Abstract
Abstract. 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. PM1, PM1–2. 5 and PM2. 5–10 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 PM1 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 PM2. 5–10 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 PM1 size fraction, i.e. crustal, pyrometallurgical-related and Au slimes dams. No meaningful factors were determined for the PM1–2. 5 and PM2. 5–10 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.
Highlights
IntroductionAtmospheric aerosols either are directly emitted into the atmosphere (primary aerosols) from natural and/or anthropogenic sources or are formed through gaseous reactions and gas-to-particle conversions (secondary aerosols)
Atmospheric aerosols either are directly emitted into the atmosphere from natural and/or anthropogenic sources or are formed through gaseous reactions and gas-to-particle conversions
Since Si and Al are considered to be the most abundant crustal elements after oxygen, the trace metal concentrations presented in this paper should be related to the limitation of nitric digestion, i.e. Si–Al–K components missing from the digestions phase
Summary
Atmospheric aerosols either are directly emitted into the atmosphere (primary aerosols) from natural and/or anthropogenic sources or are formed through gaseous reactions and gas-to-particle conversions (secondary aerosols). Aerosols have high temporal and spatial variability, which increases the need for and importance of detailed physical and chemical characterisation on a regional scale in order to assess the impacts of aerosols (Pöschl, 2005). Particulate matter (PM) is classified according to its aerodynamic diameter, as PM10, PM2.5, PM1 and PM0.1, which relates to aerodynamic diameters being smaller than 10, 2.5, 1 and 0.1 μm, respectively. Venter et al.: Atmospheric trace metals measured at a regional background site
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