Table 4.

Mean concentrations and variation of criterion pollutants during 2nd March to 21st March (before the lockdown) and 25th March to 14th April (during the lockdown) in NCT Delhi, India.

Pollutants	Type of station
	Before lockdown				During lockdown				Overall variation
	NCT Delhi avg.	Industrial locations avg.	Transport locations avg.	Residential and other locations avg.	NCT Delhi avg.	Industrial locations avg.	Transport locations avg.	Residential and other locations avg.	Net	%
PM10	176.07	190.74	195.77	160.48	84.79	91.25	90.11	76.48	−91.28	−51.85
PM2.5	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	79.8	−113.36	−60.95