Gas chromatography vs. quantum cascade laser-based N<sub>2</sub>O flux measurements using a novel chamber design
Recent advances in laser spectrometry offer new opportunities to investigate the soil–atmosphere exchange of nitrous oxide. During two field campaigns conducted at a grassland site and a willow field, we tested the performance of a quantum cascade laser (QCL) connected to a newly developed automated...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-03-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/14/1365/2017/bg-14-1365-2017.pdf |
| _version_ | 1819155261745528832 |
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| author | C. Brümmer B. Lyshede D. Lempio J.-P. Delorme J. J. Rüffer R. Fuß A. M. Moffat M. Hurkuck A. Ibrom P. Ambus H. Flessa W. L. Kutsch |
| author_facet | C. Brümmer B. Lyshede D. Lempio J.-P. Delorme J. J. Rüffer R. Fuß A. M. Moffat M. Hurkuck A. Ibrom P. Ambus H. Flessa W. L. Kutsch |
| author_sort | C. Brümmer |
| collection | DOAJ |
| description | Recent advances in laser spectrometry offer new opportunities to
investigate the soil–atmosphere exchange of nitrous oxide. During two field
campaigns conducted at a grassland site and a willow field, we tested the
performance of a quantum cascade laser (QCL) connected to a newly developed
automated chamber system against a conventional gas chromatography (GC)
approach using the same chambers plus an automated gas sampling unit with
septum capped vials and subsequent laboratory GC analysis. Through its high
precision and time resolution, data of the QCL system were used for
quantifying the commonly observed nonlinearity in concentration changes
during chamber deployment, making the calculation of exchange fluxes more
accurate by the application of exponential models. As expected, the curvature
values in the concentration increase was higher during long (60 min) chamber
closure times and under high-flux conditions
(<i>F</i><sub>N<sub>2</sub>O</sub> > 150 µg N m<sup>−2</sup> h<sup>−1</sup>)
than those values that were found when chambers were closed for only 10 min and/or
when fluxes were in a typical range of 2 to
50 µg N m<sup>−2</sup> h<sup>−1</sup>. Extremely low standard errors of
fluxes, i.e., from ∼ 0.2 to 1.7 % of the flux value, were observed
regardless of linear or exponential flux calculation when using QCL data.
Thus, we recommend reducing chamber closure times to a maximum of 10 min
when a fast-response analyzer is available and this type of chamber system is
used to keep soil disturbance low and conditions around the chamber plot as
natural as possible. Further, applying linear regression to a 3 min data
window with rejecting the first 2 min after closure and a sampling time
of every 5 s proved to be sufficient for robust flux determination while ensuring
that standard errors of N<sub>2</sub>O fluxes were still on a relatively low level.
Despite low signal-to-noise ratios, GC was still found to be a useful method
to determine the mean the soil–atmosphere exchange of N<sub>2</sub>O on longer timescales
during specific campaigns. Intriguingly, the consistency between GC and
QCL-based campaign averages was better under low than under high N<sub>2</sub>O
efflux conditions, although single flux values were highly scattered during
the low efflux campaign. Furthermore, the QCL technology provides a useful
tool to accurately investigate the highly debated topic of diurnal courses
of N<sub>2</sub>O fluxes and its controlling factors. Our new chamber design
protects the measurement spot from unintended shading and minimizes
disturbance of throughfall, thereby complying with high quality requirements
of long-term observation studies and research infrastructures. |
| first_indexed | 2024-12-22T15:34:10Z |
| format | Article |
| id | doaj.art-b979a048097b497a97bb908a36a25437 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-22T15:34:10Z |
| publishDate | 2017-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-b979a048097b497a97bb908a36a254372022-12-21T18:21:18ZengCopernicus PublicationsBiogeosciences1726-41701726-41892017-03-011461365138110.5194/bg-14-1365-2017Gas chromatography vs. quantum cascade laser-based N<sub>2</sub>O flux measurements using a novel chamber designC. Brümmer0B. Lyshede1D. Lempio2J.