Delhi’s air on Sunday was the dirtiest this year with the air quality index at 450, in the “severe” zone — worse than the post-Diwali period, when the AQI had a high of 423 two days after the festival.
NCR fared no better as Faridabad clocked 444, Ghaziabad 478, Greater Noida 457 and Noida 466, as the cold wave sweeping the region took a toll on air quality. Gurugram, surprisingly, recorded a much cleaner AQI, 300, which is classified as “poor”.
Monday is expected to be another “severe” air day in the region, according to the System of Air Quality and Weather Forecasting and Research. “Severe” (401-500) corresponds to the highest level of pollution on the 500-point AQI scale. If such levels persist for 48 hours, measures listed under “severe plus” or “emergency” category are rolled out under the Graded Response Action Plan (GRAP).
“Air quality over Delhi is in severe plus zone and it is expected to remain in severe range until tomorrow morning and thereafter improve slowly and may touch very poor range. There is a significant fall in temperature which has brought down the boundary layer considerably with huge amount of moisture beneath,” said SAFAR, in its daily pollution analysis.
Under these conditions, pollutants from local sources remain trapped very close to the surface.
3.7°C: Chilliest Dec morning in 4 years, month in line to be coldest since 2005
Delhiites woke up to the chilliest December morning in four years as the temperature dipped to 3.7 degrees Celsius on the fourth day of the cold wave sweeping across north India. This month is heading to be the coldest December in 13 years, with the average minimum temperature so far at 1 degree C below normal, reports Amit Bhattacharya. The chilly conditions are expected to persist till New Year, the Met office said. The mercury touched freezing point (0 degree C) at Muzaffarnagar in western UP. P 4
Don’t expect relief from ‘severe’ air anytime soon
According to experts, the height of the inversion layer — below which the lowest layer of air lies —continues to decline, preventing the vertical mixing of pollutants. This is trapping pollutants close to the surface, leading to a spike in pollution.
“Due to this, radiation fog is developing locally which increases the share of finer particles like PM2.5 significantly in PM10. The levels of gaseous pollutant has also increased to moderate due to advection activity,” it stated.
A senior CPCB official said it was the most polluted day of the season yet and pollution levels are expected to remain in the severe range in the next couple of days, if not worse.
CPCB’s central control room data showed Delhi-NCR’s average PM2.5 and PM10 readings to be more than five times the safe standard on Sunday. While the average PM2.5 readings at 7pm were recorded at 377 micrograms per cubic metre, the average PM10 readings at the same time were 548.6 micrograms per cubic metre. The safe standard for these particulates is 60 and 100 micrograms per cubic metres, respectively.
Under the Graded Response Action Plan, pollution is considered “severe plus” or “emergency” when readings of ultrafine particulates PM2.5 or PM10 are above 300 and 500 ug/m3, respectively.