Metrology for low-cost CO<sub>2</sub> sensors applications: the case of a steady-state through-flow (SS-TF) chamber for CO<sub>2</sub> fluxes observations

Curcoll, Roger; Morguí, Josep-Anton; Kamnang, Armand; Cañas, Lídia; Vargas, Arturo; Grossi, Claudia

doi:https://doi.org/10.5194/amt-15-2807-2022

Articles | Volume 15, issue 9

https://doi.org/10.5194/amt-15-2807-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-15-2807-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 9

Research article

|

09 May 2022

Research article |

| 09 May 2022

Metrology for low-cost CO₂ sensors applications: the case of a steady-state through-flow (SS-TF) chamber for CO₂ fluxes observations

Roger Curcoll, Josep-Anton Morguí, Armand Kamnang, Lídia Cañas, Arturo Vargas, and Claudia Grossi

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Final revised paper (published on 09 May 2022)
Preprint (discussion started on 20 Nov 2021)

Interactive discussion

Status: closed

RC1:
'Comment on amt-2021-387', Simone Baffelli, 06 Jan 2022

The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2021-387/amt-2021-387-RC1-supplement.pdf

Citation: https://doi.org/10.5194/amt-2021-387-RC1
- AC1: 'Reply on RC1', Roger Curcoll Masanes, 11 Mar 2022
  
  The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2021-387/amt-2021-387-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/amt-2021-387-AC1
RC2:
'Comment on amt-2021-387', Anonymous Referee #2, 07 Jan 2022
This paper presents a new Steady-State-Through-Flow (SS-TF) system based on low-cost Air Enquirer kits, including CO₂ and environmental parameter sensors. The CO₂ sensor is calibrated in a chamber where environmental parameters can be controlled. Multivariate regression models are derived from comparison with reference CO₂ measurements and applied to the CO₂ soil flux measurements. Conceptually, this work on application of low-cost sensors for a high temporal and spatial monitoring of CO₂ soil flux is useful, but requires more evidence on the performance evaluation of a new SS-TF system to be published in AMT.

Only 5 comparison during 2 days of experiment are provided for the evaluation. This size of dataset is extremely limited. 2 days are not enough to catch all possible range of variations in environmental parameters that might affect the correction of the low-cost CO₂ measurements and calculation of the soil flux measurements. Moreover, it would be necessary to have an explanation and a correction for the mismatch observed when NSS-NTF shows negative flux.

For the evaluation of this new SS-TF system, I would prefer to see comparison with a commercial soil flux measurement system instead of comparison to NSS-STF measurement system using the low-cost sensor.

Specific comments

Line 97-100. Detailed description on the calibration chamber system is needed. How is the calibration experiment designed? For example, at what temperatures is the experiment held and for how long?

Line 138. How well would the measurements at the top of the flux chamber represent the gas exiting the chamber? How much bias or uncertainty would be introduced with this assumption?

Line 195-196. Is concentration first averaged and then used to calculate the flux? Or is the flux calculated using the original temporal resolution of the CO₂ measurements and then averaged?

Line 197. What is the temporal resolution of the CO2 measurements? Is the RSE also calculated with 10 minutes averaged dataset? If not, the RSE would be different for the 10 minutes averaged flux.

Figure 5. What’s the difference between the 2 sigma error and the extended error?
Citation: https://doi.org/10.5194/amt-2021-387-RC2
- AC2: 'Reply on RC2', Roger Curcoll Masanes, 11 Mar 2022
  
  The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2021-387/amt-2021-387-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/amt-2021-387-AC2

Peer review completion

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

AR by Roger Curcoll Masanes on behalf of the Authors (11 Mar 2022) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (24 Mar 2022) by Reem Hannun

RR by Simone Baffelli (07 Apr 2022)

ED: Publish subject to technical corrections (08 Apr 2022) by Reem Hannun

Short summary

Low-cost air enquirer kits, including CO₂ and environmental parameter sensors, have been designed, built, and tested in a new steady-state through-flow chamber for simultaneous measurements of CO₂ fluxes in soil and CO₂ concentrations in air. A CO₂ calibration and multiparametric fitting reduced the total uncertainty of CO₂ concentration by 90 %. This system allows continuous measurement of CO₂ fluxes and CO₂ ambient air, with low cost (EUR 1200), low energy demand (<5 W), and low maintenance.

Metrology for low-cost CO2 sensors applications: the case of a steady-state through-flow (SS-TF) chamber for CO2 fluxes observations

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Interactive discussion

Peer review completion

Metrology for low-cost CO₂ sensors applications: the case of a steady-state through-flow (SS-TF) chamber for CO₂ fluxes observations