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Natascha Kljun. Photo.

Natascha Kljun

Professor

Natascha Kljun. Photo.

14C-based separation of fossil and non-fossil CO2 fluxes in cities using relaxed eddy accumulation : Results from tall-tower measurements in Zurich, Paris, and Munich

Author

  • Ann Kristin Kunz
  • Samuel Hammer
  • Patrick Aigner
  • Laura Bignotti
  • Lars Borchardt
  • Jia Chen
  • Julian Della Coletta
  • Lukas Emmenegger
  • Markus Eritt
  • Xochilt Gutiérrez
  • Josh Hashemi
  • Rainer Hilland
  • Christopher Holst
  • Armin Jordan
  • Natascha Kljun
  • Richard Kneißl
  • Changxing Lan
  • Virgile Legendre
  • Ingeborg Levin
  • Benjamin Loubet
  • Matthias Mauder
  • Betty Molinier
  • Susanne Preunkert
  • Michel Ramonet
  • Stavros Stagakis
  • Andreas Christen
Show all

Summary, in English

Relaxed eddy accumulation (REA) measurements for 14CO2 enable the estimation of fossil fuel (ff) CO2 fluxes in urban areas. This work is based on 252 REA ffCO2 flux measurements conducted on tall towers in the cities of Zurich, Paris, and Munich. The ffCO2 fluxes were compared to net eddy covariance CO2 fluxes to quantify the role of non-fossil (nf) CO2 fluxes. While the measurements in Zurich and Paris were limited by small signal-to-noise ratios, improvements in the REA setup, the 14CO2 measurement precision, the sampling strategy, and the source strength increased the significance of the results in Munich. Large nfCO2 fluxes observed in Munich from the direction of a brewery demonstrate the efficacy of the partitioning approach and illustrate the complexity of urban atmospheric measurement data. Excluding these measurements potentially influenced by large anthropogenic nfCO2 fluxes, the error-weighted average ffCO2 / CO2 flux ratio in Munich was approximately 47 % in summer and 76 % in winter, with the majority of measurements taken between 07:00 and 19:00 local time. Regional excess concentrations had much lower ffCO2 contributions (<63 % in winter and <28 % in summer, in all three cities), demonstrating fundamental differences between local and regional CO2 fluxes. The combination of 14CO2 observations and the REA method is a sophisticated approach that challenges the limits of current analytical capabilities, while providing unique opportunities for quantifying ffCO2 and nfCO2 fluxes.

Department/s

  • Department of Earth and Environmental Sciences (MGeo)
  • LU Profile Area: Nature-based future solutions
  • LTH Profile Area: Aerosols
  • MERGE: ModElling the Regional and Global Earth system
  • BECC: Biodiversity and Ecosystem services in a Changing Climate

Publishing year

2026

Language

English

Pages

4967-5003

Publication/Series

Atmospheric Chemistry and Physics

Volume

26

Issue

7

Document type

Article

Publisher

Copernicus GmbH

Topic

  • Climate Science
  • Meteorology and Atmospheric Sciences

Keywords

  • SDG 13 - Climate Action

Status

Published

Project

  • Pilot Application in Urban Landscapes - towards integrated city observatories for greenhouse gases

ISBN/ISSN/Other

  • ISSN: 1680-7316