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| Titel |
Geochemical and Hydrological limitation of carbon sequestration and methane release in anoxic peat soil from the Luther Marsh, Canada |
| VerfasserIn |
Simona Bonaiuti, Christian Blodau |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250113748
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| Publikation (Nr.) |
 EGU/EGU2015-13964.pdf |
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| Zusammenfassung |
| In deep peat layers, anaerobic respiration showed a slow-down due to the lack of solute
transport which causes an accumulation of metabolic end products (i.e. DIC and CH4). This
accumulation can lower the Gibbs free energy levels available to the terminal respiration
processes, potentially leading to an inhibition in the decomposition. In particular, this state
can affect the methanogenesis, acetogenesis and fermentation processes which occur near
thermodynamic minimum energy levels. We conducted a column experiments with an
ombrothrophic bog peat over a period of 300 days at 20Ë C, to test the hypothesis
that alteration in solute and gas transport rates can remove this biogeochemical
inactivation of DIC and methane turnover rates. To this end, we tested a i) control
treatment with no gas and solute transport, ii) advective flow treatment with a flow
water of 10 mm d-1, iii) ebullition treatment with methane removal by conduit
transport as surrogate for bubbling, and iv) an O2-free atmosphere treatment to test the
effect of remote transport of electron on anaerobic decomposition, in absence of
oxygen compared to the other treatment. We determined detailed concentration
depth profiles of dissolved inorganic carbon (DIC), methane (CH4) and relevant
decomposition intermediates (i.e. H2, Fe, nitrate, acetate, formiate and propionate), every 15
days at the beginning and every ca. 2 months after 75 days. CO2 and CH4 fluxes
were measured using a static chamber approach. Net turnover of DIC and CH4
in depth layers was calculated for individual depth intervals from mass balance
approach based on diffusive mass fluxes between adjacent depth layers and change in
storage over time. Thermodynamic energy levels of relevant electron accepting
processes were calculated over time. In the initial phase of the experiments, DIC and
CH4 concentrations increased mostly below the water table level at 10 cm depth
and over time in all treatments. After 45 days of incubation, CH4 concentrations
strongly increased in the advective flow treatment, peaked at 70 cm depth with 700
μmol L-1, and in the O2-free treatment, peaked at 20 cm depth with ca. 600 μmol
L-1. DIC concentrations after 45 days showed similar pattern in term of levels
between the different treatments, showed an increase from ca. 3000 μmol L-1 near the
water table to about 5000-6000 μmol L-1at 70-75 cm depth. Furthermore, DIC and
methane concentrations in the ebullition treatment showed a decline over time,
probably due to the export of gases through the formation of bubbles. At the end of the
experiment, we expect that a negative feedback on decomposition will mostly occur in
deeper layers in the control treatments due to the slowness of transport and where the
accumulation of CO2 and CH4 will be eased, in line with the results presented in previous
studies.
Keywords: Peatlands; Anaerobic decomposition; Methanogenesis; Net turnover rates;
Gas fluxes; Advection; Ebullition. |
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