PM2.5 Chemical Composition and Geographical Origin of Air Masses in Pretoria, South Africa

Howlett-Downing, Chantelle; Boman, Johan; Molnár, Péter; Shirinde, Joyce; Wichmann, Janine

PM2.5 Chemical Composition and Geographical Origin of Air Masses in Pretoria, South Africa

2022

Howlett-Downing, Chantelle | Boman, Johan | Molnár, Péter | Shirinde, Joyce | Wichmann, Janine

In Africa, there is a paucity of studies that reported on PM₂.₅, soot, BC, UV-PM (organic carbon) and trace element levels in rural and urban regions. PM₂.₅ samples were collected over 24 h and every third day during 19 April 2018 and 28 February 2020. The mean PM₂.₅ level was 24.1 μg.m⁻³ (range: 2.9–139 μg.m⁻³). PM₂.₅ levels exceeded the yearly World Health Organization (WHO) air quality guideline (5 μg.m⁻³). The daily WHO guideline (15 μg.m⁻³) was exceeded on 151 of the 228 days. The mean soot, black carbon and organic carbon levels were 1.43 m⁻¹ × 10⁻⁵, 2.7 μg.m⁻³ and 2.1 μg.m⁻³, respectively. Twelve PM₂.₅-bound trace elements (Br, Ca, Cl, Cu, Fe, K, Ni, S, Si, Ti, U and Zn) were analysed. The geographical origin of air masses that passed the study site was estimated using the Hybrid Single-Particle Lagrangian Integrated Trajectory software. Four air masses were identified. The observed PM₂.₅, soot, BC, UV-PM and trace element levels at this urban background study site could potentially pose a significant risk to human health.

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