The Behaviour of Particulate Matter and Carbon Dioxide Concentrations in Harare

Abstract

As African countries industrialize, the emission of various pollutants is likely to increase. Air pollution can have adverse impacts on human and animal health and ecosystems. There has been very limited air pollution monitoring activities in Southern Africa. This paper presents results of a study of the temporal behaviour of particulate matter (PM2.5), total dust precipitation (TDP) and carbon dioxide (CO2), determination of the effects of meteorological parameters on the concentrations of the PM2.5 and CO2 and the spatial distribution of TDP as well as trace elements in residential areas of Harare, Zimbabwe. The (PM2.5) concentrations were determined as scattering coefficients using a nephelometer and CO2 measurements were carried out using an infra-red gas analyser. The TDP were collected using plastic pots and samples were analysed for the trace elements (iron, lead and nickel) using an atomic absorption spectrometer. CO2 mixing ratios and PM2.5 concentration followed a similar diurnal trend, with maximum peaks observed at around 2300 and troughs around midday. High wind speeds were associated with low concentrations of both CO2 and PM2.5 and low wind speeds with high concentrations of both CO2 and PM2.5. Wind from the city centre and the industrial areas advected towards the sampling site. The concentration of (PM2.5) decreased significantly during rainfall. CO2 mixing ratios were not greatly affected by rainfall. The southern residential areas of Harare which are close to the dumping sites, busy highways, busy bus terminus and industrial areas recorded significant amounts of the trace elements and TDP than the northern residential areas which are far away from the main sources of pollution. The northern residential areas are upwind of the main sources of air pollution whilst the southern residential areas are located downwind of the main air stream of Harare and are highly polluted.