The outbreak of COVID-19, a global health challenge faced by countries worldwide, led to a lockdown in India, thereby bringing down the emissions of various air pollutants. Here, we discuss the behaviour of surface ozone (O3) concentrations and its precursors, oxides of nitrogen (NOx), carbon monoxide (CO), and volatile organic compounds (VOC) at two Indian megacities namely Mumbai and Pune, closely located yet vastly differing in meteorology due to their locations. Although levels of CO, NO2, and VOC declined sharply after the lockdown in both cities, with NO2 showing the highest reduction, ozone concentration in Pune remained unaffected, whereas Mumbai exhibited a mixed trend, touching even a maximum in between the lockdown. On a diurnal scale, the magnitude of O3 levels during the lockdown period is higher at almost all hours in Mumbai, and in Pune, it is almost identical except during night hours when it is marginally higher in the lockdown period as compared to the normal period. On a whole, the pollution levels were brought down significantly which can be used as a benchmark in the future for the implementation of policies related to air quality management and emission control in Indian megacities by the policymakers. These results also can pave a way for the scientific community for local air quality modelling.

中文翻译：

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在印度一个靠近沿海和丘陵的大都市中，COVID-19 封锁下臭氧趋势的差异

COVID-19 的爆发是世界各国面临的全球健康挑战，导致印度封锁，从而减少了各种空气污染物的排放。在这里，我们讨论了地表臭氧 (O3) 浓度及其前体、氮氧化物 (NOx)、一氧化碳 (CO) 和挥发性有机化合物 (VOC) 在两个印度大城市孟买和浦那的行为由于地理位置不同，气象也不同。尽管两个城市的二氧化碳、二氧化氮和挥发性有机化合物的含量在封锁后急剧下降，其中二氧化氮的降幅最大，但浦那的臭氧浓度并未受到影响，而孟买则呈现出喜忧参半的趋势，在封锁期间甚至达到了最大值。在昼夜尺度上，封锁期间的 O3 水平在孟买几乎所有时间都较高，在浦那，除了在夜间时段，与正常时期相比，锁定期的数值略高，几乎相同。总体而言，污染水平显着降低，可作为未来政策制定者在印度特大城市实施空气质量管理和排放控制相关政策的基准。这些结果还可以为科学界进行当地空气质量建模铺平道路。污染水平显着降低，可作为未来政策制定者在印度特大城市实施与空气质量管理和排放控制相关政策的基准。这些结果还可以为科学界进行当地空气质量建模铺平道路。污染水平显着降低，可作为未来政策制定者在印度特大城市实施与空气质量管理和排放控制相关政策的基准。这些结果还可以为科学界进行当地空气质量建模铺平道路。