Field experiments yield new insights into gas exchange and excess air formation in natural porous media

Klump, Stephan; Tomonaga, Yama; Kienzler, Peter; Kinzelbach, Wolfgang; Baumann, Thomas; Imboden, Dieter M.; Kipfer, Rolf

doi:10.1016/j.gca.2006.12.006

Cited by 69 publications

(62 citation statements)

References 21 publications

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“…doi:10. 1016/j.gca.2008.02.012 (1987) together with an 40 Ar diffusion coefficient estimated by extrapolation of their results (Ballentine et al, 2002;Kipfer et al, 2002;Rü bel et al, 2002;Holocher et al, 2003;Peeters et al, 2003;Price et al, 2003;Poreda et al, 2004;Brennwald et al, 2005;Hendry et al, 2005;Strassmann et al, 2005;Zhou et al, 2005;Hall et al, 2006;Ingram et al, 2007;Klump et al, 2007;Rodehacke et al, 2007). Diffusion coefficients of minor noble gas isotopes in liquid water for which no data exist then have routinely been estimated using the kinetic-theory model D / 1/l 0.5 [l is the solvent-solute reduced mass, l = mm 0 /(m+m 0 ), if m and m 0 are solute and solvent molecular masses (LaBolle et al, 2006)] or, more commonly, using the 'square-root' relation…”

Section: Introductionmentioning

confidence: 90%

Isotopic fractionation of noble gases by diffusion in liquid water: Molecular dynamics simulations and hydrologic applications

Bourg

Sposito

2008

Geochimica et Cosmochimica Acta

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Section: Introductionmentioning

confidence: 90%

Isotopic fractionation of noble gases by diffusion in liquid water: Molecular dynamics simulations and hydrologic applications

Bourg

Sposito

2008

Geochimica et Cosmochimica Acta

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“…Tidal inundation of the marsh platform could increase pressure in the pore space in this manner. The phenomenon of 'excess air,' or supersaturation caused by the trapping and subsequent partial or complete dissolution of air bubbles is sometimes invoked to explain groundwater supersaturations of noble gases (Heaton and Vogel 1981;Klump et al 2007); if air in the pore space was completely dissolved, the expected ratio of Ne/He in the porewater would be 3.47, and that of Xe/Ne 0.005. The measured ratios in the porewater are instead 4.25 (Ne/He) and 0.060 (Xe/Ne), with more soluble gases more enriched relative to the less soluble gases than expected for complete dissolution of trapped air, consistent with an equilibrium process (and thus the uniform saturation state of the noble gases).…”

Section: Noble Gasesmentioning

confidence: 99%

Ecosystem metabolism in salt marsh tidal creeks and ponds : applying triple oxygen isotopes and other gas tracers to novel environments

Howard¹

2017

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Salt marshes are physically, chemically, and biologically dynamic environments found globally at temperate latitudes. Tidal creeks and marshtop ponds may expand at the expense of productive grasscovered marsh platform. It is therefore important to understand the present magnitude and drivers of production and respiration in these submerged environments in order to evaluate the future role of salt marshes as a carbon sink. This thesis describes new methods to apply the triple oxygen isotope tracer of photosynthetic production in a salt marsh. Additionally, noble gases are applied to constrain air-water exchange processes which affect metabolism tracers. These stable, natural abundance tracers complement traditional techniques for measuring metabolism. In particular, they highlight the potential importance of daytime oxygen sinks besides aerobic respiration, such as rising bubbles. In tidal creeks, increasing nutrients may increase both production and respiration, without any apparent change in the net metabolism. In ponds, daytime production and respiration are also tightly coupled, but there is high background respiration regardless of changes in daytime production. Both tidal creeks and ponds have higher respiration rates and lower production rates than the marsh platform, suggesting that expansion of these submerged environments could limit the ability of salt marshes to sequester carbon. AcknowledgmentsFinancial support for my doctoral research was provided by the United States Department of Defense through the National Defense Science and Engineering Graduate Fellowship Program, the National Science Foundation under grant OCE-1233678, and the Woods Hole Oceanographic Institution (WHOI) under grants from the WHOI Coastal Ocean Institute, Ocean and Climate Change Institute, and Ocean Life Institute. WHOI Academic Programs Office also provided funding support for research, through the Ocean Ventures Fund, and for my stipend, as graduate research assistantships including an assistantship from the United States Geological Survey administered by WHOI. I am very grateful for this financial support which allowed me earn a living wage while focused on my doctoral research.In addition, the great majority of this work would not have been possible without the outstanding logistical and in kind support of many scientific teams and individuals, including the Plum Island Ecosystems Long Term Ecological Research site and TIDE experiment staff and scientists (these projects funded by NSF OCE 1238212, NSF DEB 1354494, and NE Climate Science Center grant DOI G12AC00001), Nancy Pau at the Parker River National Wildlife Refuge who granted permits for the work in Chapters 4 and 5, and Liz Kujawinski and Krista Longnecker at WHOI who invited me to participate on cruise KN210-04 in the South Atlantic (funded by NSF grant OCE 1154320).Specific acknowledgments are also found in each chapter of this thesis, but I'd like to thank a number of individuals in particular who helped me plan for, collect, and analyze the data that u...

