In October 2019, AQC reported significant reductions in ambient nitrogen oxides (NOx) concentrations across the UK over the period 2005 to 2018. This current report (available here) extends the earlier analysis to include measurements made in 2019.
The reductions in average NOx concentrations have continued through 2019. Furthermore, the average rate of reduction over the period 2013 to 2019 is considerably steeper than that for the 2010 to 2018 period reported previously. This is particularly true at roadside sites and is principally because of the non-linearity of the trend, with the steepest reductions occurring since 2016.
A separate analysis has been carried out to nominally remove the effects of inter-year differences in meteorology. This is because meteorology can obscure any underlying trends associated with factors such as emissions reductions. With these meteorological effects removed there is still a non-linear trend in average concentrations, with the greatest reductions occurring since 2016. NOx concentrations at roadside sites have reduced by an average of 5.14% per year since 2013, with the average reductions since 2016 being greater than this.
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