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dc.contributor.authorSokhi, Ranjeet S
dc.contributor.authorSingh, Vikas
dc.contributor.authorQuerol, Xavier
dc.contributor.authorFinardi, Sandro
dc.contributor.authorTargino, Admir Créso
dc.contributor.authorAndrade, Maria de Fatima
dc.contributor.authorPavlovic, Radenko
dc.contributor.authorGarland, Rebecca M
dc.contributor.authorMassagué, Jordi
dc.contributor.authorKong, Shaofei
dc.contributor.authorBaklanov, Alexander
dc.contributor.authorRen, Lu
dc.contributor.authorTarasova, Oksana
dc.contributor.authorCarmichael, Greg
dc.contributor.authorPeuch, Vincent-Henri
dc.contributor.authorAnand, Vrinda
dc.contributor.authorArbilla, Graciela
dc.contributor.authorBadali, Kaitlin
dc.contributor.authorBeig, Gufran
dc.contributor.authorBelalcazar, Luis Carlos
dc.contributor.authorBolignano, Andrea
dc.contributor.authorBrimblecombe, Peter
dc.contributor.authorCamacho, Patricia
dc.contributor.authorCasallas, Alejandro
dc.contributor.authorCharland, Jean-Pierre
dc.contributor.authorChoi, Jason
dc.contributor.authorChourdakis, Eleftherios
dc.contributor.authorColl, Isabelle
dc.contributor.authorCollins, Marty
dc.contributor.authorCyrys, Josef
dc.contributor.authorda Silva, Cleyton Martins
dc.contributor.authorDi Giosa, Alessandro Domenico
dc.contributor.authorDi Leo, Anna
dc.contributor.authorFerro, Camilo
dc.contributor.authorGavidia-Calderon, Mario
dc.contributor.authorGayen, Amiya
dc.contributor.authorGinzburg, Alexander
dc.contributor.authorGodefroy, Fabrice
dc.contributor.authorGonzalez, Yuri Alexandra
dc.contributor.authorGuevara-Luna, Marco
dc.contributor.authorHaque, Sk Mafizul
dc.contributor.authorHavenga, Henno
dc.contributor.authorHerod, Dennis
dc.contributor.authorHõrrak, Urmas
dc.contributor.authorHussein, Tareq
dc.contributor.authorIbarra, Sergio
dc.contributor.authorJaimes, Monica
dc.contributor.authorKaasik, Marko
dc.contributor.authorKhaiwal, Ravindra
dc.contributor.authorKim, Jhoon
dc.contributor.authorKousa, Anu
dc.contributor.authorKukkonen, Jaakko
dc.contributor.authorKulmala, Markku
dc.contributor.authorKuula, Joel
dc.contributor.authorLa Violette, Nathalie
dc.contributor.authorLanzani, Guido
dc.contributor.authorLiu, Xi
dc.contributor.authorMacDougall, Stephanie
dc.contributor.authorManseau, Patrick M
dc.contributor.authorMarchegiani, Giada
dc.contributor.authorMcDonald, Brian
dc.contributor.authorMishra, Swasti Vardhan
dc.contributor.authorMolina, Luisa T
dc.contributor.authorMooibroek, Dennis
dc.contributor.authorMor, Suman
dc.contributor.authorMoussiopoulos, Nicolas
dc.contributor.authorMurena, Fabio
dc.contributor.authorNiemi, Jarkko V
dc.contributor.authorNoe, Steffen
dc.contributor.authorNogueira, Thiago
dc.contributor.authorNorman, Michael
dc.contributor.authorPérez-Camaño, Juan Luis
dc.contributor.authorPetäjä, Tuukka
dc.contributor.authorPiketh, Stuart
dc.contributor.authorRathod, Aditi
dc.contributor.authorReid, Ken
dc.contributor.authorRetama, Armando
dc.contributor.authorRivera, Olivia
dc.contributor.authorRojas, Néstor Y
dc.contributor.authorRojas-Quincho, Jhojan P
dc.contributor.authorSan José, Roberto
dc.contributor.authorSánchez, Odón
dc.contributor.authorSeguel, Rodrigo J
dc.contributor.authorSillanpää, Salla
dc.contributor.authorSu, Yushan
dc.contributor.authorTapper, Nigel
dc.contributor.authorTerrazas, Antonio
dc.contributor.authorTimonen, Hilkka
dc.contributor.authorToscano, Domenico
dc.contributor.authorTsegas, George
dc.contributor.authorVelders, Guus J M
dc.contributor.authorVlachokostas, Christos
dc.contributor.authorvon Schneidemesser, Erika
dc.contributor.authorVpm, Rajasree
dc.contributor.authorYadav, Ravi
dc.contributor.authorZalakeviciute, Rasa
dc.contributor.authorZavala, Miguel
dc.date.accessioned2021-09-12T19:15:55Z
dc.date.available2021-09-12T19:15:55Z
dc.date.issued2021-08-20
dc.identifier.pmid34425482
dc.identifier.doi10.1016/j.envint.2021.106818
dc.identifier.urihttp://hdl.handle.net/10029/625238
