sediment constituent units?

Question

I'm currently setting up a lake model with the new water quality module. What are the units for the sediment constituents when setting up default values? (DEFAULT_PO4_SED, DEFAULT_FEIII_SED, etc). Are these in mg/kg? kg/m²?

Answer 1

Sediment units are g/m2

Comments

Thanks for the quick reply. If it's an areal load, what is the depth of sediment that water interfaces with in the model? I have values from lab testing that are in mg/kg and I'll need to convert.

---

Are you using the new dynamic sediment model?  I'd be cautious about using this unless you have really good sediment data and are prepared to do a rigorous dive into all the function outputs.

The depth of the sediment will be governed by the total amount of all the particulate sediment initializations, ie PIP, PIN, PON, POP, POC,  SSOL,  metal particulates etc.

The dissolved amounts will then be dependent on this total depth and the sediment porosity.

---

Yes, I was looking at using the dynamic sediments. We're attempting to simulate a lake with high levels of phosphorus in the sediment that had alum applied to the water column. We have sediment and water quality data from before and after the alum dosing operation, and would like to see if we can reasonably simulate the actual outcome. My understanding is that I'll need dynamic sediments turned on in order to do this. Is there a more detailed listing of equations and functions than what is available in the manual? Thanks for your help.

---

The dynamic sediment model will explicitly model the decomposition of particulate organics to dissolve organics and the mineralization of dissolved organics to dissolved inorganics and allows the release of dissolved components to be based on the calculated concentrations.  

This does give the user full control of the process but requires a lot of parameters.

I think for what you are simulating you could use an update boundary condition to modify the sediment release parameters of P after the alum dosing.

You would need an update file for PO4_sedflux_max_rate and PO4_sedflux_Ox_half_sat