Atmospheric Dispersion Modelling of Particulate Matter and Gaseous Emissions From Selected Cement Factories in Athi River Machakos County Kenya

Abstract

Cement manufacturing industries play a vital role in economic development through the development of infrastructure and the creation of employment opportunities. However, cement manufacturing results in the emission of particulate matter (Total Suspended Particles (TSP), coarse particles (PM10) and fine particles (PM2.5)) and flue gases (carbon monoxide (CO), carbon dioxide (CO2), sulphur dioxide (SO2) and nitrogen oxides (NOx)). These emissions cause air pollution which is unfavourable to human health. Exposure to air pollution results in adverse health effects such as pulmonary and cardiovascular diseases. In the current study, two cement factories in Athi River, Machakos County in Kenya were selected to determine the concentrations of particulate matter and flue gases emitted into the atmosphere and their subsequent downwind dispersion. Cement Factory 1 (CF1) contained one sampling point (Stack 1 with a height of 35 m) and Cement factory 2 (CF2) contained two points (Stack 2a with a height of 39 m and 2b with a height of 45 m). Particulate matter was sampled isokinetically using an isokinetic source sampler-XC-572-V and its concentration determined gravimetrically. Flue gas sampling and determination of concentration were done using an emission analyser E6000-5SC. The sampling procedure was based on the United States Environmental Protection Agency (EPA) standard methods. The stack emission concentrations were subsequently used to model the downwind dispersion of the pollutants in the atmosphere using the American Meteorological Society/Environmental Protection Regulatory Model (AERMOD). The findings show that except for carbon dioxide from CF1, stack emission concentration and modelling results of particulate matter, carbon monoxide, sulphur dioxide and nitrogen oxides from both cement factories were below the permissible limits as stipulated by the Environmental Management and Coordination (Air Quality) Regulations and World Health Organization air quality Guidelines. The average stack emission concentration of carbon dioxide was 24062±3340 mg/Nm3, the 8-hour mean maximum concentration was 8.809±1.570 mg/m3 and the 1-hour mean maximum concentration was 32.715±4.362 mg/m3. Negligible concentrations of CO, SO2 and NOx were detected in Stack 2a and Stack 2b.