Diract delta input - Mass of Diract delta pulse

A discussion forum for STANMOD users. STudio of ANalytical MODels is a software package for evaluating solute transport in porous media using analytical solutions of the convection-dispersion solute transport equation.

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Diract delta input - Mass of Diract delta pulse

Post by fabian123 » Tue Sep 20, 2022 8:45 am

Hello everyone,
I have got a problem with getting the mass of a dirac delta pulse inside of CXTFIT.

I use a water saturated column filled with biochar and want to calculate inversely parameters by using a dirac delta pulse with (conservative) tracers.

When I want to type in the mass of the dirac delta pulse CXTFIT asks about a Mass(Window"Boundary Value Problem"-Diract delta inpt). I wasn't really sure after what kind of mass unit is asked, at first I thought it wants to get the information in mg (because in "Type and Space Units" I defined mg/l as Concentration Unit), but the peak of the Breakthrough curve was far to less. However after reading the manual (and the tipps of this wonderful plattform) I read the chapter of the CXTFIT-handbook "Input Data Instructions",more exact the subchapter "Block D Boundary value problem", and after reading it I think now that CXTFIT wants to have the information in mb/v. So it seems to me that it asks after a mass unit, but wants to "hear" mb/v [M/L*T].

My calculations until now. mb=mass of tracer in mg/area of the filled column=; mb=81[mg]/9.62[cm²]= 8.42[mg/cm²]
mb/v= 8.42[mg/cm²]/ 0.026802 [cm/min]=314.154 [mg/cm*min] [M/L*T]
The peak (the highest point) o f the breakthrough curve is with this 314,154 really low, so I tried it with 314154 and the curve seems to fit quite well. Could it be that CXTFIT calculates the diract deltapulse mass with microgramm instead of my defined mg?(1.Q.)

In the hanbook there is "soil liquid phase" mentioned and I am not really sure if this refers to the with water filled biochar (soil) or just the area where water is "inside the soil". (So if I have to multiply the column area with the porosity (neglecting the air). Can I just calculate with the column area? (2.Q.)

I would be really grateful, if somebody could answer me my two questions, since I am working on this since quite a long time. I havent got the information needed from reading other posts on this plattform.

Thank you really much!

Best Regards,

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