Stubble burning contributes nearly half of the black carbon pollution in rural Punjab, with its share exceeding 90% during peak farm-fire hours, a study by researchers from the Indian Institute of Technology (IIT), Delhi, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, and Panjab University has found. It also highlights how smoke-laden air masses from Punjab are carried by northwesterly winds towards the Indo-Gangetic plain, potentially affecting air quality in downwind regions, including the National Capital Region (NCR).
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.
Hillary Victor is a Special Correspondent, with over two decades of experience in impactful, ethical, and public-interest journalism. He works in the Punjab Bureau, covering housing and urban development, transport and civil aviation, environment, science and technology, forests and wildlife, with a strong focus on governance, public policy, infrastructure, and sustainable development. His reporting reflects a deep understanding of Punjab's socio-political landscape and is driven by accuracy, accountability, and a commitment to serving the public interest. Over the course of his career, he has built a reputation for producing high-impact, exclusive stories that have shaped public discourse and prompted policy and administrative action. He has been honoured with six 'Best Journalist Awards' by the Hindustan Times management for his path-breaking reportage. In recognition of his outstanding contribution to journalism, he was also conferred the 'Best Journalist Award' by the Government of Punjab during the 2010 Republic Day celebrations.Read More