Urban air quality changes resulting from the lockdown period due to the COVID-19 pandemic

This work aims to quantify potential pollution level changes in an urban environment (Madrid city, Spain) located in South Europe due to the lockdown measures for preventing the SARS-CoV-2 transmission. Polluting 11 species commonly monitored in urban zones were attended. Except for O₃, a prompt target pollutant levels abatement was reached, intensely when implanted stricter measures and moderately along those measures' relaxing period. In the case of TH and CH₄, it is evidenced a progressive diminution over the lockdown period. While the highest decreasing average changes relapsed on NOx (NO₂: - 40.0% and NO: - 33.3%) and VOCs (C₇H₈: - 36.3% and C₆H₆: - 32.8%), followed by SO₂ (- 27.0%), PM₁₀ (- 19.7%), CO (- 16.6%), CH₄ (- 14.7%), TH (- 11.6%) and PM_2.5 (- 10.1%), the O₃ level slightly raised 0.4%. These changes were consistently dependent on the measurement station location, emphasizing urban background zones for SO₂, CO, C₆H₆, C₇H₈, TH and CH₄, suburban zones for PM_2.5 and O₃, urban traffic sites for NO and PM₁₀, and keeping variations reasonably similar at all the stations in the case of NO₂. Those pollution changes were not translated in variations on geospatial pattern, except for NO, O₃ and SO₂. Although the researched urban atmosphere improvement was not attributable to meteorological conditions' variations, it was in line with the decline in traffic intensity. The evidenced outcomes might offer valuable clues to air quality managers in urban environments regarding decision-making in favor of applying punctual severe measures for quickly and considerably relieving polluting high load occurred in urban environments.

The online version contains supplementary material available at 10.1007/s13762-022-04464-6.