A Time-Based Assessment of Particulate Matter (PM 2.5) Levels at a Highly Trafficked Intersection: Case Study of Sango-Ota, Nigeria.

Vehicle emissions have become one of the most prevailing air contamination sources, including nitrogen oxides, volatile organic compounds, carbon monoxide and particulate matter (PM). Among other air pollutants, PM limits visible sight distance and poses health risks upon inhalation into the human body. This study focused on assessing PM_2.5 concentrations in air at different periods of the day at the highly trafficked grade-separated intersection of Sango-Ota, Ogun State, Nigeria. PM_2.5 readings were taken at three at-grade points around the intersection's roundabout between 10:00 a.m. and 5:00 p.m. for four (4) days using the BR-SMART-126 Portable 4-in-1 air quality monitor. The highest level of PM_2.5 obtained on Day 1 (Monday) and Day 4 (Thursday) was about 45.1% and 38.6%, respectively, lower than that of Day 3 (Wednesday). The highest concentrations of PM_2.5 were recorded between 11:00 and 13:00 and between 16:00 and 18:00 (up to 217 µg/m³) whereas the lowest levels were recorded between 14:00 and 15:00 (as low as 86 µg/m³). The concentration of PM_2.5 at the Sango-Ota intersection is adjudged "very poor" with average hourly concentrations between 97 and 370 µg/m³. Outcomes obtained indicate the need for improved measures to control air quality along major road corridors and at intersections in Ogun State and Nigeria at large. [ABSTRACT FROM AUTHOR]