Hydrogen dynamics in soil organic matter as determined by C-13 and H-2 labeling experiments

Type Article
Date 2016-12
Language English
Author(s) Paul Alexia1, Hatte Christine2, Pastor Lucie3, Thiry Yves4, Siclet Francoise5, Balesdent Jerome1
Affiliation(s) 1 : Aix Marseille Univ, CNRS, Coll France, IRD,INRA,CEREGE,UM34, F-13545 Aix En Provence, France.
2 : Univ Paris Saclay, UMR CEA CNRS UVSQ 8212, LSCE IPSL, Lab Sci Climat & Environm, F-91198 Gif Sur Yvette, France.
3 : IFREMER, Ctr Brest, Dept REM EEP LEP, CS 10070, F-29280 Plouzane, France.
4 : Andra, Div Res & Dev, Parc Croix Blanche,1-7 Rue Jean Monnet, F-92298 Chatenay Malabry, France.
5 : LNHE, EDF R&D, F-78400 Chatou, France.
Source Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2016-12 , Vol. 13 , N. 24 , P. 6587-6598
DOI 10.5194/bg-13-6587-2016
WOS© Times Cited 4
Abstract Understanding hydrogen dynamics in soil organic matter is important to predict the fate of H-3 in terrestrial environments. One way to determine hydrogen fate and to point out processes is to examine the isotopic signature of the element in soil. However, the non-exchangeable hydrogen isotopic signal in soil is complex and depends on the fate of organic compounds and microbial biosyntheses that incorporate water-derived hydrogen. To decipher this complex system and to understand the close link between hydrogen and carbon cycles, we followed labeled hydrogen and labeled carbon throughout near-natural soil incubations. We performed incubation experiments with three labeling conditions: 1 - (CH)-C-13-H-2 double-labeled molecules in the presence of (H2O)-H-1; 2 - C-13-labeled molecules in the presence of (H2O)-H-2; 3 - no molecule addition in the presence of (H2O)-H-2. The preservation of substrate-derived hydrogen after 1 year of incubation (ca. 5% in most cases) was lower than the preservation of substrate-derived carbon (30% in average). We highlighted that 70% of the C-H bonds are broken during the degradation of the molecule, which permits the exchange with water hydrogen. Added molecules are used more for trophic resources. The isotopic composition of the non-exchangeable hydrogen was mainly driven by the incorporation of water hydrogen during microbial biosynthesis. It is linearly correlated with the amount of carbon that is degraded in the soil. The quantitative incorporation of water hydrogen in bulk material and lipids demonstrates that non-exchangeable hydrogen exists in both organic and mineral-bound forms. The proportion of the latter depends on soil type and minerals. This experiment quantified the processes affecting the isotopic composition of non-exchangeable hydrogen, and the results can be used to predict the fate of tritium in the ecosystem or the water deuterium signature in organic matter.
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