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# SURFACE_COMPLEXATION_RXN¶

Specifies parameters for a surface complexation reaction.

## Required Cards:¶

SURFACE_COMPLEXATION_RXN
Opens the block.

## Optional Cards:¶

EQUILIBRIUM
Specifies equilibrium kinetic sorption.
MULTIRATE_KINETIC
Specifies multirate kinetic sorption. Requires RATES and SITE_FRACTION cards.
KINETIC
Specifies kinetic sorption.
COMPLEX_KINETICS
Opens a block specifying forward and backward rate constants.
RATES <float ... float>
Toggles on multirate kinetic sorption. Specifies kinetic rates associated with SITE_FRACTIONs. The number of RATES must match the number of SITE_FRACTIONs.
SITE_FRACTION <float ... float>
Specifies site fractions associated with RATES for multirate kinetic sorption. The number of SITE_FRACTIONs must match the number of RATES.
MINERAL <string>
The name of the mineral with which the sorption site density is associated (required, but not yet linked to site density).
MULTIRATE_SCALE_FACTOR <float>
Floating point number that scales all rate constants for multirate kinetic sorption.
COLLOID <string>
Name of the colloid associated with surface complexation reaction.
ROCK_DENSITY
A flag which allows the calculation of surface site concentration based on rock density [i.e. (1-porosity)*soil_particle_density].
SITE <string> <float>
Name of site and site density [mol/m3].
COMPLEXES
Opens a block listing the names of surface complexes associated with the surface complexation reaction and the surface site. These are provided by the database file.

## Examples¶

SORPTION
SURFACE_COMPLEXATION_RXN
MULTIRATE_KINETIC
SITE_FRACTION \
0.02 0.02 0.02 0.02 0.02 \
0.02 0.02 0.02 0.02 0.02 \
0.02 0.02 0.02 0.02 0.02 \
0.02 0.02 0.02 0.02 0.02 \
0.02 0.02 0.02 0.02 0.02 \
0.02 0.02 0.02 0.02 0.02 \
0.02 0.02 0.02 0.02 0.02 \
0.02 0.02 0.02 0.02 0.02 \
0.02 0.02 0.02 0.02 0.02 \
0.02 0.02 0.02 0.02 0.02
RATES \
2.5722E-11  8.5000E-11  1.5972E-10  2.5139E-10  3.6111E-10 \
4.9167E-10  6.4167E-10  8.1667E-10  1.0167E-09  1.2472E-09 \
1.5111E-09  1.8111E-09  2.1528E-09  2.5389E-09  2.9722E-09 \
3.4722E-09  4.0278E-09  4.6667E-09  5.3889E-09  6.2222E-09 \
7.1389E-09  8.1944E-09  9.3611E-09  1.0722E-08  1.2278E-08 \
1.4028E-08  1.6056E-08  1.8389E-08  2.1056E-08  2.4139E-08 \
2.7750E-08  3.1944E-08  3.6944E-08  4.2778E-08  4.9444E-08 \
5.7778E-08  6.7778E-08  8.0000E-08  9.5000E-08  1.1389E-07 \
1.3806E-07  1.6944E-07  2.1111E-07  2.6861E-07  3.5000E-07 \
4.7778E-07  6.8611E-07  1.0778E-06  2.0278E-06  6.6944E-06
MULTIRATE_SCALE_FACTOR 1000.d0
MINERAL Kaolinite
SITE >SiOH 0.00636
COMPLEXES
>SiOUO3H3++
>SiOUO3H2+
>SiOUO3H
>SiOUO3-
>SiOUO2(OH)2-
/
/
SURFACE_COMPLEXATION_RXN
EQUILIBRIUM
MINERAL Kaolinite
SITE >FeOH 0.00636
COMPLEXES
>FeOHUO3
>FeOHUO2++
/
/
SURFACE_COMPLEXATION_RXN
EQUILIBRIUM
MINERAL Kaolinite
SITE >AlOH 0.00636
COMPLEXES
>AlOUO2+
/
/
END