This story is from October 30, 2020

Red alert: Delhi’s first brush with severe air this winter

Air quality in the capital entered the ‘severe’ range for the first time this winter season, with an AQI of 401 in the early hours of Thursday before returning to the ‘very poor’ category in the evening.
Red alert: Delhi’s first brush with severe air this winter
The capital has, so far, recorded two ‘severe’ days this year — January 1 and January 2 (File photo)
NEW DELHI: Air quality in the capital entered the ‘severe’ range for the first time this winter season, with an AQI of 401 in the early hours of Thursday before returning to the ‘very poor’ category in the evening.
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Delhi recorded an overall AQI of 395 (very poor), according to CPCB’s daily bulletin on Thursday evening, even as 16 out of 36 stations turned ‘severe’ on Thursday morning.
This is the highest AQI recorded this year since January 2, when the AQI touched 417 (severe).
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Delhi’s air quality had touched ‘poor’ with an AQI of 297 on Wednesday, and rose close to 100 AQI points in 24 hours. A mix of factors, including a drop in wind speed, a drop in temperature and an increase in the share of stubble burning to a season-high (36%), has led to a sharp increase in AQI over the last 24 hours. However, agencies forecast improvement for Friday with wind speeds expected to pick up once again.
Kuldeep Srivastava, scientist at IMD, said wind speed was close to ‘nil’ for the first half of Thursday, increasing to around 5 km/hr by the evening. “A combination of low temperature — the lowest so far this season — and calm wind conditions trapped pollutants locally. But this is expected to change from Friday,” said Srivastava, who says wind speed could touch 12 km/hr on Friday and average around 15 km/hr on Saturday and Sunday.

According to the System of Air Quality and Weather Forecasting Centre (SAFAR), another key factor in the spike in pollution in the region is stubble burning. It touched a season-high of 36% in terms of contribution to Delhi’s PM2.5 concentration. Last year, the highest it had touched in a single day was 44%.
CPCB data showed the stations which were in the ‘severe’ category on Thursday morning are Alipur, Shadipur, two stations in Dwarka, ITO, Punjabi Bagh, Patparganj, Sonia Vihar, Jahangirpuri, Rohini, Vivek Vihar, Narela, Wazirpur, Bawana, Mundka and Anand Vihar. At 10 am, the highest AQI was recorded at Bawana (437), followed by Wazirpur (436), Jahangirpuri (434) and Anand Vihar (433).
An AQI between 201 and 300 is classified as ‘poor’ by the CPCB, between 301 and 400 as ‘very poor’ and beyond 400 is ‘severe’ on CPCB’s index.
Data according to CPCB’s central control room showed that Delhi-NCR’s average PM2.5 and PM10 levels hovered around four times the set standards.
The 24-hour average for PM10 was recorded at 405.9 micrograms per cubic metres at 6pm on Thursday, while the 24-hour average PM2.5 levels were recorded at 224.4 micrograms per cubic metres at 6pm. The standards for PM10 and PM2.5 are 100 and 60 micrograms per cubic metres, respectively.
The capital has, so far, recorded two ‘severe’ days this year — January 1 and January 2. While the AQI on January 1 was 437, it was recorded at 417 on January 2. Since then, the AQI has remained below the 400 mark.
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