Criteria for Closed Chamber Measurements of Radon Emanation Rate

Common field methods for measuring soil denitrification in situ include monitoring the accumulation of 15N labelled N2 and N2O evolved from 15N labelled soil nitrate pool in soil surface chambers. Bias of denitrification rates derived from chamber measurements results from subsoil diffusion of 15N labelled denitrification products, but this can be corrected by diffusion modeling (Well et al., 2019). Moreover, precision of the conventional 15N gas flux method is low due to the high N2 background of the atmosphere. An alternative to the closed chamber method is to use concentration gradients of soil gas to quantify their fluxes (Maier &&#160; Schack-Kirchner, 2014). Advantages compared to the closed &#160;chamber method include the facts that (i) time consuming work with closed chambers is replaced by easier sampling of soil gas probes, (ii) depth profiles yield not only the surface flux but also information on the depth distribution of gas production and (iii) soil gas concentrations are higher than chamber gas concentration, resulting in better detectability of 15N-labelled denitrification products. Here we use this approach for the first time to evaluate denitrification rates derived from depth profiles of 15N labelled N2 and N2O in the field by closed chamber measurements published previously (Lewicka-Szczebak et al., 2020).We compared surface fluxes of N2 and N2O from 15N labelled microplots using the closed chamber method. Diffusion&#8211;based soil gas probes (Schack-Kirchner et al., 1993) were used to sample soil air at the end of each closed chamber measurement. A diffusion-reaction model (Maier et al., 2017) will be &#160;used to fit measured and modelled concentrations of 15N labelled N2 and N2O. Depth-specific values of denitrification rates and the denitrification product ratio will be obtained from best fits of depth profiles and chamber accumulation, taking into account diffusion of labelled denitrification products to the subsoil (Well et al., 2019).Depending on the outcome of this evaluation, the gradient method could be used for continuous monitoring of denitrification in the field based on soil gas probe sampling. This could replace or enhance current approaches by improving the detection limit, facilitating sampling and delivering information on depth-specific denitrification. &#160;References:Lewicka-Szczebak D, Lewicki MP, Well R (2020) N2O isotope approaches for source partitioning of N2O production and estimation of N2O reduction &#8211; validation with the 15N gas-flux method in laboratory and field studies. Biogeosciences, 17, 5513-5537.Maier M, Longdoz B, Laemmel T, Schack-Kirchner H, Lang F (2017) 2D profiles of CO2, CH4, N2O and gas diffusivity in a well aerated soil: measurement and Finite Element Modeling. Agricultural and Forest Meteorology, 247, 21-33.Maier M, Schack-Kirchner H (2014) Using the gradient method to determine soil gas flux: A review. Agricultural and Forest Meteorology, 192, 78-95.Schack-Kirchner H, Hildebrand EE, Wilpert KV (1993) Ein konvektionsfreies Sammelsystem f&#252;r Bodenluft. Zeitschrift Fur Pflanzenernahrung Und Bodenkunde, 156, 307-310.Well R, Maier M, Lewicka-Szczebak D, Koster JR, Ruoss N (2019) Underestimation of denitrification rates from field application of the N-15 gas flux method and its correction by gas diffusion modelling. Biogeosciences, 16, 2233-2246.&#160;&#160;

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Improved parameterization of the commonly used exponential equation for calculating soil-atmosphere exchange fluxes from closed-chamber measurements

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2017.03.005 ◽

2017 ◽

Vol 240-241 ◽

pp. 18-25 ◽

Cited By ~ 2

Author(s):

Antje M. Moffat ◽

Christian Brümmer

Keyword(s):

Exponential Equation ◽

Closed Chamber ◽

Soil Atmosphere ◽

Chamber Measurements

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Methane uptake in a temperate forest soil using continuous closed-chamber measurements

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2015.05.004 ◽

2015 ◽

Vol 213 ◽

pp. 1-9 ◽

Cited By ~ 9

Author(s):

Masahito Ueyama ◽

Ryota Takeuchi ◽

Yoshiyuki Takahashi ◽

Reiko Ide ◽

Mioko Ataka ◽

...

