Delhi's air quality 'very poor', likely to improve over next 2 days

air quality in Delhi-NCR region recorded a marginal improvement but remained in “very poor” category on Saturday as stubble burning incidents were "unusually high", while a government forecasting ncy said it is likely to get better due to favorable wind speed in coming days.

national capital recorded a 24-hour aver air quality index (AQI) of 367. It was 374 on Friday, 395 on Thursday, 297 on Wednesday, 312 on Tuesday, and 353 on Monday.

An AQI between 0 and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate',201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.

aver 24-hour AQI was 368 in Greater ida, 363 in Ghaziab, 358 in Gurgaon, 356 in ida and 348 in Faridab, according to CPCB's Sameer app at 4 pm on Saturday.

It was 394 in Greater ida, 382 in Ghaziab, 379 in ida, 367 in Gurgaon, 337 in Faridab on Friday.

concentration of major air pollutants PM 2.5 and PM 10 also remained high in five immediate neighbours of Delhi, according to air quality index (AQI) maintained by Central Pollution Control Board (CPCB).

On Thursday, Delhi's air quality index (AQI) touched “severe” levels for a brief period before slipping back into “very poor” category.

According to Ministry of Earth Sciences' air quality monitoring ncy, SAFAR, share of stubble burning in Delhi's PM2.5 pollution was 32 percent on Saturday.

It was 19 percent on Friday, 36 percent on Thursday -- maximum so far this season, 18 percent on Wednesday, 23 percent on Tuesday, 16 percent on Monday and 19 percent on Sunday.

According to central government's Air Quality Early Warning System for Delhi, fire count increased to an “unusual” high on Friday over Punjab (approx 4,266), Haryana (155), Uttar Presh (51) and Mhya Presh (381) which is likely to impact air quality in Delhi-NCR and or parts of rthwest India.

SAFAR said Delhi's AQI did t improve much despite better ventilation, mainly because of highly favourable rth-rthwesterly boundary level wind direction and perfect wind speed for intrusion of pollutants from farm fires in Delhi.

“Increased local surface wind speed with faster dispersion conditions are counteracting with increased fire-related emission and associated intrusion. But still, AQI is likely to improve for next two days as dispersion will eventually play a le role,” it said.

According to India Meteorological Department, predominant wind direction was rthwesterly and maximum wind speed was 15 kilometers per hour. minimum temperature was recorded at 13 degrees Celsius.

Calm winds and low temperatures trap pollutants close to ground, while favorable wind speed helps in ir dispersion.

city's ventilation index – a product of mixing depth and aver wind speed – was around 9,000 meter square per second on Saturday – favorable for dispersion of pollutants.

Mixing depth is vertical height in which pollutants are suspended in air. It reduces on cold days with calm wind speed.

A ventilation index lower than 6,000 sqm/second, with aver wind speed less than 10 kmph, is unfavourable for dispersal of pollutants.