Alternative Turbulent Trace Gas Flux Measurement Methods

Rinne, Janne; Ammann, Christof; Pattey, E.; U, Kyaw Tha Paw; Desjardins, Raymond L.

doi:10.1007/978-3-030-52171-4_56

Cited by 4 publications

(3 citation statements)

References 95 publications

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“…For the NBLA approach we measured the CH 4 mixing ratio and δ 13 C at 0.4 m above the mire surface during the nighttime. As the emitted CH 4 is accumulated in the shallow stable nocturnal surface layer, we can employ a similar two-end-member mixing model to that for the chamber measurements (Rinne et al, 2021). Thus, we obtain the δ 13 C of the emitted CH 4 by the Keeling plot approach (Eq.…”

Section: Ch 4 Emission and δ 13 C Measurementsmentioning

confidence: 99%

Spatial and temporal variation in δ¹³C values of methane emitted from a hemiboreal mire: methanogenesis, methanotrophy, and hysteresis

et al. 2022

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Abstract. The reasons for spatial and temporal variation in methane emission from mire ecosystems are not fully understood. Stable isotope signatures of the emitted methane can offer clues to the causes of these variations. We measured the methane emission (FCH4) and 13C signature (δ13C) of emitted methane by automated chambers at a hemiboreal mire for two growing seasons. In addition, we used ambient methane mixing ratios and δ13C to calculate a mire-scale 13C signature using a nocturnal boundary-layer accumulation approach. Microbial methanogenic and methanotrophic communities were determined by a captured metagenomics analysis. The chamber measurements showed large and systematic spatial variations in δ13C-CH4 of up to 15 ‰ but smaller and less systematic temporal variation. According to the spatial δ13C–FCH4 relations, methanotrophy was unlikely to be the dominating cause for the spatial variation. Instead, these were an indication of the substrate availability of methanogenesis being a major factor in explaining the spatial variation. Genetic analysis indicated that methanogenic communities at all sample locations were able to utilize both hydrogenotrophic and acetoclastic pathways and could thus adapt to changes in the available substrate. The temporal variation in FCH4 and δ13C over the growing seasons showed hysteresis-like behavior at high-emission locations, indicative of time-lagged responses to temperature and substrate availability. The upscaled chamber measurements and nocturnal boundary-layer accumulation measurements showed similar average δ13C values of −81.3 ‰ and −79.3 ‰, respectively, indicative of hydrogenotrophic methanogenesis at the mire. The close correspondence of the δ13C values obtained by the two methods lends confidence to the obtained mire-scale isotopic signature. This and other recently published data on δ13C values of CH4 emitted from northern mires are considerably lower than the values used in atmospheric inversion studies on methane sources, suggesting a need for revision of the model input.

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Section: Ch 4 Emission and δ 13 C Measurementsmentioning

confidence: 99%

Spatial and temporal variation in δ¹³C values of methane emitted from a hemiboreal mire: methanogenesis, methanotrophy, and hysteresis

et al. 2022

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“…This requirement limits the EC method to a few trace gases for which fast-response gas analyzers are available. For constituents for which only slow-response gas analyzers are available, several methods for measuring the fluxes exist (Rinne et al, 2021). Among these methods, true eddy accumulation (TEA) (Desjardins, 1977) is the most direct and the closest to EC.…”

Section: Introductionmentioning

confidence: 99%

True eddy accumulation – Part 2: Theory and experiment of the short-time eddy accumulation method

Emad¹,

Siebicke²

2023

Atmos. Meas. Tech.

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Abstract. A new variant of the eddy accumulation method for measuring atmospheric exchange is derived, and a prototype sampler is evaluated. The new method, termed short-time eddy accumulation (STEA), overcomes the requirement of fixed accumulation intervals in the true eddy accumulation method (TEA) and enables the sampling system to run in a continuous flow-through mode. STEA enables adaptive time-varying accumulation intervals, which improves the system's dynamic range and brings many advantages to flux measurement and calculation. The STEA method was successfully implemented and deployed to measure CO2 fluxes over an agricultural field in Braunschweig, Germany. The measured fluxes matched very well against a conventional eddy covariance system (slope of 1.04, R2 of 0.86). We provide a detailed description of the setup and operation of the STEA system in the continuous flow-through mode, devise an empirical correction for the effect of buffer volumes, and describe the important considerations for the successful operation of the STEA method. The STEA method reduces the bias and uncertainty in the measured fluxes compared to conventional TEA and creates new ways to design eddy accumulation systems with finer control over sampling and accumulation. The results encourage the application of STEA for measuring fluxes of more challenging atmospheric constituents such as reactive species. This paper is Part 2 of a two-part series on true eddy accumulation.

