Sandbox monod reaction not behaving similar to microbial reaction

[Bisesh Joshi]

Hi all,

I'm trying to simulate NH4+ uptake in the root zone by using the Reaction Sandbox with the following input block, where I'm using total concentrations.

REACTION_SANDBOX

  NH4_UPTAKE_MATERIALIDS

    NH4_UPTAKE_RATE_CONSTANT 8.0d-09

    NH4_UPTAKE_HALF_SATURATION_CONSTANT 5.d-5

    NH4_UPTAKE_THRESHOLD_CONCENTRATION 1.d-30

    NH4_UPTAKE_MATERIAL_IDS 5  1 2 3 4 12  

    !output Tracer1

  END  

END

Previously, I was  using  microbial equations with biomass as a placeholder for these layers with the following block:

MICROBIAL_REACTION

    REACTION    1.0000 NH4+ <-> 1.00 Tracer1

    RATE_CONSTANT 8.d-12 #TL_uptake

#    ACTIVATION_ENERGY      80.d3 

    MONOD

      SPECIES_NAME NH4+ 

      HALF_SATURATION_CONSTANT 5E-5         ! A is the donor

      THRESHOLD_CONCENTRATION 1.d-30

    /    

      BIOMASS

      SPECIES_NAME TL

      YIELD 0.00d0

    /    

/

The initial biomass of TL in this zone is 1.d3

I'm using the same seasonal multipliers to rate constants on these reactions for seasonal NH4 uptake in separate monthly input files. I was expecting the same results, but I'm getting different results.

Please let me know if anyone has any suggestions regarding this.

Thank you,

Bisesh

--

Bisesh Joshi

PhD student

Water Science and Policy

Graduate College

University of Delaware

901-297-6761