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Calibrating Defra’s Background NOx and NO2 Maps against 2017 Measurements

19-07-2018

Air Quality Consultants Ltd has carried out an analysis of the validity of Defra’s national pollution maps of ambient background concentrations in 2017. 

These maps cover the whole country on a 1x1 km grid and are published for each year from 2015 until 2030. Mapped concentrations in 2015 were based on existing emissions from a range of different sources (including road traffic) calibrated against monitoring data for that year.  Emission projections are then used to predict concentrations in all subsequent years to 2030.  


Air Quality Consultants Ltd has compared Defra’s background mapped nitrogen oxides (NOx) and nitrogen dioxide (NO2) values for 2017 with national background measurements made at Automatic Urban and Rural Network (AURN) sites during 2017.  Based on the 51 sites with more than 75% data capture for 2017, the Defra maps have been found to under-predict the background NOx and NO2 concentrations by 10.1% and 6.6% on average, respectively (analysis available here).


This analysis also has implications for Air Quality Consultants’ suggested approach to treating background concentrations of nitrogen dioxide (NO2) and nitrogen oxides (NOx) when using the Calculator Using Realistic Emissions for Diesels (CURED) V3A, which was published in 2018 (note available here).

 



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