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      A global observational analysis to understand changes in air quality during exceptionally low anthropogenic emission conditions.

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      Environment international

      Elsevier BV

      COVID-19, Carbon monoxide, Nitrogen dioxide, Ozone, Particulate matter, Sulphur dioxide

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          Abstract

          This 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.

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          Author and article information

          Journal
          Environ Int
          Environment international
          Elsevier BV
          1873-6750
          0160-4120
          Aug 20 2021
          : 157
          Affiliations
          [1 ] Centre for Atmospheric and Climate Physics (CACP) and Centre for Climate Change Research (C3R), University of Hertfordshire, Hatfield, Hertfordshire, UK. Electronic address: r.s.sokhi@herts.ac.uk.
          [2 ] National Atmospheric Research Laboratory, Gadanki, AP, India.
          [3 ] Institute of Environmental Assessment and Water Research (IDAEA), Spanish Research Council (CSIC), Barcelona, Spain.
          [4 ] ARIANET, Milan, Italy.
          [5 ] Graduate Program in Environment Engineering, Federal University of Technology, Londrina, Brazil.
          [6 ] Departamento de Ciências Atmosféricas, Universidade de São Paulo, São Paulo, Brazil.
          [7 ] Meteorological Service of Canada, Environment and Climate Change Canada, Dorval, Canada.
          [8 ] Council for Scientific and Industrial Research, Pretoria, South Africa; Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa; Department of Geography, Geo-informatics and Meteorology, University of Pretoria, Pretoria, South Africa.
          [9 ] Institute of Environmental Assessment and Water Research (IDAEA), Spanish Research Council (CSIC), Barcelona, Spain; Department of Mining, Industrial and ICT Engineering, Universitat Politècnica de Catalunya, BarcelonaTech (UPC), Barcelona, Spain.
          [10 ] Department of Atmospheric Sciences, School of Environmental Studies, China University of Geosciences, Wuhan, China.
          [11 ] Science and Innovation Department, World Meteorological Organization (WMO), Geneva, Switzerland.
          [12 ] Center for Global and Regional Environmental Research, University of Iowa, Iowa City, United States.
          [13 ] ECMWF, European Centre for Medium-Range Weather Forecasts, Shinfield Park, Reading, UK.
          [14 ] Indian Institute of Tropical Meteorology, Pune, Ministry of Earth Sciences, Govt. of India, India.
          [15 ] Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
          [16 ] Analysis and Air Quality Section, Air Quality Research Division, Environment and Climate Change Canada, Ottawa, Canada.
          [17 ] Universidad Nacional de Colombia, Bogotá, Colombia.
          [18 ] Agenzia Regionale di Protezione dell'Ambiente del Lazio, Rome, Italy.
          [19 ] Department of Marine Environment and Engineering, National Sun Yat Sen University, Kaohsiung, Taiwan.
          [20 ] Secretaria del Medio Ambiente de la Ciudad de México (SEDEMA), Mexico City, Mexico.
          [21 ] Earth System Physics, The Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy; Escuela de Ciencias Exactas e Ingenieria, Universidad Sergio Arboleda, Bogotá, Colombia.
          [22 ] Environment Protection Authority Victoria, Centre for Applied Sciences, Macleod, Australia.
          [23 ] Laboratory of Heat Transfer and Environmental Engineering, Aristotle University, Thessaloniki, Greece.
          [24 ] Université Paris-Est Créteil and Université de Paris, CNRS, LISA, Creteil, France.
          [25 ] Air Monitoring Operations, Resource Stewardship Division, Environment and Parks, Edmonton, Canada.
          [26 ] Institute of Epidemiology, Helmholtz Zentrum München, Neuherberg, Germany.