Keyword(s):

Forest Soil ◽

Temperate Forest ◽

Closed Chamber ◽

Methane Uptake ◽

Chamber Measurements

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Small Closed-Chamber Measurements for the Uptake of Trichloroethylene and Ethanol Vapor by Fibrous Surfaces

Modeling of Indoor Air Quality and Exposure ◽

10.1520/stp13098s ◽

2009 ◽

pp. 25-25-17 ◽

Cited By ~ 1

Author(s):

JE Borrazzo ◽

CI Davidson ◽

JB Andelman

Keyword(s):

Ethanol Vapor ◽

Closed Chamber ◽

Chamber Measurements

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Calculations of automatic chamber flux measurements of methane and carbon dioxide using short time series of concentrations

Biogeosciences ◽

10.5194/bg-13-903-2016 ◽

2016 ◽

Vol 13 (4) ◽

pp. 903-912 ◽

Cited By ~ 21

Author(s):

Norbert Pirk ◽

Mikhail Mastepanov ◽

Frans-Jan W. Parmentier ◽

Magnus Lund ◽

Patrick Crill ◽

...

Keyword(s):

Carbon Dioxide ◽

Time Series ◽

High Resolution ◽

Ecosystem Respiration ◽

General Applicability ◽

Closed Chamber ◽

Gas Flux ◽

Flux Measurements ◽

Concentration Changes ◽

Chamber Measurements

Abstract. The closed chamber technique is widely used to measure the exchange of methane (CH4) and carbon dioxide (CO2) from terrestrial ecosystems. There is, however, large uncertainty about which model should be used to calculate the gas flux from the measured gas concentrations. Due to experimental uncertainties the simple linear regression model (first-order polynomial) is often applied, even though theoretical considerations of the technique suggest the application of other, curvilinear models. High-resolution automatic chamber systems which sample gas concentrations several hundred times per flux measurement make it possible to resolve the curvilinear behavior and study the information imposed by the natural variability of the temporal concentration changes. We used more than 50 000 such flux measurements of CH4 and CO2 from five field sites located in peat-forming wetlands ranging from 56 to 78° N to quantify the typical differences between flux estimates of different models. In addition, we aimed to assess the curvilinearity of the concentration time series and test the general applicability of curvilinear models. Despite significant episodic differences between the calculated flux estimates, the overall differences are generally found to be smaller than the local flux variability on the plot scale. The curvilinear behavior of the gas concentrations within the chamber is strongly influenced by wind-driven chamber leakage, and less so by changing gas concentration gradients in the soil during chamber closure. Such physical processes affect both gas species equally, which makes it possible to isolate biochemical processes affecting the gases differently, such as photosynthesis limitation by chamber headspace CO2 concentrations under high levels of incoming solar radiation. We assess the possibility to exploit this effect for a partitioning of the net CO2 flux into photosynthesis and ecosystem respiration as an example of how high-resolution automatic chamber measurements could be used for purposes beyond the estimation of the net gas flux. This shows that while linear and curvilinear calculation schemes can provide similar net fluxes, only curvilinear models open additional possibilities for high-resolution automatic chamber measurements.

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Combining a Quantum Cascade Laser Spectrometer with an Automated Closed-Chamber System for δ13C Measurements of Forest Soil, Tree Stem and Tree Root CO2 Fluxes

Forests ◽

10.3390/f10050432 ◽

2019 ◽

Vol 10 (5) ◽

pp. 432

Author(s):

Andreas Brændholt ◽

Andreas Ibrom ◽

Per Ambus ◽

Klaus Steenberg Larsen ◽

Kim Pilegaard

Keyword(s):

