Explained: Why Delhi's Air Remains Toxic Despite Drop In Farm Fire Cases

Delhi is covered in a thick layer of smog as the air quality remains in the 'Severe' category. Despite a drop in cases of stubble-burning in Punjab and Haryana, which is seen as a contributor to Delhi's poor air quality, the AQI is still hovering in the 'Severe' category.

IIT Kanpur, IIT Delhi and The Energy and Resources Institute (TERI) have formulated a real-time source apportionment and forecasting for advanced air pollution management in Delhi. The real-time index calculates the sources of air pollution to help understand the major contributors behind the national capital's worsening air quality.

A three-day data of PM 2.5 or Particulate Matter 2.5, is being considered for reference to understand the major contributors to air pollution in the national capital. PM2.5 pollutants are so small that they can enter the bloodstream, causing adverse health impacts

November 27

Today, the Air Quality Index (AQI) is recorded over 400 in several monitoring stations across Delhi. Biomass Burning or stubble burning remains a big contributor to Delhi's air pollution. Around 22 per cent of all the sources came from biomass burning, but the percentage is less when compared to vehicular pollution at 38 per cent, the biggest contributor today in the national capital air pollution.

The vehicular pollution level was over 200 micrograms/cubic metre between 9 am and 11 am. Office timings and maximum movement of people in that period can be attributed to the spike in vehicular pollution level.

Farmer leaders in Punjab earlier said that vehicular and industrial pollution contributes majorly to Delhi's worsening air quality.

Secondary aerosols are particles such as sulfates and nitrates and are released from vehicles, industry, agriculture refineries, etc. Today, around 26 per cent of pollutants are secondary aerosols.

November 26

The contribution of farm fires or biomass burning, significantly dropped today from 29 per cent on November 26. The dip in percentage and a drop in the number of stubble-burning cases are correlated.

The AQI level in Delhi was recorded to be over 300 at several monitoring stations across Delhi-NCR.

Vehicular pollution and secondary aerosols contributed around 28 per cent and 25 per cent respectively. Construction activities have been banned in Delhi under the stage III of the pollution action plan and have zero contribution to pollution.

The stubble-burning or crop burning season started in late October and biomass burning had a 12 per cent contribution, which increased drastically to almost 30 per cent in November.

Though a spike was recorded, the source of over 30 per cent of pollutants was secondary aerosols and vehicles. The trend has not changed much since July.

November 25

Biomass burning contributed nearly 35 per cent to Delhi's air pollution, the highest in the last three days but has dipped since then. Secondary aerosols contributed nearly 28 per cent and the contribution of vehicular pollution stood at 23 per cent.

On November 25, the AQI level was over 300 in Delhi-NCR and has remained hazardous.

"This is the most polluted November in six years... the problem is known (and) it is your job to control stubble burning. The court's job is not to tell you how to do it. Its job is to make you do your job", the Supreme Court pulled up the AAP government in Punjab and Delhi last week over incidents of stubble burning.

"The farmer is being made a villain... and he is not being heard from. He must have some reason to burn this stubble," the Supreme Court added.