Objective: To understand the temporal characteristics of air pollutants during lockdown and to assess the impact of them on air quality. Method: We have analyzed the ambient monitoring data, from Central Pollution Control Board (CPCB), of air pollutants from 27 th January to 12 th July 2020 to compare prelockdown (27 th Jan to 22 nd March), during lockdown (23 rd March to 17 th May) and post lockdown (18 th May to 12 th July) effects over six stations in Hyderabad. Further, to understand the significant differences in PM concentrations we have evaluated rate of change (ROC) over a defined period of time. Pearson correlation analysis was used as an indicator of the relation between PM 2.5 and PM 10 for the study period. Findings: Our results show a significant decline in PM 2.5 (27%) and PM 10 (34%) concentrations during lockdown. This indicates positive effect of lockdown on air quality over Hyderabad. The contribution of PM 2.5 in PM 10 (46%) during lockdown remains same when compared to previous years though the concentrations have decreased. The PM 2.5 was highly correlated with PM 10 over all the stations. A substantial decrease in PM 2.5 (27%) and PM10(39%) compared to the same period of previous years were observed. Apart of particulate matter the concentration of NO 2 decreased by 33% during lockdown. Another noticeable point observed is that the concentrations of CO and SO 2 showed a marginal decrease and they remained below permissible limits (NAAQS) during study period. Novelty / Recommendations: Overall, this study may be helpful to understand how air pollution is affected during COVID-19 pandemic and provide important signs regarding the control of emissions by subsequently implementing stringent rules, like complete lockdown at least one day per week, imposing traffic rules, encouraging online teaching, digital shopping etc., to heal and save the environment.
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