Modelling and Simulation of Particulate Matter Dispersion from Cement Plant Stack Emissions in Ewekoro, Ogun State

Cement manufacturing is among the largest industrial sources of particulate matter air pollution in Nigeria, and the cement production cluster in Ewekoro, Ogun State, serves as a particularly significant emission source given its proximity to residential communities and agricultural areas in the South West zone. This study develops and applies a Gaussian dispersion modelling framework to simulate particulate matter dispersion from stack emissions at a cement plant in Ewekoro and assess ground-level concentration patterns in surrounding communities. Emission source characterisation was conducted through stack sampling and dispersion parameter estimation following US EPA AP-42 methodology for the cement manufacturing sector. Meteorological data including wind speed, wind direction frequency distributions, atmospheric stability class, and mixing layer height were compiled from five years of observations at the nearest Nigerian Meteorological Agency station. The AERMOD dispersion model was applied to compute annual mean and daily maximum ground-level PM10 and PM2.5 concentration fields across a 10-kilometre radius domain around the plant. Modelled concentration contours were compared against ambient air quality measurements from a five-point monitoring network established within the study domain. Model performance statistics confirmed mean bias below 15 percent and fractional bias within accepted EPA model performance criteria. Results showed that three communities within 3.5 kilometres of the plant experienced annual mean PM10 concentrations exceeding the WHO ambient air quality guideline of 15 micrograms per cubic metre. The study provides a technical basis for emission abatement prioritisation and community air quality management planning. Keywords: particulate matter, Gaussian dispersion model, cement plant, air quality, Ewekoro.