Evaluation of headspace equilibration methods for quantifying greenhouse gases in groundwater

Jahangir, M. M. R.; Johnston, Paul; Khalil, M.I.; Grant, Jim; Somers, Cathal; Richards, Karl G.

doi:10.1016/j.jenvman.2012.06.033

Cited by 32 publications

(17 citation statements)

References 19 publications

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“…In the trace gas mesocosms, 30 ml of soil gas was removed by syringe from unsaturated soil horizons to measure CH 4 concentrations and δ 13 C‐CH 4 . In saturated horizons, 10 ml of pore water was removed by syringe, and dissolved CH 4 was measured by equilibrating pore water with a pure N 2 headspace within the syringe at a 3:1 N 2 to water equilibration ratio [ Jahangir et al ., ]. Equilibrating syringes were placed on an orbital shaker for 10 min and vigorously shaken by hand prior to headspace measurements.…”

Section: Methodsmentioning

confidence: 99%

Influence of transient flooding on methane fluxes from subtropical pastures

et al. 2016

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Seasonally flooded subtropical pastures are major methane (CH 4 ) sources, where transient flooding drives episodic and high-magnitude emissions from the underlying landscape. Understanding the mechanisms that drive these patterns is needed to better understand pasture CH 4 emissions and their response to global change. We investigated belowground CH 4 dynamics in relation to surface fluxes using laboratory water table manipulations and compared these results to field-based eddy covariance measurements to link within-soil CH 4 dynamics to ecosystem fluxes. Ecosystem CH 4 fluxes lag flooding events, and this dynamic was replicated in laboratory experiments. In both cases, peak emissions were observed during water table recession. Flooding of surface organic soils and precipitation driven oxygen pulses best explained the observed time lags. Precipitation oxygen pulses likely delay CH 4 emissions until groundwater dissolved oxygen is consumed, and emissions were temporally linked to CH 4 production in surface soil horizons. Methane accumulating in deep soils did not contribute to surface fluxes and is likely oxidized within the soil profile. Methane production rates in surface organic soils were also orders of magnitude higher than in deep mineral soils, suggesting that over longer flooding regimes CH 4 produced in deep horizons is not a significant component of surface emissions. Our results demonstrate that distinct CH 4 dynamics may be stratified by depth and flooding of surface organic soils drives CH 4 fluxes from subtropical pastures. These results suggest that small changes in pasture water table dynamics can drive large changes in CH 4 emissions if surface soils remain saturated over longer time scales.Methane fluxes from flooded ecosystems are the product of CH 4 production, consumption, and transport within soils and water. Here CH 4 is produced exclusively by Archaea (methanogens) that convert end products of fermentation, most notably acetate or CO 2 and H 2 , to CH 4 for energy. Methanogens are most active in anaerobic and highly reduced environments, and their activity is generally limited by high oxygen (O 2 ) concentrations, substrate (C) availability, and the presence of alternative electron acceptors used for respiration [Conrad, 2007]. In contrast, CH 4 consuming bacteria (methanotrophs) oxidize CH 4 for energy in the presence of O 2 . Methanotrophs are primarily aerobic, and their activity is often limited by low CHAMBERLAIN ET AL.TRANSIENT FLOODING AND METHANE FLUXES 965 PUBLICATIONS

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Section: Methodsmentioning

confidence: 99%

Influence of transient flooding on methane fluxes from subtropical pastures

et al. 2016

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“…Aliquots of the sample were used to measure pH and redox potential (E H ) using calibrated probes, for monitoring Fe, Si, and other plant nutrients with ICP-OES analysis, and for As using inductivelycoupled plasma-mass spectrometry (ICP-MS). At the last sampling timepoint, dissolved CH 4 levels in the pore-waters and overlying waters were sampled using the headspace equilibration technique (Jahangir et al 2012). For overlying waters, a pre-tarred 250 mL glass serum vial was carefully submerged and filled to approximately half of the volume, allowing for a headspace.…”

