Abstract

VENTER, Andrew D.  and  LOURENS, Alexandra S. M.. Ambient air quality data reported at Sasol Secunda monitoring stations during COVID-19 lockdown - Mpumalanga, South Africa. Clean Air J. [online]. 2021, vol.31, n.1, pp.1-7. ISSN 2410-972X.  http://dx.doi.org/10.17159/caj/2021/31/1.8954.

Various local and international research has been published on the effects of COVID-19 lockdown on ambient air quality. In most cases, a reduction in ambient NO_x and PM concentrations have been observed with varying changes in ambient SO₂ levels. The Mpumalanga province of South Africa is known for its large industrial facilities utilising coal as primary feedstock and is located in the Highveld Priority Area. The ambient air quality in the Secunda region of Mpumalanga province was assessed. This region contains, amongst others, the towns of Secunda, Trichardt and eMbalenhle from which the majority of the Sasol Secunda workforce originates. This specific region was assessed due to the authors' familiarity with the Sasol facility and the strategic locations of ambient air quality stations, as well as the known changes in human behaviour during the lockdown period. Results show decreases in ambient CO, NO_x and PM concentrations, especially during the first two weeks of lockdown. Only smaller changes were observed for ambient H₂S and SO₂ concentrations at the ambient monitoring stations. An increasing trend in all ambient species was observed towards the end of- and post lockdown in addition to declining ambient temperatures with the onset of winter. This is in spite of the reduction in emissions from the factory that conducted annual maintenance in the month following lockdown (phase shutdown). This article concludes that community behaviour has a material local ambient impact on CO, NO_x and PM pollutant species, while H₂S concentration profiles are more directly related to the local industrial complex's levels of activity. Ambient SO₂ trends did not show a similar correlation with the facility's activities, but a stronger correlation was observed with diverse local and regional sources on the Highveld. The influence of effective stack emission heights for better dispersion, especially for SO₂ and on a local scale, is considered material. Meteorological factors has been shown to be a substantial contributor to observed ambient air quality levels in the study domain.

Keywords : Ambient air quality; COVID-19; highveld priority area; nitrogen oxides; particulate matter; sulphur dioxide; hydrogen sulphide.

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