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Abstract：
Restrictions on human and industrial activities due to the coronavirus (COVID-19) pandemic have resulted in an unprecedented reduction in energy consumption and air pollution around the world. Quantifying these changes in environmental conditions due to government-enforced containment measures provides a unique opportunity to understand the patterns, origins and impacts of air pollutants. During the lockdown in Pakistan, a significant reduction in energy demands and a decline of ∼1786 GWh (gigawatt hours) in electricity generation is reported. We used satellite observational data for nitrogen dioxide (NO2), carbon monoxide (CO), sulphur dioxide (SO2), aerosol optical depth (AOD) and land surface temperature (LST) to explore the associated environmental impacts of shifts in energy demands and emissions across Pakistan. During the strict lockdown period (March 23 to April 15, 2020), we observed a reduction in NO2 emissions by 40% from coal-based power plants followed by 30% in major urban areas compared to the same period in 2019. Also, around 25% decrease in AOD (at 550 nm) thickness in industrial and energy sectors was observed although no major decrease was evident in urban areas. Most of the industrial regions resumed emissions during the 3rd quarter of April 2020 while the urban regions maintained reduced emissions for a longer period. Nonetheless, a gradual increase has been observed since April 16 due to relaxations in lockdown implementations. Restrictions on transportation in the cities resulted in an evident drop in the surface urban heat island (SUHI) effect, particularly in megacities. The changes reported as well as the analytical framework provides a baseline benchmark to assess the sectoral pollution contributions to air quality, especially in the scarcity of ground-based monitoring systems across the country.
摘要：
由于冠状病毒（COVID-19）大流行，对人类和工业活动的限制导致全球能源消耗和空气污染空前减少。量化由于政府强制采取的遏制措施而导致的环境条件变化，为了解模式提供了独特的机会，空气污染物的来源和影响。在巴基斯坦封锁期间，据报道，能源需求显着减少，发电量下降了1786GWh(千兆瓦时)。我们使用了二氧化氮（NO2）的卫星观测数据，一氧化碳(CO),二氧化硫（SO2），气溶胶光学深度（AOD）和地表温度（LST），以探索整个巴基斯坦能源需求和排放变化的相关环境影响。在严格封锁期间（2020年3月23日至4月15日），与2019年同期相比，我们观察到燃煤发电厂的NO2排放量减少了40%，其次是主要城市地区的NO2排放量减少了30%。此外，尽管在城市地区没有明显的下降，但工业和能源部门的AOD（550nm）厚度下降了约25％。大多数工业区域在2020年4月第三季度恢复了排放，而城市区域在更长的时间内保持了减排。尽管如此，自4月16日以来，由于封锁实施的放松，观察到逐渐增加。对城市交通的限制导致地表城市热岛（SUHI）效应明显下降，特别是在特大城市。报告的变化以及分析框架为评估部门污染对空气质量的贡献提供了基准，特别是在全国各地缺乏地面监测系统的情况下。
