The pandemic caused by coronavirus COVID-19 is having a worldwide impact that affects health, the economy and indirectly affects the air pollution in cities. In Portugal, the number of cases increased continually (32700 confirmed cases as of 31 May 2020), which has affected the health system and caused movement restrictions which in turn affects the air pollution in the country. This article analyses the indirect effect produced by this pandemic on air pollution in Portugal, by comparison of data from a period of movement restriction of the citizens by the government – COVID lockdown period (March-May 2020) with data from baseline conditions (mean of the mirrored periods from the five previous years (March-May from 2015-2019)). Air quality data – in particular NO₂ and PM₁₀ hourly concentration - from more than 20 monitoring stations spread over mainland Portugal was used to perform this evaluation. The mean reduction observed on pollutant concentrations was higher for NO₂ (41%) than for PM₁₀ (18%). For NO₂, mean reductions were more significant in traffic (reaching values higher than 60% in some monitoring stations) and background urban sites than in rural stations. The reduction of NO₂ concentration observed in traffic sites were compared to the estimation of traffic contribution by the incremental method, suggesting that this latter approach is not consistent (lower in same sites and higher in others) and alerting to the careful use of this approach in future works.

由冠状病毒COVID-19引起的大流行正在影响全世界，影响健康，经济并间接影响城市的空气污染。在葡萄牙，病例数持续增加（截至2020年5月31日，已确诊病例32700例），这影响了卫生系统并造成了行动限制，进而影响了该国的空气污染。本文通过比较政府对公民的行动限制期（COVID锁定期（2020年3月至5月））与基线状况（平均值为前五年的镜像期（2015-2019年的3月至5月）。空气质量数据–特别是NO ₂和PM ₁₀每小时的集中度-来自遍布葡萄牙大陆的20多个监测站进行了评估。对于NO ₂（41％），观察到的污染物浓度的平均减少量高于PM ₁₀（18％）。对于NO _2而言，交通量（在某些监测站中达到的数值超过60％）和背景城市地区的平均减少量比农村地区的减少量更大。将交通站点中观察到的NO ₂浓度降低与通过增量方法估算交通贡献进行了比较，这表明后一种方法不一致（在同一站点中较低，而在其他站点中较高），并提醒谨慎使用此方法。在未来的作品中。