Water Vapour ◽

Quantum Cascade Laser ◽

Co2 Concentration ◽

Co2 Fluxes ◽

Laser Spectrometer ◽

Closed Chamber ◽

Quantum Cascade ◽

The Mean ◽

Chamber Measurements ◽

Intact Soil

Recent advances in laser spectroscopy have allowed for real-time measurements of the 13C/12C isotopic ratio in CO2, thereby providing new ways to investigate carbon cycling in natural ecosystems. In this study, we combined an Aerodyne quantum cascade laser spectrometer for CO2 isotopes with a LI-COR LI-8100A/8150 automated chamber system to measure the δ13C of CO2 during automated closed-chamber measurements. The isotopic composition of the CO2 flux was determined for each chamber measurement by applying the Keeling plot method. We found that the δ13C measured by the laser spectrometer was influenced by water vapour and CO2 concentration of the sample air and we developed a method to correct for these effects to yield accurate measurements of δ13C. Overall, correcting for the CO2 concentration increased the δ13C determined from the Keeling plots by 3.4‰ compared to 2.1‰ for the water vapour correction. We used the combined system to measure δ13C of the CO2 fluxes automatically every two hours from intact soil, trenched soil, tree stems and coarse roots during a two-month campaign in a Danish beech forest. The mean δ13C was −29.8 ± 0.32‰ for the intact soil plots, which was similar to the mean δ13C of −29.8 ± 1.2‰ for the trenched soil plots. The lowest δ13C was found for the root plots with a mean of −32.6 ± 0.78‰. The mean δ13C of the stems was −30.2 ± 0.74‰, similar to the mean δ13C of the soil plots. In conclusion, the study showed the potential of using a quantum cascade laser spectrometer to measure δ13C of CO2 during automated closed-chamber measurements, thereby allowing for measurements of isotopic ecosystem CO2 fluxes at a high temporal resolution. It also highlighted the importance of proper correction for cross-sensitivity with water vapour and CO2 concentration of the sample air to get accurate measurements of δ13C.

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Hydrogen soil deposition at an urban site in Finland

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-8559-2009 ◽

2009 ◽

Vol 9 (21) ◽

pp. 8559-8571 ◽

Cited By ~ 9

Author(s):

M. Lallo ◽

T. Aalto ◽

J. Hatakka ◽

T. Laurila

Keyword(s):

Deposition Velocity ◽

Photochemical Reactions ◽

Urban Site ◽

Two Dimensional ◽

Tracer Method ◽

Closed Chamber ◽

Radon Exhalation ◽

Radon Exhalation Rates ◽

Soil Deposition ◽

Chamber Measurements

Abstract. Hydrogen deposition velocities (vd) were estimated by field chamber measurements and model simulations. A closed-chamber method was used for soil deposition studies in Helsinki, Finland, at an urban park inhabited by broad-leaved trees. Radon tracer method was used to estimate the vd in nighttime when photochemical reactions were minimal and radon gas was concentrated in the shallow boundary layer due to exhalation from soil. A two-dimensional atmospheric model was used for the calculation of respective vd values and radon exhalation rates. The vd and radon exhalation rates were lower in winter than in summer according to all methods. The radon tracer method and the two-dimensional model results for hydrogen deposition velocity were in the range of 0.13 mm s−1 to 0.93 mm s−1 (radon tracer) and 0.12 mm s−1 to 0.61 mm s−1 (two-dimensional). The soil chamber results for vd were 0.00 mm s−1 to 0.70 mm s−1. Both models and chamber measurements revealed a relation between one week cumulative rain sum and deposition velocity. When precipitation events occurred a few days before the chamber measurements, lower vd values were observed. A snow cover also lowered vd.

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Hydrogen soil deposition at an urban site in Finland

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-14873-2009 ◽

2009 ◽

Vol 9 (4) ◽

pp. 14873-14899 ◽

Cited By ~ 2

Author(s):

M. Lallo ◽

T. Aalto ◽

J. Hatakka ◽

T. Laurila

Keyword(s):

Deposition Velocity ◽

Atmospheric Model ◽

Photochemical Reactions ◽

Urban Site ◽

Two Dimensional ◽

Tracer Method ◽

Closed Chamber ◽

Radon Exhalation ◽

Soil Deposition ◽

Chamber Measurements

Abstract. Hydrogen deposition velocities (v_d) were estimated by field chamber measurements and model simulations. A closed-chamber method was used for soil deposition studies in Helsinki, Finland, at an urban park inhabited by broad-leaved trees. Radon tracer method was used to estimate the v_d in nighttime when photochemical reactions were minimal and radon gas was concentrated to shallow boundary layer due to exhalation from soil. A two-dimensional atmospheric model was used for calculation of respective v_d values and radon exhalation rate. v_d and radon exhalation rates were lower in winter than in summer according to all methods. The radon tracer method and two-dimensional model results for hydrogen deposition velocity were in the range of 0.13 mm s−1 to 0.90 mm s−1 (radon tracer) and 0.12 mm s−1 to 0.61 mm s−1 (two-dimensional). The soil chamber results for v_d were 0.00 mm s−1 to 0.70 mm s−1. Both models and chamber measurements revealed relation between one week cumulative rain sum and deposition velocity. Lower v_d values were usually measured in high soil moisture conditions. Precipitation occurring a few days before chamber measurements decreased v_d values. The snow cover also lowered v_d.

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