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. 2021 Oct 27;29(13):18905–18922. doi: 10.1007/s11356-021-17137-7

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© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021

This article is made available via the PMC Open Access Subset for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.

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Fig. 2 — Reactions among pollutants (including NO₂ and O₃) in the troposphere; daytime versus nighttime. R1, R2, and R3 indicate the main reactions: ozone formation from NO_x and VOCs (R1) and ozone suppression through NO_x titration at daytime (R2) and at nighttime (R3)