School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
China National Environmental Monitoring Center, Beijing 100012, China.
J Environ Sci (China). 2021 Aug;106:26-38. doi: 10.1016/j.jes.2021.01.006. Epub 2021 Jan 25.
To investigate the air quality change during the COVID-19 pandemic, we analyzed spatiotemporal variations of six criteria pollutants in nine typical urban agglomerations in China using ground-based data and examined meteorological influences through correlation analysis and backward trajectory analysis under different responses. Concentrations of PM, PM, NO, SO and CO in urban agglomerations respectively decreased by 18%-45% (30%-62%), 17%-53% (22%-39%), 47%-64% (14%-41%), 9%-34% (0%-53%) and 16%-52% (23%-56%) during Lockdown (Post-lockdown) period relative to Pre-lockdown period. PM pollution events occurred during Lockdown in Beijing-Tianjin-Hebe (BTH) and Middle and South Liaoning (MSL), and daily O concentration rose to grade Ⅱ standard in Post-lockdown period. Distinct from the nationwide slump of NO during Lockdown period, a rebound (∼40%) in Post-lockdown period was observed in Cheng-Yu (CY), Yangtze River Middle-Reach (YRMR), Yangtze River Delta (YRD) and Pearl River Delta (PRD). With slightly higher wind speed compared with 2019, the reduction of PM (51%-62%) in Post-lockdown period is more than 2019 (15%-46%) in HC (Harbin-Changchun), MSL, BTH, CP (Central Plain) and SP (Shandong-Peninsula), suggesting lockdown measures are effective to PM alleviation. Although O concentrations generally increased during the lockdown, its increment rate declined compared with 2019 under similar sunlight duration and temperature. Additionally, unlike HC, MSL and BTH, which suffered from additional (> 30%) air masses from surrounding areas after the lockdown, the polluted air masses reaching YRD and PRD mostly originated from the long-distance transport, highlighting the importance of joint regional governance.
为了研究 COVID-19 大流行期间空气质量的变化，我们利用地面数据分析了中国九个典型城市群六种污染物的时空变化，并通过相关分析和不同响应下的后向轨迹分析考察了气象影响。与 lockdown 前相比，lockdown 期间（post-lockdown）九个城市群的 PM、PM、NO、SO 和 CO 浓度分别降低了 18%-45%（30%-62%）、17%-53%（22%-39%）、47%-64%（14%-41%）、9%-34%（0%-53%）和 16%-52%（23%-56%）。在北京-天津-河北（BTH）和中南部辽宁（MSL），lockdown 期间发生了 PM 污染事件，post-lockdown 期间的日 O 浓度达到了二级标准。与 lockdown 期间全国范围内 NO 浓度下降形成鲜明对比的是，在 post-lockdown 期间，成渝（CY）、长江中游（YRMR）、长江三角洲（YRD）和珠江三角洲（PRD）的 NO 浓度出现反弹（约 40%）。与 2019 年相比，后 lockdown 时期风速略高，PM（51%-62%）的降幅大于 2019 年（15%-46%），在 HC（哈尔滨-长春）、MSL、BTH、CP（中原）和 SP（山东半岛）。这表明 lockdown 措施对 PM 缓解是有效的。尽管 lockdown 期间 O 浓度普遍升高，但在阳光持续时间和温度相似的情况下，其增长率低于 2019 年。此外，与 HC、MSL 和 BTH 不同的是，这些地区在 lockdown 后还遭受了来自周边地区的额外（>30%）空气团，而到达 YRD 和 PRD 的污染空气团主要来自长途运输，这突出了联合区域治理的重要性。
