Dear all,

I just have one question about inverse solution in CXTFIT and HYDRUS 2D. when I perform column experiment but I cannot get BTCs because heavy metal have a lot of sorption capacity. However, I can know the varied depth concentration in column by sectioning column extraction. Therefore, I know concentration in each depth. How can I get the retardtion factor from these 2 models? I am not sure I saw in "Data structure Input code", it shows Z(I), C(I) for a fixed time. Can I use this option for input my data for estimating sorption parameters (retardation factor) ? In addtion, I don't know in case of HYDRUS 2D?

Could anyone please suggest to solve this problem?

Thank you very much.

Srilert

## Inverse solution

Yes, Z(I), C(I) for a fixed time is designed for concentration vs. depth. In order to estimate R, it is necessary to know v in advance. If you know exact theta, v can be estimated from water flux. We generally use nonreactive tracer to determine v based on a BTC or concentration profile. Please also note that you need to choose resident concentration c_r or total resident concentration c_t = Rc_r depending on your measurement.

Nobuo

### Re: Inverse solution

Dear Nobuo,

I'm not well known with these two form of model, and even reading the two manuals, I don't really see difference between hydrus and stanmod . Could you please explain me the difference between numerical and analytical solutions, thus between the 2 models ?

Thanks a lot for your help,

Sincerely,

Laura

I'm not well known with these two form of model, and even reading the two manuals, I don't really see difference between hydrus and stanmod . Could you please explain me the difference between numerical and analytical solutions, thus between the 2 models ?

Thanks a lot for your help,

Sincerely,

Laura

### Re: Inverse solution

Dear all,

I trie to model nonreactive bromide transport in a saturated sand column with stanmod. I trie to use the example 7 provided with the file but I don't manage to model transport of my tracer (fitted stay to 0 ...) could you help me with the set of transport parameters I should use ?

Thanks,

Laura

I trie to model nonreactive bromide transport in a saturated sand column with stanmod. I trie to use the example 7 provided with the file but I don't manage to model transport of my tracer (fitted stay to 0 ...) could you help me with the set of transport parameters I should use ?

Thanks,

Laura