Characterization and Source Apportionment of Ambient Particulate Matter (PM2.5) across Lagos, Nigeria on High Pollution Days

Abstract

Ambient particulate matter ≤2.5 μm (PM2.5) is a major public health concern in rapidly urbanizing cities such as Lagos, Nigeria, where emissions from diverse anthropogenic sources contribute to poor air quality. However, source-specific information for Lagos remains limited. PM2.5 sources were apportioned using EPA-PMF applied to a 12-month data set (August 2020–July 2021) of 24-h samples collected every third day at six sites. The top 30% of filters by mass concentration were chemically speciated. Mean PM2.5 concentration was 68 μg/m3. Eleven factors were resolved: Dust (27.86%) the dominant source; Diesel Exhaust (16.98%), Pb-Battery Recycling (12.74%), Sulfate (8.70%), Open Waste Burning (8.30%), 2-Stroke Exhaust (7.25%), and Galvanizing (6.13%). Small contributors were E-Waste Processing (3.58%), Cooking Aerosol (3.34%), Gasoline Exhaust (2.63%), and Secondary Nitrate (2.48%). Integrated statistical modeling and meteorological analyses showed that PM2.5 variation was governed by source-specific meteorological controls. Four factors─Dust, Open Waste Burning, Sulfate, and Secondary Nitrate─were directly influenced by meteorology through transport, scavenging, dispersion, and gas–particle chemistry, respectively. Diesel Exhaust was the largest local source and independent of meteorology. These findings highlight that effective PM2.5 mitigation in Lagos requires source-specific control strategies. Priority actions include reducing fossil-fuel generator use, enforcing industrial emissions controls, and upgrading vehicles.