Abstract
On the 11th of March 2020, the World Health Organization announced that the
extremely communicable COVID-19 virus had officially become a global
pandemic. To curb the spread of the virus, South Africa instituted alert level 5
lockdown restrictions from 27 March 2020. These measures halted most travel and
only permitted essential services. This study investigates the effect of COVID-19
on emissions of greenhouse gases and air pollutants from road transportation in
the Gauteng Province of South Africa for the period between 26 March 2020 to 31
March 2021. Changes in magnitude and patterns of traffic were quantified using
Google Mobility and Tomtom travel data. Reductions in activity were observed for
retail and recreation (-72% in April 2020), grocery and pharmacy (-48%) and
workplaces (-69%). Only residential areas saw increased activity compared to the
pre-COVID baseline (+36%).
Emissions from road and aviation transport were calculated from quarterly fuel use
(tier 1 approach). In quarter 2 of 2020, emissions of CO2, N2O, NOx, CO and TSP
from transport declined by 49%, 44%, 40%, 80% and 35% respectively, relative to
the 2017-2019 baseline. Ambient monitoring data was obtained from the SAAQIS
website. Ambient NO2 concentrations seem to have decreased widely across
Gauteng due to the drop in vehicle emissions. Levels of other pollutants are
influenced by other sources, both local and regional. In Vereeniging in the south
of Gauteng, concentrations of CO and black carbon increased, suggesting an
increase in a source like the residential burning of solid fuels.
The findings of this study indicate that permanent emission reduction measures
are required for meaningful improvements in air quality to be realised. These
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measures need to consider emissions and chemical transformations of pollutants
on an airshed scale and need to guard against shutting down economic activity,
which may inadvertently increase air pollution in low-income residential areas. The
work-from-home practice imposed during the COVID-19 lockdown appears to be
enduring and will have positive implications for ambient NO2 levels during the
morning and evening rush-hours, when emission levels are traditionally highest.