Delhi's air quality Saturday fell under 'very poor' category from Friday's 'severe' levels after local pollutants "reduced significantly" and the contribution from stubble burning remained "marginal" due to wind speed, authorities said.
The overall air quality index (AQI) was recorded at 394 which falls in the 'very poor' category, according to the data by the Central Pollution Control Board.
Fifteen areas in Delhi recorded 'severe' air quality while 19 areas recorded 'very poor' pollution levels, it said.
On Saturday, the PM2.5 (particles in the air with a diameter of less than 2.5 micrometres) level was recorded at 226, while the PM10 (particles in the air with a diameter of less than 10 micrometres) was recorded at 331 in Delhi.
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".
"The overall air quality index of Delhi has improved and is likely to go back to 'very poor' range against all odds and averse weather conditions," Centre-run System of Air Quality and Weather Forecasting (SAFAR) said.
"The unfavourable weather was to make dispersion very slow and could have aggravated pollution levels due to locally generated pollutants, but as the influx of fresh local emission significantly dropped and allowed already accumulated pollution to disperse slowly, the air quality improved," it said.
Authorities also said control measures also helped in improving the air quality of the national capital.
Stubble burning in neighbouring states on Thursday was the "largest-ever recorded" this year which might lead to a further deterioration in the already "severe" air quality of the national capital, a government-run agency had said Friday.
According to the Indian Institute of Tropical Meteorology (IITM), 2,100 fire counts were observed on Thursday over north western region of India.
"It was the largest-ever recorded for this year. It was around four times higher than Wednesday," IITM said.
"The PM2.5 concentration is likely to increase again from Friday afternoon and may remain 'severe' or 'severe-plus' in Delhi-NCR till Sunday," it said.
But due to slow winds from the direction of stubble burning areas, the contribution of stubble fire emissions remained marginal.
The air quality in Delhi has been 'severe' for the past two days with the highest pollution level of the year recorded a day after Diwali on Thursday at an AQI of 642.
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