Delhi: AQI stops short of ‘very poor’ | Delhi News

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NEW DELHI: Delhi’s air quality deteriorated on Tuesday with the AQI reaching the extreme end of “poor” category with a reading of 300 — 24-hour average — the highest this season. However, the AQI had touched the “very poor” category with a reading of 304 at 9.30am on Tuesday. This is just two days before the GRAP (Graded Response Action Plan) comes into effect in the National Capital Region.
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This is the first time since February that the AQI had crossed the 300-mark at any time during the day. It was recorded at 320 on February 12 this year. However, there was a slight improvement in the evening and CPCB’s daily bulletin released at 4 pm recorded the AQI at 300 which falls in the “poor” category. An AQI of 301 to 400 is classified as “very poor”.

The reasons for the AQI deteriorating from Monday’s 261 were zero wind speed and change in the wind direction on Tuesday morning. Kuldeep Srivastava, a scientist at India Meteorological Department (IMD) and head of Regional Weather Forecasting Centre in Delhi, said: “The wind speed was nil from 7 pm on Monday to 7 am on Tuesday and it caused trapping of local pollutants. However, due to a depression formed over Bay of Bengal, the wind direction changed from north-westerly to easterly on Tuesday morning which may have led to accumulation of pollutants.”
“As the easterly wind is likely to continue for two-three days, pollutants from Punjab and Haryana may not reach Delhi but it would cause local accumulation of pollutants. The wind speed was 6-8 kmph during the day. A speed of over 15-20 kmph is required for dispersion of pollutants,” said Srivastava.
System of Air Quality and Weather Forecasting And Research (SAFAR), which functions under the Union ministry of earth sciences, has stated that the AQI is likely to remain in the “very poor” to “poor” category for the next two days. “The development of strong surface-level inversion and sudden local calm surface wind conditions led to a low ventilation coefficient and accumulation of pollutants near the surface. The calm night-time surface wind condition is likely to continue for the next two days,” said SAFAR.
SAFAR observed an increase in stubble burning fires on Monday around Punjab, Haryana, and neighbouring border regions with an estimated fire count of 675. The government agency said the transport wind direction was not favourable and hence only a marginal contribution of the stubble fires to PM2.5 in the capital’s air was expected. It put the figure at 3%.
An official at Delhi Pollution Control Committee said there was a spike in pollution levels due to weather conditions and transfer of pollutants from neighbouring states.
According to Ambee, which is an environmental intelligence startup that measures, processes and analyses hyperlocal air quality data in real-time, Pooth Khurd, Chandpur, Khanjawla, Karala and Sabhapur areas in Delhi recorded highest average AQI of around 200 from October 5 to 13. While Aliganj, Lodhi Road, Kakrola, CGO Complex and Matiala recorded lowest average AQI of around 140 from October 5 to 13.



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