## Solute transport- Time variable Ks

A discussion forum for Hydrus-1D users.
Habib
Posts: 3
Joined: Wed Dec 23, 2020 8:01 am
Location: Iraq

### Solute transport- Time variable Ks

Hi,
I am new to program, and I need some advices in below topics. I will be grateful if you may help me.
I am working on solute facilitated transport by nano particles.

column height= 20 cm Diameter:5. theta s=0.43, theta r=0.04, saturated condition, up to down stream, head on top:0.2 cm, the outlet nasal are equal to bottom side of column to keep saturated conditions. solution concentration : 100 mg/L, outlet collection time step:15 min. soil texture: loamy sand (Sand:87.5, Silt:10, Clay:2.5 percent) Kf= 26.2 beta= 0.485 (from batch experiment), porosity 0.43. nano particles 2% (w/w%) mixed with soil in column.
Facilitated Transport.xlsx
1.what is the exact type and position numbers if X:time and Y:concentration?
2. It is needed to change concentration from Ct to Ct/C0?
3.what is the exact boundary condition for solute and water? {concentration :(UBC: concentration BC, LBC: zero concentration gradient); water:(UBC:constant pressure head, LBC:Seepage face)} are they OK?
4. I attached an excel file that in one of treatment the Ks decreased with time. It seems the nano particles clogging the pores. So how I can fit the best curve to it? (Ks is time variable) (Ks decreased from 0.56cm/min to 0.32 cm/min)
when I fit the data, program calculate D=4.8 cm for ions. that it seems impossible. Ion is Cadmium.
5. is Langmuir isotherm in the program ? if Yes, where?

Thank you so much,
Habib

Jirka
Posts: 5216
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

### Re: Solute transport- Time variable Ks

In general, I do not answer here in the forum questions, the answer to which can be found in the help, manual, or posted examples.
1. See the help and “Inverse” examples.
2. No
3. See the “Inverse” examples.
4. Ks cannot be time-variable in HYDRUS. You can vary flux in time by adjusting BCs.
5. Yes. See the manual.

J.

Habib
Posts: 3
Joined: Wed Dec 23, 2020 8:01 am
Location: Iraq

### Re: Solute transport- Time variable Ks

Dear Jirka,
So thanks for answers and I completely understand,
I had a conversation with Dr Abbasi about how we can define facilitated transport of cadmium by nano particles at mentioned results when (Ks in not stable because of pore clogging by nano particles). We think it needs to exclude the effects of "ks" from BTC , but we couldn't know what is the best way for this solution. Do you have a suggestion?

Jirka
Posts: 5216
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

### Re: Solute transport- Time variable Ks

You have a couple of options.
1. If you know the flux, you can adjust the gradient through the column to get a required flux (flux=-Ks*Grad)
2. Adjust time based on the flux, i.e., scaling time based on the flux (i.e., longer time for slower flux). Note that in some applications (e.g., for transfer function in the work of Dr. Jury), time is replaced with the cumulative flux.
J.

Habib
Posts: 3
Joined: Wed Dec 23, 2020 8:01 am
Location: Iraq

### Re: Solute transport- Time variable Ks

So thank you dear Jirka,
I will try to do same options.