Geoscience Reference
In-Depth Information
The HEM-3D
90
model uses kinetic processes mostly from the CE-QUAL-ICM
model. Macroalgae are added into HEM-3D as the fourth algal group.
The specific kinetic equations used in the EUTRO5 model for nitrogen (in almost
the same or similar format as for other models) are presented below.
4.1.5.1.1 Phytoplankton Nitrogen
Phytoplankton nitrogen is the nitrogen contained in phytoplankton cells
∂
(
Ca
t
)
v
D
4
nc
=
GaC DaC
−
−
S
4
aC
(4.21)
144
P
1
nc
4
144
P
1
nc
4
nc
4
∂
144
Growth
Death
Settling
where
C
4
=
phytoplankton carbon concentration [mg C l
−1
]
a
nc
=
nitrogen to carbon ratio [mg N/mg
−1
C]
G
P
1
=
specific growth rate constant of phytoplankton [day
−1
]
D
P
1
=
death plus respiration rate constant of phytoplankton [day
−1
]
V
s
4
=
net settling velocity of phytoplankton [m day
−1
]
D
=
depth of segment [m]
4.1.5.1.2
Organic Nitrogen
∂
∂
C
t
C
KC
C
v
(1
−
f
)
(
T
−
20)
7
=
Da fC
−
k
θ
4
−
S3
D
7
C
(4.22)
144
P1
nc
on
4
71
71
7
7
+
D
12
443
44
12
4444
m
4444
Pc
4
3
Death
Settling
Mineralization
where
C
7
=
organic nitrogen concentration [mg N l
−1
]
D
P
1
=
death plus respiration rate constant of phytoplankton [day
−1
]
a
nc
=
nitrogen to carbon ratio [mg N mg
−1
C]
f
on
=
fraction of dead and respired phytoplankton recycled to the organic
nitrogen pool [none]
C
4
=
phytoplankton carbon concentration [mg C l
−1
]
k
71
=
organic nitrogen mineralization rate constant at 20
°
C [day
−1
]
θ
71
=
organic nitrogen mineralization temperature coefficient [none]
T
=
water temperature [
°
C]
K
m
PC
=
half-saturation constant for recycle [mg C l
−1
]
V
S
3
=
organic matter settling velocity [m day
−1
]
f
D
7
=
fraction of dissolved organic nitrogen [none]
1 -
f
D
7
=
fraction of particulate organic nitrogen [none]
D
=
depth of segment [m]
Literature values, obtained from various coastal areas, for the kinetic rate constants
related to organic nitrogen transformations, their temperature correction coefficients,
and settling velocities of organic nitrogen are given in
Tables 4.2-
4.5.
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