Impacts of coal-fired power plants on aerosol particles in the Highveld

Abstract

Industrialisation and urbanisation of the interior plateau of South Africa (i.e. the Highveld) have resulted in air quality that infringes on South Africans' right to an environment that is not damaging to human health or well-being. In March 2022, a judgement was handed down in the Pretoria High Court, ordering the government to execute the Highveld Priority Area Air Quality Management Plan. The judgement provided that failure to meet the National Ambient Air Quality Standards (NAAQS) in the area is sufficient evidence for a violation of the right to an environment that is protected and not detrimental to human health or well-being. The Highveld has meteorological conditions that are highly unfavourable air pollution dispersion. Combined with the industrialisation and urbanisation within the region, this has resulted in fine particulate air pollution (i.e., PM2.5). PM2.5 is an air pollutant that can remain in the atmosphere for days to weeks giving it the potential to reach remote regions of South Africa or neighbouring countries. When inhaled, it can penetrate deep into the respiratory system and cause many adverse health impacts. To effectively manage ambient air quality in the Highveld, we need to understand the relationship between these air pollutants and determine their significant sources in the region. This study looks at the impact of ambient PM2.5, particularly secondary PM2.5 (i.e., PM2.5 formed in the atmosphere), attributed to coal-fired power plants in the Highveld. Coal-fired power plants are significant sources of sulphur dioxide (SO2) and nitrogen oxides (NOx), which are precursor gases of secondary PM2.5, and most of the coal-fired power plants in South Africa are concentrated in the Highveld. This study was built upon an existing modelling platform developed for the Highveld Health Study (baseline simulation). A second concept simulation was run, where all large (≥1 000 MW) coal-fired power plant emissions were excluded. The annual average PM2.5 attributable to the coal-fired power plants was determined by subtracting the concentrations in the concept simulation from those in the baseline simulation. The study found that the large coal-fired power plants were a significant source of ambient annual average PM2.5, specifically secondary PM2.5. The results show an opportunity to reduce the number of “All-cause” mortalities in the Highveld study area by up to ~1.32%. Reducing SO2 and NOx emissions from coal-fired power plants would have the greatest impact on lowering the ambient PM2.5 attributed to these plants. A monetary value of R37.6 billion (SA2016R) was estimated for the relative reduction in the estimated mortality risk attributed to the large coal-fired power plants.