-P. Delorme3J. J. Rüffer4R. Fuß5A. M. Moffat6M. Hurkuck7A. Ibrom8P. Ambus9H. Flessa10W. L. Kutsch11Thünen Institute of Climate-Smart Agriculture, Braunschweig, GermanyThünen Institute of Climate-Smart Agriculture, Braunschweig, GermanyThünen Institute of Climate-Smart Agriculture, Braunschweig, GermanyThünen Institute of Climate-Smart Agriculture, Braunschweig, GermanyThünen Institute of Climate-Smart Agriculture, Braunschweig, GermanyThünen Institute of Climate-Smart Agriculture, Braunschweig, GermanyThünen Institute of Climate-Smart Agriculture, Braunschweig, GermanyThünen Institute of Climate-Smart Agriculture, Braunschweig, GermanyDepartment of Environmental Engineering, Technical University of Denmark, Lyngby, DenmarkDepartment of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, DenmarkThünen Institute of Climate-Smart Agriculture, Braunschweig, GermanyThünen Institute of Climate-Smart Agriculture, Braunschweig, GermanyRecent advances in laser spectrometry offer new opportunities to investigate the soil–atmosphere exchange of nitrous oxide. During two field campaigns conducted at a grassland site and a willow field, we tested the performance of a quantum cascade laser (QCL) connected to a newly developed automated chamber system against a conventional gas chromatography (GC) approach using the same chambers plus an automated gas sampling unit with septum capped vials and subsequent laboratory GC analysis. Through its high precision and time resolution, data of the QCL system were used for quantifying the commonly observed nonlinearity in concentration changes during chamber deployment, making the calculation of exchange fluxes more accurate by the application of exponential models. As expected, the curvature values in the concentration increase was higher during long (60 min) chamber closure times and under high-flux conditions (<i>F</i><sub>N<sub>2</sub>O</sub> > 150 µg N m<sup>−2</sup> h<sup>−1</sup>) than those values that were found when chambers were closed for only 10 min and/or when fluxes were in a typical range of 2 to 50 µg N m<sup>−2</sup> h<sup>−1</sup>. Extremely low standard errors of fluxes, i.e., from ∼ 0.2 to 1.7 % of the flux value, were observed regardless of linear or exponential flux calculation when using QCL data. Thus, we recommend reducing chamber closure times to a maximum of 10 min when a fast-response analyzer is available and this type of chamber system is used to keep soil disturbance low and conditions around the chamber plot as natural as possible. Further, applying linear regression to a 3 min data window with rejecting the first 2 min after closure and a sampling time of every 5 s proved to be sufficient for robust flux determination while ensuring that standard errors of N<sub>2</sub>O fluxes were still on a relatively low level. Despite low signal-to-noise ratios, GC was still found to be a useful method to determine the mean the soil–atmosphere exchange of N<sub>2</sub>O on longer timescales during specific campaigns. Intriguingly, the consistency between GC and QCL-based campaign averages was better under low than under high N<sub>2</sub>O efflux conditions, although single flux values were highly scattered during the low efflux campaign. Furthermore, the QCL technology provides a useful tool to accurately investigate the highly debated topic of diurnal courses of N<sub>2</sub>O fluxes and its controlling factors. Our new chamber design protects the measurement spot from unintended shading and minimizes disturbance of throughfall, thereby complying with high quality requirements of long-term observation studies and research infrastructures.http://www.biogeosciences.net/14/1365/2017/bg-14-1365-2017.pdf |
| spellingShingle | C. Brümmer B. Lyshede D. Lempio J.-P. Delorme J. J. Rüffer R. Fuß A. M. Moffat M. Hurkuck A. Ibrom P. Ambus H. Flessa W. L. Kutsch Gas chromatography vs. quantum cascade laser-based N<sub>2</sub>O flux measurements using a novel chamber design Biogeosciences |
| title | Gas chromatography vs. quantum cascade laser-based N<sub>2</sub>O flux measurements using a novel chamber design |
| title_full | Gas chromatography vs. quantum cascade laser-based N<sub>2</sub>O flux measurements using a novel chamber design |
| title_fullStr | Gas chromatography vs. quantum cascade laser-based N<sub>2</sub>O flux measurements using a novel chamber design |
| title_full_unstemmed | Gas chromatography vs. quantum cascade laser-based N<sub>2</sub>O flux measurements using a novel chamber design |
| title_short | Gas chromatography vs. quantum cascade laser-based N<sub>2</sub>O flux measurements using a novel chamber design |
| title_sort | gas chromatography vs quantum cascade laser based n sub 2 sub o flux measurements using a novel chamber design |
| url | http://www.biogeosciences.net/14/1365/2017/bg-14-1365-2017.pdf |
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