Hagi BucknWise: Created page with "{{BreadcrumbsNutrients}} * Page authors: PRIMO * Responsible curator: Hagen Buck-Wiese ---- TOC
{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Net denitrification (N₂/Ar ratio, MIMS) |- | '''Approach:''' membrane inlet mass spectrometry (MIMS) of dissolved N₂/Ar ratio |- | '''Context:''' incubation, lab, ''in situ'' |-..."

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Created page with "{{BreadcrumbsNutrients}} * Page authors: PRIMO * Responsible curator: Hagen Buck-Wiese ---- __TOC__ <div class="model-box"> {| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Net denitrification (N2/Ar ratio, MIMS) |- | '''Approach:''' membrane inlet mass spectrometry (MIMS) of dissolved N2/Ar ratio |- | '''Context:''' incubation, lab, ''in situ'' |-..."

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{{BreadcrumbsNutrients}}

* [[Page authors|Page authors]]: [[PRIMO]]
* [[Responsible curator|Responsible curator]]: [[User:Hagi BucknWise|Hagen Buck-Wiese]]
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__TOC__
<div class="model-box">
{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;"
! Net denitrification (N2/Ar ratio, MIMS)
|-
| '''Approach:''' membrane inlet mass spectrometry (MIMS) of dissolved N2/Ar ratio
|-
| '''Context:''' incubation, lab, ''in situ''
|-
| '''Spatial scale:''' point sample to continuous underway
|-
| '''Temporal scale:''' hours
|-
| '''Units:''' µmol N2 L-1; nmol N L-1 d-1
|-
| '''Community captured:''' bulk
|-
| '''Co-measurements:''' nitrogen fixation rates, Ar concentration, temperature, salinity
|}
</div>
<div style="clear:both"></div>

== Method Overview ==

Dissolved N2 and Ar are measured simultaneously by membrane inlet mass spectrometry (MIMS), in which water is pumped through a membrane permeable to dissolved gases and the outgassing mixture is analyzed by mass spectrometry<ref name="Kana1994">Kana, T. M., Darkangelo, C., Hunt, M. D., Oldham, J. B., Bennett, G. E., & Cornwell, J. C. (1994). Membrane inlet mass spectrometer for rapid high-precision determination of N2, O2, and Ar in environmental water samples. ''Analytical Chemistry'', 66(23), 4166–4170. https://doi.org/10.1021/ac00095a009</ref>. Because Ar is biologically inert but has similar solubility and diffusivity to N2, the N2/Ar ratio corrects for physical processes (temperature, pressure, mixing) that affect dissolved gas concentrations. Excess N2 above the physically expected N2/Ar ratio indicates net biological N2 production (denitrification minus N2 fixation). In incubation mode, the method can resolve net denitrification rates. In underway mode, it provides spatial maps of net N2 flux.

=== Scale of measurement ===

Sample volumes are mL to L for discrete measurements. Underway systems sample continuously with km-scale spatial resolution. Temporal resolution is minutes per measurement.

=== Data generated ===

Dissolved N2 concentration and N2/Ar ratio; from these, excess N2 above equilibrium is calculated as a proxy for net denitrification. With air-sea gas transfer parameterizations, net N2 flux can be estimated.

=== Units & currency ===

Units are µmol N2 L-1 or nmol N L-1 d-1. The currency is nitrogen (N2).

=== Sample size ===

Sample volumes range from mL to L depending on the analytical setup.

=== Repositories & databases ===

== Limitations ==

The method measures net denitrification (denitrification minus N2 fixation). In regions of active N2 fixation, the two processes partially cancel each other out, and the net signal underestimates gross denitrification. Dissolved N2 measurements are highly sensitive to atmospheric contamination from air bubbles during sample collection and handling, requiring careful degassing protocols. Temperature and salinity corrections for equilibrium N2/Ar must be accurate.

== Example Applications & Protocols ==

=== Classic examples ===
* Kana et al. (1994) ''Membrane inlet mass spectrometer for rapid high-precision determination of N2, O2, and Ar in environmental water samples'' <ref name="Kana1994" />

=== Recent applications ===
* Steingruber et al. (2001) ''Measurement of denitrification in sediments with the 15N isotope pairing technique'' <ref name="Steingruber2001">Steingruber, S. M., Friedrich, J., Gächter, R., & Wehrli, B. (2001). Measurement of denitrification in sediments with the 15N isotope pairing technique. ''Applied and Environmental Microbiology'', 67(9), 3771–3778. https://doi.org/10.1128/AEM.67.9.3771-3778.2001</ref>

=== Common calculations/conversions ===
* Excess N2 = [N2]measured − [Ar]measured × (N2/Ar)equilibrium; equilibrium ratio from García & Gordon (1992) as a function of T and S.

== References ==

[[Category:Main Pages|Model types]]

N2:Ar ratio quantification - Revision history