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“…In contrary, in the framework of the kinetic theory, the diffusion coefficient of a dissolved species is mass dependent and the ratio between two diffusion coefficients of two isotopically distinct species is proportional to the inverse square root of their reduced masses: For diffusing gases Eq. (2) can be simplified by assuming that the mass of the molecules of the medium (M i ) is infinitively large in comparison to the diffusing molecules (M i ) m i ) (Ballentine et al, 2002;Lippmann et al, 2003;Peeters et al, 2003;Strassmann et al, 2005;Zhou et al, 2005;Richter et al, 2006;Klump et al, 2007;Bourg and Sposito, 2008). Therefore, the reduced mass in Eq.…”

Section: Introductionmentioning

confidence: 99%

Carbon and chlorine isotopologue fractionation of chlorinated hydrocarbons during diffusion in water and low permeability sediments

Wanner

Hunkeler

2015

Geochimica et Cosmochimica Acta

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To identify reactive processes in diffusion dominated water-saturated systems using compound-specific isotope analysis (CSIA), the effect of the diffusive transport process on isotope ratios needs to be known. This study aims to quantify the magnitude of carbon and chlorine isotopologue fractionation of two chlorinated hydrocarbons (trichloroethene (TCE) and 1,2-dichloroethane (1,2-DCA)) during diffusion in the aqueous phase and to relate for the first time laboratory with field results. Diffusion coefficient ratios in the aqueous phase were experimentally quantified with a modified Stokes diffusion cell. The experiment revealed a significant shift of carbon and chlorine isotopologue ratios of TCE and 1,2-DCA during diffusion. For both TCE and 1,2-DCA, the magnitude of the shift of chlorine isotopologue ratios was larger , which is consistent with the larger mass difference between stable chlorine compared to carbon isotopes. Determined diffusion coefficients for carbon and chlorine isotopologues of TCE and 1,2-DCA follow an inverse power law form (D / m Àb ) with b < 0.5 revealing that the magnitude of isotopologue fractionation of TCE and 1,2-DCA is lower than in the previously postulated kinetic theory (D / m À0:5 ). To relate laboratory with field results, a water-saturated clay core from a VOC contaminated site was retrieved and subsampled as a function of depth to assess possible shifts in isotopologue ratios during downward diffusion of VOCs into the low permeable clay. Observed small shifts of TCE carbon and chlorine isotopologue ratio profiles were consistent with laboratory determined diffusion coefficient ratios, demonstrated by a 1D-diffusion model. Further 1D-simulations for shorter diffusion periods (5-10 years) than observed in the retrieved clay core (45 years), revealed a larger effect on TCE chlorine and carbon isotopologue ratio profiles. Thus, the diffusive transport process in water-saturated low permeability sediments only impairs the identification of reactive processes using compound-specific isotope analysis (CSIA) during short diffusion periods and for reactive processes with small enrichment factors.

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Field experiments yield new insights into gas exchange and excess air formation in natural porous media

Cited by 69 publications

References 21 publications

Isotopic fractionation of noble gases by diffusion in liquid water: Molecular dynamics simulations and hydrologic applications

Isotopic fractionation of noble gases by diffusion in liquid water: Molecular dynamics simulations and hydrologic applications

Ecosystem metabolism in salt marsh tidal creeks and ponds : applying triple oxygen isotopes and other gas tracers to novel environments

Carbon and chlorine isotopologue fractionation of chlorinated hydrocarbons during diffusion in water and low permeability sediments

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