Air pollution emission inventory along a major traffic route within Ibadan Metropolis, southwestern Nigeria

Abstract

Increasing road congestion and high traffic volume is often times an indicator of atmospheric air pollution. Ibadan, being the largest metropolitan city in southwestern Nigeria, experiences steady influx of vehicular movement on daily bases. The situation is made worse as a greater number of these vehicles are old and poorly maintained. This study therefore investigated the likely impact of high traffic volume along a major roadway (the Ojoo-Mokola road) within the Ibadan metropolis on atmospheric air quality. Eight sampling points along a stretch of the roadway were identified for traffic density and air quality monitoring. Data was collected monthly over a period of four months in the morning peak, off peak and evening peak hours. Air quality parameters, carbon monoxide (CO), nitrogen dioxide (NO₂), sulphur dioxide (SO₂), hydrogen sulphide (H₂S) and ammonia (NH₃) were measured using handheld Crowcon Triple Plus+ and Crowcon Tetra-Portable Multi-Gas Detectors. The average concentration of CO range between 3.25 and 50.8 ppm with highest concentration observed during the morning and evening peak hours. There was a strong correlation (p=0.05) between ambient CO levels and traffic density. Relatively low levels of H₂S, and NH₃ were detected while NO₂ levels were relatively constant (<0.1 ppm). Sulphur dioxide was generally not detected within the study locations. Though this study did not cover the whole city of Ibadan, findings from the eight sampling points suggest that this major stretch of road may altogether not be safe from traffic related problems. There is need for constant monitoring of vehicular emissions to forestall possible air pollution.

Keywords: Air quality, vehicular emissions, traffic density, carbon dioxide