Haze envelopes Delhi; 11 stations record ‘severe’ pollution levels

Eleven out of 40 ambient air quality stations recorded “severe” pollution levels as a haze enveloped Delhi after wind speeds dropped across the city over the weekend and slowed the dispersion of pollutants. The visibility was 2,000 metres at Palam around 3:30am, which dipped to around 1,300 metres four and a half hours later.
The Central Pollution Control Board (CPCB) data at 8am showed Anand Vihar recorded an Air Quality Index of 434 and Vivek Vihar 424 (severe). The 24-hour average AQI was 373 (very poor) at 8am on Monday compared to 382 at 4pm on Sunday, the highest this winter season, eclipsing the 364 (very poor) on October 23. The worst AQI this year was recorded on January 31—392 (very poor). Delhi’s AQI was expected to remain in a very poor zone until Wednesday as the meteorological conditions were likely to be extremely unfavourable for the dispersion of pollutants.
The CPCB classifies AQI between 0-50 as “good”, between 51 and 100 as “satisfactory”, between 101 and 200 as “moderate”, between 201 and 300 as “poor”, between 301 and 400 as “very poor”, and over 400 as “severe”.
The wind direction has transitioned from north-westerly to south-easterly, making them fairly calm. The mercury has also started dipping after a fairly warm October.
Private forecaster Skymet Weather vice president Mahesh Palawat on Sunday said a spike in pollution was expected, citing changes in direction and almost calm winds. He added the wind direction was expected to switch to south-easterly by Monday. “We can expect wind speeds to be calm overnight and below 10 km per hour during the day until Tuesday.” A slight increase in wind speed was expected from Wednesday onwards.
On Sunday, the Commission for Air Quality Management (CAQM) said it was monitoring the air quality. Graded Response Action Plan (GRAP) Stage 2 was in place in the Delhi-National Capital Region (NCR) for pollution mitigation. Stage 3 can be invoked if AQI touches “severe” or is likely to touch it. “No meeting on GRAP was held on Sunday, but officials are keeping a tab on the AQI,” said a CAQM official.
The “severe” category entails a ban on all construction and demolition activities in NCR, except for emergent or essential projects, regulated operations of industries not running on cleaner fuels to a maximum of five days per week, shutting down of brick kilns, etc, as well as a ban on mining and associated activities.
Strong winds of 10-15 km per hour even at night were favourably impacting Delhi’s AQI until Saturday. This allowed a major chunk of firecracker emissions on Thursday and Friday to almost simultaneously disperse.
Delhi’s AQI on Diwali day on Thursday was 328 (very poor). It rose marginally to 339 (very poor) the next day at 4pm. This was the second lowest AQI on the day after Diwali in the last nine years.