The impacts of air pollution on the environment are diverse, which include harmful consequences for human health, vegetation, animals and the natural ecosystem.  In addition, these atmospheric pollutants affect earth’s climate through contributing to changes in energy fluxes of solar and terrestrial radiation in the atmosphere (radiative forcing). According to assessments of the Intergovernmental Panel on Climate Change (IPCC), changes in the earth’s atmosphere and climate are caused by increased human activities that contributes to higher emission of these species. There has been an incraesed awareness of air quality and climate change in the public and scientific community with a growing national concern about the rapid chemical composition changes of the atmosphere in southern Africa and the impact of these changes on sustainable development. 

Chemical species in the atmosphere can either be present in the gas phase or as aerosols (particulate solid or liquid matter suspended in the atmosphere). The main anthropogenic sources of these species in South Africa include coal-fired power plants, industrial activities (e.g. petrochemical and pyrometallurgical industries), verhicular emissions, open biomass burning (veld fires), as well ass household combustion for space heating and -cooking. These species can be directly emitted into the atmosphere or can be formed through atmospheric chemical reactions and/or gas-to-particle conversions. The main sink of these species include wet- and dry deposition through processes such as precipitation, convective transport, diffusion and adhesion to the surface. It is important to determine the chemical and, especially, for aerosols, physical properties of these species in order to quantify their impacts on air quality and climate. 

The main activities of the Atmospheric Chemistry Research Group mainly comprise monitoring temporal and spatial variations in concentrations of atmospheric gaseous and aerosols, as well as assessing deposition of these species. These activities are primarily conducted through two large projects, i.e. the Deposition of Biogeochemical Important Trace Species (DEBITS) task of the International Global Atmospheric Chemistry (IGAC) programme initiated by the Global Atmosphere Watch (GAW) network of the World Meteorological Organisation (WMO), as well as the operation of the Welgegund atmospheric measurement supersite in collaboration with the University of Helsinki and the Finnish Meteorological Institute. Welgegund is considered to be the most comprehensively equipped scientific atmospheric monitoring station in Africa, which was the most important factor contributing to the ACRG hosting the atmospheric node of BIOGRIP. Deposition work is currently conducted through the Expanded Freshwater and Terrestrial Environmental Observation Network (EFTEON) of DSI in collaboration with the University Paul-Sabatier (Laboratoire d’Aerology) in France. The South African component of DEBITS also operates within the framework of the International Network to study Deposition and Atmospheric composition in Africa (INDAAF) programme, which is aligned with the International Nitrogen Initiative (INI). In addition to these two major projects, the ACRG is also involved in smaller projects for industry and government (e.g. Sasol, Eskom, North West Provincial Government, South Africa Mercury Network programme). The ACRG has an extensive national and international collaboration network.