Fall-out dust levels around two enterprises in the Western Cape of South Africa from 2001 to 2005

Abstract

ABSTRACT Looking up at the sky, we would never guess that our atmosphere contains between one and three billion tons of dust and other particles at any given time.1 Wind assists in keeping this dust airborne, but gravity wins most of the time, forcing the dust particles earthward, proving the old adage: “what goes up, must come down.” Precipitant dust levels in the Western Cape do not follow the same pattern as the precipitant dust levels in the summer rainfall areas of South Africa. Due to the very dry summer conditions in the Western Cape, the precipitant dust levels can be very high, especially if sources of fugitive dust are ignored. An environmental consulting company positioned precipitant dust monitoring units at strategic locations, taking process and open dust sources into account. Both wet and dry depositions have been reported on in this report as one figure. Seasonal changes in, and long-term trends of, the amount of precipitant dust were documented and statistically analysed to determine if the precipitantdust levels were above the South African legislated action levels. The particle size analysis performed on the precipitant dust indicated that the dust was predominantly less than 100_μm and that about 22 percent of the particles by volume were under 15_μm. No significant decline in the precipitant dust levels around the calcining industry was noted. Recommendations are that they increase the dust control measures on site, especially near to the DHF sampling location. There was a significant decrease in the precipitant dust levels to the north and south of the smelting industry from October 2001 to April 2005, p-value 0.005 and 0.048. The recommendations for the smelting industry are that they continue to eliminate fugitive dust sources and that they continue to maintain a high awareness of dust control.