Processes > Reactive transport modelling

Am transport in groundwater

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dlparkhurst:
You are not plotting the same quantities. In advection, the X axis is pore volumes (proportional to time)  and in transport the X axis is distance.

You also have not set up the same simulations for advection and transport. You should initialize both the solutions and the surfaces in cells 1-20 between the advection and the transport calculation.

I would eliminate the second SOLUTION_SPECIES data block. You are creating inconsistencies between these species and the other aqueous species (including Am species), and you will have to explain why you made just these changes to the aqueous model.

--- Code: ---SOLUTION_MASTER_SPECIES
Am           Am+3   0.0        Am        243.0000
Am(+3)    Am+3      0.0        Am
SOLUTION_SPECIES
Am+3 = Am+3
log_k      0.0
Am+3 +  H2O - H+  = AmOH+2
log_k      -7.200
Am+3 + 2H2O - 2H+  = Am(OH)2+
log_k      -15.100
Am+3 + 3H2O - 3H+  = Am(OH)3
log_k      -26.200
Am+3 + F-  = AmF+2
log_k      3.400
delta_h    2.89 kcal
Am+3 + 2F-  = AmF2+
log_k      5.800
delta_h     10.77 kcal
Am+3 +  Cl- = AmCl+2
log_k      0.240
Am+3 + 2Cl- = AmCl2+
log_k      -0.810
delta_h    13.11 kcal
Am+3 + SO4-2 = AmSO4+
log_k      3.500
delta_h    9.56 kcal
Am+3 + 2SO4-2 = Am(SO4)2-
log_k       5.000
delta_h    16.72 kcal
Am+3 + NO3- = AmNO3+2
log_k      1.28
delta_h    0.43 kcal
Am+3 + 2NO3- = Am(NO3)2+
log_k      0.88
delta_h    2.58 kcal
Am+3 + CO3-2 = AmCO3+
log_k      8.000
Am+3 + 2CO3-2 = Am(CO3)2-
log_k      12.900
Am+3 + 3CO3-2 = Am(CO3)3-3
log_k      15.000
Am+3 + HCO3- = AmHCO3+2
log_k      3.100
Am+3 +  H3SiO4- = AmSiO(OH)3+2
log_k      8.13
delta_h     4.44 kcal

SURFACE_MASTER_SPECIES      #Surface Complexation of Am on Granite
Surf    SurfOH
SURFACE_SPECIES
SurfOH = SurfOH
log_k   0.0
##Am
SurfOH + Am+3 = SurfOAm+2 + H+
log_k   -0.60
SurfOH + Am+3 + 2H2O = SurfOAm(OH)2 + 3H+
log_k   -17.20

SOLUTION 1-21   #Repository groundwater
temp        25
pH          9.0
pe          -3
redox       pe
units       mol/L
density     1.0003
Na          3.23e-2
Ca          3.42e-4
K           1.16e-4
Mg          1.19e-4
Cl          1.79e-2
S(6)        1.15e-4
N(5)        3.67e-4
C(4)        2.05e-3   CO2(g) -5.5
Si          7.05e-5

SURFACE 1-21
SurfOH  7.35e-6    2.3      0.09
-donnan 1e-10
-equil 1
End

SOLUTION 0  Palse solution with Am
temp        25
pH          9.0
pe          -3
units       mol/L
C(4)        0.0000001  CO2(g) -2.5
Am          1.0e-7
Si          7.05e-5
End

-cells           20
-shifts          100
-punch_cells     20
-punch_frequency 1
-print_cells     20
-print_frequency 10

USER_GRAPH 1 Example 11
-axis_titles "Pore volumes" "Millimoles per kilogram water"
-axis_scale x_axis 0 auto
-axis_scale y_axis 0 auto
-plot_concentration_vs time
-start
10 x = (STEP_NO + 0.5) / cell_no
20 PLOT_XY x, TOT("Am")*1000, symbol = None
30 PUT(1, 1)
-end

END
USER_GRAPH 1
-detach
END

SOLUTION 0  Palse solution with Am
temp        25
pH          9.0
pe          -3
units       mol/L
C(4)        0.0000001  CO2(g) -2.5
Am          1.0e-7
Si          7.05e-5
SOLUTION 1-21   #Repository groundwater
temp        25
pH          9.0
pe          -3
redox       pe
units       mol/L
density     1.0003
Na          3.23e-2
Ca          3.42e-4
K           1.16e-4
Mg          1.19e-4
Cl          1.79e-2
S(6)        1.15e-4
N(5)        3.67e-4
C(4)        2.05e-3   CO2(g) -5.5
Si          7.05e-5

SURFACE 1-21
SurfOH  7.35e-6    2.3      0.09
-donnan 1e-10
-equil 1
End
USER_GRAPH 1
-chart_title "Dual Porosity, First-Order Exchange with Implicit Mixing Factors"
-axis_titles "Pore Volumes" "Millimoles per kilogram water"
-axis_scale x_axis 0 auto
-axis_scale y_axis 0 auto
-plot_concentration_vs x
-start
10 GRAPH_X TOTAL_TIME/(20*3.1536e7)
20 GRAPH_Y TOT("Am")*1000
-end
END

TRANSPORT
-cells              20
-length             50     # total  length = length *  cells  # total length is 1000m
-shifts             100   1     # total diffusion time is  shifts*time_step
-time_step          3.1536e7   # second   1a   # total time is 10a
-dispersivity       0.078
-punch_cells        20
-punch_frequency    1-20
-print              20
-print_frequency    10
-flow_direction     forward  # diffusion
-boundary_cond      flux    flux
-correct_disp       true
-diffc              2.0e-13    #diffusion coefficient
-multi_d            true  1e-9   5.8e-3   0    1
-porosities         20*5.8e-3
END

SOLUTION 0
temp        25
pH          9.0
pe          -3
units       mol/L
C(4)        0.0000001  CO2(g) -2.5
END
PRINT; -user_graph true
TRANSPORT
-shifts 60 1
END
--- End code ---

Sen:
Dear Prof. Parkhurst
Sorry for my late Reply again. The Omicron pandemic I may have experienced recurrent infections for a short period of time and did not feel slightly better until today. Thank you very much for your selfless help, which has deepened my understanding of the model. Always your work has been very rewarding. Again, thank you for all your help!

Best wishes，
Sen