Stubble burning in Punjab, Haryana contributes solely 14% of PM2.5 in Delhi-NCR: examine

Primarily based on area measurements, airmass trajectories, and particle dispersion and chemical transport mannequin simulations, a examine printed in January 2025 has discovered that there is no such thing as a linear correlation between stubble-burning occasions in Punjab and Haryana and superb particulate matter (PM2.5) focus in Delhi-NCR. The examine additionally underscores that crop residue burning in Punjab and Haryana contributes solely about 14% of PM2.5 and is subsequently not a major supply of particulate matter focus in Delhi-NCR. The focus of PM2.5 in Delhi-NCR remained pretty secure and fixed regardless of the stubble-burning occasions in Punjab and Haryana declining by over 50% from 2015 to 2023, the examine discovered. The outcomes of the examine have been printed within the journal Local weather and Atmospheric Science.

As per a November 25, 2024 PTI report, the variety of stubble-burning occasions measured by ISRO has witnessed a pointy decline on a year-to-year foundation in Punjab and Haryana between September 15 and November 18 — from 48,489 in 2022 to 33,719 in 2023 and 9,655 in 2024 in Punjab, and within the case of Haryana it dropped from 3,380 in 2022 to 2,052 in 2023 and 1,118 in 2024.

Excessive-quality measurements of superb particulate matter started on the U.S. Embassy in New Delhi in 2015. The variety of stubble-burning occasions in Punjab and Haryana declined by 31% and 37%, respectively in 2023 in contrast with 2022. But, there was a 20% enhance in PM2.5 on the U.S. Embassy in 2023, thus highlighting the absence of a linear correlation between stubble-burning occasions within the two States and PM2.5 focus in Delhi-NCR. A community of 30 sensors was established in August 2022 in rural and concrete areas in Punjab, Haryana, and Delhi. Information from the sensors positioned in Delhi-NCR are in shut settlement with the instrument on the U.S. Embassy.

“There isn’t any linearity between hearth counts in Punjab/Haryana and PM2.5 variations [in Delhi-NCR],” Dr. Prabir Ok. Patra from the Analysis Institute for Humanity and Nature (RIHN), Kyoto, Japan, and one of many corresponding authors says in an e mail to The Hindu. Many establishments from India are a part of the examine.

Stubble burning virtually ceases after November. Nonetheless, the air high quality index within the Delhi-NCR area has stubbornly remained within the “very poor” to “extreme” class since 2016 throughout the winter months — December to February — because of stagnant winds, decrease mixing heights, and inversion situations, leading to excessive air pollution. This as soon as once more means that sources apart from stubble burning considerably contribute to air air pollution in Delhi-NCR.

The authors say that the quantity of biomass burned in Punjab and Haryana “doesn’t at all times decide the air high quality of closely urbanised Delhi-NCR even throughout the core rice-stubble burning interval (October-November)”. Dr. Patra says: “Our knowledge clearly exhibits that PM2.5 stays excessive (larger than 100 microgram per metre dice) effectively past November and thru to the primary week of February till the western disturbances arrive.”

There’s a hyperlink between stubble burning and PM2.5 focus in Delhi-NCR when there may be robust wind. “Whereas the wind patterns play a vital function in pollutant transport, they don’t seem to be the only issue figuring out PM2.5 ranges. Different meteorological elements and native emissions too affect the PM2.5 ranges considerably,” Dr. Poonam Mangaraj from RIHN, Kyoto, Japan, and the primary creator of the paper says in an e mail to The Hindu. “When the dispersion situations are unfavourable — low wind speeds, temperature inversions trapping pollution close to the floor, or stagnant air stopping motion — pollution might not be successfully transported, resulting in weaker or no observable correlation.”

Information of PM2.5 and carbon monoxide (CO) have been recorded throughout the day and evening by the community sensors. Information from chosen sensor websites confirmed a persistent build-up of superb particulate matter and CO in Delhi throughout the evening, which suggests emissions from localised sources. If stubble burning in Punjab and Haryana was the main supply of air air pollution in Delhi-NCR, the CO ranges would have remained secure and never elevated throughout the evening, the authors say. “Carbon monoxide in Delhi-NCR is predominantly emitted from fossil gas combustion or native biomass burning, unbiased of the diurnal cycle in PM2.5 emission sources,” they write.

As per the examine, the day-night variations in PM2.5 are about 20% in Delhi-NCR, whereas the common CO focus is about 67% larger within the evening in comparison with the day in 2023, and about 48% in 2022. In distinction, in Punjab and Haryana, a transparent day-night variation is noticed solely throughout the intense stubble-burning intervals.

For the reason that day-night variations in superb particulate matter are larger than CO within the areas with predominant stubble burning, the upper CO emission at evening within the Delhi-NCR area factors to sources apart from stubble burning.

“It’s clear that even within the months of peak crop residue burning season (October-November), the contributions of native industrial and different anthropogenic sources to PM2.5 within the Delhi-NCR are a lot larger than crop residue burning in Punjab and Haryana,” says Dr. Mangaraj.

“In the course of the Graded Response Motion Plan (GRAP) implementation interval at stage III and IV [when AQI is “severe” and “severe plus”, respectively], the PM2.5 ranges dropped considerably when strict measures to manage transport sector and building actions have been enforced. Nonetheless, when GRAP-IV was lifted, PM2.5 ranges surged again, underscoring how essential these measures are in enhancing air high quality.” This implies that the native sources (e.g., small-scale unorganised industries, highway transport, waste administration, and building amenities and provides) [contribute significantly to fine particulate matter].”

Main contributor

In accordance with Dr. Sachchida N. Tripathi from IIT Kanpur, who is just not related to the examine, at 30%, the main contributor to superb particulate matter is the transport sector, adopted by native biomass burning at 23%, 10% by the development business and highway mud, whereas cooking and business contribute 5-7%, and 10% is unaccounted. In distinction, stubble burning in Punjab and Haryana contributes solely about 13%, and that too solely throughout October and November.