A fast and sensitive method for the continuous in situ determination of dissolved methane and its δ<sup>13</sup>C‐isotope ratio in surface waters

Hartmann, Jan; Gentz, Torben; Schiller, Amanda; Greule, Markus; Grossart, Hans‐Peter; Ionescu, Danny; Keppler, Frank; Martinez‐Cruz, Karla; Sepulveda‐Jauregui, Armando; Isenbeck‐Schröter, Margot

doi:10.1002/lom3.10244

Cited by 13 publications

(22 citation statements)

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“…The observed occurrence of a maximum in the vertical profile of dissolved CH 4 concentration in the upper layer of Lake Stechlin (Fig. 3b) is consistent with previous observations (Grossart et al, 2011;Tang et al, 2014;Hartmann et al, 2018). In Lake Arend we also observed a CH 4 peak (Fig.…”

Section: Depth Profiles Of Dissolved Ch 4 From Multiple Lakessupporting

confidence: 92%

“…3a), although the overall concentration was lower. In contrast, with the headspace method the FaRAGE allowed for the localized CH 4 concentration maximum to be described at a high vertical resolution, similar to that obtained with more sophisticated membrane filter equilibrators (Hartmann et al, 2018;Gonzalez-Valencia et al, 2014). The FaRAGE was capable of resolving differences in dissolved CH 4 concentration in lake water at decimeter scales with ease.…”

Section: Depth Profiles Of Dissolved Ch 4 From Multiple Lakesmentioning

confidence: 93%

“…CC BY 4.0 License. maximum depth of 48 m. Pronounced CH peaks in the epilimnion of Lake Stechlin have been previously reported that were measured with various methods (Grossart et al, 2011;Hartmann et al, 2018;Tang et al, 2014). This makes it ideal for our testing purpose.…”

Section: Field Testsmentioning

confidence: 99%

“…Tests were performed by adapting the FaRAGE to two other greenhouse gas analyzers (Ultraportable Los Gatos and Picarro G2132-i) and the response times are listed in Table S3. Comparisons were made in Webb et al (2016) and Hartmann et al (2018) where both CH 4 and 13 C-CH 4 were measured using a Picarro G2201-i (Picarro, USA). Here we used a similar Picarro stable isotopic gas analyzer (Picarro G2132-i) and unified all previous reported response time  to t 95% by applying the equation t 95% = 3.…”

Section: Detection Limit Equilibration Ratio and Response Timementioning

confidence: 99%

“…The headspace gas sample is then measured with a gas spectrometer and the concentration of targeted gas can be calculated according to Henry's law (Magen et al, 2014). To save sampling effort, continuous gas equilibration devices have been developed, which generally can be classified to four categories: 1) Membrane type (Schlüter and Gentz, 2008;Boulart et al, 2010;Gonzalez-Valencia et al, 2014;Hartmann et al, 2018) -gases are extracted from water by using a gas-permeable membrane; 2) Marble type (Frankignoulle et al, 2001;Santos et al, 2012) -gas exchange is enhanced by pumping water through marbles https://doi.org/10.5194/hess-2020-67 Preprint. Discussion started: 20 April 2020 c Author(s) 2020.…”

Section: Introductionmentioning

confidence: 99%

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A Fast-response automated gas equilibrator (FaRAGE) for continuous in situ measurement of methane dissolved in water

