| Summary: | Atmospheric pollution resulting from an open-cast coal mine situated 10 km southwest
of Witbank (Mpumalanga, South Africa) was investigated during summer and
winter 2004. Industrial and urban activities in and around Witbank release large
amounts of toxic and criteria pollutants into the atmosphere. Spontaneous combustion
from the many collieries in the Witbank area contributes to this problem. Direct,
automated, and continuous in situ measurements of trace gas concentrations and
prevailing meteorological parameters were carried out by a mobile monitoring unit
and an automatic weather station. The data collected show that spontaneous
combustion is a source of CO, NO, SO2 and H2S. Summer daily averages of SO2,
NO, NO2 and O3 concentrations ranged between 1 and 18 ppb, 0.3 and 40 ppb, 12 and
75 ppb and 0.9 and 19 ppb respectively. Winter daily concentrations of SO2 and O3
were much higher, ranging between 15 and 180 ppb and 14 and 30 ppb respectively.
NO and NO2, in contrast, were lower in winter (0.8 to 15 ppb and 2 to 28 ppb for
daily means). Winter daily average concentrations of H2S, CO and CO2 ranged
between 16 and 217 ppb, 2100 and 5100 ppb and 322 and 436 ppm). Synoptic
circulations over the Highveld were found to affect pollutant concentrations. During
winter, temperature inversions played a significant role in increasing the pollutant
concentrations in the early morning hours until about 10:00. Although considerable
amounts of NO, NO2 and O3 were captured; their concentrations were within the
South African Department of Environmental Affairs and Tourism’s permissible
levels as contained in the National Environmental Management: Air Quality Act
(2004). SO2 concentrations during winter 2004 exceeded the allowed standards.
Elevated concentrations of pollutants were mostly observed when the wind blew from
the SE, SSE, S and WSW directions, implicating the 2A south pits of the open-cast
mine investigated as the major source of the emissions.
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