Multiyear dual-isotope fingerprinting at South Asian receptor sites constrains carbon monoxide sources and enhanced oxidation.
5 affiliations
- 1Department of Environmental Science and Bolin Centre for Climate Research, Stockholm University, Stockholm 10691, Sweden.
- 2Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht 3584CC, The Netherlands.
- 3Maldives Climate Observatory-Hanimaadhoo, Maldives Meteorological Services, H. Dh. Hanimaadhoo 02020, Maldives.
- 4Divecha Centre for Climate Change, Indian Institute of Science, Bangalore 560012, India.
- 5Department of Chemistry, University of Dhaka, Dhaka 1000, Bangladesh.
Abstract
Carbon monoxide (CO) is an indirect short-lived climate forcer with uncertainties both in sources and its role in atmospheric oxidation. Based on nine winter-long dual-isotope campaigns at two South Asian receptor sites intercepting the continental outflow, we quantified CO source contributions and emission-sink dynamics. Combustion accounts for 68 to 74% of South Asia regional CO (including 34 to 37% from biomass burning) with secondary atmospheric oxidation contributing 26 to 32% (dominated by oxidation of nonmethane volatile organic compounds (NMVOCs) at 21 to 26%, with methane oxidation contributing 5.5 to 6.4%). These isotope-observational constraints suggest a twice higher role for atmospheric oxidation than in model estimates. Spatially, the absolute contributions of both primary and secondary CO decrease from the Indo-Gangetic Plain to the northern Indian Ocean, while the relative contribution of oxidation-derived CO increases, indicating enhanced secondary CO production near source regions. Observation-model comparison suggests that transport from the continental areas dominates CO over adjacent oceanic regions, with minor local production. During the COVID-19 emission perturbation, combustion-derived CO fell sharply in absolute terms, NMVOC-derived CO rose, and CH₄-derived CO remained stable, providing an observational constraint on the sensitivity of atmospheric oxidation to emission changes. Our results reveal a significant contribution of CO from atmospheric oxidation in South Asia, calling for a reassessment of regional emission-oxidation coupling in models and of mitigation strategies.
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BibTeX
@article{yao2026multiyear,
title = {{Multiyear dual-isotope fingerprinting at South Asian receptor sites constrains carbon monoxide sources and enhanced oxidation.}},
author = {Peng Yao and Henry Holmstrand and Carina van der Veen and Maria Elena Popa and Chloe A Brashear and Krishnakant Budhavant and Mohanan Remani Manoj and Joakim Romson and Abdus Salam and Thomas Röckmann and Örjan Gustafsson},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
year = {2026},
month = oct,
doi = {10.1073/pnas.2606200123},
url = {https://europepmc.org/article/MED/42863050},
note = {CC BY},
}
RIS
TY - JOUR
TI - Multiyear dual-isotope fingerprinting at South Asian receptor sites constrains carbon monoxide sources and enhanced oxidation.
AU - Peng Yao
AU - Henry Holmstrand
AU - Carina van der Veen
AU - Maria Elena Popa
AU - Chloe A Brashear
AU - Krishnakant Budhavant
AU - Mohanan Remani Manoj
AU - Joakim Romson
AU - Abdus Salam
AU - Thomas Röckmann
AU - Örjan Gustafsson
PY - 2026
DA - 2026/10/12
JO - Proceedings of the National Academy of Sciences of the United States of America
DO - 10.1073/pnas.2606200123
UR - https://europepmc.org/article/MED/42863050
AB - Carbon monoxide (CO) is an indirect short-lived climate forcer with uncertainties both in sources and its role in atmospheric oxidation. Based on nine winter-long dual-isotope campaigns at two South Asian receptor sites intercepting the continental outflow, we quantified CO source contributions and emission-sink dynamics. Combustion accounts for 68 to 74% of South Asia regional CO (including 34 to 37% from biomass burning) with secondary atmospheric oxidation contributing 26 to 32% (dominated by oxidation of nonmethane volatile organic compounds (NMVOCs) at 21 to 26%, with methane oxidation contributing 5.5 to 6.4%). These isotope-observational constraints suggest a twice higher role for atmospheric oxidation than in model estimates. Spatially, the absolute contributions of both primary and secondary CO decrease from the Indo-Gangetic Plain to the northern Indian Ocean, while the relative contribution of oxidation-derived CO increases, indicating enhanced secondary CO production near source regions. Observation-model comparison suggests that transport from the continental areas dominates CO over adjacent oceanic regions, with minor local production. During the COVID-19 emission perturbation, combustion-derived CO fell sharply in absolute terms, NMVOC-derived CO rose, and CH₄-derived CO remained stable, providing an observational constraint on the sensitivity of atmospheric oxidation to emission changes. Our results reveal a significant contribution of CO from atmospheric oxidation in South Asia, calling for a reassessment of regional emission-oxidation coupling in models and of mitigation strategies.
SN - 0027-8424
SN - 1091-6490
ER -