Delhi’s AQI remains in ‘very poor’ category; no respite till Oct 25

Stage-3 — the next stage of GRAP can be implemented if forecasts show ‘severe’ air ahead, with the AQI likely to cross 400

Delhi’s air quality continued to deteriorate as the air quality index (AQI) in the national Capital hovered around 359 (very poor) category on Wednesday morning.

The most polluted stations include Anand Vihar (401), Jahangirpuri (418) and Vivek Vihar (404). (PTI photo)

The AQI is a rise from Tuesday’s 4pm average AQI of 327 (very poor).

According to data from the Centre’s Decision Support System, a combination of calm surface winds, low temperature, local pollution and incursion of stubble emissions to Delhi through north-northwesterly winds has led to further deterioration in the past 24 hours.

The Centre’s Decision Support System, which estimates the contribution of different sources to Delhi’s PM (particulate matter) 2.5, said the estimated contribution from stubble burning on Wednesday should be around 11.1%, with this rising even further to 15.1% on Thursday as wind direction pre-dominantly remains northwesterly.

In comparison, the estimated contribution on Tuesday was 3.5% with the wind direction pre-dominantly southeasterly. Northwesterly winds facilitate the transport of stubble emissions in Punjab and Haryana towards the capital, where if surface winds are calm, it can accumulate over the capital.

The Central Pollution Control Board (CPCB) data showed the average AQI was calculated based on 30 out of the 40 ambient air quality monitoring stations in the city, with three of these in the ‘severe’ range this morning.

The most polluted stations include Anand Vihar (401), Jahangirpuri (418) and Vivek Vihar (404).

Barring Chandni Chowk and Dilshad Garden, which were in the ‘poor’ category, the remaining 25 stations were all in the ‘very poor’ range.

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”.

Stage-2 of the Graded Response Action Plan (GRAP) was announced by the Commission for Air Quality Management (CAQM) on Monday, when Delhi’s AQI touched ‘very poor’ for the first time since June 19.

Stage-3 — the next stage of GRAP can be implemented if forecasts show ‘severe’ air ahead, with the AQI likely to cross 400.

Centre’s Early Warning System (EWS) for Delhi showed this was unlikely immediately, with the AQI expected to remain ‘very poor’ till October 25, with the air quality then hovering between ‘poor’ and ‘very poor’ in the subsequent six days.

Delhi’s minimum temperature was 20.5°C on Wednesday, which is three degrees above normal. It was 20.4°C a day earlier. The return of cooler northwesterly winds is expected to bring down the night time temperature again, with this likely to touch around 18°C by October 26, the IMD said. Delhi’s maximum was 34°C on Tuesday and is forecast to hover around the 35°C mark today.