Mercury drops, Delhi’s air begins to worsen

The Capital is inching towards an air pollution spike, with winds slowing down and the mornings getting colder. On Sunday morning for instance, winds in the city were calm and the minimum temperature was 18.5°C, three degrees below normal.

The Capital is inching towards an air pollution spike, with winds slowing down and the mornings getting colder. On Sunday morning for instance, winds in the city were calm and the minimum temperature was 18.5°C, three degrees below normal.

A mild haze seen over Vijay Chowk, in New Delhi, India, on Thursday, September 24, 2020. (Sanjeev Verma/HT PHOTO)

The wind speed picked up to 12kmph only by noon, according to the regional weather forecasting centre.

Air quality in the national capital begins to dip from October onwards every year, when temperatures begin to dip, winds slow down, and farmers in neighbouring states begin to burn crop stubble, smoke from which travels towards the city.

According to the air quality early warning system under the Union ministry of earth sciences, air quality is likely to be ‘moderate’ (when the AQI is between 101 and 200) on October 5 and 6. However, it also noted that stubble fire points have been observed over Punjab, adjoining Pakistan, Haryana, as well as Uttar Pradesh, and are increasing over time — conditions that may adversely impact Delhi and the National Capital Region’s air quality. Winds in this region travel mainly from the northwest at this time.

Currently, the northwesterly winds travel at speeds of up to 14kmph and skies are mainly clear.

“Nights and early mornings are getting colder, and wind speeds are reducing in the evening and early morning. We are expecting minimum temperature to hover around 18 to 19°C, but maximum temperatures will be moderate, around 35 to 36°C. Pollutants do not disperse easily when winds slow down,” explained Kuldeep Srivastava, head of the regional weather forecasting centre.

He last week told HT that “there are clear skies now after the monsoon has withdrawn so day temperatures are high, but the heat is radiated back, so nights are cooler. The wind direction has changed from easterly during monsoon to north-westerly so the winds are blowing from the colder regions such as Jammu and Kashmir; Himachal Pradesh etc. If there is any rain or snow there due to western disturbance, it will get colder.”

The air quality index (AQI) on Sunday was 184 in the “moderate” category. The ventilation index was approximately 12,500m2/s on Sunday.

The ventilation index is a product of average wind speed and mixing height, and a value on the scale lower than 6,000m2/s, with average wind speeds lower than 10kmph is unfavourable for dispersion of pollutants, as per the Central Pollution Control Board (CPCB).

A large number of crop stubble fires were seen in satellite images over northwestern India on October 3 and 4.

“As soon as we have a recommendation from the member secretary of the CPCB, the Graded Response Action Plan (Grap) will kick in. We will immediately issue orders,” said Bhure Lal, Chairman of Environment Pollution Control Authority (Epca).

“State governments will have to take action on crop stubble burning. There are both in-situ and ex-situ options available to manage straw. The Centre has given funds to subsidise stubble management machinery. Subsidy of 50% is being offered to individuals who buy the machine and 80% to cooperative societies or panchayats. We have suggested that the small and marginal farmers get the machinery at concessional rates — almost free,” he added.

Grap, drawn up in 2017, defines specific measures to tackle different levels of air pollution. The Supreme Court-mandated Epca is in charge of enforcing the Grap measures.

When air quality hits ‘poor’ levels, under Grap, garbage burning is monitored and fines are levied on those caught burning garbage, apart from measures to control dust, increased focus on polluting industries, and others.

Meanwhile Citizens for Clean Air, a group of citizens, environmentalists, waste management experts wrote to EPCA appealing that it issue advisories or orders prohibiting the sale and use of firecrackers during the pandemic as it could aggravate public health issues, including Covid-19.