Processes > Inverse modelling
How to add Fertilizer formular in the Phreeqc.dat Database for Inverse modelling
evansmanu:
Dear David,
Thanks very much for your support. First of all, I conducted petrographic studies on samples of rock outcrops from the study area and established primary and secondary minerals pertaining to the geology of the area. With the issue of Plagioclase, the mineralogical studies revealed the presence of Na-rich (albite) and no Ca-rich (Anorthite). The reason I constrained my model to only include albite as a primary mineral which weathers into the clay minerals such as kaolinite.
Calcite, from the mineral studies, was found to be a secondary mineral as it is always found in the features and not as a bulk mineral. In the inverse modelling, it was constrained to precipitate only. These are the breakdown of the minerals from the petrographic analysis, Primary includes Albite, Phlogopite, K-mica, K-feldspar, Quartz, Pyrite and secondary, Kaolinite, Chlorite and Goethite.
You suggested a Transport model to help understand the cation exchange process. I will appreciate it if you can give me a lead or a simple script to start with.
Here is the updated script
TITLE Northern evolution with new conceptual model
SOLUTION 0
temp 25
pH 3.749
redox O(0)/O(-2)
units mol/kgw
density 1
O(0) 1.0 O2(g) -0.7
C(4) 1.147e-03
Ca 1.504e-03 charge
Cl 1.321e-03
K 1.559e-04
Mg 1.081e-04
Na 1.692e-04
S(6) 1.216e-03
PHASES
Phlogopite
KMg3(AlSi3)O10(OH)2 + 10 H+ = 1 Al+3 + 1 K+ + 3 Mg+2 + 3 H4SiO4
log_k 41.082
-delta_H -360.123 kJ/mol # References :92cir/nav
-analytic -1.7201279e+03 -2.6579576e-01 1.0718208e+05 6.1999929e+02 -4.7275095e+06
Plagioclase
Na0.62Ca0.38Al1.38Si2.62O8 + 8H2O = 0.62Na+ + 0.38Ca+2 + 1.38Al(OH)4- + 2.62H4SiO4
-log_k -18.65256
-delta_h 20.45592 kcal
-Vm 103.6288
Organic_matter
CH2O + H2O = 4 e- + 4 H + + CO2
-log_K = 4.8
Fertilizer
K0.18O0.72P0.22Ca0.09Mg0.06Na0.18(SO4)0.07Cl0.18 + 0.16H2O = 0.18K+ + 0.09Ca+2 + 0.06Mg+2 + 0.18Na+ + 0.32H+ + 0.22PO4-3 + 0.18Cl- + 0.07SO4-2
-log_k 0.0
EQUILIBRIUM_PHASES 1
O2(g) -0.7
CO2(g) -3.5
Kaolinite 0.0
SAVE Solution 1
END
USE Solution 1
REACTION 1
Organic_matter 1
0.001 moles in 20 steps
SAVE Solution 2
END
USE Solution 2
EQUILIBRIUM PHASES 2
CO2(g) -3.0
O2(g) -0.7
Albite 0 8.017e-04
Phlogopite 0 1.669e-04
Pyrite 0 2.166e-09
K-feldspar 0 0
Kaolinite 0 0
Fe(OH)3(a) 0
Calcite 0 0
SAVE Solution 3
END
USE Solution 3
EXCHANGE_SPECIES
X- + K+ = KX; log_k 0.7
2X- + Ca+2 = CaX2; log_k 0.8
Na+ + X- = NaX; log_k 0
EXCHANGE 1
-equilibrate 1
X 1.e-3
SAVE Solution 4
END
I am not able to include any attachments. Is there anything for me to do?
dlparkhurst:
If there are no Ca sources, it is hard to make Ca+2 the dominant cation and to make secondary calcite. Right now, all of the Ca comes from your initial solution, which begs the question, Where did it come from?
So, I think there must be a source of Ca. There can be calcite in the feldspar matrix or even if it is low-Ca feldspar, it may still be the source of the Ca.
Here is a simple model that generates a CaX2 clay related to Ca-Montmorillonite, and then allows ion exchange equilibrium with major cations (I removed FeX2). It is a little forced in that I did not allow the most stable phase, kaolinite to form. Pyrite is also removed because all of it will dissolve completely in the first step given the partial pressure of O2(g).
I don't think the calculation can be made very reliable. The equilibrium constants of the aluminosilicate minerals are uncertain; moreover, equilibrium is probably not reasonable. Uncertainty of stoichiometry of the reactive minerals plus reaction kinetics, and there are just too many degrees of freedom.
