MASS TRANSPORT OF SOLUTES

1. MASS TRANSPORT OF SOLUTES

2. Basic Processes A. Diffusion B. Advection

3. Fick’s Law II. The Finer Details • Diffusion F = -D dc dx

4. Fick’s Law II. The Finer Details • Diffusion F = -D dc dx F = mass flux of solute per unit area per unit time D = diffusion coefficient (area per time) dc = concentration gradient (mass/volume/ dx distance)

5. II. The Finer Details • Diffusion • Advection Vx = K dh ne dl

6. II. The Finer Details • Diffusion • Advection • Mechanical Dispersion Dm = aL vL where aL = dynamic dispersivity (a function of the aquifer’s physical properties, and controls the degree of ‘spread’ of the material)

7. II. The Finer Details • Diffusion • Advection • Mechanical Dispersion 1) Longitudinal 2) Transverse

8. Longitudinal

9. Transverse

10. II. The Finer Details • Diffusion • Advection • Mechanical Dispersion 1) Longitudinal 2) Transverse D. Hydrodynamic Dispersion “hard to separate diffusion and mechanical dispersion”

11. D. Hydrodynamic Dispersion “hard to separate diffusion and mechanical dispersion” DL = aL vL+ D* where DL = hydrodynamic dispersion aL = dynamic dispersivity vL = average linear velocity D*= molecular diffusion where D* = (D x n) / (tortuosity)2

12. II. Action !!! dC = DLd2C - vx dC dt dx2 dx Dispersion and Diffusion “Pure” Advection

13. Continuous source…..

14. Continuous source….. (one time source) “A slug”

17. II. The Finer Details • Diffusion • Advection • Mechanical Dispersion 1) Longitudinal 2) Transverse D. Hydrodynamic Dispersion E. Retardation