A study of PM2.5–10 pollution at three functional receptor sites in a sub-Saharan African megacity

Abstract

PM2.5–10 (aerodynamic diameter dae 2.5 µm ≥ x ≤ 10 µm) pollution is rapidly becoming a serious problem in many urban areas especially in the least and middle income countries where air quality guidelines as well as urban infrastructure are grossly lacking. In this regards, PM2.5–10 samples collected within a 12-month period from the industrial, low- and high- density residential areas in Lagos Nigeria were studied. The PM2.5–10 were analyzed using ion beam analyses techniques vis-a-vis particle induced X-ray emission and particle induced γ-ray emission, Hybrid Single-particle Lagrangian Integrated Trajectory (HYSPLIT) and surface meteorological data as well as Positive matrix factorization model (PMF). The results showed that the average mass loads ranged from 150 to 606 µg m−3 (industrial) 110 to 460 µg m−3 (high density residential) and 76 to 298 µg m−3 (low density residential) and revealed gross violations of local and international guidelines. In addition, the wind roses indicated that the wind flow patterns could have significant impacts on PM2.5–10 mass loads. HYSPLIT model revealed that most high episodes were caused by pollutant accumulation (induced by low wind speed) and transport of pollutants from highly polluted regions. Data on the concentrations of 22 elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr, and Pb) were obtained and used for receptor modeling by PMF technique. PMF results indicated that soil dust, physical construction and industrial activities were the major emissions of PM2.5–10 and could lead to negative health implications on the inhabitants of Lagos.