three questions about contaminant transport!!!

Hi, I am building a model of contaminant transport. There are three questions that I am confused.

The basic situation of my model is that we want to build an extractive factory, I need to evaluate the effect of the contaminants on groundwater when there is an accident. There are 4 layers. No.1 and No.3 are aquifers. No.2 and No.4 are aquitards.
 
First, how can I control the quantity of contaminant that infiltrates into the ground, for example, a leak occurs in a workshop, the leak area is 200 square metres, the leakage is 10 cubic meters. The concentration is 200 mg/L, so should I use "well" to achieve that? Or if I give initial value in Mass transport initials to the 200 square metres leak area, then how can I know the quantity?   

Second, how can I control the duration of the leak, I mean, I want to assign  the time that the leak occurs. But 
I do not know how to do because the Time-varying function cannot achieve this. For example, the duration of the leak is one day, the leak occurs one year after the model began. If I write the file like the following one, after the day 366, the concentration of the leak area will be 0, if I do not write"366 0","18250 0", the concentration will be 200 until the end.
!
!  t [d]      fvalue
!---------------------
0 0
1 0
2 0
364.99 200
365 200
365.99 200
366 0
18250 0
END

Third,  how can I simulate impervious layer? For example, I want to add two layers upon the No.1, they are impervious layers, and parameters in leak area of the two layers are very low. But the hydraulic head will be very high. And what is more, what statuses should I set for the two layers in Free surface editor?

Thanks !

My email: jxwking2010@gmail.com

Hi king,

You could use a fixed concentration of 200 and constrain the the boundary nodes so that when set to zero they cannot discharge mass.  Compare the simulated amount of mass injected to what you know went into the ground (10 m3 at 200 mg/l).  If the conductivity is too small to accept the amount of mass you know went in the ground then either the amount is mass is too large or the conductivity is too small.  You will probably need more layers to simulate the 4 units because FEFLOW averages vertical conductivities around nodes.

In the T-list, set the 364.99 value to 0 instead of 200.

Pete

Hi king,

Regarding your third question: As Pete stated, FEFLOW does an averaging of elemental k-values on the nodes. For transport modelling it becomes necessary to introduce additional slices to regard impervious settings.

I attached a small picture for a strategy on how the slicing can be done in 3D transport models: The idea is to put in two additional slices in the clay aquitard, close to the existing slices of the aquitards top and bottom.

For more detailed information about the best settings for the free surface, I suggest to have a look at the online help  [url=http://www.feflow.info/html/help/HTMLDocuments/reference/dialogs/problemsettings/free_surface.htm]http://www.feflow.info/html/help/HTMLDocuments/reference/dialogs/problemsettings/free_surface.htm[/url]

and the White Paper Vol. I, chapter 2 "Treatment of free surfaces in 2D and 3D groundwater modelling:
[url=http://www.feflow.info/uploads/media/white_papers_vol1_01.pdf]http://www.feflow.info/uploads/media/white_papers_vol1_01.pdf[/url]

[quote author=Pete Sinton link=topic=1141.msg2806#msg2806 date=1321841296]
Hi king,

You could use a fixed concentration of 200 and constrain the the boundary nodes so that when set to zero they cannot discharge mass.  Compare the simulated amount of mass injected to what you know went into the ground (10 m3 at 200 mg/l).  If the conductivity is too small to accept the amount of mass you know went in the ground then either the amount is mass is too large or the conductivity is too small.  You will probably need more layers to simulate the 4 units because FEFLOW averages vertical conductivities around nodes.

In the T-list, set the 364.99 value to 0 instead of 200.

Pete
[/quote]

Hi Pete.
Thanks for your answer. I will have a try.

[quote author=Bastian Rau link=topic=1141.msg2808#msg2808 date=1321878572]
Hi king,

Regarding your third question: As Pete stated, FEFLOW does an averaging of elemental k-values on the nodes. For transport modelling it becomes necessary to introduce additional slices to regard impervious settings.

I attached a small picture for a strategy on how the slicing can be done in 3D transport models: The idea is to put in two additional slices in the clay aquitard, close to the existing slices of the aquitards top and bottom.

For more detailed information about the best settings for the free surface, I suggest to have a look at the online help  [url=http://www.feflow.info/html/help/HTMLDocuments/reference/dialogs/problemsettings/free_surface.htm]http://www.feflow.info/html/help/HTMLDocuments/reference/dialogs/problemsettings/free_surface.htm[/url]

and the White Paper Vol. I, chapter 2 "Treatment of free surfaces in 2D and 3D groundwater modelling:
[url=http://www.feflow.info/uploads/media/white_papers_vol1_01.pdf]http://www.feflow.info/uploads/media/white_papers_vol1_01.pdf[/url]
[/quote]
Hi, Rau.
Thanks for your answer, I will read the materials that you recommended.