<p>Table S1. Input file for PHREEQC simulation of hydroxyapatite and autunite solubility in ORFRC Area 2 groundwater Lines starting with the pound sign (#) indicate comments.</p><p># Simulation of the solubility of hydroxyapatite and autinite in FRC Area 2 groundwater</p><p># Define U(VI) as a master species in solution SOLUTION_MASTER_SPECIES U UO2+2 0.0 238.0290 238.0290 U(6) UO2+2 0.0 238.0290</p><p>#Define aqueous-phase U(VI) species required for autunite solubility calculation SOLUTION_SPECIES UO2+2 = UO2+2 log_k 0.0 2UO2+2 + 2H2O = (UO2)2(OH)2+2 + 2H+ log_k -5.6346 2UO2+2 + H2O = (UO2)2OH+3 + H+ log_k -2.7072 3UO2+2 + 4H2O = (UO2)3(OH)4+2 + 4H+ log_k -11.929 3UO2+2 + 5H2O = (UO2)3(OH)5+ + 5H+ log_k -15.5862 3UO2+2 + 7H2O = (UO2)3(OH)7- + 7H+ log_k -31.0508 4UO2+2 + 7H2O = (UO2)4(OH)7+ + 7H+ log_k -21.9508 UO2+2 + CO3-2 = UO2CO3 log_k 9.96 UO2+2 + 2 CO3-2 = UO2(CO3)2-2 log_k 16.64 UO2+2 + 3 CO3-2 = UO2(CO3)3-4 log_k 21.86 Ca+2 + UO2+2 + 3CO3-2 = CaUO2(CO3)3-2 log_k 25.38 2 Ca+2 + UO2+2 + 3CO3-2 = Ca2UO2(CO3)3 log_k 30.43</p><p># Define solubility products for hydroxyapatite and autunite PHASES Hydroxyapatite Ca5(PO4)3OH + H+ = 5Ca+2 + 3PO4-3 + H2O log_k -44.3 Autunite Ca(UO2)2(PO4)2 = Ca+2 + 2PO4-3 + 2UO2+2 log_k -44.7 # Define mock phase to fix pH Fix_pH H+ = H+ log_k 0</p><p># Define artificial groundwater solution composition SOLUTION 1 Temp 25.0 REACTION 1 CaCO3 2.75 MgCO3 1.1 K2SO4 0.1 Ca(NO3)2 0.25 CaSO4 0.9 1 mmol in 1 steps EQUILIBRIUM_PHASES 1 Fix_pH -6.8 HCl 0.1 SAVE SOLUTION 1 END</p><p># Simulate dissolution of an initial 10 mmol/L of hydroxyapatite USE SOLUTION 1 EQUILIBRIUM_PHASES 2 Fix_pH -6.8 HCl 0.1 Hydroxyapatite 0.0 0.01 END</p><p># Simulate dissolution of an initial 10 mmol/L of autunite USE SOLUTION 1 EQUILIBRIUM_PHASES 3 Fix_pH -6.8 HCl 0.1 Autunite 0.0 0.01 END</p><p>Table S2. Excerpt of output from PHREEQC simulation of hydroxyapatite and autunite solubility in ORFRC Area 2 groundwater. The initial amount of mineral introduced into the groundwater was 1.0  10-2 mol L-1 (10 mmol L-1) for both hydroxyapatite and autunite. Note that the amount of mineral dissolved (denoted by “Delta” under “Moles in assemblage”) was 100-fold lower for hydroxapatite (1.81  10-7 moles) compared to autunite (4.83  10-5 moles).</p><p>Using solution 1. Solution after simulation 1. Using pure phase assemblage 2.</p><p>------Phase assemblage------</p><p>Moles in assemblage Phase SI log IAP log KT Initial Final Delta Hydroxyapatite 0.00 -44.30 -44.30 1.000e-02 1.000e-02 -1.813e-07</p><p>Using solution 1. Solution after simulation 1. Using pure phase assemblage 3.</p><p>------Phase assemblage------</p><p>Moles in assemblage Phase SI log IAP log KT Initial Final Delta Autunite 0.00 -44.70 -44.70 1.000e-02 9.952e-03 -4.826e-05</p>