I am trying to use the equilibrate command under SURFACE for PHREEQC. I have a water composition that I am assuming is in equilibrium with ferrihydrite. I'm trying to model the composition of the ferrihydrite and compare to the actual composition from samples I digested. When I use the -equilibrate command, the initial surface composition is virtually empty of sorbed species, possibly because there is no ferrihydrite. But the solution is supersaturated wrt ferrihydrite. So I don't understand why the initial surface does not have ferrihydrite. If you could provide any suggestions I would appreciate it very much. The input and database files are attached. Kelly Greaser Ph.D Candidate Colorado School of Mines Hydrogeology Program Geology and Geological Engineering
TITLE 207 and 208 mix 6/27/02 SOLUTION_SPREAD -units ppm # Al=0.021 Cu=0.001 P=0.095 Pb=0.012 Number Desc Al Ba Ca Cd Cu Fe K Mg Mn Na Ni P Pb S(6) Si Zn F Cl pH Alkalinity pe Temp 18 207 6/27 0.260 0.031 15.039 0.005 0.005 4.962 0.405 10.246 0.740 1.828 0.045 0.004 0.001 83.267 2.960 3.555 0.000 0.379 6.21 4.1 1.85 7.6 19 208 6/27 0.008 0.063 20.635 0.001 0.001 0.002 0.138 8.315 0.000 0.990 0.001 0.004 0.001 11.586 1.246 0.000 0.000 0.416 7.93 81.9 2.38 8.2 MIX 1 207 and 208 18 0.33 19 0.67 PHASES pH_Fix H+ = H+ log_k 0.0 pe_Fix e- = e- log_k 0.0 Clayproxy K0.08Na0.02Ca0.56Mg0.39Al1.7Si0.475O4(OH) + 7.1H+ = 0.08K+ + 0.02Na+ + 0.56Ca+2 + 0.39Mg+2 + 1.7Al+3 + 0.475H4SiO4 + 3.1H2O log_k -10 EQUILIBRIUM_PHASES 1 pH_Fix -7.17 Calcite 0.1 pe_Fix -3.35 O2(g) 0.1 SAVE solution 66 END EQUILIBRIUM_PHASES 2 pH_Fix -7.17 Calcite 0.1 pe_Fix -3.35 O2(g) 0.1 Ferrihydrite 0.0 0.0 Clayproxy 0.0 0.0 Otavite -0.72 0.0 Barite 0.11 0.0 # Zn(OH)2(s) 0.0 0.0 # Zn(OH)2(w) 0.0 0.0 # Ca-Nontronite 10.0 0.0 # Mg-Nontronite 0.0 0.0 # Kaolinite 0.0 0.0 # Ca-Montmorillonite 0.0 0.0 # Schwertmannite 1.4 0.0 SURFACE_SPECIES Hfo_wOH + Zn+2 + SO4-2 = Hfo_wOHZnSO4 log_k 6.67 #ternary surface complex formation Hfo_wOH + H+ + SO4-2 = Hfo_wSO4- + H2O log_k 7.78 #7.78 - no conf limits Hfo_wOH + SO4-2 = Hfo_wOHSO4-2 log_k 0.79 #0.79 - no conf limits Hfo_sOH + Zn+2 = Hfo_sOZn+ + H+ log_k 0.99 #0.99 + Hfo_wOH + Zn+2 = Hfo_wOZn+ + H+ log_k -1.99 #-1.99 + Hfo_sOH + Cd+2 = Hfo_sOCd+ + H+ log_k 0.47 #0.47 + Hfo_wOH + Cd+2 = Hfo_wOCd+ + H+ log_k -2.9 #-2.9 + Hfo_sOH + Pb+2 = Hfo_sOPb+ + H+ log_k 4.65 #4.65 - Hfo_wOH + Pb+2 = Hfo_wOPb+ + H+ log_k 0.30 #0.3 - derived Hfo_wOH + PO4-3 + 3H+ = Hfo_wH2PO4 + H2O log_k 31.29 #31.29 Hfo_wOH + PO4-3 + 2H+ = Hfo_wHPO4- + H2O log_k 25.39 #25.39 Hfo_wOH + PO4-3 + H+ = Hfo_wPO4-2 + H2O log_k 17.72 #17.72 Hfo_sOH + Mn+2 = Hfo_sOMn+ + H+ log_k -0.40 #-0.4 + derived Hfo_wOH + Mn+2 = Hfo_wOMn+ + H+ log_k -3.50 #-3.5 + derived Hfo_sOH + Ba+2 = Hfo_sOHBa+2 log_k 5.46 #5.46 Hfo_wOH + Ba+2 = Hfo_wOBa+ + H+ log_k -7.2 #-7.2 derived Hfo_wOH + Mg+2 = Hfo_wOMg+ + H+ log_k -4.6 #-4.6 + derived; no constant available for strong site! Hfo_sOH + Ca+2 = Hfo_sOHCa+2 log_k 4.97 #4.97 Hfo_wOH + Ca+2 = Hfo_wOCa+ + H+ log_k -5.85 #-5.85 Hfo_sOH + Cu+2 = Hfo_sOCu+ + H+ log_k 2.89 #2.89 Hfo_wOH + Cu+2 = Hfo_wOCu+ + H+ log_k 0.6 #0.6 derived Hfo_sOH + Ni+2 = Hfo_sONi+ + H+ log_k 0.37 #0.37 Hfo_wOH + Ni+2 = Hfo_wONi+ + H+ log_k -2.5 #-2.5 derived USE solution 66 SURFACE 2 -equilibrate with soltuion 66 Hfo_sOH Ferrihydrite equilibrium_phase 0.005 5.33e4 Hfo_wOH Ferrihydrite equilibrium_phase 0.2 SELECTED_OUTPUT -file 2078MixEQ.out -sim false -state false -soln false -distance false -time false -step false -ionic_strength false -percent_error false #-totals Fe S Zn -molalities Hfo_sOZn+ Hfo_sOPb+ Hfo_sOMn+ Hfo_sOCd+ Hfo_sOHCa+2 Hfo_sOHBa+2 Hfo_sOCu+ Hfo_sONi+ Hfo_wOHSO4-2 Hfo_wSO4- Hfo_wOHZnSO4 Hfo_wOZn+ Hfo_wOMg+ Hfo_wOMn+ Hfo_wOCa+ Hfo_wOPb+ Hfo_wOCd+ Hfo_wOBa+ Hfo_wOCu+ Hfo_wONi+ Hfo_wPO4-2 Hfo_wHPO4- Hfo_wH2PO4 -equilibrium_phases Ferrihydrite Clayproxy Barite Otavite -pH -pe END #Clayproxy # K0.08Na0.04Ca0.56Mg0.38Al1.6Si0.55O4(OH) + 6.8H+ = 0.08K+ + 0.04Na+ + 0.56Ca+2 + 0.38Mg+2 + 1.6Al+3 + 0.55H4SiO4 + 2.8H2O # log_k -10 #Clayproxy # K0.08Na0.04Ca0.56Mg0.38Al1.5Si0.625O4(OH) + 6.5H+ = 0.08K+ + 0.04Na+ + 0.56Ca+2 + 0.38Mg+2 + 1.5Al+3 + 0.625H4SiO4 + 2.5H2O # log_k -10 #Clayproxy # K0.04Ca0.58Mg0.4Al1.9Si0.325O4(OH) + 7.7H+ = 0.04K+ + 0.58Ca+2 + 0.4Mg+2 + 1.9Al+3 + 0.325H4SiO4 + 3.7H2O # log_k -10 #Clayproxy # Ca0.7Mg0.3Al2Si0.25O4(OH) + 8H+ = 0.7Ca+2 + 0.3Mg+2 + 2Al+3 + 0.250H4SiO4 + 4H2O # log_k -10 #Clayproxy # Ca0.72Mg0.28Al2.05Si0.2125O4(OH) + 8.15H+ = 0.72Ca+2 + 0.28Mg+2 + 2.05Al+3 + 0.2125H4SiO4 + 4.15H2O # log_k -10 #Clayproxy # Ca0.7Mg0.3Al2.1Si0.175O4(OH) + 8.3H+ = 0.7Ca+2 + 0.3Mg+2 + 2.1Al+3 + 0.175H4SiO4 + 4.3H2O # log_k -10
Attachment:
GMree.dat
Description: Binary data
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