4.2. Rivers

Try these first

1. 1.

   What is molecular diffusion?

   Hint

   It relates to concentration gradients.

2. 2.

   Define bulk flow.

   Hint

   Think of moving water in a river.

3. 3.

   What is molecular diffusion?

   Hint

   Think about gradients.

4. 4.

   True or False: In a river, diffusion is the most significant transport mechanism.

   • True
   • False

   Hint

   Consider the flow of water.

5. 5.

   Calculate the time required for a pollutant to diffuse from one end of a 100 m lake to the other, assuming a diffusion coefficient of 1.0 x 10^-5 m^2/s.

   Hint

   Use the formula for diffusion time.

6. 6.

   Discuss the environmental implications of relying solely on diffusion for pollutant transport in an unsaturated soil layer.

   Hint

   Think about pollutant persistence in time.