1. Numerical Simulations of Multi-Species Contaminant Transport in Variably Saturated Aquifers in Coastal Areas Presenter ： Yi-Ming Wei Adviser ： Chuen-Fa Ni Date ： 2010/10/14

2. Outline  Introduction  Literature review  Objectives  HYDROGEOCHEM-2D model  Test example  Future work

3. Density-driven circulation (Q d ) freshwater discharge tube Tide induced circulation (Q t ) upper saline plume wave set-up driven circulation (Q w ) fresh groundwater discharge (Q f ) Introduction Reference ： C. Robinson, L. Li, D.A. barry (2007)

4. Literature review Influence of seaward boundary condition on contaminant transport in unconfined coastal aquifers. (Q. Zhang et al., 2001) Tidal impacts on riparian salinities near estuaries. (Adrian D. Werner et al., 2005) Tidal influence on BTEX biodegradation in sand coastal aquifers. (D.A Barry et al., 2009)

5. Objectives Combine geochemical and hydrogeological simulated process into HYDROGEOCHEM model Figure out the impact of recharge and beach slope on solute transport in coastal aquifer.

6. HYDROGEOCHEM-2D model Include variably saturated fluid flow, heat transfer, and reactive chemical transport. Deal with equilibrium and kinetic reaction in terms of reaction networks. Incorporate the effect of precipitation /dissolution on the change of pore size, hydraulic conductivity, and diffusion/dispersion.

7. Flow Equations Reference ： Yeh et al., 1994

8. The rate of mass accumulation The net rate of mass flux due to advection The net mass flux due to dispersion and diffusion The rate of mass production and reduction due to chemical reactions and radioactive decay The source/sink term corresponding to artificial injection and/or withdrawal Reactive Chemical Transport Equations Reference ： Yeh, 2000

9. Test Example Pressure head = 85m 400 m 100 m Pressure head = 84m Impermeable bottom Variable boundary condition

10. 1.0 mole/liter ( Br 2 ) Pressure head = 85m 400 m 100 m Pressure head = 84m Impermeable bottom No rainfall Contaminant transport in unsaturated aquifer

11. 6000 day

12. Pressure head = 85m 400 m 100 m Pressure head = 84m I = 0.01 、 0.002 m/day Contaminant transport with recharge Impermeable bottom 1.0 mole/liter ( Br 2 )

13. I = 0.01 m/day I = 0.002 m/day

14. I = 0.01 m/day I = 0.002 m/day 3600 day

15. 6000 day I = 0.01 m/day I = 0.002 m/day

16. Pressure head = 85m 400 m 100 m Pressure head = 84m No rainfall -1.0 m 2 /day( 抽水 ) Impermeable bottom Contaminant transport with pumping well 1.0 mole/liter ( Br 2 )

17. 1140 day 3060 day

18. Contaminant transport with beach slope Pressure head = 85m 400 m 100 m Pressure head = 84m No rainfall Impermeable bottom Beach slope = 0.2 、 0.3 1.0 mole/liter ( Br 2 )

19. Beach slope = 0.2 Beach slope = 0.3

20. Beach slope = 0.2 Beach slope = 0.3 960 day

21. Beach slope = 0.2 2022 day Beach slope = 0.3

22. Future work Sea level oscillations (tidal fluctuation). Multi-species reactive transport. Geochemical reaction include precipitation, adsorption, reaction rate, and biodegradation. Aquifer heterogeneity.

23. Thanks for your attention