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. 2020 Dec 24;194:110665. doi: 10.1016/j.envres.2020.110665

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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 — Changes in the trace gas concentrations as the lockdown imposition extended from the first phase (Phase I, 25/03 to 14/04), to the second phase (Phase II, 15/04 to 03/05), third phase (Phase III, 04/05 to 17/05) and the IV Phase (Phase IV, 18/05 to 31/05).‘Pre’ represents the pre-lockdown period (15/02 to 21/03).