Department of Sanitary and Environmental Engineering, Federal University of Minas Gerais, Av. Pres. Antônio Carlos, 6627, 31270-901, Belo Horizonte, Brazil; Federal University of Technology - Paraná, Av. Dos Pioneiros, 3131, 86036-370, Londrina, Brazil.
Federal University of Technology - Paraná, Av. Dos Pioneiros, 3131, 86036-370, Londrina, Brazil; Affiliated with the Division of Water Resources Engineering, Lund University, John Ericssons Väg 1, V-Hus, Lund, Sweden.
Environ Res. 2021 Jul;198:111255. doi: 10.1016/j.envres.2021.111255. Epub 2021 May 8.
Mobility restrictions are among actions to prevent the spread of the COVID-19 pandemic and have been pointed as reasons for improving air quality, especially in large cities. However, it is crucial to assess the impact of atmospheric conditions on air quality and air pollutant dispersion in the face of the potential variability of all sources. In this study, the impact of mobility restrictions on the air quality was analyzed for the most populous Brazilian State, São Paulo, severely impacted by COVID-19. Ground-based air quality data (PM, PM, CO, SO, NO, NO, NO, and O) were used from 50 automatic air quality monitoring stations to evaluate the changes in concentrations before (January 01 - March 25) and during the partial quarantine (March 16 - June 30). Rainfall, fires, and daily cell phone mobility data were also used as supplementary information to the analyses. The Mann-Whitney U test was used to assess the heterogeneity of the air quality data during and before mobility restrictions. In general, the results demonstrated no substantial improvements in air quality for most of the pollutants when comparing before and during restrictions periods. Besides, when the analyzed period of 2020 is compared with the year 2019, there is no significant air quality improvement in the São Paulo State. However, special attention should be given to the Metropolitan Area of São Paulo (MASP), due to the vast population residing in this area and exposed to air pollution. The region reached an average decrease of 29% in CO, 28% in NO, 40% in NO, 19% in SO, 15% in PM, and 8% in PM concentrations during the mobility restrictions period compared to the same period in 2019. The only pollutant that showed an increase in concentration was ozone, with a 20% increase compared to 2019 during the mobility restrictions period. Before the mobility restrictions period, the region reached an average decrease of 30% in CO, 39% in NO, 63% in NO, 12% in SO, 23% in PM, 18% in PM, and 16% in O concentrations when compared to the same period in 2019. On the other hand, Cubatão, a highly industrialized area, showed statistically significant increases above 20% for most monitored pollutants in both periods of 2020 compared to 2019. This study reinforces that the main driving force of pollutant concentration variability is the dynamics of the atmosphere at its various time scales. An abnormal rainy season, with above average rainfall before the restrictions and below average after it, generated a scenario in which the probable significant reductions in emissions did not substantially affect the concentration of pollutants.
行动限制是预防 COVID-19 大流行传播的措施之一，被认为是改善空气质量的原因，尤其是在大城市。然而，在所有来源的潜在可变性面前，评估大气条件对空气质量和空气污染物扩散的影响至关重要。在这项研究中，分析了行动限制对巴西人口最多的州圣保罗的空气质量的影响，该州受到 COVID-19 的严重影响。利用来自 50 个自动空气质量监测站的地面空气质量数据（PM、PM、CO、SO、NO、NO、NO 和 O），评估了在部分隔离（3 月 16 日至 6 月 30 日）之前（1 月 1 日至 3 月 25 日）和期间的浓度变化。还使用了降雨、火灾和每日手机移动数据作为分析的补充信息。使用曼-惠特尼 U 检验评估了行动限制期间和之前空气质量数据的异质性。一般来说，与限制期间相比，大多数污染物的空气质量并没有实质性改善。此外，当将 2020 年的分析期与 2019 年进行比较时，圣保罗州的空气质量没有明显改善。然而，由于居住在该地区并暴露于空气污染的人口众多，因此应特别关注圣保罗大都市区（MASP）。该地区在行动限制期间，CO 浓度平均下降了 29%，NO 浓度下降了 28%，NO 浓度下降了 40%，SO 浓度下降了 19%，PM 浓度下降了 15%，PM 浓度下降了 8%。在行动限制期间，与 2019 年同期相比，臭氧浓度唯一上升，上升了 20%。在行动限制之前，与 2019 年同期相比，该地区 CO 浓度平均下降了 30%，NO 浓度下降了 39%，NO 浓度下降了 63%，SO 浓度下降了 12%，PM 浓度下降了 23%，PM 浓度下降了 18%，O 浓度下降了 16%。另一方面，高度工业化的 Cubatão 地区在 2020 年的两个时期内，大多数监测污染物的浓度均显示出统计学上显著的 20%以上的增长，与 2019 年相比。这项研究再次证实，污染物浓度变化的主要驱动因素是其各个时间尺度上的大气动态。异常的雨季，在限制之前降雨量高于平均水平，之后降雨量低于平均水平，造成了排放的可能显著减少，但并未对污染物浓度产生实质性影响。
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