Delhi air quality improves; Review of curbs on vehicles, constructions likely

The Commission for Air Quality Management (CAQM) in NCR will be holding a meeting on Sunday where restrictions imposed in the city are likely to be reviewed

Delhi’s air quality improved further on Sunday, according to a bulletin issued by the Central Pollution Control Board (CPCB), prompting the authorities concerned to call a meeting later in the day where restrictions imposed on vehicles and construction work in the city are likely to be reviewed.

The air quality index (AQI) for Delhi will improve further on Sunday but will remain in the ‘very poor’ category until Tuesday. (PTI)

The city’s air quality index (AQI) dipped to 348 (very poor) at 9am on Sunday from Saturday’s 4pm reading of 381 (very poor), according to CPCB’s national bulletin. Delhi’s AQI returned to the ‘very poor’ category from ‘severe’ on Saturday, on the back of a change in wind direction to southeasterly, while local winds speeds also picked up.

The Commission for Air Quality Management (CAQM) in NCR, which imposed Stage IV measures of the Graded Response Action Plan (Grap) on Thursday evening, will be holding a meeting later in the day, where restrictions imposed in the city are likely to be reviewed, officials said.

The curbs under Stage IV of Grap has banned all diesel Light Motor Vehicles (LMVs) that are not BS VI in Delhi and its bordering NCR districts and prohibited truck from entering Delhi.

BS or Bharat Stage emission norms are the equivalent of the European emission standards for vehicle. BS VI norms came into force from 2020 onwards, while BS IV had been the standard for vehicles since 2010. BS VI norms are more stringent, thus allowing vehicles meeting these norms to continue to ply in the region, despite being diesel.

There is also a ban on plying of all Medium Goods Vehicles (MGV) and Heavy Goods Vehicles (HGV) in the Capital that are not essential or emergency service vehicles. Under this category, all linear construction projects such as highways, roads and flyovers have also been stopped.

While states had been given suggestions under Stage IV to look at closing schools temporarily and look at ‘work from home’ for private and government offices, these closures are likely to be lifted only by the state government, if deemed necessary. In Delhi, primary schools have been closed until Tuesday and it is likely that no further restrictions on schools will be imposed after that, keeping in view the forecast, which states AQI will largely remain in ‘very poor’ and not ‘severe’.

Prior to Saturday, the wind direction had been northwesterly, which means it was bringing stubble emissions directly to the capital. The contribution of farm fires to Delhi’s PM 2.5 levels on Thursday was 34% -- a season high. It dropped to 30% on Friday, while it was 21% on Saturday. This is expected to dip further today, owing to a wind direction largely switching between northeasterly and southeasterly.

“The other factor has been local wind speed. Till Friday, it was calm at night and 5-8 km/hr during the day. On Saturday, we saw it increase to 18 km/hr and that allowed some dispersion. Similar wind speed is expected throughout Sunday and the review has therefore been planned in the wake of improving AQI, to decide whether Stage IV measures need to remain or not,” said V.K Soni, scientist at IMD and part of the CAQM sub-committee on Grap.

As per the Early Warning System (EWS) for Delhi – a pollution forecasting model developed by the Ministry of Earth Sciences and the Indian Institute of Tropical Meteorology, Delhi’s AQI is likely to remain in the ‘very poor’ category until Tuesday now.

“On Sunday, the AQI will improve further but remain in the ‘very poor’ category until Tuesday. The outlook for the subsequent six days, shows the AQI will largely stay ‘very poor’.” said the EWS forecast issued on Saturday evening.

On Thursday, Delhi recorded its worst AQI of the year, when it was 450 (severe) at 4pm. On Friday, it was 447 (severe); with the current drop a significant improvement from that peak.

The change in wind direction to southeasterly, has also meant Delhi’s minimum temperature has risen over the last 48 hours and was recorded at 17.5 degree Celsius this morning – three degrees above normal. It was 17.4 degrees on Saturday. In terms of the maximum, IMD forecasts show Delhi is likely to have a high of around 30 degree Celsius.