Xiao¹,

Liu²,

Wang³

et al. 2020

Preprint

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Abstract. Biogenic methane (CH4) emissions from inland waters contribute substantially to global warming. In aquatic systems, CH4 dissolved in freshwater lakes and reservoirs is highly heterogeneous both in space and time. To better understand the biological and physical processes that affect sources and sinks of CH4 in lakes and reservoirs, dissolved CH4 needs to be measured with a highest temporal resolution. To achieve this goal, we developed the Fast-Response Automated Gas Equilibrator (FaRAGE) for real-time in situ measurement of dissolved CH4 concentration at the water surface and in the water column. FaRAGE can achieve an exceptionally short response time (t95 % = 12 s when including the response time of the gas analyzer) while retaining an equilibration ratio of 63 % and a measurement accuracy of 0.5 %. An equilibration ratio as high as 91.8 % can be reached at the cost of a slightly increased response time (16 s). The FaRAGE is capable of continuously measuring dissolved CH4 concentrations in the nM-to-mM (10−9–10−3 mol L−1) range with a detection limit of sub-nM (10−10 mol L−1), when coupled with a cavity ring-down greenhouse gas analyzer (Picarro GasScouter). It enables the possibility of mapping dissolved CH4 concentration in a quasi three-dimensional manner in lakes. The FaRAGE is simple to operate, inexpensive, and suitable for continuous monitoring with a strong tolerance to suspended particles. The easy adaptability to other gas analyzers such as Ultra-portable Los Gatos and stable isotopic gas analyzer (Picarro G2132-i) also provides the potential for many further applications, e.g. measuring dissolved 13δC-CH4 and CO2.

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Section: Depth Profiles Of Dissolved Ch 4 From Multiple Lakessupporting

confidence: 92%

Section: Depth Profiles Of Dissolved Ch 4 From Multiple Lakesmentioning

confidence: 93%

Section: Field Testsmentioning

confidence: 99%

Section: Detection Limit Equilibration Ratio and Response Timementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Fast-response automated gas equilibrator (FaRAGE) for continuous in situ measurement of methane dissolved in water

Xiao¹,

Liu²,

Wang³

et al. 2020

Preprint

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The impact of seasonal sulfate–methane transition zones on methane cycling in a sulfate‐enriched freshwater environment

Kleint

Wellach

Schroll

et al. 2021

Limnology & Oceanography

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Lake Willersinnweiher located in south-western Germany is a small eutrophic gravel pit lake fed by sulfateenriched groundwater. The aim of this study was to investigate the total methane (CH 4 ) mass balance of Lake Willersinnweiher with a particular focus on the interaction of carbon and sulfur cycling within the lake sediments and the redoxcline of the water column. Our results show that Lake Willersinnweiher permanently releases CH 4 to the atmosphere throughout the whole year 2018 at rates ranging from 5 to 120 mol d −1 . Sediment data show the presence of intense anaerobic oxidation of CH 4 in the upper sediment layers during early summer. Here, CH 4 is most likely consumed via sulfate in sulfate-methane transition zones (SMTZs) that have been observed for a few specific freshwater environments only. Seasonal dynamics in biogeochemical processes trigger the non-steady state conditions within the sediments and the CH 4 consumption in the SMTZs. In parallel, CH 4 released from the sediments is completely consumed by aerobic oxidation processes in the redoxcline indicated by minimum CH 4 concentrations with high δ 13 C-CH 4 values. This zone acts as an effective barrier, minimizing CH 4 release into the surface water and the atmosphere and thus CH 4 oversaturation along with near-atmospheric isotopic composition indicate the presence of an additional CH 4 source in the epilimnion of Lake Willersinnweiher.The emission of the greenhouse gas methane (CH 4 ) from freshwater lakes has been suggested to play a substantial role in the global methane budget (e.g., Bastviken et al. 2004). Here, significant amounts of CH 4 are emitted, even though CH 4 produced in aquatic systems is largely consumed by anaerobic and aerobic methanotrophs (up to 30-99%; Bastviken et al. 2008). The amount of emitted CH 4 is thereby depending on bioproduction, degradation and mineralization of organic substances in the sediments and the water column of the freshwater lake.Carbon mineralization in anoxic lake sediments is affected by manganese (Mn) and iron (Fe) reducing bacteria metabolizing competitive substrates, outcompeting CH 4 forming microorganisms (methanogens) within the upper sediment layers (e.g., Whiticar 1999). Sulfate (SO 4 2− ) reduction often has minor implications on organic matter degradation due to low SO 4 2− availability in most freshwater environments (Holmer and Storkholm 2001), so that SO 4 2− is rapidly depleted with sediment depth and SO 4 2− reducing bacteria become inactive or are absent. As a consequence, methanogenesis is the most important process in overall carbon mineralization in anoxic lacustrine sediments (e.g., Rudd and Hamilton 1978). Competitive metabolisms are not only affecting methanogenesis, but also consumption of CH 4 by bacteria (methanotrophs) in the sediments. The anaerobic oxidation of methane in the sediments of lakes is usually coupled to the reduction of the energetically more favorable electron acceptors, such as nitrate and nitrite (e.g., Raghoebarsing et al. 2006) or Fe(III) and/or Mn(I...

