School of Ecology and Environment, Inner Mongolia University, 010021, Hohhot, China.
School of Ecology and Environment, Inner Mongolia University, 010021, Hohhot, China; Inner Mongolia Environmental Monitoring Center, 010011, Hohhot, China.
Environ Res. 2022 Jun;209:112806. doi: 10.1016/j.envres.2022.112806. Epub 2022 Jan 29.
To prevent the Corona Virus Disease 2019 (COVID-19) spreading, Chinese government takes a series of corresponding measures to restrict human mobility, including transportation lock-down and industries suspension, which significantly influenced the ambient air quality and provided vary rare time windows to assess the impacts of anthropological activities on air pollution. In this work, we divided the studied timeframe (2019/12/24-2020/2/24) into four periods and selected 88 cities from 31 representative urban agglomerations. The indicators of PM/PM and NO/SO were applied, for the first time, to analyze the changes in stoichiometric characteristics of ambient air pollutants pre-to post-COVID-19 in China. The results indicated that the ratios of NO/SO presented a responding decline, especially in YRD (-5.01), YH (-3.87), and MYR (-3.84), with the sharp reduction of traffic in post-COVID-19 periods (P3-P4: 2.34 ± 0.94 m/m) comparing with pre-COVID-19 periods (P1-P2: 4.49 ± 2.03 m/m). Whereas the ratios of PM/PM increased in P1-P3, then decreased in P4 with relatively higher levels (>0.5) in almost all urban agglomerations. Furthermore, NO presented a stronger association with PM/PM variation than CO; and PM with NO/SO variation than PM. In summary, the economic structure, lockdown measures and meteorological conditions could explain the noteworthy variations in different urban agglomerations. These results would be in great help for improving air quality in the post-epidemic periods.
为了防止 2019 年冠状病毒病（COVID-19）的传播，中国政府采取了一系列相应的措施来限制人员流动，包括交通封锁和行业停摆，这对环境空气质量产生了重大影响，并提供了评估人类活动对空气污染影响的难得机会。在这项工作中，我们将研究时间段（2019 年 12 月 24 日至 2020 年 2 月 24 日）分为四个时期，并从 31 个有代表性的城市群中选择了 88 个城市。首次应用 PM/PM 和 NO/SO 指标分析了 COVID-19 前后中国环境空气污染物化学计量特征的变化。结果表明，NO/SO 比值呈响应性下降，特别是在长三角（YRD）（-5.01）、京津冀（YH）（-3.87）和粤港澳（MYR）（-3.84），与 COVID-19 前时期（P1-P2：4.49 ± 2.03 m/m）相比，COVID-19 后时期（P3-P4：2.34 ± 0.94 m/m）交通流量明显减少。而 PM/PM 比值在 P1-P3 期间增加，然后在 P4 期间减少，几乎所有城市群的比值都较高（>0.5）。此外，NO 与 PM/PM 变化的相关性强于 CO，而 PM 与 NO/SO 变化的相关性强于 PM。总之，经济结构、封锁措施和气象条件可以解释不同城市群的显著变化。这些结果将有助于改善后疫情时期的空气质量。
