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Influence of Relative Humidity and Visibility on Fine Particulate Matter Concentrations in the Niger Delta: Ground Based Evidence from Edo State, Nigeria.
Subject area: Physical Sciences and Environment · Area of research: Environmental Monitoring and Assessment
DOI: 10.64388/IREV10I1-1720211
Abstract
Fine particulate matter (PM₂.₅) remains one of the most critical air pollutants affecting public health, atmospheric visibility, and environmental sustainability, particularly in rapidly urbanizing regions of developing countries. Despite growing concerns regarding air pollution in the Niger Delta region of Nigeria, empirical evidence on the influence of meteorological conditions on PM₂.₅ variability remains limited. This study investigated the influence of relative humidity and visibility on PM₂.₅ concentrations in Edo State, Nigeria, using ground based observations obtained from the Space Earth Environment Research Laboratory, Centre for Atmospheric Research, University of Benin. Weekly PM₂.₅, relative humidity, temperature, and visibility data collected between January 2022 and December 2025 were analyzed using descriptive statistics, Pearson correlation, multiple linear regression, seasonal analysis of variance (ANOVA), Tukey Honestly Significant Difference (HSD) tests, time series decomposition, and Air Quality Index (AQI) assessment. Results showed that the mean PM₂.₅ concentration was 23.31 ± 24.92 µg m⁻³, exceeding the World Health Organization (WHO) annual guideline value of 5 µg m⁻³ by more than fourfold, indicating persistent particulate pollution in the study area. Correlation analysis revealed significant negative relationships between PM₂.₅ and relative humidity (r = -0.286, p < 0.001) and between PM₂.₅ and visibility (r = -0.515, p < 0.001), while temperature exhibited a weak positive correlation with PM₂.₅ (r = 0.208, p = 0.003). Regression analysis showed that relative humidity alone explained 8.2% of the variability in PM₂.₅ concentrations (R² = 0.082), whereas the combined relative humidity visibility model explained 34.9% of the observed variability (R² = 0.349). The inclusion of temperature produced only a marginal improvement in model performance (R² = 0.366), confirming the dominant influence of visibility and relative humidity on PM₂.₅ dynamics in the study area. Seasonal analysis revealed significant differences in PM₂.₅ concentrations across atmospheric seasons (F(2,206) = 16.55, p < 0.001; η² = 0.138). The dry season recorded the highest mean PM₂.₅ concentration (33.86 µg m⁻³), followed by the early wet season (18.60 µg m⁻³) and late wet season (12.01 µg m⁻³). Tukey HSD post-hoc analysis indicated that PM₂.₅ concentrations during the dry season were significantly higher than those observed during both the early wet and late wet seasons (p < 0.001), whereas no significant difference existed between the two wet-season periods (p = 0.270). Time series decomposition further revealed recurring seasonal cycles characterized by elevated particulate concentrations during dry months and reduced concentrations during wetter periods. AQI assessment indicated that while most observations fell within the good and moderate categories, approximately 13.9% of observations were classified as unhealthy for sensitive groups or worse, indicating recurrent episodes of degraded air quality and increased health risks for sensitive populations. The study demonstrates that visibility and relative humidity are key meteorological controls of PM₂.₅ variability in the humid tropical environment of the Niger Delta. The persistent exceedance of WHO guideline values highlights potential public health risks associated with long-term exposure to fine particulate matter. These findings provide a scientific basis for incorporating meteorological parameters into air quality forecasting, exposure assessment, and pollution management strategies. Strengthening monitoring networks and implementing effective emission control measures are essential for mitigating particulate pollution and improving environmental health in rapidly urbanizing cities of southern Nigeria.
Keywords
PM₂.₅, Relative Humidity, Visibility, Air Quality Index, Seasonal Variability, Time Series Analysis, Niger Delta, Edo State, Atmospheric Pollution, Nigeria.
