Modellers can use the aed_tracer to simulate a particulate tracer that can be set to also settle and decay. In addition to suspended sediment simulated in this way, the aed_totals module has an option to assign any number of FABM variables (including non-AED variables) to contribute to a turbidity, subject to a transformation coefficient.

Modellers can also use this module to simulate the water retention time. In this case the water retention time is treated as a tracer with a growth rate of 1 with time after enterting the water body, and being mixed and transported with water.

The AED2 module tracer contains equations that describe a soluble or particle tracer, including decay, sediment interaction, and & resupension and settling

Variable Name | Description | Units | Variable Type | Core/Optional |
---|---|---|---|---|

`TRC_ss{x}` |
generic tracer / suspended solid group | $$mg\,L^{-1}$$ | pelagic | optional: set num_tracers >0 |

`TRC_ret` |
water retention time | seconds | pelagic | optional: set retention_time = .true. |

Variable Name | Description | Units | Variable Type | Core/Optional |
---|---|---|---|---|

`TRC_ss{x}_vvel` |
suspended solid group x vertical velocity | $$m\,s^{-1}$$ | pelagic diagnostic | optional: created when settling = XXX |

`TRC_d_taub` |
bottom shear stress | $$N\,m^{-2}$$ | benthic diagnostic | core |

`TRC_fs{x}` |
sediment fraction of particle size x | $$%$$ | benthic diagnostic | core |

`TRC_resus` |
resuspension rate | $$g\,m^{-2}\,s^{-1}$$ | benthic diagnostic | core |

Parameter Name | Description | Units | Parameter Type | Default | Typical Range | Comment |
---|---|---|---|---|---|---|

`retention_time` |
activates the retention time variable | - | boolean | .false. | .true./.false. | enable if you wish to keep track of the age opf water within the domain |

`num_tracers` |
number of tracers/ss's to model | - | integer | 0-10 | - | |

`decay` |
vector of decay rates for each simulated tracer group | $$day^{-1}$$ | float | -100-100' | - | |

`Fsed` |
vector of sediment flux rates for each simulated tracer group | $$g\,(m^{2}\, ^{*} s)^{-1}$$ | float | 0-100 | - | |

`Ke_ss` |
vector of specific light attenuation constants for each simulated tracer group | $$m^{-1} (g\,m^{-3})^{-1}$$ | float | 0.01-0.1 | - | |

`settling` |
settling sub-model | - | integer | 1,2,3 | 0 = none; 1 = constant; 2= constant (temp adjusted); 3 = Stokes | |

`w_ss` |
vector of sedimentation velocity | $$m\,day^{-1}$$ | float | -1 | 0-10 | used if settling = 1 or 2 |

`d_ss` |
vector of particle diameter | $$m$$ | float | 1e-06 | - | used if settling = 3 |

`rho_ss` |
vector of particle density | $$kg\,m^{-3}$$ | float | 1600 | - | used if settling = 3 |

`resuspension` |
resuspension sub-model | - | integer | - | 0 = none; 1 = constant; 2= constant adjusted; 3 = stokes | |

`fs` |
vector of particle fraction within the sediment | - | float | 0-1 | vector of length num_tracers be supplied | |

`epsilon` |
vector of resuspension rate coefficient | $$g\,m^{-2}\,s^{-1}$$ | float | 0-0.1 | - | |

`tau_0` |
vector of critical shear stress for resuspension | $$N\,m^{-2}$$ | float | 2e-02 | 0.005 - 0.05 | - |

`tau_r` |
reference shear stress | $$N\,m^{-2}$$ | float | 1 | 1 | - |

`Ktau_0` |
coefficient determining the effect of 'macrophyte_link_var' on 'tau_0' | $$N\,m^{-2}\,(mmol C m^{-2})^{-1}$$ | float | 1e-01 | - | |

`macrophyte_link_var` |
AED2 benthic variable on which the critical shear stress depends | - | string | - | e.g., 'MAC_ruppia' | optional: if resuspension = 2 |

An example `nml`

block for the tracer module is shown below:

```
```**&aed2_tracer**
!-- Optional retention time tracer
retention_time = .true.
!-- Select number of tracers/ss's and their decay/sedflux/light properties
num_tracers = 2
decay = 0, 0
Fsed = 0, 0
Ke_ss = 0.06, 0.063
!-- Configure sediment resuspension
settling = 3
w_ss = -0.000001
d_ss = 4e-6, 1e-5
rho_ss = 1.5e3, 1.8e3
!-- Configure sediment resuspension
resuspension = 1
fs = 0.7
epsilon = 0.0250
tau_0 = 0.03
tau_r = 1.0
Ktau_0 = 0.001
macrophyte_link_var = 'MAC_ruppia'
**/**