COVID-19 pandemic in Wuhan: Ambient air quality and the relationships between criteria air pollutants and meteorological variables before, during, and after lockdown

As a result of the lockdown (LD) control measures enacted to curtail the COVID-19 pandemic in Wuhan, almost all non-essential human activities were halted beginning on January 23, 2020 when the total lockdown was implemented. In this study, changes in the concentrations of the six criteria air pollutants (PM(2.5), PM(10), SO(2), NO(2), CO, and O(3)) in Wuhan were investigated before (January 1 to 23, 2020), during (January 24 to April 5, 2020), and after the COVID-19 lockdown (April 6 to June 20, 2020) periods. Also, the relationships between the air pollutants and meteorological variables during the three periods were investigated. The results showed that there was significant improvement in air quality during the lockdown. Compared to the pre-lockdown period, the concentrations of NO(2), PM(2.5), PM(10), and CO decreased by 50.6, 41.2, 33.1, and 16.6%, respectively, while O(3) increased by 149% during the lockdown. After the lockdown, the concentrations of PM(2.5), CO and SO(2) declined by an additional 19.6, 15.6, and 2.1%, respectively. However, NO(2), O(3), and PM(10) increased by 55.5, 25.3, and 5.9%, respectively, compared to the lockdown period. Except for CO and SO(2), WS had negative correlations with the other pollutants during the three periods. RH was inversely related with all pollutants. Positive correlations were observed between temperature and the pollutants during the lockdown. Easterly winds were associated with peak PM(2.5) concentrations prior to the lockdown. The highest PM(2.5) concentrations were associated with southwesterly wind during the lockdown, and northwesterly winds coincided with the peak PM(2.5) concentrations after the lockdown. Although, COVID-19 pandemic had numerous negative effects on human health and the global economy, the reductions in air pollution and significant improvement in ambient air quality likely had substantial short-term health benefits. This study improves the understanding of the mechanisms that lead to air pollution under diverse meteorological conditions and suggest effective ways of reducing air pollution in Wuhan.