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Development of a fast‐response system with integrated calibration for high‐resolution mapping of dissolved methane concentration in surface waters

Dugan,

Weber,

Kessler

2024

Limnology & Ocean Methods

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Dissolved gas concentrations in surface waters can have sharp gradients across marine and freshwater environments, which often prove challenging to capture with analytical measurement. Collecting discrete samples for laboratory analysis provides accurate results, but suffers from poor spatial resolution. To overcome this limitation, water equilibrators and gas membrane contactors (GMCs) have been used for the automated underway measurement of dissolved gas concentrations in surface water. However, while water equilibrators can provide continuous measurements, their analytical response times to changes in surface water concentration can be slow, lasting tens of minutes. This leads to spatial imprecisions in the dissolved gas concentration data. Conversely, while GMCs have proven to have much faster analytical response times, often lasting only a few minutes or less, they suffer from poor accuracy and thus require routine calibration. Here we present an analytical system for the high accuracy and high precision spatial mapping of dissolved methane concentration in surface waters. The system integrates a GMC with a cavity ringdown spectrometer for fast analytical response times, with a calibration method involving two Weiss‐style equilibrators and discrete measurements in vials. Data from both the GMC and equilibrators are collected simultaneously, with discrete vial samples collected periodically throughout data collection. We also present a mathematical algorithm integrating all data collected for the routine calibration of the GMC dataset. The algorithm facilitates comparison between the GMC and equilibrator datasets despite the substantial differences in response times (0.7–2.1 and 4.1–17.6 min, respectively). This measurement system was tested with both systematic laboratory experiments and field data collected on a research cruise along the US Atlantic margin. Once calibrated, this system identified numerous sharp peaks of dissolved methane concentration in the US Atlantic margin dataset that would be poorly resolved, or outright missed with previous measurement techniques. Overall, the precision and accuracy for the technique presented here were determined to be 11.2% and 10.4%, respectively, the operating range was 0–1000 ppm methane, and the e‐folding response time to changes in dissolved methane concentration was 0.7–2.1 min.

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A fast and sensitive method for the continuous in situ determination of dissolved methane and its δ¹³C‐isotope ratio in surface waters

Cited by 13 publications

References 64 publications

A Fast-response automated gas equilibrator (FaRAGE) for continuous in situ measurement of methane dissolved in water

A Fast-response automated gas equilibrator (FaRAGE) for continuous in situ measurement of methane dissolved in water

The impact of seasonal sulfate–methane transition zones on methane cycling in a sulfate‐enriched freshwater environment

Development of a fast‐response system with integrated calibration for high‐resolution mapping of dissolved methane concentration in surface waters

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A fast and sensitive method for the continuous in situ determination of dissolved methane and its δ13C‐isotope ratio in surface waters

Cited by 13 publications

References 64 publications

A Fast-response automated gas equilibrator (FaRAGE) for continuous in situ measurement of methane dissolved in water

A Fast-response automated gas equilibrator (FaRAGE) for continuous in situ measurement of methane dissolved in water

The impact of seasonal sulfate–methane transition zones on methane cycling in a sulfate‐enriched freshwater environment

Development of a fast‐response system with integrated calibration for high‐resolution mapping of dissolved methane concentration in surface waters

Contact Info

Product

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A fast and sensitive method for the continuous in situ determination of dissolved methane and its δ¹³C‐isotope ratio in surface waters