Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Nanjing University of Information Science & Technology, Nanjing, 210044, China.
Department of Physics, Sree Krishna College Guruvayur, Kerala, 680102, India.
Environ Pollut. 2022 Aug 15;307:119468. doi: 10.1016/j.envpol.2022.119468. Epub 2022 May 16.
The Community Multi-Scale Air Quality (CMAQ) model was applied to evaluate the air quality in the coastal city of Kannur, India, during the 2020 COVID-19 lockdown. From the Pre1 (March 1-24, 2020) period to the Lock (March 25-April 19, 2020) and Tri (April 20-May 9, 2020) periods, the Kerala state government gradually imposed a strict lockdown policy. Both the simulations and observations showed a decline in the PM concentrations and an enhancement in the O concentrations during the Lock and Tri periods compared with that in the Pre1 period. Integrated process rate (IPR) analysis was employed to isolate the contributions of the individual atmospheric processes. The results revealed that the vertical transport from the upper layers dominated the surface O formation, comprising 89.4%, 83.1%, and 88.9% of the O sources during the Pre1, Lock, and Tri periods, respectively. Photochemistry contributed negatively to the O concentrations at the surface layer. Compared with the Pre1 period, the O enhancement during the Lock period was primarily attributable to the lower negative contribution of photochemistry and the lower O removal rate by horizontal transport. During the Tri period, a slower consumption of O by gas-phase chemistry and a stronger vertical import from the upper layers to the surface accounted for the increase in O. Emission and aerosol processes constituted the major positive contributions to the net surface PM, accounting for a total of 48.7%, 38.4%, and 42.5% of PM sources during the Pre1, Lock, and Tri periods, respectively. The decreases in the PM concentrations during the Lock and Tri periods were primarily explained by the weaker PM production from emission and aerosol processes. The increased vertical transport rate of PM from the surface layer to the upper layers was also a reason for the decrease in the PM during the Lock periods.
采用社区多尺度空气质量（CMAQ）模型评估了印度喀拉拉邦沿海城市 Kannur 在 2020 年 COVID-19 封锁期间的空气质量。从 Pre1（2020 年 3 月 1 日至 24 日）时期到 Lock（2020 年 3 月 25 日至 4 月 19 日）和 Tri（2020 年 4 月 20 日至 5 月 9 日）时期，喀拉拉邦政府逐步实施了严格的封锁政策。模拟和观测结果均表明，与 Pre1 时期相比，Lock 和 Tri 时期的 PM 浓度下降，O 浓度增加。采用综合过程速率（IPR）分析来分离各个大气过程的贡献。结果表明，上层的垂直输送主导了地表 O 的形成，在 Pre1、Lock 和 Tri 时期，分别占 O 源的 89.4%、83.1%和 88.9%。光化学过程对地表层 O 浓度的贡献为负。与 Pre1 时期相比，Lock 时期 O 的增加主要归因于光化学的负贡献降低以及水平输送的 O 去除率降低。在 Tri 时期，气相化学消耗 O 的速度较慢，上层到地表的垂直输入较强，这是 O 增加的原因。排放和气溶胶过程是净地表 PM 的主要正贡献，分别占 Pre1、Lock 和 Tri 时期 PM 源的 48.7%、38.4%和 42.5%。Lock 和 Tri 时期 PM 浓度的降低主要归因于排放和气溶胶过程中 PM 生成的减弱。地表层到上层的 PM 垂直传输率增加也是 Lock 时期 PM 减少的原因之一。
