Kolkata air quality turns poorer than that on Diwali evening

The Air quality in Kolkata turned poorer on November 15 from what it was 24 hours ago on the Kali puja and Diwali day, but it was still better when compared to that recorded a day after the festivals in 2019 ,  an official of the West Bengal Pollution Control Board said.

The Air Quality Index (AQI) was higher than November 15 figure across the city. Though the air quality remained 'poor' in north Kolkata, it continued to be moderate elsewhere. The automated air monitoring station at Rabindra Bharati University campus in congested north Kolkata recorded the AQI at 287 (PM 2.5) at 8 pm on November 15 while it was 226 at the same time on November 14, the WBPCB official said.

An AQI between 101 and 200 is considered 'moderate', 201-300 'poor', 301-400 'very poor' and 401-500 'severe', while the AQI above 500 falls in the severe plus category.

On November 15, the AQI was 187 at Ballygunge in south Kolkata, 186 at Victoria in the central part of the city and 146 in east Kolkata’s Bidhan Nagar. On the Diwali evening, the AQI at those three places were 142, 115 and 151, respectively.

The AQI measured at Rabindra Bharati University was beyond 700 on the evenings of Kali Puja and Diwali evenings in 2019, the official said.

However, the AQI elsewhere in the city had hovered between 300 and 500.

Diwali is celebrated during the transition of two seasons – post-monsoon and pre-winter – when meteorological conditions do not support dilution and dispersion of pollutants due to low atmospheric boundary layer, low ventilation and low wind speed, the official said. In this transition phase, the ambient temperature, particularly at night, decreases and allows all pollutants to come close to ground level, especially in entire Indo-Gangetic plains, he said.

The impact of the bursting of firecrackers was alarming in 2019, and there was a blanket ban on fireworks this year. But lowering of night temperature was much significant, he said attributing the rise of the AQI to the night temperature conditions.

The Calcutta High Court had last week ordered a blanket ban on the use of fireworks in West Bengal during Kali puja, Diwali, Chhath and other pujas during this festive season to curb pollution amid the COVID-19 pandemic.

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In the previous years, only firecrackers that emit over 90 decibels of sound were not allowed by the WBPCB, and there was no ban on fireworks that emit light.

"Our control room is monitoring the situation 24×7 7even today. We are collating figures. So far the situationremains largely under control," he said.