7.1. Solving the Retardation Equation

Try these first

1. 1.

   Define the term effective diffusivity.

   Hint

   Think about how solids might affect the movement of fluids.

2. 2.

   What does the mass balance equation represent?

   Hint

   Consider inflow, outflow, and accumulation.

3. 3.

   What is the main principle of mass balance?

   • Conservation of energy
   • Conservation of mass
   • Conservation of volume

   Hint

   Relate it to what you studied before regarding materials in systems.

4. 4.

   True or False: High porosity decreases effective diffusivity.

   • True
   • False

   Hint

   Think about ways water can flow through rocks.

5. 5.

   If the effective diffusivity of a pollutant is measured to be 0.5 m²/day in water and the porosity of the sediment is 0.4, how would you assess the retardation factor if the partitioning coefficient is 3.5?

   Hint

   Keep in mind the base number when calculating the retardation factor.

6. 6.

   Explain how variations in sediment types might alter the effective diffusivity and retardation factor for a contaminant. Provide examples of two sediment types.

   Hint

   Consider how water moves differently through coarse versus fine materials.