Distance Based Assessment of Ambient Air Quality in Residential Areas Surrounding Major Market Hubs in Awka South LGA, Anambra State

Abstract

Rapid urbanization in developing countries has intensified ambient air pollution, particularly within mixed residential–commercial environments. This study assessed distance-based variation in ambient air quality surrounding major market hubs in Awka South Local Government Area (LGA), Anambra State, Nigeria. A cross-sectional field measurement design was adopted using structured radial buffers (0–50 m, 50–100 m, and >100 m) extending from the geometric centers of Amaenyi and Eke Awka markets into adjacent residential zones. A portable multi-parameter air quality monitor measured wind speed, formaldehyde (HCHO), total volatile organic compounds (TVOC), carbon monoxide (CO), carbon dioxide (CO₂), fine particulate matter (PM₂.₅), temperature, humidity, and Air Quality Index (AQI). Results indicate that pollutant concentrations were generally highest within the immediate 0–50 m commercial interface and declined with increasing distance, particularly at Amaenyi Market, supporting the distance-decay principle. CO decreased from 4 ppm (0–50 m) to 1 ppm (>100 m), while CO₂ declined from 823 ppm to 510 ppm across the same gradient. However, Eke Awka exhibited a pronounced pollution hotspot within 0–50 m, where CO (74 ppm), CO₂ (1505 ppm), and TVOC (7.343) were markedly elevated. PM₂.₅ concentrations (15–27 µg/m³) exceeded the WHO 24-hour guideline (15 µg/m³) at most sampling points. Wind speed demonstrated an inverse relationship with pollutant concentrations, indicating meteorological mediation of dispersion. The findings confirm that residential proximity to major market hubs significantly influences exposure intensity, with localized emission clustering and low wind conditions amplifying pollution levels. The study provides spatially differentiated evidence to inform urban zoning, buffer regulation, and environmental health policy in rapidly urbanizing Nigerian cities.