Table 1.

Average concentrations and variations of criterion pollutants in NCT Delhi, India from 2 March to21 March 2020 (before lockdown) and 25 March to 14 April 2020 (during lockdown).

Pollutants	Before lockdown					During lockdown			Overall variation	Percentage
	NCT Delhi Avg.	Industrial location Avg.	Transport location Avg.	Residential and other location Avg.	NCT Delhi Avg.	Industrial location Avg.	Transport location Avg.	Residential and other location Avg.	Net	(%)
PM10	176.07	190.74	195.77	160.48	84.79	91.25	90.11	76.48	−91.28	−51.85
PM 2.5	80.51	88.05	94.83	72.67	37.75	39.67	44.23	31.09	−42.76	−53.11
SO2	16.08	15.48	14.56	14.17	13.19	14.07	12.53	11.20	−2.89	−17.97
NO2	42.59	34.81	47.35	48.75	20.16	18.80	23.38	18.79	−22.44	−52.68
CO	1.03	1.33	1.13	1.01	0.72	1.04	0.71	0.64	−0.31	−30.35
O3	34.05	26.37	35.07	37.36	34.32	31.00	38.87	37.97	0.27	0.78
NH3	33.93	38.43	38.02	30.66	29.75	35.84	33.06	25.97	−4.18	−12.33
NAQI	185.99	196.38	215.29	174.78	72.64	92.45	87.29	79.80	−113.36	−60.95