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ISOTHERM_REACTIONS

Specifies parameters for a sorption reaction defined by an isotherm (e.g. linear, Langmuir, Freundlich).

Required Cards:

ISOTHERM_REACTIONS

Opens the block.

<Species_Name>

Name of primary species that sorbs.

DISTRIBUTION_COEFFICIENT <float>

The value of K_D [kg_water / m³ _bulk]. For K_D values provided in e.g. mL / g, convert to kg_w / m³ _bulk by multiplying by rho_water and rho_bulk , with proper units conversion. If KD_MINERAL_NAME is included, the units of K_D become [mL_water / g_rock].

Optional Cards:

TYPE <string>

Type of isotherm, where the options for <string> include:

• LINEAR : Linear isotherm (KD) – C_sorb = K_D C_aq

• LANGMUIR : Langmuir isotherm – C_sorb = K C_aq b / ( 1 + K C_aq)

• FREUNDLICH : Freundlich isotherm – C_sorb = K_D (C_aq) ^1/n

LANGMUIR_B <float>

b coefficient for Langmuir isotherm. Automatically sets the type to LANGMUIR.

FREUNDLICH_N <float>

n exponent in Freundlich isotherm. Automatically sets the type to FREUNDLICH.

KD_MINERAL_NAME <string>

Name of mineral, the volume fraction of which will be used in conjunction with the distribution coefficient to calculate the PFLOTRAN internal distribution coefficient of kg water per cubic meter bulk. The distribution coefficient then has units of L_water / kg_soil. The conversion equation is K_D (kg_water / m³_bulk) = K_D (mL_water / g_soil) * water density * (1 - porosity) * soil particle density * 10^-3 * mineral volume fraction. Note that the mineral volume fraction has no units in this case; it is solely a scaling parameter for varying the KD in space.

Examples

ISOTHERM_REACTIONS
  Tracer
    DISTRIBUTION_COEFFICIENT 0.25d3
  /
  Tracer2
    DISTRIBUTION_COEFFICIENT 0.5d3
    FREUNDLICH_N 1.67  ! 1/n = 0.6
  /
END

ISOTHERM_REACTIONS
  Tracer
    !   Kd units = mL water/kg soil
    ! assuming:
    !   water_density = 1000 kg/m^3
    !   soil particle density = 2500 kg/m^3
    !   porosity = 0.25
    DISTRIBUTION_COEFFICIENT 0.133333
    KD_MINERAL_NAME Calcite
  /
END