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The hourly average PM2.5 concentration in Delhi reached 910 micrograms per cubic meter (g / m3) at midnight, more than 15 times the safe standard, before falling due to an increase in wind speed. While the general Air quality index (AQI) touched “severe” on Diwali day with a reading of 414, it registered at 435 on Sunday.
In terms of AQI, this was the worst diwali Since 2016, when a reading of 431 and 445 was recorded the next day, they showed data from both the Central Pollution Control Board (CPCB) and the Weather and Air Quality Research and Forecast System (SAFAR).
Last year, an AQI of 337 (very poor) was recorded on Diwali day, which rose marginally to 368 (very poor) the next day. A further increase was seen in 2018 when the AQI increased from 281 (poor) on Diwali day to 390 (very poor) the next day due to firecrackers.
SAFAR had predicted that pollution would hit the “severe” level the day after Diwali, even if no firecrackers were exploding. He said that additional emissions through firecrackers and crop stubble led to the hourly PM2.5 concentration crossing more than 1,000 g / m3 at various locations in Delhi.
Data from the CPCB showed that pollution peaked between midnight and 1 am The AQI gradually increased from 414 (severe) at 4 pm to 446 at 8 pm and 460 at 1 am “This year, Diwali was celebrated in mid-November with unfavorable weather conditions for the dispersion of pollutants compared to 2019 when the festival was in the last week of October, “added CPCB.
“The surface temperature was the lowest in the last five years, which could have contributed to more inversion conditions and lower average mixing height, limiting vertical dispersion. Wind speed both in the day pre-Diwali as it was on Diwali day was similar. Overall, this Diwali witnessed higher background levels of pollutants and greater addition of particles during the night of the firecrackers, “said CPCB.
However, a period of rain through a western disturbance not only helped settle pollutants, but also increased wind speeds in the region, allowing air quality to improve Sunday morning. Delhi’s base station Safdarjung recorded 0.4mm of rain as of 5:30 pm, while Palam received 1.8mm.
Kuldeep Srivastava, IMD scientist and head of the Regional Weather Forecast Center, said: “East winds were recorded with a speed of between 18 and 24 km / h, which helped disperse pollutants. The rain also helped settle some pollutants “.
LS Kurinji, a research analyst at the Council on Energy, Environment and Water, said that normally the impact of firecrackers could linger in the air for several days, but the rain controlled it in a matter of hours.
“Air quality stations observed a sharp rise in PM2.5 levels, which went from 250 g / m3 to more than 600 g / m3 on the night of Diwali. However, on the night of November 15, a light rain accompanied by gusts of wind removed pollutants and improved air quality, reducing PM2.5 levels to 100 g / m3, “added Kurinji.
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