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| Titel |
Can Membrane Inlet Mass Spectrometer Measure Short-term Denitrification Enzyme Activity and Denitrification Potentials of Soils? |
| VerfasserIn |
M. I. Khalil, K. G. Richards |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250019734
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| Zusammenfassung |
| Denitrifier population size and potential activity combined with the relevant environmental
factors regulate the rates of denitrification in terrestrial and aquatic ecosystems. Due to the
high atmospheric background of di-nitrogen (N2), denitrification enzyme activity
(DEA) in soils is traditionally measured using the acetylene block or stable isotope
techniques under non-limiting substrates and anaerobic/saturated conditions for
periods from a few hours to several days so as to estimate denitrification potential
(DP). This research investigated the estimation of DEA and DP by quantifying the
N2/Ar ratio changes in waters/sediments using membrane inlet mass spectrometry
(MIMS). Two experiments were conducted with soils of A, B and C horizons collected
from grazed grassland to obtain optimal NO3- and available carbon (C) rates. In
experiment 1, 30 g soil (oven dry basis) followed by helium-flushed deionized
water was taken in triplicate 160 mL glass bottles and sealed with rubber stoppers
without any air entrapments. Then N as potassium nitrate (0 to 120 mg NO3 - N
kg-1 soil) and readily available C as glucose (0 to 240 mg glucose-C) plus 30 mg
NO3 - N, kg-1 soil were amended. Laboratory incubation was performed in the dark
at 21oC under water to reduce the risk of N2 contamination. After six hours, the
treated water samples were transferred into 12 mL exetainers and kept under water
at 4oC before analysis using MIMS. The N2/Ar ratios, representing DEA, varied
between soil horizons and declined with decreasing soil depths. The maximum
peak for N2/Ar ratios were observed with the 30 mg NO3 - N kg-1 soil in all soil
horizons and coupled with the 60 mg glucose-C kg-1 soil for C horizon, and 120
mg glucose-C kg-1 for A and B horizons. Experiment 2 was conducted to assess
simulated unsaturated and saturated subsoil (C horizon) denitrification capacity
(NO3 - Nonly amendment), and DP (both C and N amendment) using the same
methodology as experiment 1 and incubated for 3 days using groundwater. The optimal
substrate rates (30 mg NO3 - N |
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