Delhi’s air quality improves but still ‘severe’, PM content below emergency mark

On Friday morning, at around 8am, the Air Quality Index — a measure of pollutants in the air — had come down to 418 after having shot up to 469 on Thursday.

delhi Updated: Dec 22, 2017 09:50 IST
HT Correspondent
HT Correspondent
Hindustan Times
Delhi air quality,Delhi pollution,Delhi AQI
As the sun came out and the winds picked up speed in Delhi, visibility also showed signs of improvement. (Sushil Kumar/HT FILE)

The air quality of Delhi showed improvement on Friday morning, even though pollution levels were still in ‘severe’ zone. Experts said conditions are likely to improve further during the day.

On Friday morning, at around 8am, the Air Quality Index — a measure of pollutants in the air — had come down to 418 after having shot up to 469 on Thursday. An AQI value above 400 on a scale of 0 – 500 is interpreted as ‘severe’ pollution.

The levels of particulate matter — PM10 and PM2.5 — also saw significant improvement.

The concentration of PM10 in the air dropped to 386ug/m3 at around 8am on Friday from around 499ug/m3 around 1pm on Thursday. The level of PM2.5 also dropped from 321ug/m3 to 239ug/m3 around the same time. If PM10 and PM2.5 hits 500 and 300 it is considered as ‘emergency’.

“Concentration of particulate matter is now out of ‘emergency’ zone. It is likely to improve further during the day,” said D Saha head of the air quality laboratory at CPCB, the country’s apex pollution monitoring body.

Experts said the improvement in air quality was primarily because the wind was gathering speed. The velocity of wind had dropped from 15km/hour on Sunday to around 3km/hour on Thursday morning. On Friday morning at around 5.30am the wind was blowing at a speed of 10km per hour.

As the sun came out and the winds picked up speed, visibility also showed signs of improvement. At Safdarjung, visibility improved from around 500m at 5.30am to around 700m at 8.30am. At Palam, the visibility, which had dropped to around 350m at 5.30am, improved to 400m at 8.30am.

Delhi’s air quality had plunged to ‘severe’ zone on Thursday after a gap of over a month. The last time the National Capital witnessed such foul air was on November 13.

Delhi had witnessed around six days of ‘severe’ pollution in December 2016. In December 2015, however, there were no severe days of pollution.

As the air quality deteriorated throughout Thursday a CPCB-led task force recommended the closure of all coal-based industries operating in Delhi-NCR for a fortnight from January 15 to contain air pollution during the upcoming ASEAN summit. The Supreme Court-mandated panel EPCA also directed the states in the region to gear up for another round of action under the ‘emergency’ category.

Emergency measures such as shutting down of schools, ban on construction activities and rolling out of odd-even road rationing are enforced if the levels of PM10 and PM2.5 stay above 500 and 300, respectively, for at least two consecutive days.

First Published: Dec 22, 2017 09:49 IST