Delhi's air quality deteriorates to 'poor' category

Delhi's air quality slipped back into the poor category on Saturday, a day after favourable wind speed helped it improve significantly.

With winds slowing down, government agencies said the air quality is likely to deteriorate further .

The city's 24-hour average air quality index (AQI) was 231 on Saturday. It was 137 on Friday, 302 on Thursday and 413 on Wednesday.

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'.

Stronger winds and a drastic reduction in the contribution of stubble burning were two major reasons for cleaner skies over Delhi on Friday. However, the winds slowed down at night allowing the pollutants to accumulate.

The maximum wind speed was 15 kmph on Saturday. It is likely to be eight to 12 kmph on Sunday and Monday, according to the India Meteorological Department.

The share of stubble burning in Delhi's pollution has also reduced significantly as the harvesting season has ended.

The contribution of stubble burning in neighbouring states to Delhi's PM2.5 levels was 4 per cent on Saturday, 2 per cent on Friday and just 1 per cent on Thursday, according to the Ministry of Earth Sciences' air quality monitor, SAFAR.

Winds are predicted to slow down on Sunday. Therefore, Delhi's air quality is likely to deteriorate further and remain in the 'poor' to 'very poor' category over the next two days, it said.

The minimum temperature in the national capital was 10.1 degrees Celsius on Saturday and the maximum 26.4 degrees Celsius, the weather department said.