Delhi's Diwali started with "very poor" air quality which later turned "severe" following the bursting of crackers.
"Overall air quality in the 'severe' category today after bursting of firecrackers on Diwali and the presence of bio-mass pollutants in Delhi. The air quality and fog condition to improve once windspeed picks up. No wind and high moisture is causing fog conditions," an IMD official said.
An air quality index (AQI) between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.
Northwesterly winds carry smoke from farm fires in Punjab and Haryana towards the national capital.
Last year, the share of stubble burning in Delhi's pollution had peaked at 42 per cent on November 5. In 2019, crop residue burning accounted for 44 per cent of Delhi's PM2.5 pollution on November 1.
Delhi Environment Minister Gopal Rai had Wednesday urged the Centre to issue an advisory to Punjab, Haryana and Uttar Pradesh to completely stop stubble burning during the Diwali period so that people could breathe easy after the festival.
The contribution of stubble burning in Delhi's PM2.5 concentration was 32 per cent on Diwali day last year as compared to 19 per cent in 2019.
The contribution of farm fires in Delhi's air pollution has remained low this season so far due to the record-breaking rainfall in October and "unfavourable" wind direction for transport of smoke from stubble burning.
SAFAR said "very calm" local Delhi wind conditions with little ventilation is expected for the next three days which will be unfavourable for dispersion of pollutants.
Under a zero firecracker emission scenario, Delhi's PM2.5 concentration is predicted to be in the upper end of the 'very poor' category from November 4 to November 6.
"However, even if we consider 50 per cent of firecracker load of 2019, the AQI is predicted to degrade to the 'severe' category during the period," SAFAR said.
The PM2.5 concentration in the national capital can surpass 500 micrograms per cubic metre on November 5. The safe limit is 60 micrograms per cubic metre.
On October 27, the Delhi government had launched the 'Patakhe Nahi Diye Jalao' campaign to create awareness against the bursting of crackers.
Action is being taken under relevant IPC provisions and the Explosives Act against anyone found burning crackers under the campaign.
On September 28, the Delhi Pollution Control Committee ordered a complete ban on the sale and bursting of firecrackers in the national capital till January 1, 2022.
According to the government, more than 13,000 kg of illegal firecrackers have been seized and 33 people arrested under the anti-cracker campaign.
(With agency inputs)
