Parida Bikash Ranjan, Bar Somnath, Roberts Gareth, Mandal Shyama Prasad, Pandey Arvind Chandra, Kumar Manoj, Dash Jadunandan
Department of Geoinformatics, School of Natural Resource Management, Central University of Jharkhand, Ranchi, 835222, India.
Department of Geoinformatics, School of Natural Resource Management, Central University of Jharkhand, Ranchi, 835222, India.
Environ Res. 2021 Aug;199:111280. doi: 10.1016/j.envres.2021.111280. Epub 2021 May 21.
The SARS CoV-2 (COVID-19) pandemic and the enforced lockdown have reduced the use of surface and air transportation. This study investigates the impact of the lockdown restrictions in India on atmospheric composition, using Sentinel-5Ps retrievals of tropospheric NO concentration and ground-station measurements of NO and PM between March-May in 2019 and 2020. Detailed analysis of the changes to atmospheric composition are carried out over six major urban areas (i.e. Delhi, Mumbai, Kolkata, Chennai, Bangalore, and Hyderabad) by comparing Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth (AOD) and land surface temperature (LST) measurements in the lockdown year 2020 and pre-lockdown (2015-2019). Satellite-based data showed that NO concentration reduced by 18% (Kolkata), 29% (Hyderabad), 32-34% (Chennai, Mumbai, and Bangalore), and 43% (Delhi). Surface-based concentrations of NO, PM, and AOD also substantially dropped by 32-74%, 10-42%, and 8-34%, respectively over these major cities during the lockdown period and co-located with the intensity of anthropogenic activity. Only a smaller fraction of the reduction of pollutants was associated with meteorological variability. A substantial negative anomaly was found for LST both in the day (-0.16 °C to -1 °C) and night (-0.63 °C to -2.1 °C) across select all cities, which was also consistent with air temperature measurements. The decreases in LST could be associated with a reduction in pollutants, greenhouse gases and water vapor content. Improvement in air quality with lower urban temperatures due to lockdown may be a temporary effect, but it provides a crucial connection among human activities, air pollution, aerosols, radiative flux, and temperature. The lockdown for a shorter-period showed a significant improvement in environmental quality and provides a strong evidence base for larger scale policy implementation to improve air quality.
严重急性呼吸综合征冠状病毒2（SARS-CoV-2，即新冠病毒）大流行以及强制封锁措施减少了地面和航空运输的使用。本研究利用哨兵-5P卫星反演的对流层一氧化氮（NO）浓度以及2019年和2020年3月至5月期间地面站对NO和颗粒物（PM）的测量数据，调查了印度封锁限制措施对大气成分的影响。通过比较2020年封锁期间和封锁前（2015 - 2019年）的中分辨率成像光谱仪（MODIS）气溶胶光学厚度（AOD）和陆地表面温度（LST）测量数据，对六个主要城市地区（即德里、孟买、加尔各答、钦奈、班加罗尔和海得拉巴）的大气成分变化进行了详细分析。基于卫星的数据显示，NO浓度在加尔各答降低了18%，在海得拉巴降低了29%，在钦奈、孟买和班加罗尔降低了32 - 34%，在德里降低了43%。在封锁期间，这些主要城市地面的NO、PM和AOD浓度也分别大幅下降了32 - 74%、10 - 42%和8 - 34%，且与人为活动强度相关。污染物减少中只有较小一部分与气象变化有关。在所有选定城市，白天（-0.16℃至-1℃）和夜间（-0.63℃至-2.1℃）的LST均出现显著负异常，这也与气温测量结果一致。LST的下降可能与污染物、温室气体和水汽含量的减少有关。由于封锁导致城市温度降低，空气质量得到改善，这可能是一种暂时的效应，但它为人为活动、空气污染、气溶胶、辐射通量和温度之间提供了关键联系。较短时期的封锁使环境质量有显著改善，并为实施更大规模改善空气质量的政策提供了有力的证据基础。
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