October 25, 2020 2:37:49 am
Delhi’s air quality remained ‘very poor’ on Saturday, but on a lower level than a day earlier and is forecast to further improve by Monday, as per government agencies. The 24-hour average air quality index (AQI) of the city on Saturday was 345, lower than 366 recorded on Friday, as per data from the Central Pollution Control Board (CPCB).
AQI of neighbouring NCR towns of Noida and Gurgaon also remained in the ‘very poor’ range, but on lower levels than Friday.
At Ghaziabad, it worsened to 356 from 344 a day earlier while at Faridabad, it increased to 367 from 360 on Friday.
Clear skies during day time is helping increase solar radiation over Delhi-NCR, which slightly improved the atmospheric mixing depth on Saturday and could improve it further by Monday, as per the daily bulletin of the Ministry of Earth Sciences’ Air Quality Early Warning System (EWS) for Delhi. Mixing depth is the height available in the atmosphere for pollutants to disperse. On colder days with low sunlight and wind speed, this height reduces, which increases concentration of pollutants closer to surface. The mixing depth was predicted to be around 2,400 metres on Saturday, and is expected to increase to around 3,000 metres on Sunday and to 3,900 metres on Monday.
The EWS has forecast that AQI over Delhi-NCR will remain in the ‘very poor’ category on Sunday and could fluctuate between ‘very poor’ and ‘poor’ on Monday.
There has also been a drop in the share of pollutants from stubble burning, transported to Delhi through wind from Punjab and Haryana. The share dropped to around 9% on Saturday from an estimated 17% on Friday, as per the Central government’s System of Air Quality and Weather Forecasting and Research (SAFAR). The reduction was due to low wind speed and a change in the direction of wind, as per a report from SAFAR. As of 5 pm, two out of 34 air quality monitoring stations in Delhi were in the ‘severe’ category — AQI higher than 400 — including East Delhi’s Anand Vihar and West Delhi’s Mundka. The remaining were in the ‘very poor’ range, except Sri Aurobindo Marg and Lodhi Road, which were in ‘poor’ category.
Concentration of PM 10 and PM 2.5 — fine particles suspended in the air — were lower than Friday’s levels in Delhi-NCR, as per CPCB data. As of 6 pm, PM 10 levels were 350 µg/m3 and PM 2.5 levels were 175 µg/m3, against their 24-hour exposure limit of 100 and 60 µg/m3. The concentration of PM 10 and PM 2.5 on Friday had peaked at 380 and 200 µg/m3 around 11 am.
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