dc.description.abstractThis global study, which has been coordinated by the World Meteorological Organization Global Atmospheric Watch (WMO/GAW) programme, aims to understand the behaviour of key air pollutant species during the COVID-19 pandemic period of exceptionally low emissions across the globe. We investigated the effects of the differences in both emissions and regional and local meteorology in 2020 compared with the period 2015-2019. By adopting a globally consistent approach, this comprehensive observational analysis focuses on changes in air quality in and around cities across the globe for the following air pollutants PM2.5, PM10, PMC (coarse fraction of PM), NO2, SO2, NOx, CO, O3 and the total gaseous oxidant (OX = NO2 + O3) during the pre-lockdown, partial lockdown, full lockdown and two relaxation periods spanning from January to September 2020. The analysis is based on in situ ground-based air quality observations at over 540 traffic, background and rural stations, from 63 cities and covering 25 countries over seven geographical regions of the world. Anomalies in the air pollutant concentrations (increases or decreases during 2020 periods compared to equivalent 2015-2019 periods) were calculated and the possible effects of meteorological conditions were analysed by computing anomalies from ERA5 reanalyses and local observations for these periods. We observed a positive correlation between the reductions in NO2 and NOx concentrations and peoples' mobility for most cities. A correlation between PMC and mobility changes was also seen for some Asian and South American cities. A clear signal was not observed for other pollutants, suggesting that sources besides vehicular emissions also substantially contributed to the change in air quality. As a global and regional overview of the changes in ambient concentrations of key air quality species, we observed decreases of up to about 70% in mean NO2 and between 30% and 40% in mean PM2.5 concentrations over 2020 full lockdown compared to the same period in 2015-2019. However, PM2.5 exhibited complex signals, even within the same region, with increases in some Spanish cities, attributed mainly to the long-range transport of African dust and/or biomass burning (corroborated with the analysis of NO2/CO ratio). Some Chinese cities showed similar increases in PM2.5 during the lockdown periods, but in this case, it was likely due to secondary PM formation. Changes in O3 concentrations were highly heterogeneous, with no overall change or small increases (as in the case of Europe), and positive anomalies of 25% and 30% in East Asia and South America, respectively, with Colombia showing the largest positive anomaly of ~70%. The SO2 anomalies were negative for 2020 compared to 2015-2019 (between ~25 to 60%) for all regions. For CO, negative anomalies were observed for all regions with the largest decrease for South America of up to ~40%. The NO2/CO ratio indicated that specific sites (such as those in Spanish cities) were affected by biomass burning plumes, which outweighed the NO2 decrease due to the general reduction in mobility (ratio of ~60%). Analysis of the total oxidant (OX = NO2 + O3) showed that primary NO2 emissions at urban locations were greater than the O3 production, whereas at background sites, OX was mostly driven by the regional contributions rather than local NO2 and O3 concentrations. The present study clearly highlights the importance of meteorology and episodic contributions (e.g., from dust, domestic, agricultural biomass burning and crop fertilizing) when analysing air quality in and around cities even during large emissions reductions. There is still the need to better understand how the chemical responses of secondary pollutants to emission change under complex meteorological conditions, along with climate change and socio-economic drivers may affect future air quality. The implications for regional and global policies are also significant, as our study clearly indicates that PM2.5 concentrations would not likely meet the World Health Organization guidelines in many parts of the world, despite the drastic reductions in mobility. Consequently, revisions of air quality regulation (e.g., the Gothenburg Protocol) with more ambitious targets that are specific to the different regions of the world may well be required.en_US
dc.language.isoenen_US
dc.rightsCopyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.
dc.subjectCOVID-19en_US
dc.subjectCarbon monoxideen_US
dc.subjectNitrogen dioxideen_US
dc.subjectOzoneen_US
dc.subjectParticulate matteren_US
dc.subjectSulphur dioxideen_US
dc.titleA global observational analysis to understand changes in air quality during exceptionally low anthropogenic emission conditions.en_US
dc.typeArticleen_US
dc.identifier.eissn1873-6750
dc.identifier.journalEnviron Int 2021; 157:106818 advance online publication (ahead of print)en_US
dc.source.journaltitleEnvironment international
dc.source.volume157
dc.source.beginpage106818
dc.source.endpage
dc.source.countryNetherlands


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