Abstract
Abstract. Molecular hydrogen (H2) is the second most abundant reduced trace gas (after methane) in the atmosphere, but its biogeochemical cycle is not well understood. Our study focuses on the soil production and uptake of H2 and the associated isotope effects. Air samples from a grass field and a forest site in the Netherlands were collected using soil chambers. The results show that uptake and emission of H2 occurred simultaneously at all sampling sites, with strongest emission at the grassland sites where clover (N2 fixing legume) was present. The H2 mole fraction and deuterium content were measured in the laboratory to determine the isotopic fractionation factor during H2 soil uptake (αsoil) and the isotopic signature of H2 that is simultaneously emitted from the soil (δDsoil). By considering all net-uptake experiments, an overall fractionation factor for deposition of αsoil = kHD / kHH = 0.945 ± 0.004 (95 % CI) was obtained. The difference in mean αsoil between the forest soil 0.937 ± 0.008 and the grassland 0.951 ± 0.026 is not statistically significant. For two experiments, the removal of soil cover increased the deposition velocity (vd) and αsoil simultaneously, but a general positive correlation between vd and αsoil was not found in this study. When the data are evaluated with a model of simultaneous production and uptake, the isotopic composition of H2 that is emitted at the grassland site is calculated as δDsoil = (−530 ± 40) ‰. This is less deuterium depleted than what is expected from isotope equilibrium between H2O and H2.
Highlights
H2 is considered an alternative energy carrier to replace fossil fuels in the future
Several studies suggested that the atmospheric H2 mole fraction might increase substantially in the future due to the leakage during production, storage, transportation and use of H2, which could significantly affect atmospheric chemistry (Schultz et al, 2003; Tromp et al, 2003; Van Ruijven et al, 2011; Warwick et al, 2004)
This study investigated the isotope effects associated with the production and uptake of atmospheric H2 by soil
Summary
H2 is considered an alternative energy carrier to replace fossil fuels in the future. Several studies suggested that the atmospheric H2 mole fraction might increase substantially in the future due to the leakage during production, storage, transportation and use of H2, which could significantly affect atmospheric chemistry (Schultz et al, 2003; Tromp et al, 2003; Van Ruijven et al, 2011; Warwick et al, 2004). H2 can affect atmospheric chemistry and composition in several ways. It increases the lifetime of the greenhouse gas methane (CH4) via its competing reaction with the hydroxyl radical (OH) (Schultz et al, 2003; Warwick et al, 2004). H2O that is produced through the oxidation of H2 increases humidity, which can result in increased formation of polar stratospheric clouds and O3 depletion (Tromp et al, 2003), but this effect may be weaker than estimated initially (Warwick et al, 2004; Vogel et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
