von Schneidemesser Erika, Sibiya Bheki, Caseiro Alexandre, Butler Tim, Lawrence Mark G, Leitao Joana, Lupascu Aurelia, Salvador Pedro
Institute for Advanced Sustainability Studies e.V., Berlinerstrasse 130, 14467, Potsdam, Germany.
Institut für Meteorologie, Freie Universität Berlin, Germany.
Atmos Environ X. 2021 Dec;12:100122. doi: 10.1016/j.aeaoa.2021.100122. Epub 2021 Jul 28.
Urban air pollution is a substantial threat to human health. Traffic emissions remain a large contributor to air pollution in urban areas. The mobility restrictions put in place in response to the COVID-19 pandemic provided a large-scale real-world experiment that allows for the evaluation of changes in traffic emissions and the corresponding changes in air quality. Here we use observational data, as well as modelling, to analyse changes in nitrogen dioxide, ozone, and particulate matter resulting from the COVID-19 restrictions at the height of the lockdown period in Spring of 2020. Accounting for the influence of meteorology on air quality, we found that reduction of ca. 30-50 % in traffic counts, dominated by changes in passenger cars, corresponded to reductions in median observed nitrogen dioxide concentrations of ca. 40 % (traffic and urban background locations) and a ca. 22 % increase in ozone (urban background locations) during weekdays. Lesser reductions in nitrogen dioxide concentrations were observed at urban background stations at weekends, and no change in ozone was observed. The modelled reductions in median nitrogen dioxide at urban background locations were smaller than the observed reductions and the change was not significant. The model results showed no significant change in ozone on weekdays or weekends. The lack of a simulated weekday/weekend effect is consistent with previous work suggesting that NOx emissions from traffic could be significantly underestimated in European cities by models. These results indicate the potential for improvements in air quality due to policies for reducing traffic, along with the scale of reductions that would be needed to result in meaningful changes in air quality if a transition to sustainable mobility is to be seriously considered. They also confirm once more the highly relevant role of traffic for air quality in urban areas.
城市空气污染对人类健康构成重大威胁。交通排放仍是城市地区空气污染的主要来源。为应对新冠疫情而实施的出行限制提供了一个大规模的现实世界实验，有助于评估交通排放的变化以及空气质量的相应变化。在此，我们利用观测数据以及模型分析了2020年春季封锁高峰期因新冠疫情限制导致的二氧化氮、臭氧和颗粒物的变化。考虑到气象条件对空气质量的影响，我们发现，以乘用车变化为主的交通流量减少约30%-50%，对应工作日期间观测到的二氧化氮中位数浓度降低约40%（交通和城市背景地点），城市背景地点的臭氧浓度升高约22%。周末在城市背景站点观测到的二氧化氮浓度降幅较小，臭氧浓度未发生变化。模型模拟的城市背景地点二氧化氮中位数降幅小于观测降幅，且变化不显著。模型结果显示，工作日和周末臭氧均无显著变化。缺乏模拟的工作日/周末效应与之前的研究结果一致，即欧洲城市交通排放的氮氧化物可能被模型显著低估。这些结果表明，减少交通流量的政策有可能改善空气质量，同时也表明，如果要认真考虑向可持续出行的转变，为实现空气质量的显著变化所需的减排规模。它们还再次证实了交通在城市空气质量中具有高度相关性。
