Assessment of stable carbon isotope ratios and source characterization of aerosols in ambient PM2.5 from the Indian COALESCE network

Debajyoti Paul; Gyanesh Kumar Singh; Tarun Gupta; Abhijit Chatterjee; Binoy K Saikia; Ramya Sunder Raman; Gazala Habib; Harish Phuleria; Chandra Venkataraman

doi:10.1038/s41598-025-03987-5

Assessment of stable carbon isotope ratios and source characterization of aerosols in ambient PM_2.5 from the Indian COALESCE network

Sci Rep. 2025 Jun 4;15(1):19503. doi: 10.1038/s41598-025-03987-5.

Authors

Debajyoti Paul¹, Gyanesh Kumar Singh^{2

3}, Tarun Gupta⁴, Abhijit Chatterjee⁵, Binoy K Saikia⁶, Ramya Sunder Raman⁷, Gazala Habib⁸, Harish Phuleria⁹, Chandra Venkataraman¹⁰

Affiliations

¹ Department of Earth Sciences, Indian Institute of Technology Kanpur, Kanpur, 208 016, India. dpaul@iitk.ac.in.
² Department of Civil Engineering and APTL at Center for Environmental Science and Engineering (CESE), Indian Institute of Technology Kanpur, Kanpur, 208 016, India. gyanesh.singh@npl.co.uk.
³ Air Quality and Aerosol Metrology (AQAM) Group, National Physical Laboratory (NPL), Teddington, London, TW11 0LW, UK. gyanesh.singh@npl.co.uk.
⁴ Department of Civil Engineering and APTL at Center for Environmental Science and Engineering (CESE), Indian Institute of Technology Kanpur, Kanpur, 208 016, India.
⁵ Department of Chemical Sciences, Bose Institute, Block-EN, Sector-V, Salt Lake, Kolkata, 700091, India.
⁶ Coal & Energy Group, Coal Energy & Materials Sciences Division, CSIR North-East Institute of Science & Technology, Jorhat, 785006, India.
⁷ Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal, 462066, India.
⁸ Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi, 110 016, India.
⁹ Environmental Science and Engineering Department, Indian Institute of Technology Bombay, Mumbai, 400076, India.
¹⁰ Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, 400076, India.

Abstract

This study explores the potential of stable carbon isotope (δ¹³C) composition of ambient carbonaceous aerosols in assessing the nature and apportionment of their sources. As part of the CarbOnaceous AerosoL Emissions, Source apportionment & ClimatE Impacts (COALESCE) network, δ¹³C measurements (n = 1120) were conducted on aerosol samples collected from eight key locations spread across India. The δ¹³C values of aerosols exhibit distinct spatial/temporal isotopic variabilities between background and polluted (urban) sites, and indicate an origin primarily from C₃-biomass, fossil fuels, vehicular emission sources, etc. Spatial δ¹³C distribution over India shows more negative δ¹³C values in all seasons at the north Indian Himalayan (Kashmir) and east Indian sites (Jorhat) compared to other locations, implying that anthropogenic inputs contribute to more isotopic variability and a typical ¹³C-rich signature. Our study shows that although δ¹³C provides qualitative information on source characteristics, it is not a robust standalone proxy for such applications. We conclude that δ¹³C of aerosols could be a robust proxy for quantification studies if the extent of isotopic fractionation involved during aerosol formation/transport processes is well known and if it is assessed with one or more chemical markers like radiocarbon (Δ¹⁴C), trace elements/organic species, and specific biomarkers (e.g., levoglucosan or K⁺ _BB).

Keywords: Aerosol proxy; Carbonaceous aerosols; Fractionation; Source signature; Stable isotope.

Grants and funding

Grant 14/10/2014-CC(Vol.II)/Ministry of Environment, Forest and Climate Change