Ambient PM2.5 chemical composition in a residential area in Johannesburg, South Africa

Le résumé fourni par la source

Abstract PM 2.5 is associated with multiple adverse health outcomes, yet data on its concentration, composition and sources in African cities remain limited. This study presents the first detailed characterisation of outdoor PM 2.5 in Johannesburg, South Africa. Twenty-four-hour filter samples were collected every sixth day from 3 October 2020 to 12 October 2021 at a residential site in the suburb of Buccleuch. Samples were analysed using gravimetric methods, smoke-stain reflectometry, optical transmissometry and X-ray fluorescence. Source contributions were assessed using principal component analysis (PCA), enrichment factor (EF) analysis and Hybrid Single Particle Lagrangian Integrated Trajectory model for backward trajectories. The mean PM 2.5 concentration was 8.1 µg.m −3 (range: 0.04–30 µg.m −3 ), exceeding the World Health Organization (WHO) annual guideline (5 µg.m −3 ). Daily concentrations surpassed the WHO daily guideline (15 µg.m −3 ) on seven of the 55 sampling days. Mean black carbon (BC) and organic carbon (OC) concentrations were 0.51 and 0.46 µg.m −3 , respectively. Twelve trace elements were detected, with Fe, K, S and Si most abundant. PM 2.5 , BC, OC and several elements were significantly higher in winter and autumn, reflecting increased combustion activities and unfavourable meteorological conditions. Trajectory analysis indicated contributions from regional mining and coal-related activities. Integrated PCA and EF results showed that PM 2.5 comprised resuspended dust, traffic-related non-exhaust emissions, local residential combustion and regionally transported pollution. These findings highlight multi-source exposure and the need for coordinated air quality management at municipal and regional scales.

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