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HP1: A coupled numerical code for variably saturated water flow, solute transport and biogeochemical reactions in soils

2. . HP1: HYDRUS1D-PHREEQCPossibilities of the codeBenchmarkingPCE-dissolutionMigration of decay chain of adsorbing contaminants during precipitation/evaporationIllustration of coupled' effectsTNT degradation under steady state flowCd leaching in an acid podzol: lysimeter experimentsLong-

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HP1: A coupled numerical code for variably saturated water flow, solute transport and biogeochemical reactions in soils

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    1. 1 HP1: A coupled numerical code for variably saturated water flow, solute transport and biogeochemical reactions in soils and sediments D. Mallants, D. Jacques, J. Šimunek, and M.Th. van Genuchten

    2. 2 Outline

    3. 3

    4. 4 Simulation Tool

    5. 5 Coupling procedure

    6. 6

    7. 7 HP1 – model features

    8. 8 HP1 examples Transport of heavy metals (Zn2+, Pb2+, and Cd2+) subject to multiple cation exchange Transport with mineral dissolution of amorphous SiO2 and gibbsite (Al(OH)3) Heavy metal transport in a medium with a pH-dependent cation exchange complex Infiltration of a hyperalkaline solution in a clay sample (kinetic precipitation-dissolution of kaolinite, illite, quartz, calcite, dolomite, gypsum, …) Long-term transient flow and transport of major cations (Na+, K+, Ca2+, and Mg2+) and heavy metals (Cd2+, Zn2+, and Pb2+) in a soil profile. Kinetic biodegradation of TNT (multiple degradation pathways)

    9. 9 Typical application and processes involved

    10. 10

    11. 11 Test I: PCE degradation PCE degradation pathway (Schaerlaekens et al., Hydrological Processes, 1999)

    12. 12 Test I: PCE degradation Comparison with analytical solution

    13. 13 Test II: Migration of decay chain species Problem definition

    14. 14 Test II: Migration decay chain species Water flow boundary conditions

    15. 15 Test II: Migration decay chain species Water content profiles

    16. 16 Test II: Migration decay chain species Concentration-depth profiles

    17. 17

    18. 18

    19. 19

    20. 20

    21. 21 Cd leaching in acid podzol Introduction

    22. 22 Cd leaching in acid podzol Objectives

    23. 23 Cd leaching in acid podzol Problem definition (Seuntjens et al., 2000)

    24. 24 Cd leaching in acid podzol Leaching experiment set-up

    25. 25 Cd leaching in acid podzol Leaching experiment modelling (1)

    26. 26 Cd leaching in acid podzol Leaching experiment modelling (2)

    27. 27 Cd leaching in acid podzol Multi-component modelling results (1)

    28. 28 Cd leaching in acid podzol Multi-component modelling results (2)

    29. 29 Cd leaching in acid podzol Multi-component modelling results (3)

    30. 30 Cd leaching in acid podzol Multi-component modelling results (4)

    31. 31 Cd leaching in acid podzol Cd remobilisation due to complex formation

    32. 32 Cd leaching in acid podzol Conclusion

    33. 33

    34. 34 Geochemical transport under transient variably-saturated flow

    35. 35 Long-term transient flow and transport Transient infiltration at surface

    36. 36 Long-term transient flow and transport Effect of transient infiltration on Cd migration

    37. 37 Long-term transient flow and transport Cd mobility and bio-availability as function of ?, pH, Cl- (1)

    38. 38 Long-term transient flow and transport Cd mobility and bio-availability as function of ?, pH, Cl- (2)

    39. 39 Long-term transient flow and transport Conclusions Temporal variability of physical soil variables (?) results in temporal variability in geochemical variables (pH, Cl-,…) Applied to heavy metal mobility and bio-availability: Water content variations linearly related to pH and inversely to Cl- variations pH inversely related to dissolved metal concentration (multi-site cation exchange f(pH)) Cl- concentration linearly related to dissolved metal concentration (complex formation)

    40. 40

    41. 41 Introduction / objectives (1)

    42. 42 Introduction / objectives (2) Multiple lines of reasoning

    43. 43 Introduction A new biogeochemical transport code:HP1 Problem statement: soil, geochemical reactions, BC/IC Simulation results U-fluxes from soil vs. surface repository Conclusions

    44. 44 Problem statement (1) Multilayered soil profile

    45. 45 Problem statement (2) Geochemical equilibrium reactions

    46. 46 Problem statement (3) Multi-site cation exchange reactions

    47. 47 Problem statement (4) pH-dependent negative charge

    48. 48 Problem statement (5) Surface complexation Surface complexation model 0.875 reactive sites/mol Fe (Waite et al., 1994. G.C. Acta) Surface complex: ?FeOUO2+ (Dzombak & Morel, 1990) Changing processes in U adsorption with increasing pH

    49. 49 Problem statement (6) Initial and Boundary conditions

    50. 50 Introduction A new biogeochemical transport code:HP1 Problem statement: soil, geochemical reactions, BC/IC Simulation results U-fluxes from soil vs. surface repository Conclusions

    51. 51 Simulation results (1) Total Ca, P, and U depth profiles

    52. 52 Simulation results (2) Transient flow conditions => transient geochemical conditions

    53. 53 Simulation results (3) ?pH results in time variations of U-mobility

    54. 54 Simulation results (4) U-fluxes: steady-state vs. transient

    55. 55 Introduction A new biogeochemical transport code:HP1 Problem statement: soil, geochemical reactions, BC/IC Simulation results U-fluxes from soil vs. surface repository Conclusions

    56. 56 Comparison of U-fluxes

    57. 57 Introduction A new biogeochemical transport code:HP1 Problem statement: soil, geochemical reactions, BC/IC Simulation results U-fluxes from soil vs. surface repository Conclusions

    58. 58 Conclusions (1)

    59. 59 Conclusions (2)

    60. 60 Use of Geochemical Transport Models Process Coupling and Interactions Tools for investigating the impacts of multiple coupled biogeochemical reactions in the presence of complex flow fields and spatial heterogeneity. Enable extrapolation to environmentally relevant temporal and spatial scales. Interpretation of Laboratory and Field Data Provide a useful framework for interpreting experimental results. Serve as a tool for understanding qualitative and quantitative trends and relationships present in the data. Sensitivity Analysis Permit the systematic evaluation of the impact of model parameters (both reactive and hydrogeological), initial conditions, and boundary conditions upon the model output. Integration and Synthesis Tool for integrating all of the knowledge obtained from simulation, sensitivity analyses, and laboratory and field experimentation.

    61. 61 Find out more about HP1! www.sckcen.be/hp1

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