Chandigarh: AQI turns ‘very poor’ on Diwali night, but improves faster than previous years
The reason, experts say, was the relatively warm weather which helped disperse the pollutants quickly
The city’s air quality index (AQI) slipped into the ‘very poor’ category in half of Chandigarh’s monitoring stations on Diwali night, but improved rapidly within hours — a marked improvement from previous years, according to data from the Chandigarh Pollution Control Committee (CPCC).
The reason, experts say, was the relatively warm weather which helped disperse the pollutants quickly.
As per the CPCC data, the AQI crossed 300 at three stations – IMTech, Sector 39 (318); Punjab Engineering College, Sector 12 (312); and CAAQMS, Sector 53 (304), all in the ‘very poor’ category, during the peak celebrations. Sector 25 and Sector 22 recorded poor air quality with AQI levels of 296 and 234, respectively, while Sector 17 remained moderate at 183.
At 6 pm on Tuesday, the AQI of two of the three CAAQMS was in the moderate category, while at the CAAQMS in Sector 53, the AQI was 95, which is considered moderate.
UT director environment and member secretary, CPCC, Saurabh Kumar explained, “If one station has a higher AQI, it doesn’t mean people in that area burst more crackers. A multitude of factors affect the AQI, while weather conditions and winds also play a role in this. This year, Diwali was scheduled earlier than previous years. The relatively higher temperature due to this played a role in stopping temperature inversion – a phenomenon where warm air sits above a colder, denser layer near the surface, acting like a lid that prevents pollutants from rising and dissipating.”
Kumar added that the fact that it was windy and sunny on Tuesday from the morning itself helped scatter the pollutants from the air.
In 2024, Diwali was celebrated on October 31 while in 2023, it fell on November 12. In 2022, it was celebrated on October 24.
Not only did the particulate matter disperse quickly, four of the six stations saw a drop in AQI, which means the air here was cleaner. Sector 22 saw the highest drop in AQI, which was the lowest since 2022. The Sector 39 and Sector 12 stations, however, recorded a rise in AQI.
The AQI has been developed as a tool for communication of the air quality status in easy to understand terms. It has no units. As per the Central Pollution Control Board (CPCB), the sub-indices for individual pollutants at a monitoring location are calculated using its 24-hourly average concentration value (8-hourly in case of CO and O3) and health breakpoint concentration range. The worst sub-index is the AQI for that location.
Total eight pollutants are included for this, while particulate matter PM 2.5 and PM 10 become the most important during Diwali or during reports of stubble burning in the region.
AQI is considered moderate between 101-200 and can cause breathing discomfort to the people with lungs, asthma and heart diseases. Between 201-300, it is considered poor and can cause breathing discomfort to most people on prolonged exposure. Between 301-400, it is considered very poor and it can cause respiratory illness on prolonged exposure.
Usually during these days, air quality stays either in the moderate bracket or in the satisfactory bracket which is between 51-100 and can cause minor breathing discomfort to sensitive people.
Even Delhi enjoyed the same weather benefits as Chandigarh but its AQI remained in the very poor category until Tuesday evening. Speaking about what City Beautiful had done differently, Kumar added that all the departments, including the municipal corporation and the UT administration, had been working in tandem for the past month. As confirmed by cracker dealers, even the sale of firecrackers is seeing a decline, and campaigns being run in schools by the department are bearing fruit as not as many school children come to buy crackers now.
Sector 22 was the loudest
Noise levels, meanwhile, remained consistently higher than a normal day. The loudest was Sector 22 where noise levels over 80 decibels were recorded between 9 pm and 10 pm. In Sector 39, it went up to 75.3 decibels between 10 pm to 11 pm. PEC went up to 70.6 decibels between 9 pm to 10 pm. Sector 17 went up to 72.9 decibels, Sector 25 up to 68.4 decibels and Sector 53 went up to 69.6 decibels.