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How to cite this paper
@article{1720211,
author = {Blessed C. Anyanwu, Oboh Osabhuohien; Ruth I. Ojombo; Chinyere Williams; Jeremiah K. Ogah, Augustine O. Otum; Christian O. Ofoegbu; Murphy E. Obinyan; Barka Wakawa, Chijioke Okpara; Godwin C. Ogor-igbosuah; Asaju K. Olamide; Shagaya H. Emmanuel, Mayowa O. Bankole; Suleiman A. Zakari; Jibril A. Salihu; Jabes Anyuabaga; Mahmud Ibrahim},
title = {Influence of Relative Humidity and Visibility on Fine Particulate Matter Concentrations in the Niger Delta: Ground Based Evidence from Edo State, Nigeria.},
journal = {Iconic Research And Engineering Journals},
year = {2026},
volume = {10},
number = {1},
pages = {3920-3939},
issn = {2456-8880},
url = {https://www.irejournals.com/formatedpaper/1720211.pdf},
abstract = {Fine particulate matter (PM₂.₅) remains one of the most critical air pollutants affecting public health, atmospheric visibility, and environmental sustainability, particularly in rapidly urbanizing regions of developing countries. Despite growing concerns regarding air pollution in the Niger Delta region of Nigeria, empirical evidence on the influence of meteorological conditions on PM₂.₅ variability remains limited. This study investigated the influence of relative humidity and visibility on PM₂.₅ concentrations in Edo State, Nigeria, using ground based observations obtained from the Space Earth Environment Research Laboratory, Centre for Atmospheric Research, University of Benin. Weekly PM₂.₅, relative humidity, temperature, and visibility data collected between January 2022 and December 2025 were analyzed using descriptive statistics, Pearson correlation, multiple linear regression, seasonal analysis of variance (ANOVA), Tukey Honestly Significant Difference (HSD) tests, time series decomposition, and Air Quality Index (AQI) assessment. Results showed that the mean PM₂.₅ concentration was 23.31 ± 24.92 µg m⁻³, exceeding the World Health Organization (WHO) annual guideline value of 5 µg m⁻³ by more than fourfold, indicating persistent particulate pollution in the study area. Correlation analysis revealed significant negative relationships between PM₂.₅ and relative humidity (r = -0.286, p < 0.001) and between PM₂.₅ and visibility (r = -0.515, p < 0.001), while temperature exhibited a weak positive correlation with PM₂.₅ (r = 0.208, p = 0.003). Regression analysis showed that relative humidity alone explained 8.2% of the variability in PM₂.₅ concentrations (R² = 0.082), whereas the combined relative humidity visibility model explained 34.9% of the observed variability (R² = 0.349). The inclusion of temperature produced only a marginal improvement in model performance (R² = 0.366), confirming the dominant influence of visibility and relative humidity on PM₂.₅ dynamics in the study area. Seasonal analysis revealed significant differences in PM₂.₅ concentrations across atmospheric seasons (F(2,206) = 16.55, p < 0.001; η² = 0.138). The dry season recorded the highest mean PM₂.₅ concentration (33.86 µg m⁻³), followed by the early wet season (18.60 µg m⁻³) and late wet season (12.01 µg m⁻³). Tukey HSD post-hoc analysis indicated that PM₂.₅ concentrations during the dry season were significantly higher than those observed during both the early wet and late wet seasons (p < 0.001), whereas no significant difference existed between the two wet-season periods (p = 0.270). Time series decomposition further revealed recurring seasonal cycles characterized by elevated particulate concentrations during dry months and reduced concentrations during wetter periods. AQI assessment indicated that while most observations fell within the good and moderate categories, approximately 13.9% of observations were classified as unhealthy for sensitive groups or worse, indicating recurrent episodes of degraded air quality and increased health risks for sensitive populations. The study demonstrates that visibility and relative humidity are key meteorological controls of PM₂.₅ variability in the humid tropical environment of the Niger Delta. The persistent exceedance of WHO guideline values highlights potential public health risks associated with long-term exposure to fine particulate matter. These findings provide a scientific basis for incorporating meteorological parameters into air quality forecasting, exposure assessment, and pollution management strategies. Strengthening monitoring networks and implementing effective emission control measures are essential for mitigating particulate pollution and improving environmental health in rapidly urbanizing cities of southern Nigeria.},
keywords = {PM₂.₅, Relative Humidity, Visibility, Air Quality Index, Seasonal Variability, Time Series Analysis, Niger Delta, Edo State, Atmospheric Pollution, Nigeria.},
month = {July},
doi = {https://doi.org/10.64388/IREV10I1-1720211}
}