Source Apportionment of PM_2.5 and PM_2.5-Bound Trace Elements in Pretoria, South Africa

Abstract

Outdoor PM_2.5 samples were collected for 34 months in Pretoria, South Africa from 18 April 2017 to 28 February 2020. The average total PM_2.5 concentration was 23.2 ± 17.3 µg.m³ (0.69–139 µg.m⁻³), with the highest mean recorded during winter and the lowest during summer (p < 0.05). The sources were determined by means of cross referencing the US EPA PMF 5.0 program and the NOAA HYsplit model. The sources of the total PM_2.5 were mining (33%), resuspended dust (24%), industry (15%), general exhaust (12%), vehicular emissions (12%) and biomass burning (4%). Sources of air pollutants are both ubiquitous and seasonal.

Highlights

• In central Pretoria, the largest contributing sources of PM_2.5 are resuspended dust matrix and mining from surrounding areas;

• A winter analysis was run where As, Se and Pb was included in the dataset, confirming biomass burning sources which were typically higher during the winter season; and

• Air quality management policies should address both ubiquitous and seasonal sources.

Keywords:

• PMF
• HYsplit
• PM_2.5
• trace elements
• seasonal
• ubiquitous sources

Acknowledgments

The authors gratefully acknowledge the NOAA Air Resources Laboratory for providing the HYSPLIT model and the NCEP Reanalysis datasets, as well as the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA. The authors would like to thank the South African Weather Service for the air pollution and meteorological data, University of Pretoria. The author would like to thank A Adeyemi for data collection from 16 April 2017 to 15 April 2018, and N Mwazi for data collection from 18 April 2018 to 23 April 2019.

Ethics Approval

The Research Ethics Committee, Faculty of Health Sciences, University of Pretoria, approved ethics approval (reference 300/2020) in 2020.

Disclosure Statement

The authors declare that they have no conflict of interest.

Author Contribution

JW conceptualized the research. The research design, methodology, analysis of findings and writing of the manuscript were all the responsibility of CHD. The statistical analyses were carried out by CHD. JB was responsible for the chemical analysis. PM did the data management of the trace elements results prior to statistical analysis and PMF application. All authors read and approved the final manuscript.

Data Availability

The datasets generated and/or analyzed during this study are not publicly available due to university’s intellectual property right but are available from the corresponding author on reasonable request.

Additional information

Funding

JW received funding from the South African National Research Foundation under the Collaborative Postgraduate Training Programme grant (CPT160424162937).