Selected gaseous pollutants level in ambient air around the vicinity of chemical industry in Kwekwe, Zimbabwe

Abstract

The integrity of the natural composition of air have been compromised by the emission of chemical, biological and particulate substances from diverse sources, and this has led to the changing dynamics of the cloud density of naturally occurring gases. There is paucity of information on the levels, characterization and real time variability of ambient air contaminants in the atmospheric environments of most urban and industrial layouts in many Africa cities. In this study, the ambient air concentrations of selected gaseous pollutants was investigated in nine sampling stations, randomly identified in the vicinity of a Chemical and Fertilizer Production Industry in Kwekwe, Zimbabwe. An electrochemical measuring transducer (Drager 5000-x Sensor) was used for the measurement of gaseous concentration of ammonia, sulphur dioxide and nitrogen dioxide under atmospheric conditions, in all wind directions at each station. The concentrations of NH3, SO2 and NO2 measured at all sampling stations within and around the study site were variable and ranged; 0.36-7.36 ppm; 0.02- 84.61 ppm; and 0.61-34.78 ppm, respectively. The observed concentrations were significantly higher (p < 0.05) than measured at the control sampling station, 5 km from the industry (NH3; 0.01-0.05 ppm: SO2; 0.03-0.18 ppm: NO2; 0.17-1.30 ppm). This may probably be because of air diffusion arising from the dispersion of the contaminants vis-a-viz molecular diffusion and convection through the air. Isokinetic and dissipation of the measured gases confirmed a distance dissipation pattern; hence the cloud concentrations of ammonia, sulphur dioxide and nitrogen dioxide thins out at distances further away from the Industry. The contaminants variability within the plant may not be unconnected with releases from hotspots such as ammonia loops and valve leakage areas, and the prevailing meteorological conditions.