Volatile organic compound measurements point to fog-induced biomass burning feedback to air quality in the megacity of Delhi

H. Hakkim, V. Sinha*, B. P. Chandra, A. Kumar, A. K. Mishra, B. Sinha, G. Sharma, H. Pawar, B. Sohpaul, Sachin D. Ghude, P. Pithani, R. Kulkarni, R. K. Jenamani, M. Rajeevan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We report the first ambient measurements of thirteen VOCs for investigations of emissions and air quality during fog and non-fog wintertime conditions at a tower site (28.57° N, 77.11° E, 220 m amsl) in the megacity of Delhi. Measurements of acetonitrile (biomass burning (BB) tracer), isoprene (biogenic emission tracer in daytime), toluene (a traffic exhaust tracer) and benzene (emitted from BB and traffic), together with soluble and reactive oxygenated VOCs such as methanol, acetone and acetaldehyde were performed during the winters of 2015–16 and 2016–17, using proton transfer reaction mass spectrometry. Remarkably, ambient VOC composition changes during fog were not governed by solubility. Acetaldehyde, toluene, sum of C8-aromatics (e.g. xylenes), sum of C9-aromatics (e.g. trimethyl benzenes) decreased by ≥30% (>95% confidence interval), whereas acetonitrile and benzene showed significant increases by 20% (>70% confidence interval), even after accounting for boundary layer dilution. During fog, the lower temperatures appeared to induce an emissions feedback from enhanced open BB within Delhi for warming, releasing both gaseous and aerosol pollutants with consequences for fog chemistry, sustenance and intensity. The potential feedback is important to consider for improving current emission parametrizations in models used for predicting air quality and fog in such atmospheric environments.
Original languageEnglish
Pages (from-to)295-304
Number of pages10
JournalScience of the Total Environment
Early online date27 Jun 2019
Publication statusPublished - 2019

Bibliographical note

Funding Information:
We thank the past and present Directors of the Indian Institute of Science Education and Research (IISER), Mohali, the Director General of the Indian Meteorological Department (IMD) and Director of the Indian Institute of Tropical Meteorology (IITM), Pune for their kind support and encouragement. We acknowledge the IISER Mohali Atmospheric Chemistry Facility, Ministry of Human Resource Development (MHRD), India and Ministry of Earth Sciences (MoES) for support and funding. We thank Prof. G.S. Bhat (Indian Institute of Science (IISc), Bengaluru) for his leadership of the Delhi winterfog experiments as well the MS students of IISER Mohali, Mr. Muhammed Shabin and Ms. Nimya Sunil for technical support.

Publisher Copyright:
© 2019 Elsevier B.V.


  • Biomass burning
  • Delhi air quality
  • Fog
  • Proton transfer reaction mass spectrometry
  • Volatile organic compounds

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