Temporal air quality (NO2, O3, and PM10) changes in urban and rural stations in Catalonia during COVID-19 lockdown: an association with human mobility and satellite data

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 & 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.

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Temporal Air Quality (NO2, O3 and PM10) Changes in Urban and Rural Stations in Catalonia During COVID-19 Lockdown: An Association with Human Mobility and Satellite Data

10.21203/rs.3.rs-311721/v1 ◽

2021 ◽

Author(s):

Eva Gorrochategui ◽

Isabel Hernandez ◽

Eva Pérez-Gabucio ◽

Sílvia Lacorte ◽

Romà Tauler

Keyword(s):

Air Quality ◽

Metropolitan Area ◽

Satellite Data ◽

Satellite Images ◽

Human Mobility ◽

Control Site ◽

Air Monitoring ◽

Mobility Index ◽

Ski Resort ◽

Monitoring Stations

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 (Observatori Fabra), 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 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 & 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.

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Subtle Changes or Dramatic Perceptions of Air Pollution in Sydney during COVID-19

Environments ◽

10.3390/environments8010002 ◽

2021 ◽

Vol 8 (1) ◽

pp. 2

Author(s):

Peter Brimblecombe ◽

Yonghang Lai

Keyword(s):

Air Pollution ◽

Air Quality ◽

New South ◽

Human Mobility ◽

Ground Level ◽

Physical Reality ◽

Social Perceptions ◽

Search Terms ◽

South Wales ◽

Significant Difference

The COVID-19 pandemic made it critical to limit the spread of the disease by enforcing human isolation, restricting travel and reducing social activities. Dramatic improvements to air quality, especially NO2, have often characterised places under COVID-19 restrictions. Air pollution measurements in Sydney in April 2019 and during the lockdown period in April 2020 show reduced daily averaged NO2 concentrations: 8.52 ± 1.92 and 7.85 ± 2.92 ppb, though not significantly so (p1~0.15) and PM2.5 8.91 ± 4.94 and 7.95 ± 2.64 µg m−3, again a non-significant difference (p1~0.18). Satellite imagery suggests changes that parallel those at ground level, but the column densities averaged over space and time, in false-colour, are more dramatic. Changed human mobility could be traced in increasing times spent at home, assessed from Google Mobility Reports and mirrored in decreased traffic flow on a major road, suggesting compliance with the restrictions. Electricity demand for the State of New South Wales was low under lockdown in early April 2020, but it recovered rapidly. Analysis of the uses of search terms: bushfires, air quality, haze and air pollution using Google Trends showed strong links between bushfires and pollution-related terms. The smoke from bushfires in late 2019 may well have added to the general impression of improved air quality during lockdown, despite only modest changes in the ground level measurements. This gives hints that successful regulation of air quality requires maintaining a delicate balance between our social perceptions and the physical reality.

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