I hope you have gone back and tried some inverse modeling again. With your mineralogy and analyses of water samples, seems like you should be able to convince yourself of some reasonable reactions. One of the major uses of inverse modeling is helping to establish that your preconceived notions are plausible.
--- Code: ---PHASES
Phlogopite
KMg3(AlSi3)O10(OH)2 + 10 H+ = 1 Al+3 + 1 K+ + 3 Mg+2 + 3 H4SiO4
log_k 41.082
-delta_H -360.123 kJ/mol # References :92cir/nav
-analytic -1.7201279e+03 -2.6579576e-01 1.0718208e+05 6.1999929e+02 -4.7275095e+06
Plagioclase
Na0.62Ca0.38Al1.38Si2.62O8 + 8H2O = 0.62Na+ + 0.38Ca+2 + 1.38Al(OH)4- + 2.62H4SiO4
-log_k -18.65256
-delta_h 20.45592 kcal
-Vm 103.6288
Organic_matter
CH2O + H2O = 4 e- + 4 H + + CO2
-log_K = 4.8
END
EXCHANGE_SPECIES
X- + K+ = KX; log_k 0.7
2X- + Ca+2 = CaX2; log_k 0.8
Na+ + X- = NaX; log_k 0
Fe+2 + 2X- = FeX2; log_k -20
TITLE Northern evolution with new conceptual model
SOLUTION 0
temp 25
pH 3.749
redox O(0)/O(-2)
units mol/kgw
density 1
O(0) 1.0 O2(g) -0.7
C(4) 1.147e-03
Ca 1.504e-03 charge
Cl 1.321e-03
K 1.559e-04
Mg 1.081e-04
Na 1.692e-04
S(6) 1.216e-03
END
SOLUTION 0-3
END
EQUILIBRIUM_PHASES 1
#Pyrite 0 #2.166e-09
#Fe(OH)3(a) 0 0
K-feldspar 0 1 dis
#Albite 0 8.017e-04
Plagioclase 0 10
Phlogopite 0 #1.669e-04
CO2(g) -2.0
O2(g) -0.7
Calcite 0 0
Ca-Montmorillonite 0 1e-8
#Kaolinite 0 0
Quartz 0 0
END
USE solution 1
USE equilibrium_phases 1
SAVE solution 1
END
EXCHANGE 1
CaX2 Ca-Montmorillonite equilibrium_phase 0.165
END
TRANSPORT
-cells 1
-shifts 10
USER_GRAPH 1
-headings step CaX2 MgX2 NaX KX
-axis_scale y_axis auto auto auto auto log
-initial_solutions false
-connect_simulations true
-plot_concentration_vs x
-start
10 GRAPH_X STEP_NO
20 GRAPH_Y MOL("CaX2"), MOL("MgX2"), MOL("NaX"), MOL("KX"),
-end
-active true
USER_GRAPH 2
-headings step Ca Mg Na K
-axis_scale y_axis auto auto auto auto log
-initial_solutions false
-connect_simulations true
-plot_concentration_vs x
-start
10 GRAPH_X STEP_NO
20 GRAPH_Y MOL("Ca+2"), MOL("Mg+2"), MOL("Na+"), MOL("K+"),
-end
-active true
--- End code ---
evansmanu:
Hello David,
I performed a new inverse modelling using pure water instead of rainwater. The final inverse modelling resulted in a major mineral assemblages as shown bellow.
INVERSE MODELLING USING RAINWATER (Old phases used): Other minor mineral assemblages also includes: Calcite, Ca-Mont, Goethite and K-feldspar
delta
Albite -8.017e-04
K-mica 3.228e-04
Phlogopite -1.669e-04
Pyrite -2.166e-09
INVERSE MODELLING USING PURE WATER (New phases): Other minor mineral phases also includes: Calcite, Fe(OH)3, and Kaolinite
delta
Chalcedony -3.168e-04
Hematite 2.321e-08
K-mica 3.568e-06
Phlogopite -1.079e-05
Pyrite -4.652e-08
From these two results, dissolution of phlogopite, pyrite and the precipitation of k-mica, calcite and some iron oxides are common in both models. In-congruent dissolution of Phlogopite is responsible for the precipitation of K-mica whiles oxidation of pyrite also causes the formation of iron oxides such as Fe(OH)3 and Hematite.
in the coming days i will test the models with these two mineral assemblages from 1) using a pure water and 2) using rainwater.
FEW COMMENTS ON YOUR CODE
1) what is the meaning SOLUTION 0-3
2) I do not understand this "CaX2 Ca-Montmorillonite equilibrium_phase 0.165" in the EXCHANGE data block. Is the number 0.165 arbitrary?
