Impact of residential combustion on black carbon levels in Palapye, Botswana: Field measurements and GEOS-chem simulations

Over half of the population in Africa still rely on solid fuels such as wood, coal, dung, crop waste, and charcoal for household heating and cooking. Combustion of such fuels leads to high levels of PM_2.5 emissions, where a large fraction of PM_2.5 is composed of black carbon (BC) and organic carbon (OA). Additionally, there is a lack of continuous ground-based monitors in Africa to measure emissions and chemical composition, which is essential for monitoring changes in air quality. To better understand air pollution in Africa, we conducted a five-week field campaign in June and July of 2022 at Botswana International University of Science and Technology (BIUST) located in Palapye, Botswana and ran numerous GEOS-Chem simulations to understand which anthropogenic sources had the potential to impact the field-measured BC. BC field measurements were collected using a micro-aethalometer. Simulations were used to quantify the effect of four anthropogenic sources (energy, industry, residential, and transportation) on ambient BC in Southern Africa during June and July of 2018 and 2022. The average BC concentrations from field measurements at BIUST were 0.34 μg m⁻³. GEOS-Chem, simulation results showed that those residential emissions contributed 52 % and 49 % of the average ambient BC during both months in 2018 and 2022, respectively, at the observation site at BIUST. Compared to the other three combustion sources, residential emissions contributed the largest to the average ambient BC concentrations in this region.