Ahead of Diwali, air quality in Delhi slips to season's worst

Less wind on Diwali day as well a fog incident the day after will make the situation worse

By Shagun
Published: Friday 25 October 2019
Photo: Wikipedia

The air quality in Delhi slipped to the season's worst on October 25, 2019, ahead of the festival of Diwali on October 27.

The air quality touched 'very poor' levels on October 24 and the trend continued on the morning of October 25. The average of the 24 hours Air Quality Index (AQI) stood at 311 (out of 500), according to the AQI bulletin of the Central Pollution Control Board (CPCB). 

The situation in the neighbouring towns of the National Capital Region (NCR) was equally bad or even worse in some cases. Ghaziabad, Greater Noida, and Noida all had AQIs worse than Delhi's at 335, 320, and 319 respectively. 

Other north Indian towns like Bagpath in Uttar pradesh, Ballabhgarh, Jind, Sirsa, Panipat, Karnal in Haryana, and Bhiwadi in Rajasthan also slipped to 'very poor' levels of air quality. 

While crop residue burning in the towns of Punjab and Haryana increased significantly since the second week of October, the rise in vehicular traffic ahead of Diwali, early celebrations through fire crackers, and local garbage burning might also have added to the pollution load in Delhi. 

At the start of October, the number of fires owing to stubble burning was just three. By October 18, it had risen to 343, followed by 367 on the 19th, and 491 on 22nd.

A screen shot of the CPCB's AQI index. Photo: CPCB websiteOn October 23, 158 such fires were recorded, according to data available with the Ministry of Earth Sciences (MoES)'s early warning system. 

According to the forecast by the System of Air Quality and Weather Forecasting and Research (SAFAR) under MoES, the air quality was set to deteriorate further till Diwali. 

However, AQI this year was slightly better than the same period last year when it was at 328 and 331 on October 24 and 25 respectively. 

With temperatures dipping since the beginning of the month, meteorological factors like wind speed, moisture level and boundary layer height become unfavourable.

Rise in moisture content, along with low wind speed is one of the main reasons for pollutants getting trapped in Delhi’s air, thus leading to smog episodes.

The crisis deepens if it is encountered with any additional emissions sources like firecrackers or stubble burning sources.

The India Meteorological Department (IMD) has predicted calm winds on Diwali morning and slightly better wind speed by afternoon.

With low wind speed, the pollutants will not be able to disperse from ambient atmosphere. A fog episode is also expected on October 28, a day after Diwali, which could further worsen the situation.

According to the assessment of a CPCB task force, the air quality situation during the next few days due to festival, meteorology, stubble burning was expected to be challenging.

The Environment Pollution (Prevention and Control) Authority has written a letter to authorities in Delhi and neighbouring states on the recommendations of the task force to be on high alert and strictly enforce law for pollution-control activities.

The directions include banning hot mix plants, stone crushers, and construction activities such as earthwork, which have potential to generate dust between 6 pm to 6 am during October 26-30 in Delhi and its satellite towns.

Other directions include the closing of industries which have not shifted to piped natural gas during the same period, deploying additional manpower to ensure smooth traffic in all areas, especially identified high traffic corridors in Delhi and impounding of visibly polluting vehicles.

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