Due to the COVID-19 pandemic, many countries across the world, including India, have imposed nationwide lockdowns to contain the spread of the virus. Many studies reported that the air quality had improved much due to the lockdown. This study examines the variation of Volatile Organic Compounds (VOCs) over the Indian metropolitan cities during the lockdown period by using ground-based and satellite observations. Ground-based BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes) measurements from various metropolitan cities have shown a drastic drop of about 82% in the first phase of lockdown when compared with the pre-lockdown period. Whereas the spatial distribution of formaldehyde (HCHO), obtained from the TROPOspheric Monitoring Instrument (TROPOMI) onboard Sentinal-5P satellite, did not show any significant variation due to COVID-19 lockdown, indicating the major source of HCHO is biogenic or pyrogenic. The BTEX ratios were evaluated for a better understanding of the source and photochemical age of the air samples. The ozone forming potential of BTEX in all locations was found reduced; however, the corresponding decrease in ozone concentrations was not observed. The increase in ozone concentrations during the same period indicates alternative sources contributing to ozone formation.

由于 COVID-19 大流行，包括印度在内的世界许多国家/地区都实施了全国封锁以遏制该病毒的传播。许多研究报告说，由于封锁，空气质量有了很大改善。本研究使用地面和卫星观测来检查封锁期间印度大都市挥发性有机化合物 (VOC) 的变化。来自各个大城市的基于地面的 BTEX（苯、甲苯、乙苯和二甲苯）测量显示，与封锁前相比，封锁的第一阶段急剧下降了约 82%。鉴于从 Sentinal-5P 卫星上的对流层监测仪器 (TROPOMI) 获得的甲醛 (HCHO) 的空间分布没有因 COVID-19 锁定而显示任何显着变化，表明 HCHO 的主要来源是生物源或热源。评估 BTEX 比率是为了更好地了解空气样本的来源和光化学年龄。发现所有位置的 BTEX 臭氧形成潜能都降低了；然而，并未观察到臭氧浓度相应下降。同一时期臭氧浓度的增加表明有其他来源促成了臭氧的形成。