\(\newcommand{\p}[1]{\frac{\partial }{\partial #1}}\) \(\newcommand{\pp}[2]{\frac{\partial #1}{\partial #2}}\) \(\newcommand{\dd}[2]{\frac{d #1}{d #2}}\) \(\newcommand{\h}{\frac{1}{2}}\) \(\newcommand{\op}[1]{\operatorname{#1}}\)

8.7.3.9. Denitrification

When DARWIN_ALLOW_DENIT is defined in DARWIN_OPTIONS.h, denitrification occurs, provided \({\mathrm{O}}_2<{\mathrm{O}}_2^{{\text{crit}}}\),

\[ \begin{align}\begin{aligned}D_{\op{NH4}} &= R_{\op{DON}} + [R_{\op{PON}}]\\D_{\op{NO3}} &= R^{\mathrm{NO3}:\mathrm{P}}_{\op{denit}} \cdot \bigl( R_{\op{DOP}} + [R_{\op{POP}}] \bigr)\end{aligned}\end{align} \]

(the particulate organic terms are not present with DARWIN_ALLOW_CDOM).

The diagnostic ‘Denit’ is this:

\[\op{Denit} = R^{\mathrm{N}:\mathrm{P}}_{\op{denit}} \bigl( R_{\op{DOP}} + [R_{\op{POP}}] \bigr)\]

Also, when \({\mathrm{O}}_2<{\mathrm{O}}_2^{{\text{crit}}}\) and \(\op{NO}_3<\op{NO}_3^{{\text{crit}}}\), all remineralization, denitrification and CDOM degradation (except bleaching) stops. Bacteria are not affected.

Table 8.39 Denitrification parameters

Param	Symbol	Default	Units	Description
denit_NP	\(R^{\mathrm{N}:\mathrm{P}}_{\op{denit}}\)	120.0	mmol N / mmol P	ratio of n to p in denitrification process
denit_NO3	\(R^{\mathrm{NO3}:\mathrm{P}}_{\op{denit}}\)	104.0	mmol N / mmol P	ratio of NO3 uptake to phos remineralization in denitrification
O2crit	\(\mathrm{O}_2^{\op{crit}}\)	6.0	mmol O2 m-3	critical oxygen for O2/NO3 remineralization
NO3crit	\(\op{NO}_3^{\op{crit}}\)	0.01	mmol N m-3	critical nitrate below which no denit (or remin) happens