New Delhi:
Delhi’s air quality remained very poor on Tuesday and is predicted to turn “severe” this week due to unfavorable meteorological conditions.
The city’s 24-hour average air quality index (AQI) was 367. It was 318 on Monday and 268 on Sunday, according to the India Meteorological Department.
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 maximum wind speed was 8 kmph on Tuesday and is expected to be 10 kmph on Wednesday, the IMD said.
The minimum temperature was 8.1 degrees Celsius on Tuesday and the maximum 27.2 degrees Celsius, it said.
Calm winds and low temperatures trap pollutants close to the ground, while favourable wind speed helps in their dispersion.
The central government’s Air Quality Early Warning System for Delhi said air quality is likely to remain in the upper end of the “very poor” category due to unfavorable meteorological conditions.
There is a possibility of the air quality reaching the “severe” category between December 4 and December 7, it said.
The city’s ventilation index — a product of mixing depth and average wind speed was 2,500 m2/s on Tuesday.
Mixing depth is the vertical height in which pollutants are suspended in the air. It reduces on cold days with calm wind speed.
A ventilation index lower than 6,000 sqm/second, with the average wind speed less than 10 kmph, is unfavourable for dispersal of pollutants.
The contribution of stubble burning in neighbouring states to Delhi’s PM2.5 levels was 4 percent on Tuesday, 7 percent on Monday and 6 percent on Sunday, according to the Ministry of Earth Sciences’ air quality monitor, SAFAR.
