the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 01 Sep 2026
Technical note: Cavity ring-down spectroscopy is a precise and accurate method for measuring 15N-NO3– in soil extracts from 15N tracer experiments
Abstract. Cavity ring-down spectroscopy (CRDS) provides a low-cost alternative to isotope ratio mass spectrometry (IRMS) for the analysis of 15N-NO3⁻ in nitrogen cycle assays, but its performance has not been tested systematically for highly enriched samples. Here we report results from 271 parallel analyses of 15N-NO3⁻ in soil extracts after chemical conversion to N2O, including low (0.36–1.45 at%) and high labelled samples (0.46–8.49 at%). We demonstrate that CRDS measurements deliver comparable accuracy and precision to continuous-flow Gas Bench-IRMS analysis (slope: 0.982 and 0.972, RMSE: 0.0018 and 0.254 at% for low- and high-labelled samples, respectively), thereby offering a robust and affordable alternative for classic 15N-NO3⁻ analysis.
- Preprint
(816 KB) - Metadata XML
-
Supplement
(310 KB) - BibTeX
- EndNote
Status: open (until 05 Nov 2026)
- RC1: 'Comment on egusphere-2026-5050', Anonymous Referee #1, 18 Sep 2026 reply
-
RC2: 'Comment on egusphere-2026-5050', Anonymous Referee #2, 25 Sep 2026
reply
This is a short, but concise paper comparing 15N analysis of enriched samples conducted via laser spectroscopy and isotope ratio mass spectrometry (IRMS). The focus lies on the analysis of 15N-NO3- from 15N labelling experiments, after conversion to nitrous oxide (N2O).
While the paper is concise, I think that the discussion could be broadened. In this paper the 15N analysis in NO3- is discussed, after conversion to N2O. Therefore, the analysis actually conducted is for N2O, and the implications for 15N-N2O analysis in tracer experiments could be included in the discussion.
It seems that for the laser spectroscopy, the N2O concentration was about 25-times lower compared to the IRMS analysis (Line 78-82). This is only very briefly stated again in the last paragraph, but could be highlighted and discussed more.
Specific comments:
Line 25-29: When introducing 15N pool dilution and tracer approaches, I am not sure that the best reference is used, as the cited paper focusses on 15N analysis, not experimentation.
Line 41: Could the “lower capital and running costs” quantified, to support this statement?
Line 57: This is strictly speaking not true, as the NO3- pool also contain natural abundance 15N.
Line 98: The individual samples (grey circles) are not visible in the figure. Either, if it is important to show individual samples, they need to be made more visible, or the authors might only show means and uncertainties. I also noted that the colours mentioned in the caption do not match the actual colours in the figure.
Line 124: From my perspective, using a 68 hour time step is not common in isotope pool dilution experiments, but rather long, with the risk of e.g. remobilization. This might not be crucial for the scope of the paper, but I would still recommend rephrasing.
Citation: https://doi.org/10.5194/egusphere-2026-5050-RC2
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 294 | 114 | 62 | 470 | 57 | 69 | 58 |
- HTML: 294
- PDF: 114
- XML: 62
- Total: 470
- Supplement: 57
- BibTeX: 69
- EndNote: 58
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
This paper is a timely contribution to the measurements of 15N in inorganic substances in nature. I cannot see any flaw in it.