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Initial conditions with two kinetic site sorption

Posted: Fri Mar 13, 2020 6:08 pm
by ReubenD

I am working on setting up a model using the modified version of HYDRUS 1D with transient air water interface sorption ( ... oids_Theta).

I need to model repeated applications of municipal biosolids to farmed fields (once/year) and look at concentrations through the vadose zone considering solid phase and air water interface sorption.

The issue I'm having is I don't see a way to to use the output concentration distribution in water, sorbed to first sites, and sorbed to the second sites as initial conditions for a subsequent model run. I am only able to specify concentration in the fluid and on the first sites. The file lets me specify to move the concentration initialized on the first site to the second sites, but then this leaves the concentration on the first sites empty. Without being able to initialize the model with concentration in all three locations (then add a concentration representing re-application of biosolids) I don't see a way to model multiple applications of biosolids.

So my questions are: is there a way to set initial conditions in all three locations (fluid phase, first sites, and second sites) for the two site kinetic sorption model? If not do you know of a different way to model this scenario? I have been thinking of using a variable concentration boundary condition, but I'm thinking this wouldn't work as the solute quickly moves from fluid phase to the AWI and if I hold the concentration in the fluid phase to some number it will act as a 'limitless' source for the AWI to keep accumulating solute.

Thank's for any help anyone is able to provide.