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<< Click to Display Table of Contents >> Diffusion |
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Diffusion is the process where chemicals contaminants in the soil will migrate from areas of high chemical concentration (potential) to areas of low chemical concentration (potential). The mass flux transported by diffusion is proportional to the concentration gradient and is given by:
f = - n De dc/dz
where,
n = effective porosity of the soil,
De = effective diffusion coefficient,
dc/dz = concentration gradient.
The negative sign in the above equation arises from the fact that contaminants move from areas of high concentration to areas of low concentrations. By integrating the above equation the total mass of contaminant transported by diffusion from a landfill can be obtained viz.:
md = A ʃ (- n De dc/dz ) dτ