Best
dlparkhurst:
For ADVECTION and TRANSPORT modeling you need solutions defined for solution 0 (for forward flow direction) and each cell of the column. SOLUTION 0-3 defines solutions numbered 0, 1, 2, and 3. I ended up using only one cell, so solutions 2 and 3 were not used.
0.165 is the stoichiometry of Ca in Ca-Montmorillontite. This definition makes all of the Ca that precipitates in Ca-Montmorillonite exchangeable.
evansmanu:
Dear all,
I am uncertain about the ion exchange component of my script. What I want to do is to equilibrate the preceding solution with an ion exchange given an exchanger amount.
For instance, after running a code that saves the resulting reaction into Solution 3 and then applies the exchange with solution 3. Must I change the number after the equilibrate to 3 as well? Find the entire script below.
.
.
.
.
USE Solution 3
EXCHANGE 1
equilibrate 1
X 0.015
SAVE Solution 4
TITLE Simulation of groundwater chemical evolution along the flow path considering mineral reactions (evaporated rainwater as the initial solution)
SOLUTION 0 Precipitation from the literature (evaporation until groundwater Cl concentration is matched)
temp 25
pH 3.749
pe 4
redox O(0)/O(-2)
redox pe
units mol/kgw
density 1
O(0) 0.01 O2(g) -0.7
C(4) 1.147e-03 as HCO3 #CO2(g) -3.5
Ca 1.504e-03 charge
Cl 1.321e-03
K 1.559e-04
Mg 1.081e-04
Na 1.692e-04
S(6) 1.216e-03
EQUILIBRIUM_PHASES 1 ##----------- equilibrated with the potential phases in the unsaturated zone (Saprolite)
Kaolinite 0.0
Hematite 0.0
SAVE Solution 1
END
SELECTED_OUTPUT
-file organic_matter.dat
-reaction true
-totals C(4) S(6) Fe
-molalities SO4-2 Ca+2 Na+ Cl- Mg+2 K+
USE Solution 1
REACTION 1 ## --------- decomposition of organic matter
Organic_matter 1
2.680e-03 moles ##0.004 moles in 100 steps #2.800e-03 moles (1.56E-05) ## --------- manual input through try and error
SAVE Solution 2
END
USE Solution 2 ## --------- Equilibration with mineral phases identified from the combinatorial inverse model in the Northern Zone.
EQUILIBRIUM PHASES 2
CO2(g) -1.7 ## -------- considered for soil zone CO2
Albite 0 8.017e-02
# Anorthite 0
# Phlogopite 0 1.669e-02
# Pyrite 0 #2.166e-04
K-feldspar 0
# K-mica 0 0
# Kaolinite 0 0
Fe(OH)3(a) 0
Chalcedony 0
# Calcite 0 0
pe_Fix -4.672 O2(g) 0.5 ## ---- for redox optimization derived from the combinatorial inverse calculation
SAVE Solution 3
END
USE Solution 3
EXCHANGE 1 ## ----- Ion exchange reaction
equilibrate 1
X 0.015 ## Exchange capacity estimated (currently, there is no value from literature)
SAVE Solution 4
END
TITLE Simulation of evolution from Northern zone through Central zone ---------------------------------------------------------
USE Solution 4
EQUILIBRIUM_PHASES 3 ## Potential phase assemblages from the Combinatorial inverse calculation in the Central zone
CO2(g) -1.75 ## considered for soil zone CO2 (estimated)
Chalcedony 0 #2.806e-04
# Anorthite 0
# Pyrite 0 #1.38e-08
K-mica 0 2.044e-04
# K-feldspar 0 0
# Fe(OH)3(a) 0 0
Kaolinite 0 0
pe_Fix -1.900623 O2(g) 0.5
SAVE Solution 5
END
USE Solution 5
EXCHANGE 2
equilibrate 2
X 0.015 #working 0.015
SAVE Solution 6
END
TITLE Simulation of evolution from Central zone to Southern zone -- here we equilibrate with the aquifer mineralogy --------------------
USE Solution 6
EQUILIBRIUM_PHASES 3 ##----- Mineral assemblages from the combinatorial inverse model in the Southern zone
# CO2(g) -2.0
Calcite 0 0
# K-feldspar 0
K-mica 0
Phlogopite 0 10
Chalcedony 0 2.82e6-04
Fe(OH)3(a) 0
pe_Fix -4.35 O2(g) 0.5
SAVE Solution 7
END
USE Solution 7
EXCHANGE 3
equilibrate 3
X 0.00009
SAVE Solution 8
END
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version