Abstract: The COVID-19 pandemic and the unprecedented nationwide lockdown imposed across India from March 2020 onwards presented an unplanned, but ecologically significant natural experiment in urban air quality management. The present study is a spatial assessment of the change in the concentration of particulate matter, PM2.5 and PM10 over Udaipur city, Rajasthan during six time defined phases (pre-lockdown, four successive lockdown stages and initial unlock period) (15 March to 30 June 2020). Ambient air quality data were collected from Continuous Ambient Air Quality Monitoring Station (CAAQMS) of Rajasthan State Pollution Control Board (RSPCB) situated at four spatial locations of the city i.e. Ashok Nagar, Town Hall, Ambamate and Regional Office (Transport Nagar). Point data were geo-referenced in Google Earth Pro by the use of KML files, which were converted to shape files in ArcGIS, and then subjected to Inverse Distance Weighting (IDW) interpolation to produce continuous spatial surfaces for each phase and each pollutant. Both PM2.5 and PM10 concentrations are significantly reduced during Lockdown 1 relative to pre-lockdown baseline conditions, consistent with the near-complete suppression of vehicular traffic, industrial activity and construction during this period. The subsequent phases of lockdown saw a gradual deterioration of air quality as the easing of economic activities led to higher concentrations during Lockdown 4. This could be due to the influx of the patients from the neighbouring districts for the treatment at the healthcare facilities of Udaipur. Lockdown 1 saw a partial bounce back to cleaner air, indicative of the behavioural inertia of a population still wary of public exposure. These spatially explicit results contribute to the growing evidence of the pivotal role of anthropogenic emissions on urban air quality, with direct implications for post-pandemic environmental governance.

Keywords: COVID-19 lockdown; PM2.5; PM10; GIS; IDW interpolation; Udaipur; air quality; spatial analysis; Rajasthan.