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Daily variation of pollution parameters (a) Kolkata (a1; PM10, PM 2.5 & a2: NO2, SO2 & CO) and (b) Ahmedabad during 15 March 2020 to 10 April 2020. A dark black line is used to distinguish the before (before 24 March 2020) and after (after 24 March 2020) lockdown period
