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

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Cumulative views and downloads (calculated since 04 Aug 2025)

Month	HTML	PDF	XML	Total
Aug 2025	1,302	64	28	1,394
Sep 2025	1,108	14	10	1,132
Oct 2025	98	56	14	168
Nov 2025	68	64	20	152
Dec 2025	436	114	35	585
Jan 2026	239	92	22	353
Feb 2026	372	66	20	458
Mar 2026	136	73	16	225
Apr 2026	92	57	11	160
May 2026	73	55	3	131
Jun 2026	30	6	4	40
Jul 2026	100	25	15	140
Aug 2026	42	40	18	100
Sep 2026	39	80	79	198

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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.