Impact of COVID-19 lockdown on air pollutant concentrations: a case study of South Indian states.

The COVID-19 pandemic provided a unique opportunity to evaluate the impact of reduced anthropogenic activities on air quality. This study assesses variations in atmospheric concentrations of carbon monoxide (CO), nitrogen dioxide (NO₂), and sulphur dioxide (SO₂) across selected regions of South India during three phases: pre-COVID (2019), during lockdown (2020), and post-COVID (2021). Satellite observations from Sentinel-5P and NASA Giovanni datasets were used to analyse spatial and temporal trends. The results indicate a clear reduction in pollutant concentrations during the lockdown period, particularly for NO₂, followed by a noticeable rebound as restrictions were relaxed. These trends highlight the strong influence of transportation, industrial activity, and energy consumption on regional air quality. Although variations exist between datasets due to differences in retrieval approaches and resolution, the overall patterns consistently demonstrate improved air quality during reduced human activity. The findings emphasise the potential for achieving significant air quality improvements through effective emission control strategies. This study provides insights for sustainable urban planning and air pollution management, underscoring the need for long-term policies that balance economic development with environmental protection.