Air quality starts falling, pollution board cites temperature dip

With the withdrawal of the monsoon season, air quality deteriorated to the ‘poor’ category of the Central Pollution Control Board’s (CPCB) air quality index (AQI) over the weekend. Officials cited lower temperatures in the morning and evening hours as the main cause and dismissed concerns that stubble burning was causing pollution.

According to the CPCB’s daily bulletin, the city recorded poor AQI on Saturday, following which it improved to the moderate category on Sunday, after weeks of satisfactory air quality.

In the past week, the air quality in the city has dropped from the satisfactory category, with an AQI of 92 recorded on October 3, to the poor category, with an AQI of 201 recorded on Saturday. On Sunday, an AQI of 170 was recorded.

The air quality is likely to deteriorate further over the next five days but remain in the moderate category, according to a weather bulletin issued for Delhi-NCR by Air Quality Early Warning System. The bulletin also mentioned that crop residue burning fire points have been observed over Haryana and Punjab, which is blamed for poor air quality in the National Capital Region (NCR).

However, officials said that the drop in air quality was mainly due to falling temperatures.

Kuldeep Singh, the regional officer of Haryana State Pollution Control Board for Gurugram (north), said, “The dip in air quality is primarily due to drop in temperature during the morning and evening hours, as pollutants accumulate in lower temperatures. We are taking all measures to ensure that air quality does not deteriorate this winter season.”

When asked if crop residue burning in other districts of Haryana could be a reason, Singh said, “Stubble burning is quite controlled in Haryana, this (dip in air quality) is mainly due to drop in temperature.”

Every winter, the air quality in the NCR plummets due to incoming pollutants from stubble or crop residue burning in neighbouring districts of Haryana. This year, Haryana has put in place a robust strategy, including incentives and punitive steps to stop the practice, ahead of the paddy stubble burning season. Most of the fires are usually reported from Karnal, Kaithal, Kurukshetra, Fatehabad and Ambala districts.

“It is too early to say what the causes are behind poor air quality in the city as monsoon has just started withdrawing. All agencies are also working on implementation of measures to control air pollution. We will see for a few more days and take action accordingly if any external factors are found,” S Narayanan, member secretary of HSPCB, said.

A week ago, the state pollution control board released guidelines for different agencies in the city to start working to manage air quality in the city. However, HT found that sufficient measures were not being taken to control dust pollution during a visit to the Sohna Road construction site in the city on Sunday.

Officials also said that discussions are underway for implementing a Graded Response Action Plan (Grap), an emergency set of measures implemented between October 15 and March 15 every year to control air pollution in Delhi-NCR.

Under Grap, a ban on diesel generator sets is announced for the entire period and depending on the air quality, measures such as stopping construction work, levying heavy fines for garbage burning and shutting brick kilns, among other measures, are taken.

Abhishek Srivastava, a city-based environmental engineer said, “There are three primary reasons for the dip in air quality: stubble burning has started, wind direction has changed from northwest directions and also surface winds have slowed down. The wind direction changed around October 6 and the city also witnessed light rain in the early days of this month, so the air quality was normal then. But now, the wind speed has slowed down which has brought over dip in temperature in the morning and evening hours, so they are all connected.”