ARVAAN KUMAR AND SRIROOP CHAUDHURI
Abstract
In this study, we take Kolkata, a mega-city in India, as case example to assess (i) if COVID-19 Lockdown (LD) helped âhealingâ urban air pollution, and (ii) if the trend continued through the Unlockdown as well (UNLD) when restrictions were lifted. Our results indicated significant reductions in PM2.5 (significant at p<0.01, 56% reduction in 2020 as compared to 2019), PM10 (p<0.01; 65% reduction); NO2 (p<0.05; 40% reduction); and CO (p<0.05; 28% reduction) through LDs. Within 2020, highest reductions since pre-Lockdown was observed for the PMs, CO, and NO2, during LD 2-4. However, average PMs, CO and SO2 levels began soaring as restrictions were lifted. Average SO2 (p<0.05) and O3 (p<0.01) levels remained higher in 2020 than 2019. Computation of Enrichment Factor (EF) indicated that particulate matter (PM) levels did not comply with the World Health Organization (WHO) benchmarks. Correlation analyses revealed significant differences in patterns of interactions between air pollutants in LD as against UNLD. In the concluding section we reflect of state governmentâs lockdown policies to probe into the observed patterns in air quality.