EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Air quality studies using long-term observations at Welgegund, South Africa

Ville Vakkari1,2, Kerneels Jaars2, Miroslav Josipovic2, Markku Kulmala3, Lauri Laakso1,2, Tuukka Petäjä3, and Pieter G. van Zyl2
Ville Vakkari et al.
  • 1Finnish Meteorological Institute, Helsinki, Finland (
  • 2Atmospheric Chemistry Research Group, Chemical Resource Beneficiation, North-West University, Potchefstroom, South Africa
  • 3Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki, Finland

Quality-controlled long-term measurements of atmospheric composition are central in identifying the sources and processes that are most important for air quality in a particular environment. In South Africa, continuous measurements of various atmospheric constituents have been carried out at the Welgegund measurement station since May 2010 in close collaboration between North-West University, Finnish Meteorological Institute and University of Helsinki. Welgegund is a regionally representative continental site approx. 100 km west of Johannesburg with no local sources. Before Welgegund, measurements were operated at Marikana village, which is an urban location with large industrial point sources in the vicinity. At both sites measurements included particulate matter smaller than 10 µm in diameter (PM10), black carbon (BC) and trace gases (SO2, NO, NOx, O3, CO) among others.

Numerous industrial point sources surrounding Johannesburg result in elevated NOx and SO2 levels in the region, but these concentrations remain below air quality standards. On the other hand, PM10 does exceed 50 µg m3 rather frequently and more often at Marikana than at Welgegund. However, strong correlation with CO suggests that the periods of elevated PM10 are related to incomplete combustion rather than the industrial emissions at both locations. At Marikana the major source appears to be domestic heating during winter time, while at Welgegund landscape fires seem more important. Also, O3 exceeds air quality standards frequently at both sites and the highest O3 cases appear to be linked with landscape fires. Furthermore, our observations suggest that O3 formation is not NOx-limited but rather VOC-limited.

How to cite: Vakkari, V., Jaars, K., Josipovic, M., Kulmala, M., Laakso, L., Petäjä, T., and van Zyl, P. G.: Air quality studies using long-term observations at Welgegund, South Africa, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8742,, 2023.