Abstract
AbstractNitrogen dioxide (NO2) pollution is an important contributor to poor air quality (AQ) and a significant cause of premature deaths in the UK. Although transboundary (i.e., international) transport of pollution to the UK is believed to have an impact on UK pollutant concentrations, large uncertainties remain in these estimates. Therefore, the extent to which emission reductions in neighbouring countries would benefit UK AQ relative to local emission reductions also remains unknown. We have used a back‐trajectory model in conjunction with synoptic scale classifications of UK circulation patterns (Lamb Weather Types [LWT]), to quantify the accumulation of nitrogen oxide (NO x = NO2 + NO) emissions in air masses en‐route to the UK. This novel method presents a computationally inexpensive and useful method of quantifying the accumulation of pollutants under different circulation patterns. We find the highest accumulated NO x totals occur under south‐easterly and southerly flows (>15 μg⋅m−2), with a substantial contribution from outwith the UK (>25%). In contrast, the total accumulated NO x under northerly and westerly flows is lower (∼10 μg⋅m−2), and dominated by UK emissions (>95%). This indicates that European emissions can contribute substantially to UK local‐scale pollution in urban areas under south‐easterly and southerly flows. The sensitivity of integrated NO x emission totals under different air masses is investigated by modelling future European emission contributions based on emission reduction targets. Under targets set by the European Union, there would be a decrease in accumulated NO x emissions in London under most wind directions except for north‐westerly, westerly and northerly flow. The largest benefits to UK AQ from transboundary contributions occur with emission reductions in the Benelux region, due to its close proximity and high NO x emission rates, emphasising the importance of international cooperation in improving local AQ.
Highlights
Poor air quality (AQ) has a significant impact on human health, inducing heath ailments such as asthma, cancer, diabetes and heart disease (Royal College of Physicians, 2016)
Jones et al (2013) used the automated scheme created by Jenkinson and Collison (1977) with the National Centers for Environment Prediction (NCEP) reanalysis data (Kalnay et al, 1996) to generate an objective LWT timeseries based on grid-point mean sea level pressure at midday (12:00 UTC)
We have shown that transboundary pollution can be an important contributor to NOx accumulated by air masses arriving at UK urban locations
Summary
Poor air quality (AQ) has a significant impact on human health, inducing heath ailments such as asthma, cancer, diabetes and heart disease (Royal College of Physicians, 2016). A further 37 zones failed to meet the annual mean limit value of 40 μgÁm−3 for NO2 (DEFRA, 2018b). Pollutant contributions from both local and transboundary emission sources can lead to poor air quality. Few studies have quantified the contribution of transboundary pollution sources in enhancing local pollutant concentrations. We present a computationally inexpensive method of quantifying the accumulation of pollutants along 4-day trajectories arriving at several UK cities between 2010 and 2013. In this case, we address nitrogen oxide (NOx = NO2 + NO) pollution under different atmospheric circulation patterns over the UK. We estimate the potential benefits to be gained from neighbouring countries achieving future emission targets
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