## 4 Results and Discussion
### Uranium Speciation in Groundwater
\begin{table}
\begin{tabular}{c c c} \hline
**Sample 1, Eh \(-\)190 mV, pH 7** & **Sample 2, Eh \(-\)28 mV, pH 6.8** & **Sample 3, Eh 90 mV, pH 6.97** \\ Fe(II) 1.791 \(\times\) 10\({}^{-7}\) total & Fe(II) 1.916 \(\times\) 10\({}^{-4}\) total & Fe(II) 1.789 \(\times\) 10\({}^{-7}\) total \\ Fe\({}^{2+}\) 5.063 \(\times\) 10\({}^{-8}\) & Fe\({}^{2+}\) 1.174 \(\times\) 10\({}^{-4}\) & Fe\({}^{2+}\) 1.228 \(\times\) 10\({}^{-7}\) \\ FeHCOO3\({}^{+}\) 1.221 \(\times\) 10\({}^{-7}\) & FeHCOO\({}_{3}\)\({}^{+}\) 5.211 \(\times\) 10\({}^{-5}\) & FeHCOO\({}_{3}\)\({}^{+}\) 4.586 \(\times\) 10\({}^{-8}\) \\ - & FeSO4 2.004 \(\times\) 10\({}^{-5}\) & FeSO4 5.715 \(\times\) 10\({}^{-9}\) \\ Fe(III) 9.0 \(\times\) 10\({}^{-16}\) total & Fe(II) 3.672 \(\times\) 10\({}^{-10}\) total & Fe(II) 2.042 \(\times\) 10\({}^{-10}\) total \\ Mn(II) 7.2 \(\times\) 10\({}^{-6}\) total & Mn(II) 4.187 \(\times\) 10\({}^{-5}\) total & Mn(II) 2.348 \(\times\) 10\({}^{-5}\) total \\ Mn\({}^{2}\) 6.500 \(\times\) 10\({}^{-6}\) & Mn\({}^{2+}\) 3.364 \(\times\) 10\({}^{-5}\) & Mn\({}^{2+}\) 1.995 \(\times\) 10\({}^{-5}\) \\ MnCO3 4.273 \(\times\) 10\({}^{-7}\) & MnCO3 2.279 \(\times\) 10\({}^{-7}\) & MnCO3 1.624 \(\times\) 10\({}^{-7}\) \\ MnSO4 1.230 \(\times\) 10\({}^{-7}\) & MnSO4 7.171 \(\times\) 10\({}^{-6}\) & MnSO4 1.445 \(\times\) 10\({}^{-6}\) \\ - & MnNO3\({}^{+}\) 2.215 \(\times\) 10\({}^{-7}\) & MnNO3\({}^{+}\) 5.278 \(\times\) 10\({}^{-7}\) \\ U(IV) 4.2 \(\times\) 10\({}^{-5}\) total & U(IV) 4.032 \(\times\) 10\({}^{-5}\) total & U(IV) 1.981 \(\times\) 10\({}^{-9}\) total \\ U(OH)4 4.2 \(\times\) 10\({}^{-5}\) & U(OH)4 4.032 \(\times\) 10\({}^{-5}\) & U(OH)4 1.981 \(\times\) 10\({}^{-9}\) \\ U(VI) 6.8 \(\times\) 10\({}^{-11}\) total & U(VI) 1.684 \(\times\) 10\({}^{-6}\) total & U(VI) 4.201 \(\times\) 10\({}^{-5}\) total \\ UO2(CO3)2\({}^{-}\) 2.630 \(\times\) 10\({}^{-11}\) & UO2(CO3)2\({}^{-}\) 8.494 \(\times\) 10\({}^{-7}\) & UO2(CO3)2\({}^{-}\) 1.569 \(\times\) 10\({}^{-5}\) \\ UO2(CO3)3\({}^{4-}\) 4.052 \(\times\) 10\({}^{-11}\) & UO2(CO3)3\({}^{4}\) 4.590 \(\times\) 10\({}^{-7}\) & UO2(CO3)3\({}^{4-}\) 2.311 \(\times\) 10\({}^{-5}\) \\ UO2(OH)2 4.781 \(\times\) 10\({}^{-13}\) & UO2(OH)2 1.299 \(\times\) 10\({}^{-7}\) & UO2(OH)2 4.695 \(\times\) 10\({}^{-7}\) \\ - & (UO2)2 CO3(OH)3\({}^{-}\) 7.597 \(\times\) 10\({}^{-8}\) & (UO2)2 CO3(OH)3\({}^{-}\) 1.177 \(\times\) 10\({}^{-6}\) \\ S(-2) 3.805 \(\times\) 10\({}^{-5}\) total & - & - \\ S(VI) 2.743 \(\times\) 10\({}^{-4}\) total & S(VI) 6.976 \(\times\) 10\({}^{-3}\) total & S(VI) 4.894 \(\times\) 10\({}^{-3}\) total \\ SO4\({}^{-}\) 2.358 \(\times\) 10\({}^{-4}\) & SO4\({}^{2-}\) 5.117 \(\times\) 10\({}^{-3}\) & SO4\({}^{2-}\) 3.075 \(\times\) 10\({}^{-3}\) \\ CaSO4 3.601 \(\times\) 10\({}^{-5}\) & CaSO4 1.640 \(\times\) 10\({}^{-3}\) & CaSO4 1.345 \(\times\) 10\({}^{-3}\) \\ NaSO4 2.314 \(\times\) 10\({}^{-6}\) & NaSO4\({}^{-}\) 1.921 \(\times\) 10\({}^{-4}\) & NaSO4\({}^{-}\) 4.715 \(\times\) 10\({}^{-4}\) \\ - & FeSO4 2.004 \(\times\) 10\({}^{-5}\) & \\ \hline \end{tabular}
\end{table} 
Table 2: Main species and molality in water samples under different redox conditions (PHEREQC modelling). Figure 2: The number of cells of different functional groups in the formation fluid samples, cells/mL. and (b) the content of ferrous iron (Fe(II)), a potential electron donor, increases from 0.01 to 10.7 mg/L. According to calculations and a review [26], for the intense reduction of nitrates at pH 7, Eh \(\leq\) 0 mV is necessary. In our case, such values are characteristic only for Sample 1 (background water). Even in this case, at an Eh of -190 mV, sulphate is predominant over sulphide species in the solution (Table 2), with values of 3.8 \(\times\) 10\({}^{-5}\) H\({}_{2}\)S\({}_{\text{total}}\) and 2.74 \(\times\) 10\({}^{-4}\) SO\({}_{4}\)\({}^{2-}\) total. Modelling experiments of the metabolism of biota were therefore designed to attain the reduction of nitrates and sulphates during NCCP groundwater treatment.