          [27 ] Universidade Veiga de Almeida, Rio de Janeiro, Brazil.
          [28 ] Agenzia Regionale di Protezione dell'Ambiente della Lombardia, Milano, Italy.
          [29 ] Escuela de Ciencias Exactas e Ingenieria, Universidad Sergio Arboleda, Bogotá, Colombia.
          [30 ] Department of Geography, University of Calcutta, Kolkata, India.
          [31 ] A.M. Obukhov Institute of Atmospheric Physics, Moscow, Russia.
          [32 ] Service de l'Environnement, Division du Contrôle des Rejets et Suivi Environnemental, Montréal, Canada.
          [33 ] Conservación, Bioprospección y Desarrollo Sostenible, Universidad Nacional Abierta y a Distancia, Bogotá, Colombia.
          [34 ] Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa.
          [35 ] National Smog Analysis, Analysis and Air Quality Section, Air Quality Research Division, Environment and Climate Change Canada, Ottawa, Canada.
          [36 ] Institute of Physics, University of Tartu, Tartu, Estonia.
          [37 ] Institute for Atmospheric and Earth System Research (INAR/Physics), University of Helsinki, Helsinki, Finland.
          [38 ] Department of Community Medicine and School of Public Health, PGIMER, Chandigarh, India.
          [39 ] Department of Atmospheric Sciences, Yonsei University, Seoul, South Korea.
          [40 ] Helsinki Region Environmental Services Authority, Helsinki, Finland.
          [41 ] Centre for Atmospheric and Climate Physics (CACP) and Centre for Climate Change Research (C3R), University of Hertfordshire, Hatfield, Hertfordshire, UK; Finnish Meteorological Institute, Helsinki, Finland.
          [42 ] Finnish Meteorological Institute, Helsinki, Finland.
          [43 ] Direction de la qualité de l'air et du climat, Direction générale du suivi de l'état de l'environnement, Ministère de l'Environnement et de la Lutte contre les changements climatiques Québec, Canada.
          [44 ] Air Quality Monitoring & Reporting, Nova Scotia Environment, Halifax, Canada.
          [45 ] National Oceanic and Atmospheric Administration, Chemical Sciences Laboratory, Boulder, USA.
          [46 ] Molina Center for Energy and the Environment, CA, USA.
          [47 ] National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands.
          [48 ] Department of Environment Studies, Punjab University, Chandigarh, India.
          [49 ] Department of Chemical, Material and Production Engineering (DICMAPI), Naples, Italy.
          [50 ] Estonian University of Life Sciences, Tartu, Estonia.
          [51 ] Environment and Health Administration, City of Stockholm, Sweden.
          [52 ] Computer Science School, ESMG, Technical University of Madrid (UPM), Madrid, Spain.
          [53 ] Air Quality and Climate Change, Metro Vancouver Regional District, Burnaby, Canada.
          [54 ] Independent Researcher, Mexico City, Mexico.
          [55 ] National Meteorology and Hydrology Service, Lima, Peru.
          [56 ] Atmospheric Pollution Research Group, Universidad Nacional Tecnológica de Lima Sur, Lima, Peru.
          [57 ] Center for Climate and Resilience Research (CR)2, Department of Geophysics, University of Chile, Santiago, Chile.
          [58 ] Environmental Monitoring and Reporting Branch, Ontario Ministry of the Environment, Conservation and Parks, Toronto, Canada.
          [59 ] School of Earth, Atmosphere and Environment, Monash University, Clayton, Australia.
          [60 ] Institute for Advanced Sustainability Studies, Potsdam, Germany.
          [61 ] Centre for Atmospheric and Climate Physics (CACP) and Centre for Climate Change Research (C3R), University of Hertfordshire, Hatfield, Hertfordshire, UK.
          [62 ] Grupo de Biodiversidad, Medio Ambiente y Salud (BIOMAS), Universidad de Las Americas, Quito, Ecuador.
          Article
          S0160-4120(21)00443-8
          10.1016/j.envint.2021.106818
          34425482
          a29af97c-af4a-429d-887d-eb6f9fe56470

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