Organic and Elemental Carbon in PM2.5 from an Urban Residential Area of Lagos, Nigeria

Exposure to ambient organic matter can influence human health and is a source of poor quality contributing to the formation of photochemical smog. In this study, organic carbon (OC) and elemental carbon (EC) concentrations were determined in PM2.5 particle fraction during the height of the rainy season in Lagos, Nigeria (JuneJuly 2021). The daily average PM2.5 mass concentration (27 mu g m(3)) exceeded the World Health Organization (WHO) limit of 15 mu g m(-3). The 24-h average EC and OC concentrations values were 0.8 and 2.2 mu g m(-3), respectively, with both OC and EC contributing 11% of the total PM2.5 mass. A good correlation existed between OC and EC, suggesting the same origin. Considering the OC/EC ratio in the range of 2 to 5.1 mu g m(-3), the most likely common sources of carbonaceous aerosols in the investigated residential area are vehicular emissions, motorbikes, and generator fumes. The observed relatively high PM2.5 mass and the proportion of carbonaceous components in the total PM2.5 mass in the residential area indicate that the air quality in Lagos is already at risk and needs immediate monitoring.