A global observational analysis to understand changes in air quality during exceptionally low anthropogenic emission conditions
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DOI:
10.1016/j.envint.2021.106818
Publication Date:
2021-08-20T23:41:02Z
AUTHORS (97)
ABSTRACT
This global study, which has been coordinated by the World Meteorological Organization Global Atmospheric Watch (WMO/GAW) programme, aims to understand behaviour of key air pollutant species during COVID-19 pandemic period exceptionally low emissions across globe. We investigated effects differences in both and regional local meteorology 2020 compared with 2015–2019. By adopting a globally consistent approach, this comprehensive observational analysis focuses on changes quality around cities globe for following pollutants PM2.5, PM10, PMC (coarse fraction PM), NO2, SO2, NOx, CO, O3 total gaseous oxidant (OX = NO2 + O3) pre-lockdown, partial lockdown, full lockdown two relaxation periods spanning from January September 2020. The is based situ ground-based observations at over 540 traffic, background rural stations, 63 covering 25 countries seven geographical regions world. Anomalies concentrations (increases or decreases equivalent 2015–2019 periods) were calculated possible meteorological conditions analysed computing anomalies ERA5 reanalyses these periods. observed positive correlation between reductions NOx peoples' mobility most cities. A was also seen some Asian South American clear signal not other pollutants, suggesting that sources besides vehicular substantially contributed change quality. As overview ambient species, we up about 70% mean 30% 40% PM2.5 same However, exhibited complex signals, even within region, increases Spanish cities, attributed mainly long-range transport African dust and/or biomass burning (corroborated NO2/CO ratio). Some Chinese showed similar periods, but case, it likely due secondary PM formation. Changes highly heterogeneous, no overall small (as case Europe), 25% East Asia America, respectively, Colombia showing largest anomaly ~70%. SO2 negative (between ~25 60%) all regions. For decrease America ~40%. ratio indicated specific sites (such as those cities) affected plumes, outweighed general reduction (ratio ~60%). Analysis primary urban locations greater than production, whereas sites, OX mostly driven contributions rather concentrations. present study clearly highlights importance episodic (e.g., dust, domestic, agricultural crop fertilizing) when analysing large reductions. There still need better how chemical responses emission under conditions, along climate socio-economic drivers may affect future implications policies are significant, our indicates would meet Health guidelines many parts world, despite drastic mobility. Consequently, revisions regulation Gothenburg Protocol) more ambitious targets different world well be required.
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