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| Titel |
Numerical evaluation of subsoil diffusion of 15N labelled denitrification products during employment of the 15N gas flux method in the field |
| VerfasserIn |
Reinhard Well, Caroline Buchen, Dominika Lewicka-Szczebak, Nicolas Ruoss |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250131873
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| Publikation (Nr.) |
 EGU/EGU2016-12322.pdf |
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| Zusammenfassung |
| Common methods for measuring soil denitrification in situ include monitoring the
accumulation of 15N labelled N2 and N2O evolved from 15N labelled soil nitrate pool in soil
surface chambers. Gas diffusion is considered to be the main accumulation process. Because
accumulation of the gases decreases concentration gradients between soil and chamber over
time, gas production rates are underestimated if calculated from chamber concentrations.
Moreover, concentration gradients to the non-labelled subsoil exist, inevitably causing
downward diffusion of 15N labelled denitrification products. A numerical model for
simulating gas diffusion in soil was used in order to determine the significance of
this source of error. Results show that subsoil diffusion of 15N labelled N2 and
N2O – and thus potential underestimation of denitrification derived from chamber
fluxes - increases with cover closure time as well as with increasing diffusivity.
Simulations based on the range of typical gas diffusivities of unsaturated soils show
that the fraction of subsoil diffusion after chamber closure for 1 hour is always
significant with values up to >30 % of total production of 15N labelled N2 and N2O.
Field experiments for measuring denitrification with the 15N gas flux method were
conducted. The ability of the model to predict the time pattern of gas accumulation
was evaluated by comparing measured 15N2 concentrations and simulated values. |
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