Reppie non-engineered landfill is a rudimentary destination of solid waste that comes from Addis Ababa city. Recently, the landfill site has engulfed due to the expansion of the capital. Due to the engulfment, dispersion of pollutant gases like H2S, NH3, and CH4 that produce from the landfill reach nearby residence with high concentration. High concentration of the pollutant gases increases the risk of offensive odor, asphyxiation, and explosion hazards. The main objective of this research was

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... ssessing Reppie landfill gas dispersion through field measurement and Semi-physical model simulation. The semiphysical model simulation depends on the field measurement values. After experimental design was performed using temporal and spatial variation as independent variable, observation and field measurement was continued. Through series of field measurement, the average maximum concentrations of CH4, H2S, and NH3 were recorded at sample station (Ss-13) with 307.72 mg/m3, 142.18 mg/m3, and 3635.52 mg/m3 respectively. After having the field measurement values, meteorological data and other remote sensing data, the semi-physical model of and CH4, H2S, and NH3 was simulated separately in Lake Aermod®. Gaussian dispersion model is the governing mathematical model behind the semi-physical model simulation. After running the semi-physical model simulation using the field value, concentration gases were estimated in all over the landfill site. The semiphysical model simulation result shows high at the active site with 13.09 mg/m3 methane at (468417.77, 992379.64), 121.95 mg/m3 ammonia at the location of (468417.77, 992379.64) and 0.13 mg/m3 hydrogen sulfide at (467975.9, 992297.13). The semi-physical model indicates that concentration of the landfill gases is inversely related with temporal and special variation. Concentration of CH4, H2S, and NH3 varies when the average dilution time varies from 1-hour to 24 hours as 13.09 to 7.43 mg/m3, 0.13 to 0 [...]