Atmospheric trace metals measured at a regional background site (Welgegund) in South Africa
Andrew D. Venter1, Pieter G. van Zyl1, Johan P. Beukes1, Micky Josipovic1, Johan Hendriks1, Ville Vakkari2, and Lauri Laakso1,21Unit of Environmental Sciences and Management, North-West University, Potchefstroom, South Africa 2Finnish Meteorological Institute, Helsinki, Finland
Received: 22 Sep 2016 – Accepted for review: 10 Oct 2016 – Discussion started: 11 Oct 2016
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 metals concentrations in aerosols collected at 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 that 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 % and 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 pyrometallurgical smelting were lower. Annual average Ni was four times higher and annual average As was marginally higher than their respective European standards limit 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.
Venter, A. D., van Zyl, P. G., Beukes, J. P., Josipovic, M., Hendriks, J., Vakkari, V., and Laakso, L.: Atmospheric trace metals measured at a regional background site (Welgegund) in South Africa, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-845, in review, 2016.