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

Abstract

We offer an 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 the pervasive fear that using public transport might increase the risk of SARS-CoV-2 infection, which need to be reverted as soon as possible. NO 2 levels fell below 50% of the WHO annual air quality guidelines (WHOAQGs), but those of PM 2.5 were reduced less than expected due to the lower contributions from traffic, increased contributions from agricultural and domestic biomass burning, or meteorological conditions favoring high secondary aerosol formation yields. Even during the lockdown, the annual PM 2.5 WHOAQG was exceeded in cities within the NE and E regions with high NH 3 emissions from farming and agriculture. Decreases in PM 10 levels were greater than in PM 2.5 due to reduced emissions from road dust, vehicle wear, and construction/demolition. Averaged O 3 daily maximum 8-h (8hDM) experienced a generalized decrease in the rural receptor sites in the relaxation (June–July) with −20% reduced mobility. For urban areas O 3 8hDM responses were heterogeneous, with increases or decreases depending on the period and location. Thus, after canceling out the effect of meteorology, 5 out of 11 cities experienced O 3 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 O 3 season (June–July), most cities experienced decreases. However, the O 3 WHOAQG was still exceeded during the lockdown and full relaxation periods in several cities. For secondary pollutants, such as O 3 and PM 2.5 , further chemical and dispersion modeling along with source apportionment techniques to identify major precursor reduction targets are required to evaluate their abatement potential.

Characterizing the interruption-recovery patterns of urban air pollution under the COVID-19 lockdown in China

“…Research focusing on South Asia critically investigated lockdown effects toward concentrations of air pollutants and found that a significant reduction of air quality index (AQI) was observed over most polluted ranked cities like Delhi, Dhaka, Kathmandu, Colombo due to the total shutdown [ [20] , [21] , [22] , [23] ]. Similar results have also been found at the all-countries level [ 24 ] such as Australia [ 25 ], UK [ 26 ], Italy [ 27 ], Spain [ 28 ], and Brazil [_Nakada_and_Urban_2020]. Above all, existing research mainly focuses on the air pollution change during the earlier stage of the COVID-19.…”

Evolution of Gaseous and Particulate Pollutants in the Air: What Changed after Five Lockdown Weeks at a Southwest Atlantic European Region (Northwest of Spain) Due to the SARS-CoV-2 Pandemic?

“…On the other hand, an increase in O 3 levels (from +5 to +16%), most likely due to the low O 3 consumption by NO x oxidation, was accounted for after lockdown implementation. Similar reductions in pollutants levels (i.e., NO x , SO 2 , CO, O 3 , PM 10 , PM 2.5 , and BC) were reported in several cities of Spain during the lockdown period [5][6][7][8][9][10][11][12][13][14][15] Due to the increases in agricultural and domestic biomass burning during the lockdown, PM 2.5 and CO levels were also reduced less than expected, in agreement with results from other Spanish cities [5].…”

“…These measures have had good impacts on the air quality of cities around the world, alleviating air pollutants and improving air quality during the lockdown weeks as a consequence of reductions in road traffic, shipping, and industrial activities. The effect of the SARS-CoV-2 pandemic on the air quality of several cities of Spain confirmed these findings [5][6][7][8][9][10][11][12][13][14][15]. Similar positive impacts on air quality have been reported around several European cities [11,[16][17][18][19].…”

Aerosol transmission of human pathogens: From miasmata to modern viral pandemics and their preservation potential in the Anthropocene record

“…Levels of NO 2 for example fell by as much as 30%–50% in cities such as Delhi, Madrid and Wuhan, mainly because of road traffic decline (e.g. Querol et al, 2021 , Shi et al, 2021 ). Large areas of the world recorded similarly significant reductions in ambient PM 2.5 ( Bonardi et al, 2021 ), and CO 2 emissions from fossil fuel combustion fell by an estimate 2.6GtCO 2 in 2020, around 7% below that of 2019 ( Friedlingstein et al, 2020 , Le Quéré et al, 2021 ).…”