Day after seeing worst air, Chandigarh breathes bit easy

A day after experiencing the worst air quality in the country, the residents of the City Beautiful got some relief from pollution today.

Around 11 am, the average air quality index (AQI) was recorded at 323. It was 425 at the same time a day before, which was the highest in the country followed by Delhi at 423. Chandigarh had witnessed its AQI plunging to the ‘severe’ category for the first time in the season yesterday.

What led to drop in AQI

High moisture content in the air

Lesser vehicles on roads due to Gurpurb holiday

Significant fall in number of farm fire cases in region

Since it was a holiday today due to Gurpurb, there was a lesser movement of vehicles. The AQI dropped by over 100 points and the quality of air improved to ‘very poor’ category.

Listing key factors and processes that helped improve the air quality in Chandigarh, Dr Ravindra Khaiwal, Professor of Environment Health, Department of Community Medicine and School of Public Health, PGIMER, said, “The high moisture content in the air, as indicated by relative humidity levels nearing 99%, likely contributed significantly to the reduction in air pollution.”

“High moisture content facilitates the settling of suspended particles due to gravity and when relative humidity exceeds 95%, conditions favour particles sticking together and eventually settling out of the air,” he added.

The improvement in air quality also correlated with a marked reduction in stubble burning. Fire counts in the region dropped to 42 on November 14, a sharp decrease of 88.4% compared to the previous week’s average of 362, said Khaiwal.

Reduced vehicle traffic due to the holiday is another significant factor. Fewer vehicles on the road led to a substantial decrease in vehicular emissions, a major source of PM2.5 and other air pollutants, he said. Furthermore, wind pattern data showed that the speed ranged between 9 and 12 km per hour on November 15, with slightly higher speeds during daytime, helping to disperse pollutants. These consistent but moderate wind speeds were effective for pollutant dispersion contributing to improved air quality, he added.

Chandigarh recorded the AQI of 309 at 6 pm, according to the Central Pollution Control Board. The Air Quality Monitoring Station in Sector 22 registered the AQI at 288 at 6 pm and it was 460 around 11 am yesterday. At the Sector 53 air monitoring station, bordering Mohali district, the AQI was 285, against 452 recorded yesterday. At the Sector 25 station, the AQI was 354, a slight improvement from yesterday’s 363. In view of the worsening air quality in Chandigarh, announcements are being made through speakers installed at traffic signals, urging motorists to switch off the engines while waiting at red lights to reduce air pollution.