## 3 Results
### Leachate Geochemistry  
The pH values and concentrations of the main dissolved species (in mg\(\cdot\)L\({}^{-1}\)) determined by leaching tests with CO\({}_{2}\)-saturated MilliQ water are listed in Table 5. The pH varied from weakly acidic (6.63) to alkaline (8.35). The cation triangular diagram, where the concentrations in meq L\({}^{-1}\) were recalculated to 100%, is reported in Figure 3, demonstrating that Ca\({}^{2+}\) and Mg\({}^{2+}\) are the dominant species. This feature is also similar to the groundwaters collected from the mining area of ASS where in the past the roasting products were used to fill a small valley [27]. The anion triangular diagram is not reported, since the use of CO\({}_{2}\)-saturated MilliQ water artificially increased the HCO\({}_{3}\)\({}^{-}\) concentration. The Ca\({}^{2+}\) and SO\({}_{4}\)\({}^{2-}\) concentrations varied from 100 and 270 mg\(\cdot\)L\({}^{-1}\) and 2.7 and 60 mg\(\cdot\)L\({}^{-1}\), respectively. Na\({}^{+}\) and Cl\({}^{-}\) were always below 7 mg\(\cdot\)L\({}^{-1}\). Mg\({}^{2+}\), NH\({}_{4}\)\({}^{+}\), K\({}^{+}\) and NO\({}_{3}\)\({}^{-}\) never exceeded 18, 3.4, 40 and 306 mg\(\cdot\)L\({}^{-1}\), respectively. It is worth mentioning that the highest values of K\({}^{+}\) corresponded to those samples where the highest contents of NO\({}_{3}\)\({}^{-}\) were also found. Finally, F\({}^{-}\), Br\({}^{-}\) and PO\({}_{4}\)\({}^{3-}\) were detected in a few samples, but never exceeded 1.4, 0.2 and 0.2 mg\(\cdot\)L\({}^{-1}\), respectively. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Metals** & **N.obs.** & **Min.** & **Max.** & **Mean** & **Median** & **S.D.** & **Skewness** \\ \hline
**As** & 35 & 10 & 616 & 92.6 & 44.85 & 114.5 & 3.14 \\
**Hg** & 35 & 4 & 1910 & 235.0 & 108.5 & 366.3 & 3.37 \\
**Sb** & 31 & 0.18 & 1610 & 237.7 & 14.0 & 408.3 & 2.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Main descriptive statistics concerning As, Hg and Sb. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **As** & **Hg** & **Sb** \\ \hline
**LM22** & 24.5 & 384.0 & 5.3 \\
**LM23** & 25.5 & 321.0 & 3.4 \\
**LM24** & 15.8 & 124.0 & 6.9 \\
**LM25** & 150.0 & 113.0 & 442.0 \\
**LM26** & 32.1 & 151.0 & 8.8 \\
**LM27** & 33.8 & 18.5 & 7.1 \\
**LM28** & 53.9 & 39.7 & 4.3 \\
**LM29** & 46.7 & 236.0 & 5.3 \\
**LM30** & 124.0 & 38.2 & 162.0 \\
**LM31** & 306.0 & 323.0 & 8.5 \\
**LM32** & 616.0 & 173.0 & 1610.0 \\
**LM33** & 131.0 & 1910.0 & 398.0 \\
**LM34** & 151.0 & 90.1 & 109.0 \\
**LM35** & 131.0 & 206.0 & 15.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._ \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Sample** & **pH** & **HCO\({}^{-}\)\({}_{3}\)** & **F\({}^{-}\)** & **Cl\({}^{-}\)** & **Br\({}^{-}\)** & **NO\({}_{3}\)\({}^{-}\)** & **PO\({}_{4}\)\({}^{3-}\)** & **SO\({}_{4}\)\({}^{2-}\)** & **Ca\({}^{2+}\)** & **Mg\({}^{2+}\)** & **Na\({}^{+}\)** & **K\({}^{+}\)** & **NH\({}_{4}\)\({}^{+}\)** \\ \hline
**LM1** & 6.90 & 544 & 2.3 & 22 & 11 & 191 & 5 & 1.9 & 10 & 0.4 \\
**LM2** & 7.72 & 502 & 7.0 & 306 & 32 & 245 & 18 & 4.0 & 40 & 1.8 \\
**LM3** & 6.63 & 516 & 1.3 & 33 & 10 & 181 & 7 & 1.5 & 15 & 0.5 \\
**LM4** & 6.95 & 420 & 1.6 & 45 & 22 & 151 & 7 & 0.8 & 8 & 0.7 \\
**LM5** & 7.89 & 475 & 1.0 & 22 & 6 & 159 & 7 & 1.4 & 11 & 0.2 \\
**LM6** & 7.20 & 763 & 0.2 & 11 & 19 & 270 & 6 & 0.9 & 6 & 0.4 \\
**LM7** & 7.36 & 420 & 3.7 & 10 & 45 & 157 & 5 & 7.0 & 13 & 0.2 \\
**LM8** & 7.44 & 265 & 1.7 & 4 & 2.7 & 87 & 2.2 & 1.1 & 12 & 0.3 \\
**LM9** & 8.22 & 712 & 3.2 & 59 & 17 & 248 & 12 & 2.0 & 29 & 2.0 \\
**LM10** & 7.46 & 400 & 2.5 & 75 & 10 & 130 & 5 & 1.6 & 19 & 0.8 \\
**LM11** & 7.44 & 716 & 1.6 & 0.1 & 5 & 10 & 219 & 9 & 1.1 & 8 & 0.9 \\ \hline \hline \end{tabular}
\end{table}