Delhi’s AQI settles at far end of very poor due to change in wind pattern, may turn severe by Saturday
Delhi’s air quality plunged to the far end of the ‘very poor’ zone on Friday as the wind speed and pattern changed, resulting in the slow dispersion of pollutants. At least 17 of the 35 monitoring stations had turned deep red, reaching the ‘severe’ zone on Friday.
The overall air quality index (AQI) is likely to deteriorate further over the next two days and may touch ‘severe’ by Saturday morning, government agencies have forecast.
According to the Central Pollution Control Board’s (CPCB) 4 pm bulletin, the AQI was 382, higher than 341 on Thursday. It was 373 on Wednesday. Most of the monitoring stations that are in ‘severe’ category include hot spots such as Anand Vihar, ITO, Vivek Vihar, Ashok Vihar, Bawana, Narela and Mundka, among others.
On a scale of 0-500, an AQI value between 301-400 is considered ‘very poor’ while 401-500 is ‘severe’. According to weather scientists at the India Meteorological Department (IMD), with stubble burning incidents being negligible at present, local pollutants that have accumulated in the atmosphere have not been able to disperse because of unfavourable weather conditions.
Kuldeep Srivastava, head of IMD’s regional weather forecasting centre, said the wind speed was just around 6-7 kmph during the day, which is not favourable for dispersal. “Besides, the wind direction changed to easterly from northwesterly. Whenever there is a change in wind direction, it impacts the air quality as winds turn calm for a while and do not allow dispersion. The night temperature is also below normal, which again is not favourable for dispersion. There was increased moisture because of easterly winds, which traps pollutants close to the ground, resulting in deterioration in air quality,” Srivastava said.
He said the air quality may turn ‘severe’ over the weekend and any improvement is likely only after December 7 when northwesterly winds are likely to return. “From December 7-9, there may be an improvement in air quality as winds speed is expected to remain on the higher side,” he said.
The Safdarjung Observatory, the official marker for the city’s weather, recorded a minimum temperature of 8 degrees C, a notch below normal. The maximum settled at 28.8 degrees C, four notches above normal.
The System for Air Quality and Weather Forecasting and Research (SAFAR), the union ministry’s air quality forecasting wing, said the share of stubble burning to the city’s PM 2.5 level was just 1%. “The air quality is likely to deteriorate further over the next couple of days because of reduced ventilation and increase in moisture. However, it is likely to recover around December 6-7 with the return of good wind speed,” the SAFAR bulletin stated.
According to experts, every year after peak pollution in November, which is mostly attributed to contribution from stubble burning, bad air episodes are seen towards December-end and early January. This is mainly because as compared to November, meteorological conditions are even more unfavourable during this time while the baseline pollution (local emission from Delhi and neighbouring regions) stays the same. This includes local waste burning, industrial fumes, vehicular emissions and dust suspension, among others.
The CPCB on Friday wrote to the Delhi government, asking various civic agencies to act immediately on emission from open burning of waste; improper handling of construction waste; industrial emissions; dust from unpaved roads and open spaces, which have been reported by citizens on the Centre’s Sameer app.
The letter said while stubble burning is almost over, the major sources of pollution are open dumping and burning of garbage, construction/demolition activity, unpaved roads and pits and re-suspension of road dust. “The areas of concern are hot spots, namely Narela, Anand Vihar, Mundka, Dwarka and Punjabi Bagh in Delhi and Faridabad, Jhajjar, Noida and Bhiwadi in NCR,” the letter said.
Anumita Roychowdhury, executive director (research and advocacy), Centre for Science and Environment (CSE), said an aggressive strategy is required to curb local sources of pollution to prevent these peak pollution episodes. “We have been raising it time and again that surveillance on the ground and effective monitoring are required across Delhi-NCR to reduce local emissions. The agencies across NCR have to have a combined strategy and effort to bring any real change in minimising local emissions,” she said.
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