New Delhi:
The national capital’s air quality remained “very poor” on Friday but no drastic decline is expected in the next three days as strong winds are likely to blow in the region.
The city’s overall air quality index (AQI) read 330 at 4 pm. It decreased to 320 at 8 pm.
Air quality in the satellite towns of Faridabad (337), Ghaziabad (355), Greater Noida (367) and Gurgaon (306) remained ‘very poor’.
An AQI between 201 and 300 is ‘poor’, 301-400 ‘very poor’ and 401-500 ‘severe’. An AQI above 500 falls in the ‘severe plus’ category.
After a brief relief, the city’s air quality plunged to the ‘very poor’ category again because of high humidity due to light rains on Thursday.
“Isolated drizzle, cloudy weather and calm winds prevented boundary layer growth and led to the accumulation of local emissions (on Thursday),” the government’s air quality monitoring and forecasting service SAFAR said.
Delhi experienced “slight secondary particulate formation in the early hours (on Friday) but (it) could not multiply much”.
Secondary particles are products of complicated atmospheric reactions between primary particles, such as particulate matter, sulphur dioxide and nitrogen dioxide directly emitted by stubble burning and vehicles, in the presence of other factors such as sunlight and moisture.
Examples of secondary particles include sulphates, nitrates, ozone and organic aerosols.
Weather experts said pollution levels will come down gradually over the next two days with winds picking up pace.
The wind direction will change to northwesterly and stubble plume intrusion is expected on Saturday, SAFAR said.
Though the predicted wind direction is favourable for fire plume transport, strong winds, favourable for efficient ventilation, are likely to blow in the region in the next three days, it said.
According to SAFAR data, the share of stubble burning in Delhi’s PM2.5 pollution was just 2 percent on Thursday and 3 percent on Friday.
“The surface and boundary-layer winds are from the southeast and stubble fire contribution was negligible,” it said.
The effective biomass fire count observed on November 7 was 200. It should be noted that Punjab and Haryana were under a heavy cloud cover; and satellite’s capability to detect fires reduces in such a situation, SAFAR said.
Smoke from crop residue burning is expected to account for 8 per cent of Delhi’s PM2.5 concentration on Saturday.
Meanwhile, Delhi Chief Secretary Vijay Kumar Dev on Friday directed various implementing agencies to check encroachments on major traffic corridors, remove construction and demolition (C&D) waste, and close down polluting industries by November 13.
The directions follow the Supreme Court’s recent orders asking various agencies to control factors contributing to pollution in Delhi such as open dumping of waste, garbage burning, unpaved roads, road dust and traffic congestion.
In an order to all the agencies, the chief secretary also marked the officers responsible for each task.
“In case of non-compliance, the HODs/nodal officers will be held personally responsible and appropriate action will be taken against them,” the order read.
