Atmospheric trace metals measured at a regional background site (Welgegund) in South Africa
Atmospheric trace metals can cause a variety of health-related and environmental problems. Only a few studies on atmospheric trace metal concentrations have been conducted in South Africa. Therefore the aim of this study was to determine trace metal concentrations in aerosols collected at a regional...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/4251/2017/acp-17-4251-2017.pdf |
| Summary: | Atmospheric trace metals can cause a variety of health-related and
environmental problems. Only a few studies on atmospheric trace metal
concentrations have been conducted in South Africa. Therefore the aim of
this study was to determine trace metal concentrations in aerosols
collected at a regional background site, i.e. Welgegund, South Africa.
PM<sub>1</sub>, PM<sub>1–2. 5</sub> and PM<sub>2. 5–10</sub> samples were collected for 13 months, and 31 atmospheric trace metal species were detected. Atmospheric
iron (Fe) had the highest concentrations in all three size fractions, while
calcium (Ca) was the second-most-abundant species. Chromium (Cr) and sodium
(Na) concentrations were the third- and fourth-most-abundant species,
respectively. The concentrations of the trace metal species in all three
size ranges were similar, with the exception of Fe, which had higher
concentrations in the PM<sub>1</sub> size fraction. With the exception of titanium
(Ti), aluminium (Al) and manganese (Mg), 70 % or more of the trace metal
species detected were in the smaller size fractions, which indicated the
influence of industrial activities. However, the large influence of
wind-blown dust was reflected by 30 % or more of trace metals being
present in the PM<sub>2. 5–10</sub> size fraction. Comparison of trace metals
determined at Welgegund to those in the western Bushveld Igneous Complex
indicated that at both locations similar species were observed, with Fe being
the most abundant. However, concentrations of these trace metal species were
significantly higher in the western Bushveld Igneous Complex. Fe
concentrations at the Vaal Triangle were similar to levels thereof at
Welgegund, while concentrations of species associated with pyrometallurgical
smelting were lower. Annual average Ni was 4 times higher, and annual
average As was marginally higher than their respective European standard
values, which could be attributed to regional influence of pyrometallurgical
industries in the western Bushveld Igneous Complex. All three size fractions
indicated elevated trace metal concentrations coinciding with the end of the
dry season, which could partially be attributed to decreased wet removal and
increases in wind generation of particulates. Principal component factor
analysis (PCFA) revealed four meaningful factors in the PM<sub>1</sub> size
fraction, i.e. crustal, pyrometallurgical-related and Au slimes dams. No
meaningful factors were determined for the PM<sub>1–2. 5</sub> and PM<sub>2. 5–10</sub>
size fractions, which was attributed to the large influence of wind-blown
dust on atmospheric trace metals determined at Welgegund. Pollution roses
confirmed the influence of wind-blown dust on trace metal concentrations
measured at Welgegund, while the impact of industrial activities was also
substantiated. |
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| ISSN: | 1680-7316 1680-7324 |