Delhi’s pollution levels remain in severe plus category

Gopal Rai, Delhi’s environment minister, is scheduled to hold a review meeting at 12pm on Friday to review the implementation of the measures to check the rising pollution levels

Delhi’s pollution levels remained in the severe plus category on Friday morning with an hourly Air Quality Index (AQI) of 453 at 7am. They reached this category for the first time this year on Thursday and prompted the central pollution control authority to call for a series of restrictions under category 4 of the Graded Response Action Plan such as a ban on the entry of diesel trucks and the use of older private diesel vehicles. The authority urged the government to consider shutting schools and asking offices to go for remote working.

The 24-hour average AQI clocked 450 at 4pm on Thursday. (HT PHOTO)

Gopal Rai, Delhi’s environment minister, is scheduled to hold a review meeting at 12pm on Friday to review the implementation of these measures.

An AQI between zero and 50 is considered good, 51 and 100 satisfactory, 101 and 200 moderate, 201 and 300 poor, and 301 and 400 very poor. AQI above 401 comes under the severe category and over 450 severe plus.

The 24-hour average AQI clocked 450 at 4pm on Thursday. PM2.5 and PM10 particles were the main air pollutants.

Union earth sciences ministry’s monitoring agency System of Air Quality and Weather Forecasting and Research said the air quality deteriorated significantly due to strong upper level (700-1000 m) wind blowing from stubble-burning areas towards Delhi.

“Stubble emissions with a fire count of 2994 contribute 34% to PM2.5 in Delhi. Fine particles (size < 2.5 micrometre) contribute around 66% to PM10. Local surface winds are 10 to 12 km/h for [the] next three days that cause moderate dispersion of pollutants. Low ‘Mixing layer height’ during daytime results in weak vertical mixing and accumulation of pollutants.”

It added the air quality is likely to remain within the severe category on Friday and is expected to improve to very poor levels from Saturday due to upper-level wind reversal that prevents the inflow of stubble-related pollutants. A higher surface wind speed on Saturday is likely to disperse pollutants.

The maximum temperature is expected to be 31 degrees Celsius while the minimum of 15 degrees on Friday. On Thursday, the minimum temperature was 15.8 degrees Celsius, one degree below normal, and the maximum was 31 degrees Celsius, a notch above normal.