The question about how to use nonequilibrium transport model (two-site model) in HP1

[Bowen Luo]

Dear all,
I am working on a heavy metal migration problem that considers reaction processes. I am working on a heavy metal migration problem that considers reaction processes. I used the inverse solution module of the HYDRUS base module before adding a specific chemical reaction equation using the HP1 add-on module. And the results show that the fitting results of the nonequilibrium transport model (two-site model) is the best. Now I need to substitute the well-fitted parameters of the two-site model into the HP1 module for the next step.
I notice that only the equilibrium adsorption model can be used in module HP1, and the interface for Reaction Parameter input will not be displayed. I tried to modify the model parameters directly in the selector.in file by changing iNonEqul from 0 to 2 and then modifying the parameters Frac, Kd, Beta. It turns out that when I changed the Frac parameter, the program stopped running. When I modify only Kd and Beta parameters, the program runs. It turns out that when I changed the Frac parameter, the program stopped running. When I modify only Kd and Beta parameters, the program runs.
I have referred to the instructions and examples of HP1 provided by you, but I have not found a way to solve this problem, that is, how to use nonequilibrium transport model (two-site model) in HP1. I have seen an example of using the nonequilibrium transport model in HP1 in an article. I'm very much looking forward to getting a solution to this problem from here. Here is my HP1 file.

HP1_non-eq.zip

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Best regards,
Bowen

[Jirka]

In HP1, the standard HYDRUS solver handles only physical processes, i.e., water flow and solute transport. Reactions (including instantaneous and kinetic sorption, which are involved in the two-site sorption model) are handled by PHREEQC, and thus have to be defined in its inputs (and not using the HYDRUS reaction parameters). J.