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Title (Primary) Stable hydrogen isotope fractionation of hydrogen in a field injection experiment: Simulation of a gaseous H2 leakage
Author Löffler, M.; Schrader, M.; Lüders, K.; Werban, U.; Hornbruch, G.; Dahmke, A.; Vogt, C.; Richnow, H.H.
Journal ACS Earth and Space Chemistry
Year 2022
Department ISOBIO; MET
Volume 6
Issue 3
Page From 631
Page To 641
Language englisch
Topic T7 Bioeconomy
T5 Future Landscapes
Keywords H2; gas injection; subsurface; shallow aquifer; field scale; stable isotopes; hydrogenase
Abstract In the context of the shift toward clean, carbon-free energy, hydrogen (H2) has received growing attention as an energy carrier. We monitored a simulated leakage of gaseous molecular H2, e.g., from a pipeline. H2 was injected into a shallow aquifer, and the resulting biogeochemical processes were monitored. For the first time, stable isotopes of hydrogen were used to track in situ H2 transport and consumption. Isotopic composition of injected H2 was δ2H = −161.1 ± 0.4‰. During the injection, initial shifts in the isotope signature of about Δ2H = +8‰ in well D06 (1 m from injection) and Δ2H = −120‰ in well D04 (2 m from injection) were observed, probably caused by a mass-dependent isotope effect associated with the pressure of the injection and the migration of the gas phase through pores and channels in the aquifer. After the injection, H2 concentrations decreased and an equilibrium isotope exchange with water led to an isotopic depletion of H22H = −710.7 ± 2.7‰) within 28 days, presumably catalyzed by hydrogenase enzymes of microbes. The theoretical equilibrium between H2 and water was however not reached. We hypothesize that a continuous isotopic shift in available H2 as a result of physical transport processes resulted in a new isotope equilibrium with water, catalyzed by hydrogenases. Acetate detected in groundwater samples indicates in situ H2 oxidation by microbial homoacetogenesis. In laboratory experiments using H2-amended sediments sampled from the same site, microbial H2 oxidation was accompanied by equilibrium isotope exchange with water and homoacetogenesis and ferric iron reduction were the main microbial H2-consuming processes. Overall, the H2 isotope ratio was considerably impacted by physical and microbial processes occurring in the shallow aquifer. Monitoring of the equilibrium isotope exchange between H2 and water could be used as a proxy for ongoing microbial H2 oxidation.
Persistent UFZ Identifier
Löffler, M., Schrader, M., Lüders, K., Werban, U., Hornbruch, G., Dahmke, A., Vogt, C., Richnow, H.H. (2022):
Stable hydrogen isotope fractionation of hydrogen in a field injection experiment: Simulation of a gaseous H2 leakage
ACS Earth Space Chem. 6 (3), 631 - 641