Biogeochemical Cycles - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 125

TABLE 4.18
POP to DOP Rate Constant (day − 1 )

Avg. Location Reference As Cited in Explanation

0.22 Potomac River Estuary Thomann and

Fitzpatrick, 1982

Bowie et al. 93

0.075 Chesapeake Bay Cerco and Cole, 1994 Cerco and Cole 91 Labile POP to

DOP

0.005 Chesapeake Bay Cerco and Cole, 1994 Cerco and Cole 91 Refractory

POP to DOP

0.075 San Juan Bay Estuary Bunch et al., 2000 Bunch et al. 92 Labile POP to

DOP

0.005 San Juan Bay Estuary Bunch et al., 2000 Bunch et al. 92 Refractory

POP to DOP

The literature values obtained from various coastal waters for kinetic rate con-
stants related to organic phosphorus transformations, temperature correction coeffi-
cients, and settling velocities for organic phosphorus are given in Tables 4.18 - 4.21 .
A complete analysis of the phosphorus fluxes from the sediment would require a
rather complex and elaborate computation of solute-precipitate chemistry. Computa-
tion of solute-precipitate chemistry was outside the scope of WASP/EUTRO5. Instead,
a simplified approach, which relies largely on empiricism, was taken. Anaerobic
decomposition of detrital algal phosphorus yields both organic and inorganic phos-
phorus. Organic phosphorus then undergoes anaerobic decomposition and dissolved
inorganic phosphorus is produced. DIP, which remains in the interstitial water, is not
involved in the formation of precipitates and is not sorbed onto benthic solids. The
effect of anaerobic conditions on sediment phosphorus flux was not included in
WASP/EUTRO5 modeling. 78
In CE-QUAL-W2, 58 two processes are defined for phosphate release from sed-
iment. One is a first-order release process that is coupled with aerobic organic matter
decay in the sediment. The second is a zero-order phosphate release process that is
operative only when the oxygen concentration is less than a specified minimum
value at which anaerobic processes are initiated. The default minimum dissolved
oxygen concentration is 0.1 mg l −1 .
CE-QUAL-R1 57 models macrophytes. Thus, phosphate uptake of macrophytes
from sediment is included. Anaerobic phosphate release, aerobic decomposition of
organic matter, and settling of adsorbed phosphate are all simulated in the sediment
compartment of the model.
Benthic mass balance equations for organic and inorganic phosphorus are given
in the following subsections.

4.1.5.2.4 Organic Phosphorus (Benthic)

∂ ()

8

C
t

( T − 20) ( T − 20)

= k θ a f C − k θ f C (4.32)

12 444 444 3 1 44 2 44 3

PZD PZD PC OP 4 OPD OPD D 88

∂

Algal Decomposition Mineralization