Abstract
In this study, changes in air quality by NO2, O3, and PM10 in Barcelona metropolitan area and other parts of Catalonia during the COVID-19 lockdown with respect to pre-lockdown and to previous years (2018 and 2019) were evaluated. Selected air monitoring stations included 3 urban (Gràcia, Vall d’Hebron, and Granollers), 1 control site (Fabra Observatory), 1 semi-urban (Manlleu), and 3 rural (Begur, Bellver de Cerdanya, and Juneda). NO2 lockdown levels showed a diminution, which in relative terms was maximum in two rural stations (Bellver de Cerdanya, − 63% and Begur, − 61%), presumably due to lower emissions from the ceasing hotel and ski resort activities during eastern holidays. In absolute terms and from an epidemiologic perspective, decrease in NO2, also reinforced by the high amount of rainfall registered in April 2020, was more relevant in the urban stations around Barcelona. O3 levels increased in the transited urban stations (Gràcia, + 42%, and Granollers, + 64%) due to the lower titration effect by NOx. PM10 lockdown levels decreased, mostly in Gràcia, Vall d’Hebron, and Granollers (− 35, − 39%, and − 39%, respectively) due to traffic depletion (− 90% in Barcelona's transport). Correlation among mobility index in Barcelona (− 100% in retail and recreation) and contamination was positive for NO2 and PM10 and negative for O3 (P < 0.001). Satellite images evidenced two hotspots of NO2 in Spain (Madrid and Barcelona) in April 2018 and 2019 that disappeared in 2020. Overall, the benefits of lockdown on air quality in Catalonia were evidenced with NO2, O3 and PM10 levels below WHOAQG values in most of stations opposed to the excess registered in previous years.Graphical abstract Supplementary InformationThe online version of this article (10.1007/s11356-021-17137-7) contains supplementary material, which is available to authorized users.
Highlights
Monitoring studies of environmental pollution have always been necessary in order to evaluate the impact of air contaminants on human health and the environment
The benefits of lockdown on air quality in Catalonia were evidenced with N O2, O3 and PM10 levels below World Health Organization Air Quality Guideline (WHOAQG) values in most of stations opposed to the excess registered in previous years
More in-depth evaluation on the effects of the lockdown on air contamination covering the largest period of time, a wider region, and different types of geographical locations will provide new insights on the reasons and social aspects related to such reductions
Summary
Monitoring studies of environmental pollution have always been necessary in order to evaluate the impact of air contaminants on human health and the environment. Various studies that evaluate the effects of COVID-19 lockdown on air contamination have already been performed in different parts of the world (Delhi (Srivastava et al 2020): London (Kumari and Toshniwal 2020), Milan (Altuwayjiri et al 2020), Lima (Kumari and Toshniwal 2020), Ghaziabad (Lokhandwala and Gautam 2020), Nigeria (Zabbey et al 2020), Tunisia (Chekir and Ben Salem 2021), Baghdad (Hashim et al 2021), and Spain (Tobías et al 2020; Briz-Redón et al 2021)) All these studies agree on the association between contingency measures and improvement in air quality, and in clean beaches and environmental noise reduction (Zambrano-Monserrate et al 2020). More in-depth evaluation on the effects of the lockdown on air contamination covering the largest period of time (i.e., pre, during, and post-lockdown), a wider region (i.e., the metropolitan region of Barcelona extended to Catalonia too), and different types of geographical locations (i.e., urban, semi-urban, and rural) will provide new insights on the reasons and social aspects related to such reductions
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