The air quality in Delhi-NCR (National Capital Region) dipped to "very poor" on Tuesday for the first time since the coronavirus lockdown was imposed in March.
The air quality in the region usually worsens this time of year due to stubble burning by farmers in neighboring states.
However, government scientists said farm fires are contributing little to Delhi's pollution currently.
Several air monitoring stations across Delhi recorded PM2.5 levels five times above the prescribed daily standards and PM10 levels over twice the standard limit.
Monitoring stations at Delhi's Shadipur, Rohini, ITO, Punjabi Bagh, Mathura Road, Nehru Nagar, Pusa, Dwarka Sector 8, Patparganj, Ashok Vihar, Sonia Vihar, Jahagirpuri, Vivek Vihar, Narela, Bawana, and Mundka recorded 'very poor' air quality.
Delhi recorded an AQI (Air Quality Index) of 304 at 9:30 am on Tuesday, which falls in the "very poor" category. The 24-hour average AQI was 261 on Monday, the worst since February this year. It was 216 on Sunday and 221 on Saturday.
Usually, Delhi's poor air quality ahead of winter is attributed to stubble burning.
However, farm fires currently account for less than 10% of the pollution in the capital, government scientists who issue air quality forecasts told News18.
The share of pollution due to farm fires is expected to rise soon since the peak period of stubble burning is around the corner, the scientists noted.
Sachin Ghude, a scientist at the Pune-based Indian Institute of Tropical Meteorology, told News18, "We run two models of the pollution load in North India, one that is fed data of farm fires along with local pollution and another model that reflects the pollution load without farm fires data. This showed that the share of local sources was dominant as of now."
According to SAFAR (System of Air Quality and Weather Forecasting And Research), the recent spike in pollution in the NCR is due to an unprecedented weather situation involving a strong surface level inversion that traps pollutants closer to the ground.
Coupled with the sudden calmness in surface winds, this phenomenon has led to the accumulation of pollutants in Delhi.
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