A study published this year shows Punjab farm fires significantly impact NCR air quality. Researchers found crop-residue burning caused 48% of black carbon levels between October 27 and November 18, 2023. Winds carried these pollutants toward the Indo-Gangetic plain, where fine particles got deep into the respiratory systems of many people.

Published in the peer-reviewed journal Environmental Monitoring and Assessment this year, the study, titled Ambient black carbon and its dependence on in situ stubble burning, is based on an intensive field campaign conducted at Khera village in Punjab from October 27 to November 18, 2023. It provides a quantitative assessment of the contribution of crop-residue burning to ambient black carbon concentrations during the post-monsoon paddy harvesting season.

Researchers found that crop-residue burning accounted for an average 48% of the black carbon recorded during the study period. Its contribution periodically crossed 90% between 1 pm and 6 pm, coinciding with active burning hours.

Black carbon is a light-absorbing pollutant produced by the incomplete combustion of biomass and fossil fuels. Its fine particles can penetrate deep into the respiratory system and are associated with adverse cardiovascular and respiratory effects. It also contributes to atmospheric warming by absorbing sunlight.

The monitoring station was set up amid agricultural fields, with the Rajpura Thermal Power Plant located around 10 km away. Researchers used advanced monitoring instruments and two statistical techniques — the Aethalometer Model and Positive Matrix Factorisation (PMF) — to identify and estimate the contribution of different pollution sources.

Black carbon concentrations ranged from 1.45 to 85 micrograms per cubic metre (µg/m³), with an average of 12.6 µg/m³.

The researchers also examined the movement of air masses using a 72-hour forward trajectory model. The analysis showed that air masses originating from the sampling region frequently travelled towards the Indo-Gangetic plain, with predominantly northwesterly winds facilitating the transport of smoke and black carbon beyond the source region. The findings point to the potential for farm-fire emissions to affect downwind areas, including the NCR.

However, the researchers cautioned that the findings were based on measurements at a single rural location during one post-monsoon season. They recommended multi-site monitoring, longer-term datasets and further atmospheric modelling to assess the wider regional impact.