Section: Rice Residue Incorporation Experimentsmentioning

confidence: 99%

Biogeochemical impacts of silicon-rich rice residue incorporation into flooded soils: Implications for rice nutrition and cycling of arsenic

et al. 2015

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Aim Soil incorporation of Si-rich rice residues may aid smallholder rice farmers in improving crop yields and may affect As uptake. Here, the biogeochemical impacts of rice residue incorporation into flooded soil without plants were evaluated. Methods Various particle sizes of fresh rice straw (FS), fresh rice husk (FH), rice straw ash (RSA) and rice husk ash (RHA) residues were incorporated into soil (1 % w/w) in a flooded pot experiment. Pore-water chemistry was monitored weekly and dissolved CH 4 concentrations and genes specific for methanotrophy and methanogenesis in DNA extracts of soil were evaluated. Results FH-amended soil had the highest level of dissolved Si, followed by FS and then ash (RHA or RSA). Particle size had little effect on the dissolved Si concentration for any residue tested. No amendments had any substantial effect on pore-water pH. FS-amended soil had much higher As, Fe, and CH 4 concentrations in pore-water compared to ash and FH, and its extracted DNA also had higher amplifications of genes indicative of methanogenesis. Conclusion FH, RHA, or RSA are attractive amendments for smallholder rice farmers to increase plantavailable Si without exacerbating CH 4 emissions, which may improve rice nutrition through the beneficial impacts of Si on combating biotic and abiotic stress including decreased arsenic uptake.

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“…Note the equilibration and the extract efficiency vary with the different treatments (gas/water volume ratio, shaking time, standing time), which have been discussed in detail (Jahangir et al 2012;Magen et al 2015;Roberts et al 2015). In this method, the 40 mL headspace is required for allow enough volume to purge the water trap (1 mL) and the 1 mL sample loop.…”

Section: Headspace Equilibration Treatmentsmentioning

confidence: 99%

Development and application of a gas chromatography method for simultaneously measuring H₂ and CH₄ in hydrothermal plume samples

Wang

Zhou

Qinye

et al. 2015

Limnology & Ocean Methods

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A robust, simple and efficient gas chromatography (GC) method is presented for determining H 2 and CH 4 concentrations simultaneously in water samples. The GC system consists of one detector (pulsed discharge helium ionization detector-PDHID), two columns in two ovens, respectively, and two 2-position-6-port purge valves. In this method, H 2 and CH 4 in water samples were first extracted into the headspace of syringes, then injected into the GC system. Both H 2 and CH 4 were detected by a PDHID. The separation of CH 4 from O 2 and N 2 in seawater is achieved by switching the O 2 and N 2 out of the carrier gas flow at the appropriate time window. H 2 and CH 4 concentrations in water samples collected from hydrothermal plumes at the Southwest Indian Ridge were determined successfully using this method.

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Evaluation of headspace equilibration methods for quantifying greenhouse gases in groundwater

Cited by 32 publications

References 19 publications

Influence of transient flooding on methane fluxes from subtropical pastures

Influence of transient flooding on methane fluxes from subtropical pastures

Biogeochemical impacts of silicon-rich rice residue incorporation into flooded soils: Implications for rice nutrition and cycling of arsenic

Development and application of a gas chromatography method for simultaneously measuring H₂ and CH₄ in hydrothermal plume samples

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Evaluation of headspace equilibration methods for quantifying greenhouse gases in groundwater

Cited by 32 publications

References 19 publications

Influence of transient flooding on methane fluxes from subtropical pastures

Influence of transient flooding on methane fluxes from subtropical pastures

Biogeochemical impacts of silicon-rich rice residue incorporation into flooded soils: Implications for rice nutrition and cycling of arsenic

Development and application of a gas chromatography method for simultaneously measuring H2 and CH4 in hydrothermal plume samples

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Development and application of a gas chromatography method for simultaneously measuring H₂ and CH₄ in hydrothermal plume samples