Air quality is affected by economic activities which introduces pollutants into the atmosphere that pose threats to human health and other life forms on earth. It furthermore has the potential to change the climate with unpredictable, but potentially severe consequences on a local and global scale. Because large bodies of air cannot be contained, atmospheric pollution can only be controlled at its source. At present there is no comprehensive information on air quality or on the levels of emissions entering the atmosphere from different sources. Major areas of concern are high levels of smoke and other pollutants in poorer urban and rural households without electricity, and the impacts of the mining, energy, mineral and petro-chemical industries on air quality standards (Environmental Management Policy for South Africa, 1998).
Air pollution is a major environmental problem throughout the whole of South Africa. South Africa derives 75,2 % of its energy from coal (a non-renewable resource), and most air pollution problems thus result from man’s pattern of energy use and production. The rest of the energy comes from the following sources: 10,1% from crude oil, 9,8% from renewable bagasse and wood, 3,1% from nuclear power, 1,6% from gas and 0,2% from hydro power (Surridge, 1999).
The worst levels of air pollution in South Africa is found in the Eastern Highveld of Mpumalanga (formerly the Eastern Transvaal). It covers an area of 30 000 km2 and is home to ten ESKOM power stations, of which five are the largest in the world. The three main power stations, Matla, Duvha and Arnot produce 860 tons of SO2 per km2 per year. The area also contains coal mines, Sasol petrochemical plants and other industries. The major dust dome in South Africa is the Vaal Triangle to the south of Gauteng (Tyson et.al., 1988).
The worst polluted areas in Greater Johannesburg are the surrounding Highveld areas due to the combustion of fuels for the generation of electricity, and Soweto, due to the burning of coal for heating and cooking. In the winter, smoke and SO2 from the townships are the main forms of air pollution, while vehicles and industries contribute to air pollution throughout the year.
Factors influencing the pollution problem in South Africa and Greater Johannesburg (Preston-Whyte & Tyson, 1988):
Unstable air circulates and dissipates pollutants in summer due to the low pressure over the land.
In winter there is a high pressure over the country and pollutants are trapped in stable air and not dissipated or transported elsewhere.
In the winter warm air rises from artificially heated cites or the sides of valleys. Cold night air moves in below the hot air, and temperature thus rises with height, called a low-level inversion. Pollutants are trapped in the cold layer by the warmer air above and can not be dissipated. Low level inversion of hundreds of meters deep commonly occur over Johannesburg in the winter.
Even if the pollutants manage to escape the low-level inversion they still become trapped in high level inversions, which occur when cooler rural air moves in beneath warmer city air. These inversions commonly occur over Greater Johannesburg at a height of 1 200 – 1 600m above the ground.
Height above sea level
Due to Greater Johannesburg being about 1 600 – 2000 m above sea level, the levels of oxygen on the Highveld are 20% less than that at the coast. This means that incomplete combustion of fossil fuels takes place.
Wind speed and direction influences the rate of diffusion of pollutants. The following table gives the average wind speeds (m/s) and direction at the Johannesburg Internation Airport for 1993-1998 (Weather Bureau, 1999). The prevailing wind on the reef in Greater Johannesburg is north-northwest, especially in the wintertime. The wind can turn around and blow from the southeast in summer when it brings rain.
North North east East South east South South west West North west
University/College: University of California
Type of paper: Thesis/Dissertation Chapter
Date: 24 December 2016
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