## 4 Results
### Water Chemistry
\begin{table}
\begin{tabular}{l c c c c c c c c c c c c c} \hline \hline
**Sample** & \begin{tabular}{c} **Deep** \\ **(m)** \\ \end{tabular} & **T** (°C) & \begin{tabular}{c} **HCO\({}_{3}\)** \\ **(mg/L)** \\ \end{tabular} & **pH** & \begin{tabular}{c} **O\({}_{2}\)** \\ **(mg/L)** \\ \end{tabular} & **pH** & \begin{tabular}{c} **O\({}_{2}\)** \\ **(mg/L)** \\ \end{tabular} & **(μS/cm)** & \begin{tabular}{c} **N\({}^{\star}\)** \\ **(mg/L)** \\ \end{tabular} & **(mg/L)** & \
\begin{tabular}{c} **K\({}^{\star}\)** \\ **(mg/L)** \\ \end{tabular} & **Mg\({}^{2\star}\)** & **Ca\({}^{2\star}\)** & **Cl\({}^{-}\)** &
\begin{tabular}{c} **NO\({}_{3}\)** \\ **(mg/L)** \\ \end{tabular} & **SO\({}_{4}\)**\({}^{-}\)** & **NH\({}_{4}\)**\({}^{+}\)** \\ W-124 & 9.0 & 15.7 & 541 & 7.3 & 3.8 & 808 & 14.4 & 1.9 & 20.8 & 132 & 20.0 & n.d & 3.9 & 1.0 \\ W-126 & 22.0 & 17.1 & 317 & 7.4 & n.d & 659 & 17.1 & 7.5 & 15.3 & 102 & 21.6 & 1.0 & 43 & 1.5 \\ W-132 & 30.0 & 16.8 & 254 & 7.0 & n.d & 638 & 12.6 & 2.0 & 10.3 & 93 & 20.0 & n.d & 81 & 0.05 \\ W-133 & 18.0 & 18.2 & 206 & 7.5 & n.d & 674 & 9.9 & 1.5 & 11.6 & 91 & 16.6 & 4.0 & 103 & 0.05 \\ W-140 & 25.0 & 13.4 & 204 & 7.3 & 7.1 & 859 & 10.6 & 1.5 & 10.9 & 100 & 16.7 & 8.6 & 88 & n.d \\ W-147 & n.d & 15.9 & 231 & 6.9 & 8.5 & 709 & 11.0 & 1.1 & 12.2 & 122 & 16.9 & 8.7 & 131 & 0.8 \\ W-157 & 10.0 & 17.8 & 329 & 7.6 & n.d & 587 & 15.5 & 2.2 & 14 & 117 & 22.9 & 7.2 & 51 & n.d \\ W-160 & 66.0 & 16.6 & 254 & 7.0 & n.d & 520 & 13.3 & 2.3 & 7.0 & 84 & 21.1 & 13.2 & 18.8 & 0.05 \\ W-163 & 66 & 15.5 & 329 & 6.9 & 8.4 & 550 & 15.0 & 3.3 & 5.9 & 101 & 22.8 & 13.4 & 19.0 & n.d \\ W-164 & 66 & 15.8 & 310 & 7.1 & n.d & 578 & 14.5 & 1.9 & 6.1 & 100 & 23.4 & 14.1 & 19.5 & 0.05 \\ W-165 & 8.0 & 13.3 & 260 & 6.9 & 8.3 & 594 & 10.0 & 7.2 & 11.2 & 89 & 21.2 & 6.7 & 76 & n.d \\ W-166 & 67 & 15.4 & 248 & 6.6 & 4.3 & 547 & 16.0 & 4.1 & 13.1 & 77 & 26.2 & 5.0 & 57 & n.d \\ W-167 & 5.0 & 13.6 & 237 & 6.6 & 8.1 & 523 & 11.0 & 3.2 & 12.0 & 94 & 22.7 & 7.3 & 90 & n.d \\ W-168 & 37 & 17.2 & 31 & 5.9 & n.d & 187 & 14.4 & 0.20 & 3.2 & 15 & 24.3 & 11.9 & 20.3 & 0.05 \\ W-169 & 9.0 & 15.3 & 232 & 6.6 & 4 & 583 & 14.0 & 5.5 & 12.9 & 100 & 26.8 & 7.4 & 97 & n.d \\ W-170 & 72 & 16.1 & 305 & 7.2 & n.d & 879 & 19.6 & 1.4 & 24.7 & 138 & 27.3 & 1.8 & 207 & 0.10 \\ W-171 & 8.0 & 15.2 & 246 & 6.6 & 6.6 & 438 & 12.0 & 6.0 & 5.5 & 77 & 18.3 & 10.7 & 22.0 & n.d \\ W-172 & n.d & 15.7 & 234 & 6.9 & 8.2 & 641 & 11.0 & 7.7 & 7.9 & 93 & 21.4 & 18.3 & 53 & n.d \\ \hline \hline \end{tabular}
\end{table} 
Table 1: \(Cont.\)  
Figure 5: Piper diagram for the studied groundwater (black circles), indicating the different prevailing hydrofacies with Ca-HCO\({}_{3}\) type. The water chemistry of Baccatoio stream water is superimposed (red triangles) (Data source: [42]). drainages in the Baccatoio stream basin; in particular, speciation analysis (Geochemist's Workbench(r)) indicates that As in groundwater occurs mostly as As(OH)\({}_{3}\) or HAsO\({}_{4}\)\({}^{2-}\) species, depending on redox conditions. It is also worth noting that As(III) is generally considered more toxic and mobile than pentavalent arsenate. Saturation indices show that waters approach saturation with calcite, dolomite and witherite; some samples (W-34, W-48, W-51 and W-84, among those with As exceeding the 10 \(\mu\)g/L threshold) were strongly supersaturated with Mn-oxides (birnessite, pyrolusite, todorokite and hausmannite) and Fe-oxyhydoxides (hematite, goethite and ferrihydrite). The log f\({}_{\text{CO2}}\) calculated on the basis of carbonate equilibria ranged between \(-1.3\) and \(-2.6\), exceeding the air-saturated value and indicating that carbon in organic matter in the aquifer is oxidized to CO\({}_{2}\).