Lessons from the COVID-19 air pollution decrease in Spain: Now what?

Authors: Xavier Querol^a, Jordi Massagué^a,b, Alastuey^a, Teresa Moreno^a, Gotzon Gangoiti^c, Enrique Mantilla^d, José Jaime Duéguez^d, Miguel Escudero^e, Eliseo Monfort^f, Carlos Pérez García-Pando^g,h, Hervé Petetin^g, Oriol Jorba^g, Víctor Vázquez^i,j, Jesús de la Rosa^k, Alberto Campos^l, Marta Muñóz^l, Silvia Monge^l, María Hervás^l, Rebeca Javato^l, María J. Cornide^l

Accepted: 05.03.2021

Journal: Science of the Total Environment

DOI: 10.1016/j.scitotenv.2021.146380

E-mail address: victor.vazquez@coccosphere.es

Affiliations

Abstract

We offer and overview of the COVID-19 -driven air quality changes across 11 metropolises in Spain with the focus on lessons learned on how continuing abating pollution. Traffic flow decreased by up to 80% during the lockdown and remained relatively low during the full relaxation (June and July). After the lockdown a significant shift from public transport to private vehicles (+21% in Barcelona) persisted due to fair to infection, which need to be reverted as soon as possible. NO₂ levels fell below 50% of the WHO annual air quality guidelines (WHOAQGs), but PM_2.5 were reduced less than expected due to its lower contributions from traffic, increased contributions from agricultural and domestic biomass burning, or large secondary aerosol contributions. Even during the lockdown, the annual PM_2.5 WHOAQG was exceeded in cities within the NE and E regions with high NH₃ emissions from farming and agriculture. Decreases in PM₁₀ levels were greater than in PM_2.5 due to reduced emissions from road dust, vehicle wear, and construction/demolition activities. Averaged O₃ daily maximum 8-hours (8hDM) experienced a generalized decrease in the rural receptor sites in the relaxation (June-July) with -20% reduced mobility. For urban areas O₃ 8hDM responses were heterogeneous, with increases or decreases depending on the period and location. Thus, after cancelling out the effect of meteorology, 5 out of 11 cities experienced O₃ decreases during the lockdown, while the remaining 6 either did not experience relevant reductions or increased. During the relaxation period and coinciding with the growing O₃ season (June-July), most cities experienced decreases. However, the O₃ WHOAQG was still exceeded during the lockdown and full relaxation periods in several cities For secondary pollutants such as O₃, further chemical and dispersion modeling along with source apportionment techniques to identify major precursor reduction targets are required to evaluate the O₃ abatement potential.