Articles | Volume 17, issue 10
Atmos. Chem. Phys., 17, 6177–6196, 2017
Atmos. Chem. Phys., 17, 6177–6196, 2017

Research article 19 May 2017

Research article | 19 May 2017

Spatial, temporal and source contribution assessments of black carbon over the northern interior of South Africa

Kgaugelo Euphinia Chiloane1, Johan Paul Beukes1, Pieter Gideon van Zyl1, Petra Maritz1, Ville Vakkari2, Miroslav Josipovic1, Andrew Derick Venter1, Kerneels Jaars1, Petri Tiitta1,3, Markku Kulmala4, Alfred Wiedensohler5, Catherine Liousse6, Gabisile Vuyisile Mkhatshwa7, Avishkar Ramandh8, and Lauri Laakso1,2 Kgaugelo Euphinia Chiloane et al.
  • 1Unit for Environmental Sciences and Management, North-West University, Potchefstroom Campus, South Africa
  • 2Finnish Meteorological Institute, Helsinki, Finland
  • 3Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 1627, Kuopio, Finland
  • 4Department of Physics, University of Helsinki, Helsinki, Finland
  • 5Leibniz Institute for Tropospheric Research, Leipzig, Germany
  • 6Laboratoire d'Aérologie, Université Paul Sabatier-CNRS, OMP, 14 Avenue Edouard Belin, Toulouse, France
  • 7Research, Testing and Development, Eskom SOC Ltd, Rosherville, South Africa
  • 8Sasol Technology R&D (Pty) Limited, Sasolburg, South Africa

Abstract. After carbon dioxide (CO2), aerosol black carbon (BC) is considered to be the second most important contributor to global warming. This paper presents equivalent black carbon (eBC) (derived from an optical absorption method) data collected from three sites in the interior of South Africa where continuous measurements were conducted, i.e. Elandsfontein, Welgegund and Marikana, as well elemental carbon (EC) (determined by evolved carbon method) data at five sites where samples were collected once a month on a filter and analysed offline, i.e. Louis Trichardt, Skukuza, Vaal Triangle, Amersfoort and Botsalano.

Analyses of eBC and EC spatial mass concentration patterns across the eight sites indicate that the mass concentrations in the South African interior are in general higher than what has been reported for the developed world and that different sources are likely to influence different sites. The mean eBC or EC mass concentrations for the background sites (Welgegund, Louis Trichardt, Skukuza, Botsalano) and sites influenced by industrial activities and/or nearby settlements (Elandsfontein, Marikana, Vaal Triangle and Amersfoort) ranged between 0.7 and 1.1, and 1.3 and 1.4 µg m−3, respectively. Similar seasonal patterns were observed at all three sites where continuous measurement data were collected (Elandsfontein, Marikana and Welgegund), with the highest eBC mass concentrations measured from June to October, indicating contributions from household combustion in the cold winter months (June–August), as well as savannah and grassland fires during the dry season (May to mid-October). Diurnal patterns of eBC at Elandsfontein, Marikana and Welgegund indicated maximum concentrations in the early mornings and late evenings, and minima during daytime. From the patterns it could be deduced that for Marikana and Welgegund, household combustion, as well as savannah and grassland fires, were the most significant sources, respectively.

Possible contributing sources were explored in greater detail for Elandsfontein, with five main sources being identified as coal-fired power stations, pyrometallurgical smelters, traffic, household combustion, as well as savannah and grassland fires. Industries on the Mpumalanga Highveld are often blamed for all forms of pollution, due to the NO2 hotspot over this area that is attributed to NOx emissions from industries and vehicle emissions from the Johannesburg–Pretoria megacity. However, a comparison of source strengths indicated that household combustion as well as savannah and grassland fires were the most significant sources of eBC, particularly during winter and spring months, while coal-fired power stations, pyrometallurgical smelters and traffic contribute to eBC mass concentration levels year round.

Short summary
This paper presents atmospheric black carbon (BC) data collected in South Africa (SA). In general, BC level were higher than in the developed world. At one site, five sources were identified, with household combustion as well as savannah and grassland fires the most significant sources during winter and spring, while coal-fired power stations, pyrometallurgical smelters and traffic contributed year round.
Final-revised paper