New Delhi, Oct 27 (PTI) Pollution levels reduced marginally in Delhi on Tuesday, even as the share of stubble-burning in the city's PM2.5 concentration rose to 23 per cent, the maximum so far this season.
A senior scientist at the India Meteorological Department (IMD) said the air quality index (AQI) is likely to improve further with the wind speed picking up.
The city recorded a 24-hour average AQI of 312 on Tuesday. It was 353 on Monday, 349 on Sunday, 345 on Saturday and 366 on Friday.
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'.
According to the Ministry of Earth Sciences' air quality monitor, SAFAR, the wind direction and speed were favourable for the transport of pollutants from the farm fires in Punjab, Haryana and other neighbouring regions.
It, however, said an improvement in the local wind speed will counter the effect.
The number of farm fires in the neighbouring states was 1,943 on Monday -- the highest so far this season -- the SAFAR said.
'Stubble-burning share in Delhi PM2.5 concentration was 23 per cent on Tuesday due to favourable transport level wind direction and speed,' it said.
It was 16 per cent on Monday, 19 per cent on Sunday and nine per cent on Saturday.
According to the IMD, the predominant wind direction was westerly-northwesterly and the maximum wind speed was 15 kilometres per hour. The minimum temperature was recorded at 14.4 degrees Celsius.
Calm winds and low temperatures trap pollutants close to the ground, while a favourable wind speed helps in their dispersal.
The AQI is likely to improve slightly on Wednesday, but the pollution levels will rise again on Thursday, the SAFAR said.
The Centre's Air Quality Early Warning System for Delhi said the city's air quality is likely to remain 'very poor' till October 31.
It said the ventilation index -- a product of mixing depth and average wind speed -- was around 11,500 square metres per second on Tuesday -- favourable for the dispersal of pollutants.
The mixing depth is the vertical height in which pollutants are suspended in the air. It reduces on cold days with a calm wind speed.
A ventilation index lower than 6,000 sq.mtr per second with an average wind speed of less than 10 kmph is unfavourable for the dispersal of pollutants.
Earlier in the day, Environment Minister Gopal Rai said Chief Minister Arvind Kejriwal will launch the 'Green Delhi' mobile application on Thursday, using which citizens can bring pollution-causing activities to the government's notice.
There will be a deadline to address the complaints and the chief minister will get a daily report about the resolved and pending grievances.
This year, the Delhi government has launched a massive anti-air pollution campaign -- 'Yuddh Pradushan Ke Viruddh' -- which is being led by Kejriwal and Rai.
A 'green war room' has also been set up at the Delhi Secretariat to monitor the steps being taken to bring down pollution levels in the city this winter.
A 10-member team has been deployed under senior scientists Mohan George and B L Chawla to monitor the levels of primary pollutants, the measures taken to curb pollution and the status of the complaints received through the 'Green Delhi' mobile application.
Severe air pollution is a year-round problem in Delhi, which can be attributed to unfavourable meteorological conditions, farm fires in the neighbouring regions and local sources of pollution.
The Centre told the Supreme Court on Monday that it will bring a legislation to curb air pollution in Delhi-NCR.
According to an analysis by the Council on Energy, Environment and Water, a Delhi-based think tank, transportation contributes the most -- 18 to 39 per cent -- to the city's air pollution.
Road dust is the second-largest source of air pollution in the city (18 to 38 per cent), followed by industries (two to 29 per cent), thermal power plants (three to 11 per cent) and construction (eight per cent). PTI GVS RC