Delhi air to be ‘poor’ on Diwali, worsen afterwards: Experts

Air quality is considered poor when the air quality index is 201-300 and very poor when it is 301-400

By DTE Staff
Published: Monday 01 November 2021

The air quality in Delhi and the National Capital Region will be ‘poor’ in the run-up to Diwali and will start to deteriorate significantly November 5 and 6, 2021, reaching the upper end of the ‘very poor’ category, according to the latest forecast by the Union Ministry of Earth Sciences.

The wind direction as well as the bursting of crackers during Diwali will also worsen air quality, according to experts.

The air quality is considered to be ‘very poor’ when the Air Quality Index (AQI) is from 301-400, according to the Central Pollution Control Board guidelines. An AQI of 0-50 is considered ‘good’, 51-100 ‘satisfactory’, 101-200 ‘moderate’, 201-300 ‘poor’ and 401-500 ‘severe’. Above 500 is the ‘severe-plus or emergency’ category.

The Delhi Pollution Control Committee has banned the sale and use of firecrackers in the national capital till January 1, 2022.

The wind will flow into Delhi November 1 from the southeast, according to the forecast by the Air Quality Early Warning System for Delhi under the Union earth sciences ministry. The speed of the wind will be 8-12 kilometres per hour (kmph).

The wind November 2 will flow from the east / southeast with a speed of 8-12 kmph. On November 3, the direction of the wind flow will be the southeast and the  wind speed will be 04-08 kmph

The ventilation index is likely to be 4,500 square metres November 1 and 2 and 5,500 on November 3. A ventilation index lower than 6,000 sq m, with an average wind speed less than 10 kmph is unfavourable for dispersion of pollutants, including paticulate matter (PM)2.5.

The burning of crop stubble had increased significantly in Punjab (2,895 points), Haryana (353) and UP (170) October 31, the forecast said. 

Avikal Somvanshi, programme manager, Clean Air, Centre for Science and Environment, said the Delhi-based non-profit in its pre-winter analysis released October 22, 2021, had predicted that this winter might show a severe peak in smog.

CSE had based its estmate on the fact that due to the prolonged rainy season, the farm stubble fire counts might get more concentrated around early November as farmers had not been able to burn the stubble so far, Somvanshi said.

“Futher, due to colder weather conditons and low wind, dispersion of smoke will be hampered. Diwali amid these conditons will only worsen the situation. SAFAR data since has strengthened this fear as fire counts reached 3,941 October 31, the highest this year so far,” he added.

If drastic steps were not taken, Delhi might be witness worse air on Diwali day than it did in 2018 when the PM2.5 concentration went beyond 600 microgram per cubic metre, Somvanshi said.

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