Pandemic restrictions in 2020 highlight the significance of non-road NOx sources in central London

Cliff, Samuel J.; Drysdale, Will; Lee, James D.; Helfter, Carole ORCID: https://orcid.org/0000-0001-5773-4652; Nemitz, Eiko ORCID: https://orcid.org/0000-0002-1765-6298; Metzger, Stefan; Barlow, Janet F.. 2023 Pandemic restrictions in 2020 highlight the significance of non-road NOx sources in central London. Atmospheric Chemistry and Physics, 23 (4). 2315-2330. 10.5194/acp-23-2315-2023

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Abstract/Summary

Fluxes of nitrogen oxides (NOx = NO + NO2) and carbon dioxide (CO2) were measured using eddy covariance at the British Telecommunications (BT) Tower in central London during the coronavirus pandemic. Comparing fluxes to those measured in 2017 prior to the pandemic restrictions and the introduction of the Ultra-Low Emissions Zone (ULEZ) highlighted a 73 % reduction in NOx emissions between the two periods but only a 20 % reduction in CO2 emissions and a 32 % reduction in traffic load. Use of a footprint model and the London Atmospheric Emissions Inventory (LAEI) identified transport and heat and power generation to be the two dominant sources of NOx and CO2 but with significantly different relative contributions for each species. Application of external constraints on NOx and CO2 emissions allowed the reductions in the different sources to be untangled, identifying that transport NOx emissions had reduced by >73 % since 2017. This was attributed in part to the success of air quality policy in central London but crucially due to the substantial reduction in congestion that resulted from pandemic-reduced mobility. Spatial mapping of the fluxes suggests that central London was dominated by point source heat and power generation emissions during the period of reduced mobility. This will have important implications on future air quality policy for NO2 which, until now, has been primarily focused on the emissions from diesel exhausts.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.5194/acp-23-2315-2023
UKCEH and CEH Sections/Science Areas:	Atmospheric Chemistry and Effects (Science Area 2017-)
ISSN:	1680-7316
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
NORA Subject Terms:	Atmospheric Sciences
Date made live:	20 Feb 2023 16:19 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/534049

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