New Delhi, Nov 9 (PTI) Delhi's air quality slipped to the "severe" category again on Tuesday with stubble burning accounting for 27 per cent of its PM2.5 pollution, authorities said.
Low temperature -- Delhi recorded a minimum of 13.5 degrees Celsius on Tuesday, the season's lowest so far -- allowed accumulation of pollutants, said Mahesh Palawat, vice president (meteorology and climate change), Skymet Weather.
The minimum temperature is expected to dip to 10 degrees by November 15, the India Meteorological Department said.
According to the Central Pollution Control Board, Delhi's 24-hourly average air quality index stood at 404 at 4 pm, up from 390 on Monday.
An AQI between zero 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".
The share of farm fires in Delhi's pollution rose to a three-year high of 48 per cent on Sunday.
On Monday, government agencies reported 5,450 farm fires, the highest this season, in neighbouring states of the national capital.
Palawat said the share of stubble burning in Delhi-NCR's air pollution is expected to remain high for another week.
"No major improvement in air quality is likely in the next four to five days," he said.
Delhi recorded "severe" air quality for three days on the trot till Sunday due to accumulation of emissions from fireworks on Diwali and stubble burning amid unfavourable meteorological conditions -- low temperature, wind speed and mixing height.
Last year, the share of stubble burning in Delhi's pollution had peaked at 42 per cent on November 5.
In 2019, crop residue burning accounted for 44 per cent of Delhi's PM2.5 pollution on November 1.
