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After a very short breather, Delhi and NCR on Sunday saw a considerable dip in the air quality, which was back under 'severe' category at several places, while pollution levels at some places during morning hours were 12 to 19 times the permissible limit.
According to the Central Pollution Control Board, on Sunday, the Air Quality Index (AQI) at Uttar Pradesh's Ghaziabad, and Noida was 439 (396 on Sat) and 423 (365 on Sat) respectively, while at Rajasthan's Bhiwadi it was 407 (369 on Sat), all considered "severe".
Delhi's air quality was placed under "very poor" category with AQI recorded at 368 against 351 on Saturday. Meanwhile, at Haryana's Gurugram, AQI was 345 against 338 on Saturday and Faridabad had an AQI of 334 against 338 on Saturday.
Delhi also saw, due to several meteorological reasons, a shoot in the major air pollutant PM2.5, or particles with diameter less than 2.5 mm, around the morning hours with volume ranging 12 to 19 times the permissible limits at several places.
Meanwhile, the satellite images from NASA's FIRMS web Fire Mapper showed a slight hike in the stubble burning in neighbouring Punjab and Haryana, where farmers are trying to make up for the small window between summers and winters crops. As the wind direction changed on Sunday, the fine particles are being carried from Punjab and Haryana.
According to the data from Delhi Pollution Control Committee, PM2.5 ranged between 317 to 492 microgramme per cubic metre at different locations between 10 am to 11.30 pm.
The permissible range for PM2.5 is 60 as per national standards and 25 by the international standards.
The worst PM2.5 situation was at Anand Vihar in east Delhi, ranging highest between 410 and 492 between 10 to 11.30 am.
Mandir Marg in central Delhi saw PM2.5 peaking up at 339 at 10 a.m., while in Punjabi Bagh in west Delhi, it was at 372 and the level ranged between 224 to 317 from 9 am to 11.30 am at R. K Puram in south Delhi.
The air quality improved slightly from 1 p.m. onwards, but PM2.5 levels was still four to seven times over the safe limit, ranging between 123 to 184 at 17 different areas across Delhi.
According to the weather analysts, the sudden drop in air quality could be due to sudden change in the wind directions, as the north-westerly winds from neighbouring Punjab and Haryana started entering Delhi again, changing from earlier short-spanned south-easterly winds.
"The speed of the winds is about 10 kmph. However, this time, north-westerly winds shall be short spanned," Mahesh Palawat, director of private weather analyst Skymet told IANS. Sunday also saw a slight dip in the minimum temperature over past 24 hours.