Source apportionment of ambient fine and coarse aerosols in Embalenhle and Kinross, South Africa

Abstract

The South African Highveld is recognised as a region having significant negative ambient air quality impacts with its declaration as an Air Quality Priority Area in 2007. Such areas require the implementation of specific air quality intervention strategies to address the air quality situation. A greater understanding of the composition of the atmospheric aerosol loading and the contributing air pollution sources will assist with the formulation and implementation of these strategies. This study aims to assess the composition and sources of the aerosol loading in Embalenhle and Kinross located on the Highveld. Fine (PM_2.5) and coarse (PM_2.5-10) aerosol samples were collected during summer and winter, which were quantified using the gravimetric method. Wavelength-Dispersive X-Ray Fluorescence (WD-XRF) and Ion Chromatography (IC) analysis were used to determine the chemical composition of aerosols. Mean PM_2.5 concentrations in Embalenhle and Kinross ranged from 16.3 to 34.1 µg/m³ during winter and 7.4 to 19.0 µg/m³ during summer. Mean PM_10-2.5 concentrations ranged from 10.3 to 114 µg/m³ during winter and 5.9 to 11.2 µg/m³ during summer. Si, Al, S, Na (winter only), Ca (summer only), SO₄^2- and NH₄⁺ were the most abundant species in PM_2.5 during both seasons. In PM_10-2.5, Si, Al, Na (winter only), SO₄^2- and F^- were the most abundant species during both seasons. The elements S and Ca also had high abundances at Embalenhle and Kinross, respectively, during summer. Source apportionment was undertaken using Positive Matrix Factorisation, which identified five sources. Dust, secondary aerosols, domestic combustion, wood and biomass burning, and industry were determined to be the contributing sources. Any measures to mitigate particulate air pollution on the Highveld should consider these key sources.