## 3 Results and Discussion
### Data Focus
Analyses and comparisons with regulatory limits showed no exceedances for the heavy metals under investigation, except for the Arsenic value in samples SG_S5 and SG_S6, the presence of which could be related to several factors: alluvial deposits containing layers of organic matter, peat, which acts as a metals concentrator, in which arsenic contents are usually particularly conspicuous; algal organic matter in the lake environment, which also leads to the accumulation of other metals; sedimentary rocks, concentrated in the upstream area of the watershed, where it is usually significant; the use of some pesticides and herbicides, mainly used in the past; the use of phosphate and organic fertilizers; the reducing environment of the upstream area of the reservoir (as denoted by the dark-grey coloring of the sediments), which facilitates the transition from oxidation state V to oxidation state III, which is much more soluble and therefore more prone to leaching. The Arsenic content in the remaining environment is below the threshold and, therefore, of little \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Heavy Metal** & **Al** & **As** & **Ba** & **Be** & **Cd** & **Co** & **Cr** & **Cu** & **Fe** \\ LoQ & 1000 & 1 & 5 & 0.1 & 0.1 & 1 & 5 & 5 & 2000 \\ \hline SG\_B & n.a. & \textless{}1 & 0.022 & \textless{}0.1 & \textless{}0.1 & 7.6 & 24 & 26 & n.a. \\ SG\_S1 & 13,226 & 12 & 100 & 0.9 & 0.1 & 10 & 39 & 17 & 27,848 \\ SG\_S2 & 1288 & 8 & 30 & 0.2 & \textless{}0.1 & 4 & 7 & \textless{}5 & 9487 \\ SG\_S3 & 2248 & 15 & 18 & 0.2 & \textless{}0.1 & 4 & 12 & 6 & 11,067 \\ SG\_S4 & 4529 & 16 & 51 & 0.5 & \textless{}0.1 & 9 & 26 & 11 & 18,732 \\ SG\_S5 & 12,435 & **55** & 82 & 1.0 & \textless{}0.1 & 19 & 57 & 27 & 37,195 \\ SG\_S6 & 14,862 & **31** & 84 & 1.0 & \textless{}0.1 & 12 & 57 & 17 & 30,423 \\ SG\_S7 & 6655 & 9 & 45 & 0.6 & \textless{}0.1 & 5 & 25 & 8 & 14,264 \\ SG\_S8 & 21,151 & 6 & 81 & 1.5 & \textless{}0.1 & 11 & 66 & 26 & 32,774 \\ SG\_S9 & 14,079 & 7 & 64 & 1.0 & \textless{}0.1 & 10 & 55 & 19 & 27,365 \\ SG\_S10 & 9167 & 5 & 49 & 0.9 & \textless{}0.1 & 8 & 36 & 16 & 21,712 \\ SG\_S11 & 16,147 & 7 & 63 & 1.0 & \textless{}0.1 & 10 & 56 & 21 & 29,644 \\ SG\_S12 & 4351 & 5 & 33 & 0.4 & \textless{}0.1 & 4 & 17 & 7 & 10,929 \\ Limit value & n.a. & 20 & n.a. & 2 & 2 & 20 & 150 & 120 & n.a. \\ \hline
**Heavy Metal** & **Hg** & **Mn** & **Ni** & **Pb** & **Sb** & **Se** & **T1** & **V** & **Zn** \\ LoQ & 0.1 & 20 & 1 & 1 & 0.1 & 1 & 0.1 & 5 & 5 \\ \hline SG\_B & \textless{}0.1 & n.a. & 33 & 16 & n.a. & \textless{}1 & n.a. & \textless{}5 & 66 \\ SG\_S1 & 0.1 & 626 & 34 & 13 & 0.54 & 1.26 & 0.5 & 76 & 54 \\ SG\_S2 & \textless{}0.1 & 469 & 10 & 3 & 0.24 & \textless{}1 & \textless{}0.1 & 14 & 11 \\ SG\_S3 & \textless{}0.1 & 314 & 313 & 4 & 0.29 & \textless{}1 & \textless{}0.1 & 17 & 15 \\ SG\_S4 & \textless{}0.1 & 323 & 24 & 8 & 0.79 & \textless{}1 & \textless{}0.1 & 32 & 29 \\ SG\_S5 & \textless{}0.1 & 547 & 59 & 2 & 0.67 & \textless{}1 & 0.2 & 74 & 54 \\ SG\_S6 & \textless{}0.1 & 488 & 50 & 10 & 0.39 & \textless{}1 & 0.2 & 70 & 51 \\ SG\_S7 & \textless{}0.1 & 336 & 21 & 5 & 0.15 & \textless{}1 & 0.1 & 33 & 26 \\ SG\_S8 & \textless{}0.1 & 469 & 47 & 12 & 0.20 & \textless{}1 & 0.3 & 85 & 81 \\ SG\_S9 & \textless{}0.1 & 545 & 46 & 10 & 0.13 & \textless{}1 & 0.2 & 60 & 59 \\ SG\_S10 & \textless{}0.1 & 568 & 30 & 9 & 0.13 & \textless{}1 & 0.2 & 45 & 51 \\ SG\_S11 & \textless{}0.1 & 582 & 39 & 10 & 0.13 & \textless{}1 & 0.2 & 70 & 70 \\ SG\_S12 & \textless{}0.1 & 318 & 15 & 5 & 0.12 & \textless{}1 & 0.1 & 23 & 22 \\ Limit value & 1. & n.a. & 120 & 100 & 10 & \textless{}1 & 1 & 90 & 150 \\ \hline \hline \end{tabular} Note: LoQ = Limit of Quantification; n.a. = not available.  
\end{table} 
Table 6: Heavy metals concentration (mg/kg) in San Giuliano sediments (limit concentration under CTC column A, Table 1, attachment V, Italian Legislative Decree 152/06). relevance.