The improvement in the air quality of Brussels after a month and a half of confinement results in a drop in nitric oxide concentrations of up to 75% in sites usually highly exposed to emissions from car traffic , according to reports from Bruxelles Environnement presented on Friday by the cabinet of regional minister Alain Maron.
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The concentrations of pollutants recorded in various stations characteristic of certain traffic (such as the Arts-Loi station or the Uccle station) from March 19 to April 19, then over a period extended to May 3 in a second report, were compared to 2010-2019 data.
Weather conditions, which influence the dispersion of pollutants, were considered to be similar to, if not slightly better than, that of a “normal” March or April. In stations heavily exposed to traffic, nitrogen monoxide (NO), which remains localized near its emission sources, decreased by 75% and carbon dioxide (NO2) by 50%. The latter has harmful effects on the respiratory tract and the environment.
This is more than likely an effect related to containment measures
Its concentration decreases over the years, but still usually exceeds the European limit of 40 micrograms / m3 in stations with high traffic in Brussels. In stations with little exposure, the concentration of NO has decreased by 30% and that of NO2 40%. “Since NO2 is a pollutant capable of being transported over long distances (unlike NO2), these values demonstrate that pollution imported into the Brussels Region has also decreased significantly”, comments the head of the Air Quality laboratory at Bruxelles Environnement, Olivier Brasseur.
“This is more than likely an effect linked to the containment measures taken in Belgium and in the neighboring countries.”
Black carbon, a particulate compound less than 0.5 µm which is primarily related to road traffic, fell with it during containment. By comparing Sundays and working days, it is recognized that cars could explain 15 to 25% of PM10 concentrations (less than 10 µm) and 5% of PM2.5 concentrations (less than 2.5 µm), more dangerous to health.
By adopting a simplified reasoning, the impact of the Covid-19 measures would be around 10% for PM10 and 2% for PM2.5. However, the concentrations of fine particles during confinement were generally equivalent to, or even higher than, the normal values.
The study suggests that the few rainy days contributed to the resuspension of the particles, that the wind from the northeast was able to transport fine particles over long distances and that the spreading which takes place in March- April may have had consequences, but since people stayed at home with confinement when there were cold days, the impact of heating could also be interesting to assess.
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