4.1. Diffusion in Fluid Phase

Try these first

1. 1.

   What is diffusion?

   Hint

   Think about how a drop of food dye behaves in water.

2. 2.

   Define porosity.

   Hint

   Consider the water retention capability of soil.

3. 3.

   What does diffusion result in?

   • Movement from low to high concentration
   • Movement from high to low concentration
   • No movement

   Hint

   Remember the food dye example!

4. 4.

   True or False: Effective diffusivity is unrelated to porosity.

   • True
   • False

   Hint

   Think about how fluids navigate through porous materials.

5. 5.

   A soil sample has a porosity of 0.4. If the diffusion coefficient for a substance in the fluid is 1.0 cm²/s, calculate its effective diffusion coefficient using the Millington-Quirk equation.

   Hint

   Remember to apply the Millington-Quirk formula correctly.

6. 6.

   Discuss how increasing porosity in a material affects the transport of a pollutant over time.

   Hint

   Consider the ease of moving through a denser versus a less dense medium.