CaltechAUTHORS
Published September 29, 2025 | Version Published
Journal Article Open

Isoprene chemistry under upper-tropospheric conditions

Creators

  • 1. ROR icon Goethe University Frankfurt
  • 2. ROR icon Max Planck Institute for Chemistry
  • 3. ROR icon University of Helsinki
  • 4. ROR icon Carnegie Mellon University
  • 5. ROR icon Cyprus Institute
  • 6. ROR icon European Organization for Nuclear Research
  • 7. ROR icon University of Lisbon
  • 8. ROR icon Laboratory of Instrumentation and Experimental Particles Physics
  • 9. ROR icon University of Tartu
  • 10. ROR icon Aerodyne Research
  • 11. ROR icon Stockholm University
  • 12. ROR icon University of Colorado Boulder
  • 13. ROR icon Cooperative Institute for Research in Environmental Sciences
  • 14. ROR icon Paul Scherrer Institute
  • 15. ROR icon Universität Innsbruck
  • 16. ROR icon Karlsruhe Institute of Technology
  • 17. ROR icon University of Vienna
  • 18. ROR icon University of Beira Interior
  • 19. ROR icon University of North Carolina Wilmington
  • 20. ROR icon Leibniz Institute for Tropospheric Research
  • 21. ROR icon California Institute of Technology
  • 22. ROR icon Tofwerk (Switzerland)
  • 23. ROR icon Ionicon Analytik (Austria)
  • 24. ROR icon Nanjing University
  • 25. ROR icon Beijing University of Chemical Technology
  • 26. ROR icon Finnish Meteorological Institute
  • 27. ROR icon University of Eastern Finland
  • 28. ROR icon University of Cambridge

Abstract

Isoprene (C5H8) is the non-methane hydrocarbon with the highest emissions to the atmosphere. It is mainly produced by vegetation, especially broad-leaved trees, and efficiently transported to the upper troposphere in deep convective clouds, where it is mixed with lightning NOx. Isoprene oxidation products drive rapid formation and growth of new particles in the tropical upper troposphere. However, isoprene oxidation pathways at low temperatures are not well understood. Here, in experiments at the CERN CLOUD chamber at 223 K and 243 K, we find that isoprene oxygenated organic molecules (IP-OOM) all involve two successive OH oxidations. However, depending on the ambient concentrations of the termination radicals (HO₂, NO and NO₂), vastly-different IP-OOM emerge, comprising compounds with zero, one or two nitrogen atoms. Our findings indicate high IP-OOM production rates for the tropical upper troposphere, mainly resulting in nitrate IP-OOM but with an increasing non-nitrate fraction around midday, in close agreement with aircraft observations.

Copyright and License

© The Author(s) 2025. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Acknowledgement

We thank CERN for supporting CLOUD with important technical and financial resources and for providing a particle beam from the CERN Proton Synchrotron. Funding: This work was supported by the European Union’s MSCA Doctoral Network CLOUD-DOC 101073026 (D.M.R., A.C., A.M., B.Y., C.X., G.R.U., H.B., I.Z., M.K.S., P.R., W.Y. and Z.Z.). Federal Ministry of Education and Research (BMBF) financed project CLOUD-22 01LK2201A (L.C.-P., J.C.), 01LK2201B (O.M.), 01LK2201C (G.R.U.). Research Council of Finland grant numbers 346371 (S.S.) and 359331 (X.-C.H.). US National Science Foundation awards AGS-2215522 (R.V.), AGS-2027252 (R.V.), AGS-2215527 (R.C.F.), AGS-2431817 (N.M.D.), CHE-2336463 (J.De., N.M.D.), AGS-2215489 (N.M.D.). Swiss National Science Foundation grants 200021_213071 (I.E.H.) and 216181 (L.D.). European Union’s Horizon 2020 research and innovation programme under grant agreement No. 856612 (T.C.). Estonian Research Council projects PRG2738 (H.J.), RVTT3 (H.J.), TT18 (H.J.).

Funding

Open Access funding enabled and organized by Projekt DEAL.

Data Availability

Data for all figures in the main text and supplementary materials are publicly available at the Zenodo repository (https://doi.org/10.5281/zenodo.16276710)62.

Code Availability

The Modular Earth Submodel System (MESSy, https://doi.org/10.5281/zenodo.8360186)63 is continuously further developed and applied by a consortium of institutions. The usage of MESSy and access to the source code is licensed to all affiliates of institutions which are members of the MESSy Consortium. Institutions can become a member of the MESSy Consortium by signing the MESSy Memorandum of Understanding. More information can be found on the MESSy Consortium Website (http://www.messy-interface.org).

Supplemental Material

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Additional details

Identifiers

PMCID
PMC12479858
PMID
41022896

Describes
Journal Article: PMC12479858 (PMCID)
Journal Article: 41022896 (PMID)
Journal Article: https://rdcu.be/eLl10 (ReadCube)
Is supplemented by
Supplemental Material: https://static-content.springer.com/esm/art%3A10.1038%2Fs41467-025-64229-w/MediaObjects/41467_2025_64229_MOESM1_ESM.pdf (URL)
Dataset: 10.5281/zenodo.16276710 (DOI)
Software: 10.5281/zenodo.8360186 (DOI)

Funding

European Union
CLOUD-DOC 101073026
Federal Ministry of Education and Research
01LK2201A
Federal Ministry of Education and Research
01LK2201B
Federal Ministry of Education and Research
01LK2201C
Research Council of Finland
346371
Research Council of Finland
359331
National Science Foundation
AGS-2215522
National Science Foundation
AGS-2027252
National Science Foundation
AGS-2215527
National Science Foundation
AGS-2431817
National Science Foundation
CHE-2336463
National Science Foundation
AGS-2215489
Swiss National Science Foundation
200021_213071
Swiss National Science Foundation
200021_216181
European Union
856612
Estonian Research Council
PRG2738
Estonian Research Council
RVTT3
Estonian Research Council
TT18

Dates

Accepted
2025-09-09

Caltech Custom Metadata

Caltech groups
Division of Chemistry and Chemical Engineering (CCE)
Publication Status
Published