Delhi's air quality touches 'severe' category; GRAP Stage III kicks in

The blanket of haze over Delhi thickened on Friday morning with the national capital's pollution levels increasing overnight by around 50 points, taking to ‘severe’ levels with the overall air quality index (AQI) to 400 at 12:10 am.

23 of the 36 air quality monitoring stations across Delhi recorded air quality in the severe category on Saturday morning. Anand Vihar was the most-polluted area with an AQI of 450, followed by Wazirpur (444) and Shadipur (444), Punjabi Bagh (432).

Experts attribute the increase to the low temperatures and calm winds, and an increase in incidents of stubble burning in Punjab. So far this season the AQI had not touched the ‘server’ mark.

An AQI between 0-50 is considered ‘good’, 51-100 ‘satisfactory’, 101-200 'moderate’, 201-300 ‘poor’, 301-400 ‘very poor’, and 401-500 ‘severe’. Above 500 is the ‘severe-plus or emergency’ category.

The India Meteorological Department (IMD) said calm winds prevailed at night. It added that moderate wind speed (up to 8 kmph) is predicted during the day. In cold conditions, pollutants are trapped close to the ground because of low mixing height — the vertical height at which pollutants are suspended in the air.

Unusually high wind speeds have also helped disperse local emissions.

According to the Central Pollution Control Board (CPCB), the concentration of lung-damaging fine particles known as PM2.5 was above 400 micrograms per cubic metre at 10 am, around seven times the safe limit of 60 micrograms per cubic metre, in many areas.

Northwest winds from the neighbouring states of Punjab, Haryana and western Uttar Pradesh will also pick up speed gradually, carrying smoke from stubble burning into Delhi, according to the air quality forecast agency System of Air Quality and Weather Forecasting And Research (SAFAR).

This is expected to worsen air quality in the national capital. The stubble burning got postponed this season due to the delayed monsoon. But crop burning has picked up pace since Diwali and is expected to increase in the coming days.

Stubble-burning cases in the northern states have increased by 17 per cent from the previous year. A total of 13190 burning events were detected in the six states — Punjab (10214), Haryana (1701), Uttar Pradesh (632), Delhi (5), Rajasthan (190) and Madhya Pradesh (448) — from September 15 to October 28.

Residue-burning incidents saw an increase of 33 per cent in Punjab from the previous year.

According to the India Meteorological Department (IMD) forecast, the air quality is likely to deteriorate and remain in the Severe category from Monday. The outlook for the subsequent 6 days is likely to remain largely in the Severe to Very Poor category.

Commission for Air Quality Management on Saturday invoked the Stage III of the  Graded Response Action Plan (GRAP).

"Due to unfavourable meteorological conditions with slower wind speed and sudden spike in the farm fire incidents, it was considered necessary to implement Stage III of GRAP with immediate effect in the entire National Capital Region (NCR)", the CAQM said.

Under GRAP Stage III, the industries, brick kilns, the hot mix plants which are not operating on fuels, as in the standard list of approved fuels for NCR will be closed.

Stone crushers, mining and associated activities in the NCR will be shut down. State Governments in NCR/ Government of National Capital Territory of Delhi may impose restrictions on BS III petrol and BS IV diesel Light Motor Vehicles (4-wheelers).

The CAQM has also ordered the Pollution Control Boards (PCBs) of NCR and the Delhi Pollution Control Committee for implementing strict measures under the GRAP.