Characterisation of ambient Total Gaseous Mercury concentrations over the South African Highveld

Abstract

Mercury is considered a ubiquitous, toxic, and global pollutant. In this study, ambient Total Gaseous Mercury (TGM) concentrations over the South African Highveld are characterised. Studies on ambient mercury in this region is important because of various anthropogenic emission sources. In this pilot study, concentrations of TGM and criteria pollutants (O3, SO2, NO, NO2, and CO) were measured concurrently with meteorological parameters at Balfour (BF), Middelburg (MB), and Standerton (ST) from January 2009 to December 2009. The spatial variation of TGM concentrations ranged from 0.40 to 28.72 ng/m3 (1.99 0.94 ng/m3), 0.12–9.91 ng/m3 (1.04 0.62 ng/m3), and 0.21–32.10 ng/m3 (1.25 1.38 ng/m3), at BF, MB, and ST, respectively. Generally, concentrations fell within the Northern Hemisphere background range of 1.5–1.7 ng/m3 and Cape Point, South Africa background of 1.2–1.4 ng/m3, with the exception of outliers. The outliers were much higher than the background values and may be the result of pollution events. Seasonal variation varied with descending orders of summer, spring, winter, autumn, at BF; summer, winter, autumn, spring at MB; and winter, spring, summer at ST (no data available for autumn). This study observed no profound diurnal patterns at BF and MB where sparse local and regional sources appear to have been the predominant sources. An interesting phenomena, however, was observed at ST where the diurnal cycle suggests a potential significant influence from local domestic combustion sources