Particulate matter (PM2.5) characterization and air quality level in an urban background in Pretoria

Background: More than ever before, air pollution has become a great importance to the world because of it deleterious effect on human and the environment coupled with the effect of global warming. The presence of PM2.5 in the ambient air have showed strong association of adverse health outcomes for morbidity and mortality such as respiratory problems, cardiovascular diseases, asthma. Chemical characteristics and sources of trace elements in PM2.5, as well as the air quality index, were investigated. Method:24-h fine aerosol particles were collected in an urban area in Pretoria, South Africa, from 17 April 2017 - 18 April 2018. Eighteen trace elements were determined using an XEPOS 5 energy-dispersive X-ray fluorescence (EDXRF) spectrometer (SPECTRO Analytical Instruments, Germany), while black and organic carbon were estimated using an optical transmissometer from the samples collected. The HYPLIT model (version 4.9) was used to estimate air mass trajectories. Potential health risk was calculated by comparing it to the World Health Organization's air quality index (AQI). Result:The overall mean PM2.5 concentration of the collected sample equals 21μg/m3, this value exceeds WHO air quality limit but below the European Union annual air quality standards. Among these constituents C and S had the highest, greater than 1μg/m3. Ni, Se, Br and Sb showed they were extremely enriched, (EF>10) and suggestive of anthropogenic or non-crustal origin. The 24-h PM, soot, BC and OC were significantly different by the geographical origin of air masses (p<0.05). The AQI showed that 70% of the samples showed levels above the AQI range of good and healthy air. Conclusion: The findings include details on the concentration, composition, and potential sources of fine PM2.5, which is essential for policy formulation and mitigation strategies in South Africa’s fight against air pollution. Key words: Air pollution, transport cluster, particulate matter, trace elements, biomass burning, South Africa.