category_img

Calculator 17 - Effective Diffusion Calculator

EFFECTIVE DIFFUSION CALCULATOR


Back to Calculators


The effective diffusion coefficient takes into account the fact that diffusion can only take place through pore openings because mineral grains block many of the possible pathways.

Cation Dd (10-6 cm2/s) Anion Dd (10-6 cm2/s)
H+ 93.1 OH- 52.7
Na+ 13.3 F- 14.6
K+ 19.6 Cl- 20.3
Rb+ 20.6 Br- 20.1
Cs+ 20.7 HS- 17.3
Mg2+ 7.05 HCO3- 11.8
Ca2+ 7.93 CO32- 9.55
Sr2+ 7.94 SO42- 10.7
Ba2+ 8.48    
Ra2+ 8.89    
Mn2+ 6.88    
Fe2+ 7.19    
Cr3+ 5.94    
Fe3+ 6.07  

 

Using these values, the effective diffusion coefficient can then be calculated using one of the following equations/calculators:

Greenkorn(1983)

Dd'=nDd

Where is an empirical value less than one, and n is porosity.

Dd   cm2/s

n

Dd':   cm2/s

 

Greenkorn & Kissler(1972)

Dd'=(n/)Dd

Where is tortuosity, which will be discussed in the next newsletter.

Dd   cm2/s

n

Dd':   cm2/s

 

Hellferich(1966)

The Hellferich equations give a range of values for the effective diffusion coefficient from:

Dd'=(n/2)Dd

to:

Dd'=(n/(2-n))2Dd

Dd   cm2/s

n

Dd': from to   cm2/s

References

Domenico P.A. and Schwartz, F.W. (1998). Physical and Chemical Hydrogeology. Published by John Wiley & Sons, Inc. New York, NY.

Fetter, C.W. (1994). Applied Hydrogeology; Third Edition.  Published by Prentice-Hall, Inc., Englewood Cliffs, NJ.

Freeze, R.A. and Cherry, J.A. (1979). Groundwater. Published by Prentice-Hall, Inc., Englewood Cliffs, NJ.