Contaminant Transport

Question 1

What is conservative flow?

Answer 1

the transport of contaminants without changing the contaminants properties

Question 2

What is non conservative flow?

Answer 2

The chemical can biological processes that redistribute contaminants and in the process alter them

Question 3

What is advection?

Answer 3

conservative flow. Solute move with the velocity of the groundwater flow. no change in shape or chemistry

Question 4

What is a plug flow?

Answer 4

A plug contaminant remains unchanged in shape and size as it migrates through a porous media

Question 5

What is molecular diffusion

Answer 5

a solute in water will move due to concentration gradients from high to low concentration even if the fluid is not flowing

Question 6

what is mechanical dispersion

Answer 6

mechanical dispersion is spreading due to microscopic heterogeneity along a flow path. Causes solute to dilute because it is spreading over a larger area

Question 7

what is the advective flux?

Answer 7

The advective flux is the mass flux through a unit cross sectional area due to groundwater advection and is equal to the quantity of water multiplied by the concentration of dissolved solids

Question 8

what is hydrodynamic dispersion?

Answer 8

the combined effect of mechanical dispersion and molecular diffusion

Question 9

what are the dimensions for a flux?

Answer 9

[M L-2 T-1]

Question 10

what is Ficks first law?

Answer 10

diffusive flux is still water is proportional too the concentration gradient

Question 11

what is the total contaminant flux?

Answer 11

The total contaminant flux is the sun of the advective flux and the hydrodynamic dispersive flux.

Question 12

what does a high longitudinal v transverse dispersivity ration mean?

Answer 12

Elongated plume - high longitudinal dispersion and low transverse dispersion.

Question 13

What does the advection-dispersion equation assume?

Answer 13

-conservative tracer
-contaminant concs do not affect GW viscosity
- single porosity aquifer
- effective porosity is total porosity

Question 14

What is the Pe number equation?

Answer 14

Pe = L.v/D
Pe = peclet number
L = length between source and receptor
D = coefficient of hydrodynamic dispersion

Question 15

What does the Pe number mean?

Answer 15

Determines if the flow is advective or disperse dominated.
High Pe = advection dominated
Low Pe = dispersion dominated. Pe >2 means the numerical scheme is unstable.

Question 16

What is the Courant number?

Answer 16

the distance travelled by a contaminant due to advection in one time step as a fraction of the grid spacing. For stability and accuracy, Courant number must be less than or equal to one