From Farm Fires to Engine Exhaust: Decoding Delhi’s Hazy, Toxic Air with PTR-MS
An investigation led by the Indian Institute of Science Education and Research (IISER) Mohali, with logistical support from the Indian Institute of Tropical Meteorology (IITM) Pune and the India Meteorological Department (IMD), precisely traced the origins of particulate matter and Volatile Organic Compounds (VOCs) in Delhi's atmosphere.
The team used high-resolution Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) and advanced source apportionment methods to achieve this.
Separating Smoke from Toxins
Every winter, Delhi’s skyline dissolves into a grey soup and the conversation lands on stubble burning. A new, year-long investigation confirms that those fires really do load the air with the soot that makes the city look and feel suffocating. But the same research also shows that several toxic compounds in Delhi’s air come from somewhere else entirely: vehicles and industry. This distinction is critical, and it took a cross-institutional Indian team, armed with cutting-edge instruments, to prove it.
The scientific work was led by IISER Mohali (Atmospheric Chemistry & Emissions Research Group and Aerosol Research Group) with partners at IITM Pune and the India Meteorological Department (IMD). The IMD also hosted the central measurement site at its Lodhi Road campus of the Ministry of Earth Sciences, which funded the project. This collaboration is crucial:
- IISER Mohali provided VOC measurement expertise.
- IITM’s atmospheric modeling team will use the data to improve Air Quality (AQ) forecasts.
- IMD’s national observing network and logistical support were combined to differentiate what makes Delhi’s air thick from what makes it toxic.
Surprising Source Apportionment Results
After the intensive research the findings show, that open fires of crop-residue burning across the Indo-Gangetic Plain, plus local waste and residential burning – drive more than half of the city’s particulate haze in the post-monsoon season. That’s the visible smoke or fog that irritates throats and stings eyes. But when the team turned to VOCs – the reactive, often carcinogenic gases that seed ozone and secondary particles – they discovered that transport and industrial emissions dominated the VOC burden and the potential to form new toxic pollution, while stubble burning contributed only a small share. In short: Seasonal farm fires drive the visible haze, but vehicles and industry drive the toxic chemical burden. Both sources contribute to respiratory distress.
High-Mass-Resolution PTR-TOFMS for Speciated Analysis
Researchers deployed an extended-volatility-range, high-mass-resolution PTR-MS (IONICON's PTR-TOF 10k) at IMD-Lodhi Road in Central Delhi site. The inlet was positioned above 30 meters to sample regional air masses. This sophisticated instrument continuously quantified 111 speciated VOCs at parts-per-trillion sensitivity and, thanks to a heated, inert inlet designed for low-volatility compounds, captured the heavier, stickier molecules that standard setups miss. Marrying that molecular fingerprint with PM10/PM2.5 and advanced positive matrix factorization let the team resolve sources that usually blur together. This allowed them to distinguish, for example, petrol four-wheelers from two-wheelers and paddy-stubble burning from other biomass burning.
Further Resources: IONICON Technology and Study Findings
To explore the advanced PTR-MS technology that made this research possible explore IONICON technology and case studies:
Discover the IONICON Products used for high-resolution analysis
Read more Environmental Research Case Studies using PTR-MS
To go deeper into the precise results of the source apportionment study, examine the full scientific methodology used, and read the original reporting on this groundbreaking work by IISER Mohali, explore the articles and academic papers linked below.
Read the full article in The Times of India: What makes Delhi’s air thick isn’t what makes it toxic: Study finds farm fires choke lungs, vehicles poison blood | Delhi News - The Times of India
Explore the papers on the topic:
Reactive chlorine-, sulfur-, and nitrogen-containing volatile organic compounds impact atmospheric chemistry in the megacity of Delhi during both clean and extremely polluted seasons
Images courtesy of the Indian Institute of Science Education and Research (IISER) Mohali.