Abstract
M.Sc.
Aerosol samples were collected at stations using simple filter unit, loaded
with a 4 7 mm diameter pore size Nuclepore membrane filter. The sampling
duration was 24 hours for each sample, with the total of 11 samples: seven
for Thohoyandou and four for Bethlehem. The samples were analyzed with
energy dispersive X-ray fluorescence spectrometry for up to 20 elements.
Comparison for elemental concentrations of the data showed that the
samples fall into three clusters on average (major: Ca, Cl, Si. S, Fe and AI;
intermediate: K, Ti, Pb, Brand Zn; minor: Mn, Cr, As, Sr, Ni and Cu), with
the samples collected from Bethlehem having high concentrations in all
clusters. High concentrations in the samples collected on Bethlehem were
attributed to entrainement of dust particles during the dry winter period. The
results also show that the elements are associated with anthropogenic
emissions. Therefore, the sampling station at Thohoyandou is considered as
a background station due to the low aerosol concentration.
The aerosol concentration levels at Thohoyandou can be attributed to
biogenic sources because of the large presence of large forest areas in the
region and in the vicinity of the sampling location.
The samples collected in both regions reveal highly enriched sulphur,
chlorine, zinc and lead. It is clearly proved that these elements come from
local soil. Chromium and copper were both slightly enriched in
Thohoyandou, but the concentration data for these two elements are not
available. However it is supposed that these elements come from local soil
as well.
In another aerosol analysis, passive (diffusive) samplers were used to
measure concentration levels for sulphur dioxide and nitrogen dioxide. The
measurement campaign was carried out from Soweto in Johannesburg and
Bohlokong in Bethlehem with the campaign lasting for two months during
the w~nter season. A very clear result derived for sulphur dioxide was the
dominating source contribution from use of coal for heating and cooking in
both areas. For nitrogen dioxide, it was found that contribution from traffic
in highly populated areas and from industrial activities in the neighbourhood
of the two areas was the source. The role played by wood burning, is also
another additional source used for domestic heating and even cooking.