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“…Yet, many constituents critical to atmospheric chemistry and ecosystem dynamics, such as stable isotopes, nitrogen oxides, and volatile organic compounds, only have slow-response analyzers. For these, several alternative micrometeorological methods compatible with slower analyzers have been developed [Rinne et al, 2021]. The true eddy accumulation (TEA) method realizes the product between w and c by accumulating air samples with mass proportional to the vertical wind velocity, enabling the direct measurement of the flux from the accumulated mass difference [Desjardins, 1977, Hicks andMcMillen, 1984].…”

Section: Introductionmentioning

confidence: 99%

Compressibility of air effects on eddy accumulation flux measurements

Emad¹,

Siebicke²

2020

Preprint

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Eddy accumulation is a direct flux measurement technique for trace gas exchange between the land surface and the atmosphere. Eddy accumulation complements the now common eddy covariance method in its ability to measure even small fluxes accurately with slow response gas analyzers and being power efficient. However, the physically most direct way of eddy accumulation, also known as true eddy accumulation (TEA), requires the sampling of air at a rate proportional to the vertical wind velocity at a fast rate of typically 10 Hz or more. Lack of suitable methods for high-speed air sampling has been a primary limitation for the practical application of eddy accumulation in the past. The compressibility of air causes a variation of pressure inside the sampling system, which affects the ability to control the sample flow rate accurately, potentially compromising the derived flux measurements. It is therefore essential to quantify the effect of compressibility on fluxes and understand the parameters which allow for mitigating the effect at the design stage. In this study, we present successful true eddy accumulation measurements over the old-growth forest at the Fluxnet site Hainich (DE-Hai) and quantify the compressibility effects on fluxes. Performing simulations on high-frequency data of CO2 and vertical wind velocity for a range of system configurations, we are able to quantify the impact of compressibility on fluxes and explain why our measurements were successful. We find that different system configurations lead to flux changes over a representative range of 1 to 25 percent of the flux. Key controlling parameters are the size and arrangement of internal buffer volumes and the appropriate control of the inlet flow rate sampling device as a function of internal and external pressure states. This knowledge allows to mitigate compressibility effects and design accurate true eddy accumulation flux measurements for a range of atmospheric constituents.

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Alternative Turbulent Trace Gas Flux Measurement Methods

Cited by 4 publications

References 95 publications

Spatial and temporal variation in δ¹³C values of methane emitted from a hemiboreal mire: methanogenesis, methanotrophy, and hysteresis

Spatial and temporal variation in δ¹³C values of methane emitted from a hemiboreal mire: methanogenesis, methanotrophy, and hysteresis

True eddy accumulation – Part 2: Theory and experiment of the short-time eddy accumulation method

Compressibility of air effects on eddy accumulation flux measurements

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Alternative Turbulent Trace Gas Flux Measurement Methods

Cited by 4 publications

References 95 publications

Spatial and temporal variation in δ13C values of methane emitted from a hemiboreal mire: methanogenesis, methanotrophy, and hysteresis

Spatial and temporal variation in δ13C values of methane emitted from a hemiboreal mire: methanogenesis, methanotrophy, and hysteresis

True eddy accumulation – Part 2: Theory and experiment of the short-time eddy accumulation method

Compressibility of air effects on eddy accumulation flux measurements

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Spatial and temporal variation in δ¹³C values of methane emitted from a hemiboreal mire: methanogenesis, methanotrophy, and hysteresis

Spatial and temporal variation in δ¹³C values of methane emitted from a hemiboreal mire: methanogenesis, methanotrophy, and hysteresis