Abstract
Air quality in urban areas is a cause of concern because of increased industrial activities that contribute to large quantities of emissions. The study assess levels and variations of carbon monoxide (CO), nitrogen dioxide (NO2) and sulfur dioxide (SO2) in Blantyre, Malawi using a stationary environmental monitoring station (EMS). Results show that CO level (2.47 ± 1.23 mg m-3) were below the Malawian limit value (10.31 mg m-3). Although, NO2 (4.02 ± 2.47 mg m-3) and SO2 (8.58 ± 2.88 mg m-3) were significantly higher than allowable Malawian Standards (0.52 and 0.23 mg m-3, respectively). Discernible variations in hourly, diurnal, monthly and seasonal CO, SO2 and NO2 were apparent. Independent t-test confirmed that day time values were higher than those at night (p < 0.05). Thus, variations in local weather affect the disparity in hourly and diurnal values. Analysis of variance (ANOVA) confirmed significant variations in monthly observations. Moreover, independent t-test showed that wet season CO (2.32 mg m-3), SO2 (5.10 mg m-3) and NO2 (9.41 mg m-3) levels were higher than dry season values (CO = 2.32 mg m-3; SO2 = 3.42 mg m-3; NO2 = 8.13 mg m-3). A hierarchical cluster analysis (HCA) divided the 10 months into three groups based on distribution of CO, SO2 and NO2, air temperature, wind speed and wind direction. Furthermore, factor analysis (FA) showed that air temperature had significant contribution to variations in mean values of CO, SO­2 and NO2 for the entire study period. The study shows a need for constant urban air quality monitoring in Blantyre and all urban areas in Malawi. It is recommended that the experimental site widen the scope of the study by utilizing the flexibility of the EMS. Key words: Air pollutants, principal component analysis, developing countries, environmental monitoring station, Kaiser normalization.
Highlights
Malawi, like many developing countries, has faced increased levels of urbanization and population growth over the last few years
Diesel engines emit large quantities of NOx and SOx as compared to petrol (Chan et al, 1997). These factors and challenges in waste management have contributed to the atmospheric deterioration such as acid rain, formation of smog and different ailments to people living in polluted air environment
The test results for SO2 (4.02 mg m-3) and NO2 (8.58 mg m-3) were significantly higher than standard limit values averaged over a 1 h period (Table 4)
Summary
Like many developing countries, has faced increased levels of urbanization and population growth over the last few years. Most cities in developing countries have population sizes more than twice that of 50 or so years ago (Baldasano et al, 2003). Diesel engines emit large quantities of NOx and SOx as compared to petrol (Chan et al, 1997). These factors and challenges in waste management have contributed to the atmospheric deterioration such as acid rain, formation of smog and different ailments to people living in polluted air environment
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