conditions. Despite growing concern, comprehensive nationwide assessments of long-term temporal trends and seasonal variability of multiple ambient air pollutants remain limited. This study investigated the spatiotemporal behaviour of major atmospheric pollutants across Nigeria between 2010 and 2024 using satellite-derived datasets integrated with statistical trend analyses. Annual and seasonal concentrations of particulate matter (PM₂.₅), nitrogen dioxide (NO₂), ozone (O₃), and carbon monoxide (CO) were evaluated using descriptive statistics, Mann–Kendall trend analysis, Sen's slope estimator, analysis of variance, and seasonal decomposition techniques to quantify long-term changes and identify significant pollution patterns. The results revealed a persistent deterioration of air quality over the fifteen-year period. National annual mean PM₂.₅ concentrations increased significantly from 48.7 ± 5.2 μg m⁻³ in 2010 to 62.8 ± 6.4 μg m⁻³ in 2024, representing an overall increase of 28.9% with a Sen's slope of 0.95 μg m⁻³ year⁻¹ (Mann–Kendall Z = 4.86, p < 0.001). Mean NO₂ concentrations rose from 14.8 ± 2.1 ppb to 22.1 ± 2.8 ppb, corresponding to a 49.3% increase (Sen's slope = 0.47 ppb year⁻¹; p < 0.001), while O₃ increased moderately from 30.6 ± 3.2 ppb to 35.9 ± 3.7 ppb (17.3% increase; p = 0.011). Carbon monoxide exhibited relatively small interannual variability, increasing from 0.54 ± 0.08 ppm to 0.68 ± 0.09 ppm (25.9% increase; p = 0.032). Seasonal analysis demonstrated pronounced dry-season pollution, with average PM₂.₅ concentrations reaching 69.4 ± 7.8 μg m⁻³, compared with 42.7 ± 5.1 μg m⁻³ during the wet season (p < 0.001). Similar seasonal patterns were observed for NO₂, O₃, and CO, with elevated pollutant levels during the Harmattan months due to enhanced Saharan dust transport, biomass burning, reduced atmospheric dispersion, and increased anthropogenic emissions. Regional assessment showed substantial spatial heterogeneity, with northern Nigeria consistently recording higher particulate concentrations than southern Nigeria, largely because of desert dust intrusion and increasing land degradation, while industrialized southern urban centres exhibited elevated gaseous pollutant concentrations associated with vehicular emissions, industrial activities, and gas flaring. Overall, more than 86% of annual PM₂.₅ observations exceeded the World Health Organization annual guideline value, indicating chronic exposure of the Nigerian population to unhealthy atmospheric conditions. The findings demonstrate that ambient air pollution in Nigeria has intensified significantly over the past decade and a half and exhibits strong seasonal dependence driven by both natural and anthropogenic processes. The study provides valuable nationwide evidence to support the strengthening of air quality monitoring networks, satellite-based environmental surveillance, emission-control policies, cleaner energy adoption, sustainable urban planning, and climate-resilient environmental management strategies aimed at improving air quality and protecting public health.