1. Mass Transport of Pollutants

2. Dense Non-Aqueous Phase Liquids
NAPLs –
Insoluble in water and
Separate phase
Dense NAPLs –
More dense than water
Chlorinated hydrocarbons
Trichloroethylene-TCE
Tetrachloroethylene-PCE
Density increases with increasing halogenation
Density difference of 0.1% causes sinking

3. Light Non-Aqueous Phase Liquids
Light NAPLs
Lighter than water
Petroleum hydrocarbons
Oil
Gasoline
Density difference between water and NAPL of 1% can influence flow
Low viscosity NAPLs migrate more rapidly than high viscosity NAPLs

4. Transport Processes
Conservation of Mass for dissolved substances in groundwater
Rate of change of mass =
Flux of mass out – Flux of mass in ± gain or loss of mass due to reactions x y z
Mass flux in
Mass flux out

5. Solutes Conservative (nonreactive) Nonconservative (reactive)
Do not react with water or soil, do not biologically or radioactively decay
Nonconservative (reactive)

6. Physical Processes Controlling Flux
Advection
Solutes carried along by flowing groundwater
Diffusion
Transport by molecular diffusion
Dispersion
Transport by mechanical mixing

7. Solute Spreading

8. Advection Advection f = porosity vx = average velocity
Solutes carried along by flowing groundwater
f = porosity
vx = average velocity
F = Advective flux = Total mass of solute which is carried across a unit area oriented normal to the bulk fluid motion

9. Diffusion Diffusion Molecular-based phenomenon
Net movement toward areas of lower concentration
F = mass flux per unit area per unit time (M/L2/T)
D* = apparent diffusion coefficient in soil (L2/T)
C = solute concentration (M/L3)
∂C/∂x = concentration gradient (M/L3/L)

10. Dispersion Mechanical Dispersion
Transport by mechanical mixing
F = mass flux per unit area per unit time (M/L2/T)
Dx = dispersion coefficient (L2/T)
C = solute concentration (M/L3)
∂C/∂x = concentration gradient (M/L3/L)

11. Advection-Dispersion Equation
F = mass flux per unit area per unit time (M/L2/T)
Dx = dispersion coefficient (L2/T)
C = solute concentration (M/L3)
∂C/∂x = concentration gradient (M/L3/L)

12. Mass Flux x y z
Mass flux in
Mass flux out

13. Mass Balance Equation
Mass accumulation

14. Solution
Solution

15. Error Function

16. Error Function Values
Homework: Problems 881 and 884

17. Groundwater Monitoring

20. T08_10_04