The air quality in Delhi has been recorded to score high on the ‘severe’ category on Saturday and ‘very poor’ on Sunday. Slow wind speed resulted in the accumulation of “locally-generated” pollutants, according to officials of the India Meteorological Department (IMD). The situation is likely to improve in the next couple of days due to a predicted increase in wind speed.
At 9 a.m. on Saturday, Delhi’s Air Quality Index (AQI) was recorded at 394. The 24-hour average for that day was 404, which come under the severe category. It deteriorated prominently from the previous days as the AQI was recorded at 382 on Friday, 341 on Thursday, 373 on Wednesday, 367 on Tuesday, 318 on Monday and 268 on Sunday.
The situation is worse in the neighbouring cities of Ghaziabad (AQI 430), Greater Noida (404) and Noida (404), which remained in the severe zone.
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 slow wind speed had allowed the accumulation of pollutants generated locally, according to V K Soni, the head of IMD’s environmental research centre. “Easterly winds carrying moisture also led to the formation of secondary particulate matter. All these factors together pushed the air quality in the ‘severe’ zone,” he said. However, he has also said that the situation is likely to improve by Monday, getting the air quality into the poor category caused by an increase in the wind speed.
The maximum wind speed is expected to be 8 kmph on Sunday and 15 kmph on the next day, according to IMD. On Sunday, the minimum temperature was recorded at 11.4 degrees Celsius while the maximum is likely to settle around 28 degrees Celsius, the weather department said. Pollutants get trapped close to the ground due to calm winds and low temperatures, and favourable wind speed helps in their dispersion.
The lead pollutant remains to be PM 2.5 instead of PM10 due to the winter weather. The contribution of stubble burning by neighbouring states to PM 2.5 was estimated to be only 1% on Saturday. The fire count in neighbouring states was also recorded at just 296, according to System of Air Quality and Weather Forecasting And Research (SAFAR).
“The overall air quality in Delhi has deteriorated as forecast from Friday’s condition. Surface-level winds are calm. Boundary layer wind direction is not favourable for stubble fire-related transport. A stubble fire count from SAFAR-multi-satellite products is around 302 and % share is negligible. Air quality is likely to improve marginally by Saturday evening within the higher end of very poor category owing to calm wind condition. AQI is likely to marginally improve further on 6th and 7th December due to better ventilation,” the SAFAR prediction said.