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. 2020 Nov 12;250:105362. doi: 10.1016/j.atmosres.2020.105362

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Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

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Fig. 2 — Trend of 24 h average concentrations of PM_2.5, PM₁₀, NO₂, O₃, CO, and SO₂ before, during and after the 2020 lockdown period in Wuhan. The vertical lines separate the Pre-, During-, and Post-LD periods.