Nitrogen 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.

中文翻译：

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量化氮氧化物对英国空气质量的跨界贡献

在英国，二氧化氮（NO ₂）污染是导致空气质量（AQ）下降的重要原因，也是造成过早死亡的重要原因。尽管人们认为，跨界（即国际）污染向英国的运输对英国污染物的浓度有影响，但这些估算仍存在很大的不确定性。因此，相对于本地排放量而言，邻国的排放量减少能使英国空气质量局受益的程度仍然未知。我们结合英国天气模式的天气尺度分类（羔羊天气类型[LWT]）使用了回弹模型来量化氮氧化物的积累（NO _x = NO ₂  + NO）途中到达英国的空气质量排放量。这种新颖的方法提出了一种计算便宜且有用的方法，可以量化不同循环模式下污染物的积累。我们找到最高累积NO _X在东南发生的总数和南风流（> 15μg⋅m ^-2），与outwith英国（> 25％）作出了重大贡献。相反，总的累积NO _X下偏北偏西流是低（〜10μg⋅m ^-2），和由英国的排放（> 95％）为主。这表明在东南向和南向流动的情况下，欧洲的排放量可对英国城市范围内的局部污染做出重大贡献。集成NO _x的灵敏度 通过基于减排目标对欧洲未来的排放贡献进行建模，研究了不同空气质量下的排放总量。根据欧盟设定的目标，也就会积累NO的减少_X下，除了向西北最风向在伦敦的排放量，西风和北风流动。从跨界的贡献，英国AQ最大的好处发生在比荷卢地区的减排量，由于其靠近和高NO _X排放率，强调改善当地AQ国际合作的重要性。