Assessing the responses of aviation-related SO₂ and NO₂ emissions to COVID-19 lockdown regulations in south Africa

Aircraft emit harmful substances, such as carbon dioxide (CO₂), water vapour (H₂O), nitrogen oxides (NO_x), sulphur oxides (SO_x), particulates, and other trace compounds. These emissions degrade air quality and can deteriorate human health and negatively impact climate change. Airports are the nucleus of the ground and low-altitude emissions from aircraft during approach, landing, take-off, and taxi. During the global lockdown due to the COVID-19 pandemic, tight restrictions of the movement were imposed, leading to temporary closures of airports globally. In this study, we look at the variability of emissions at two major airports in South Africa, namely the OR Tambo international airport (FAOR) and the Cape Town international airport (FACT). Trend analysis of aircraft movements, i.e., departures and arrivals, showed a sharp decline at the two airports coinciding with the lockdowns to prevent the spread of the COVID-19. Consequently, a decrease in NO² emissions by 70.45% (12.6 × 10^-5 mol/m²) and 64.58% (11.6 × 10^-5 mol/m²) at FAOR and FACT were observed, respectively. A noticeable SO₂ emission decline was also observed, particularly over FAOR during the lockdown period in South Africa. Overall, this study observed that the global lockdown regulations had a positive impact on the air quality, causing a brief decline in emissions from commercial aviation at the South African major airports.