Challenges and benefits of using NOx as a quantitative proxy for fossil fuel CO2 in an urban area based on radiocarbon measurements

Juchem, Hannes; Maier, Fabian; Levin, Ingeborg; Jordan, Armin; Pöhler, Denis; Rosendahl, Claudius; Della Coletta, Julian; Preunkert, Susanne; Hammer, Samuel

doi:10.5194/acp-25-18373-2025

Articles | Volume 25, issue 24

https://doi.org/10.5194/acp-25-18373-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-25-18373-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 25, issue 24

Research article

|

17 Dec 2025

Research article |

| 17 Dec 2025

Challenges and benefits of using NO_x as a quantitative proxy for fossil fuel CO₂ in an urban area based on radiocarbon measurements

Hannes Juchem, Fabian Maier, Ingeborg Levin, Armin Jordan, Denis Pöhler, Claudius Rosendahl, Julian Della Coletta, Susanne Preunkert, and Samuel Hammer

Data sets

14C-based ΔffCO2 estimates and NOx measurements for Heidelberg (2020-2021) Hannes Juchem et al. https://doi.org/10.11588/DATA/KI8DTQ

Short summary

This study explores how in situ NO_x observations can be used to estimate fossil fuel CO₂ (ffCO₂) enhancements in an urban context, based on radiocarbon measurements. Even with a simple approach to account for atmospheric chemistry and ratio variability, a strong correlation could be observed, allowing the construction of a high temporal resolution NO_x-based ffCO₂ record with uncertainties comparable to the use of CO as proxy. Comparisons with independent records show good agreement between them.