Diwali: Delhi's air quality 'very poor', likely to become 'severe' by evening

Delhi's air quality remained “very poor” on Saturday morning and emission from firecrackers and calm winds may push it to the “severe” zone, according to government agencies and weather experts.

The Ministry of Earth Sciences' air quality monitor, SAFAR, said the PM2.5 concentration in Delhi on Diwali is likely to be the “lowest” in the last four years if no firecrackers are burnt.

Pollution levels in Delhi during the Diwali period are likely to remain in the higher end of the “very poor” category in the absence of emissions due to fireworks, it said.

But two factors – smoke from farm fires and stagnant surface winds – will keep the air quality in the higher end of the “very poor” category to the lower end of the “severe” on Diwali night, it said.

The central government's Air Quality Early Warning System for Delhi said, “The air quality in Delhi-NCR is likely to deteriorate further and enter the 'severe' category by evening.”  SAFAR said transport-level winds have become northwesterly and the stubble burning-induced impact on air quality index (AQI) is expected to increase.

A spike in PM2.5 levels in the early hours of Sunday is likely if fire crackers are burnt, it said.

The city recorded an AQI of 373 at 10 am on Saturday, which falls in the “very poor” category. However, several monitoring stations, including at ITO (406), Alipur (422), Jahangirpuri (431), Rohini (403), Vivek Vihar (415), Narela (418), Bawana (430), Mundka (405) and Anand Vihar (429), recorded their AQI in the “severe” category.

The 24-hour average AQI was 339 on Friday and 314 on Thursday.

The neighbouring cities of Faridabad (323), Ghaziabad (412), Noida (362), Greater Noida (350), and Gurgaon (338), which fall in the National Capital Region (NCR), also recorded their AQI is the "very poor" and “severe” categories.

Delhi recorded a 24-hour average AQI of 337 on Diwali last year (October 27), and 368 and 400 in the next two days. Thereafter, pollution levels remained in the “severe” category for three days on the trot.

In 2018, the 24-hour average AQI (281) on Diwali was recorded in the “poor” category. It deteriorated to 390 the next day and remained in the “severe” category on three consecutive days thereafter.

In 2017, Delhi's 24-hour average AQI on Diwali (October 19) stood at 319. It, however, slipped into the “severe” zone the next day.

This time, the India Meteorological Department has said that a fresh western disturbance is likely to increase the wind speed and improve the air quality in Delhi-NCR post Diwali.

Light rain is likely on Sunday under the influence of a western disturbance. It is still to be seen if it is enough to wash away pollutants, Kuldeep Srivastava, the head of the IMD's regional forecasting centre, said.

"However, Delhi-NCR's air quality is likely to improve post Diwali due to an expected increase in the wind speed on Sunday,” he said.

V K Soni, the head of the IMD's environment research centre, said calm winds and firecrackers emissions may push the air quality to the “severe” zone on Diwali night.  The wind speed is expected to pick up thereafter and the wind direction will be east-southeasterly, he said.

There will be a significant improvement in air quality by November 16, Soni said.

The Air Quality Early Warning System for Delhi also said the situation is likely to “improve significantly” on Sunday.  “Under the influence of a Western Disturbance, isolated rainfall over plains of northwest India and adjoining central India is likely on Sunday. The predominant surface wind is likely to be coming from East-Southeast direction of Delhi with wind speed up to 20 kmph,” it said.

“Generally cloudy sky, light rain, thundershowers accompanied with gusty winds (speed 30-40 kmph) is likely towards afternoon-evening on Sunday,” the central agency said.

The Commission for Air Quality Management (CAQM) on Friday directed the CPCB and states concerned to ensure there is no lapse in the implementation of the National Green Tribunal's directions in view of the air quality scenario during the Diwali period.

“In pursuance of NGT order dated November 9 and considering the concerns of air quality scenario in the NCR and its adverse health impact, the Commission directed CPCB, state governments and authorities concerned for strict compliance of the directions of NGT, with zero tolerance on violation,” it said.

The National Green Tribunal (NGT) had on Monday imposed a total ban on sale or use of all kinds of firecrackers in the National Capital Region (NCR) from November 9 midnight to November 30 midnight, saying "celebration by crackers is for happiness and not to celebrate deaths and diseases".

A bench headed by NGT Chairperson Justice Adarsh Kumar Goel clarified that the direction will apply to all cities and towns in the country where the average of ambient air quality during November 2019 was in "poor" and above categories.  "At other places, restrictions are optional for the authorities but if there are more stringent measures under orders of the authorities, the same will prevail," the NGT had said.

The Central Pollution Control Board (CPCB) had on Wednesday ordered closure of hot mix plants and stone crushers in Delhi-NCR till November 17 in view of a likely increase in pollution levels during the festive season.

It also asked the governments of Punjab and Haryana to take immediate stringent actions to curb stubble burning and authorities in Delhi-NCR to strictly check biomass burning.