Limitations of the radon tracer method (RTM) to estimate regional greenhouse gas (GHG) emissions – a case study for methane in Heidelberg

Levin, Ingeborg; Karstens, Ute; Hammer, Samuel; DellaColetta, Julian; Maier, Fabian; Gachkivskyi, Maksym

doi:https://doi.org/10.5194/acp-21-17907-2021

Articles | Volume 21, issue 23

https://doi.org/10.5194/acp-21-17907-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-21-17907-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 23

Research article

|

07 Dec 2021

Research article |

| 07 Dec 2021

Limitations of the radon tracer method (RTM) to estimate regional greenhouse gas (GHG) emissions – a case study for methane in Heidelberg

Ingeborg Levin, Ute Karstens, Samuel Hammer, Julian DellaColetta, Fabian Maier, and Maksym Gachkivskyi

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Final revised paper (published on 07 Dec 2021)
Preprint (discussion started on 10 Sep 2021)

Interactive discussion

Status: closed

RC1:
'Comment on acp-2021-661', Alastair Williams, 23 Sep 2021

See comments in attached PDF

Citation: https://doi.org/10.5194/acp-2021-661-RC1
- AC1: 'Reply on RC1', Ingeborg Levin, 05 Oct 2021
  
  The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2021-661/acp-2021-661-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/acp-2021-661-AC1
RC2:
'Comment on acp-2021-661', Claudia Grossi, 27 Sep 2021

In this study the authors apply the Radon Tracer Method (RTM) using a 24-year dataset of atmospheric methane (CH₄) and radon (²²²Rn) concentrations, measured at the Heidelberg city, to estimate the trend of methane emissions over the city surrounding area. Then they compare the RTM based CH₄ emissions with results obtained using the EDGARv6.0 bottom-up inventory. Authors, who were the first to introduce the RTM in Levin et al., 1999, also analyze the strength and weakness of the RTM application mainly in regards to the radon flux value used in it and the representability of the catchment area of the atmospheric station depending on the heterogeneity of the GHGs sources.

The aim of this paper follows completely within the scope of this journal. The study is well designed and the English of the manuscript has been already reviewed by the other reviewer, who is a native speaker. The work behind the achievement of the 24-year dataset is impressive and it gives a really robust statistics to the results obtained in this study.

On the other hand, some aspects of the manuscript could be improved for the fluency of the reading and to clearly identify what has been done so far in the field of the RTM application. The state of the art and the discussion of the results of this study are not updated and they did not consider past outcomes from others researchers.

The paper deserves to be published in the ACP journal after that some changes will be made as explained in details in the following sections presented in the attached document

Citation: https://doi.org/10.5194/acp-2021-661-RC2
- RC3: 'corrigendum to the report of R2', Claudia Grossi, 30 Sep 2021
  
  Corrigendum: 'For example, in Grossi et al., 2020 the correlation of the same ARMON (Grossi et al., 2012) with two ANSTO monitors (located respectively at Saclay (100 m.a.g.l.) and at Orme des Mérisiers (2 m.a.g.l.)) had slopes of 0.97 ± 0.01 and 0.96 ± 0.01 with intercepts of 0.01 ± 0.06 and −0.23 ± 0.03, respectively.
  
  Citation: https://doi.org/10.5194/acp-2021-661-RC3

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Ingeborg Levin on behalf of the Authors (26 Oct 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (27 Oct 2021) by Heini Wernli

RR by Claudia Grossi (27 Oct 2021)

RR by Alastair Williams (28 Oct 2021)

ED: Publish as is (28 Oct 2021) by Heini Wernli

Short summary

The radon tracer method is applied to atmospheric methane and radon observations from the upper Rhine valley to independently estimate methane emissions from the region. Comparison of our top-down results with bottom-up inventory data requires high-resolution footprint modelling and representative radon flux data. In agreement with inventories, observed emissions decreased, but only until 2005. A limitation of this method is that point-source emissions are not captured or not fully captured.