With a change in wind direction and accumulation of pollutants after effigies were burnt on Dussehra, Delhi’s air quality nosedived to ‘poor’ Thursday. Over the next two days, air quality is expected to dip further.
The Air Quality Index (AQI) value was recorded at 211, with primary pollutants being PM 2.5 and PM 10. Over the past three months, air quality in the city has oscillated between ‘satisfactory’ and ‘moderate’.
Senior IMD officials said the wind direction had changed and more pollutants were being carried into the city from the North West, where seasonal crop stubble burning is underway against efforts from the Punjab and Haryana governments.
Officials at SAFAR said that among the reasons for the dip was the retreating South West monsoon. During the monsoon season, moisture-laden winds from Eastern India pass through Delhi. As monsoon retreats, the pattern changes to westerly winds, which, at this time of the year, bring pollutants to the city. Calm local winds also aid accumulation of particulate matter.
While Delhi has performed better on pollution indices this year, winter will remain a challenge. Unfavourable weather conditions and events such as stubble burning and Diwali will impact air quality. At the same time, local pollution sources such as vehicles and dust also need to be controlled. The Delhi government has decided to implement the odd-even scheme between November 4 and 15 and is looking to stagger work timings. Ban on open burning, covering construction material will also help reduce pollution.
“Wind speed continues to be slow and variable with predominant direction from the west. Under these conditions, air quality is predicted to deteriorate… Indications of increased fire activity during the last 48 hours are visible from satellite imagery and further deterioration of AQI is expected for the next two days,” a statement issued by SAFAR said.
Monsoon began retreating Wednesday after the longest recorded delay. The retreat at this time is also going to impact the air quality negatively.
“Conditions are becoming favourable for further withdrawal from parts of North West India and adjoining Central India during the next four-five days. Late monsoon withdrawal is not good for air quality in North India. During the third and fourth week of October, temperature will also start to drop… The anticyclone… will make the atmosphere very stable with significantly calm surface winds. Both will lead to stagnant weather conditions which favour rapid fine particulate matter formation and accumulation of pollutants. The situation becomes bad if it is encountered with any additional internal (like firecrackers) or external (like stubble) emission source,” SAFAR officials said.
Delhi has managed to clean its air significantly as compared to seven years ago, data shows. This September was the cleanest in nine years.