x (downgradient location of interest):
t (time of interest):
Co (constant source concentration):
v (groundwater velocity):
Go to groundwater velocity calculator
R (retardation factor):
Go to retardation calculator
**KEEP UNITS CONSISTENT**
* Concentration will have same units as Co
Example (from Fetter, 1994):
A landfill is leaking leachate with a chloride concentration of 725 mg/L, which enters an aquifer with the following properties:
Hydraulic conductivity = 3.0 x 10-3 cm/s
dh/dl (hydraulic gradient) = 0.0020
Effective porosity = 0.23
Dispersion = 2.4 x 10-7 m2/s
Compute the concentration of chloride in 1 y at a distance 15m from the point where the leachate entered the groundwater. Chloride has a retardation factor of 1.0.
Determine the groundwater velocity:
vx = K(dh/dl)/ne (click to go to velocity calculator)
vx = 3.0 x 10-5 m/s x 0.0020/0.23 = 2.6 x 10-7 m/s
Using all this data, and converting the time from 1 year into 3.15 x 107 seconds, the concentration at 15 m would be approximately 30 mg/L.
Fetter, C.W. (1994). Applied Hydrogeology, Third Edition. Published by Prentice-Hall Inc., New Jersey, USA.