## 2 Materials and Methods
### Sediment Characterization  
To determine the main geotechnical, physic-chemical, and environmental parameters, laboratory tests were conducted on the sediments in according with national and international standards identified in Table 3.  
Figure 4: Sampling site of the San Giuliano reservoir: (**a**) view on the right bank, (**b**) view on the left bank. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Properties or Parameters** & **Tests** & **Standards** \\ \hline Grain size distribution GSD & Sieving analysis & UNI EN 933-1:2012 \\ \hline Total organic carbon TOC & Oxidation & DM 13/09/1999 GU 248 del 21/10/1999 Method VII.3 \\  & Oxidation & DM 25/03/02 GU 84 del 10/04/02 \\  & Piemonte Region Compost analysis 1998 Method C 6.1 \\ \hline Heavy metals & Atomic Emission Spectrometry & ISO 17402:2008 \\ \hline Asbestos & Fourier transform infrared spectroscopy (FTIR) & D.M. 06/09/1994 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Standards used to test the physical, chemical, contamination, toxicology properties and parameters. Figure 3: Sampling site of the Camastra reservoir: (**a**) top view on reservoir banks, (**b**) view near the Inferno river bridge. The geotechnical analysis involved the determination of the leading grain size fractions, performed by sieving and evaluating the percentage passing through sieves with different diameters to identify the distribution of sandy, silty, and clayey components within each sediment sample. To assess the pollution level of the sediments sampled at the two reservoirs, the concentration of heavy metals was determined [43; 44]. The test was carried out using ICP-MS spectroscopy (mass spectrometer NexION 1000 model, manufactured by PerkinElmer Inc., based in Waltham, MA, USA, with inductively coupled plasma), which exploits the administration of relatively high energy to cause dissociation into atoms and their excitation [45]. Because of unique spectral pattern of different substances, it was possible to trace the unknown species as a function of the emitted wavelength; at the same time, the concentration of each heavy metal was calculated from the emission intensity measurement. Prior to spectrometric analyses, the digestion method used for sediment samples was the microwave mineralization, according to EPA 3051A standard, on 0.5 g of sample per sediment, to which 9 mL of HCl and 3 mL of HNO\({}_{3}\) were added. The temperature of each sample was increased to 175 \(\pm\) 5 \({}^{\circ}\)C in approximately 5.5 \(\pm\) 0.25 min, remaining at the same value for 4.5 min, or for the remainder of the 10-min digestion period, with subsequent cooling. Further tests were conducted to assess the organic matter content of sediments of both reservoirs. Analyses were carried out to determine the Total Organic Carbon (_TOC_) content using the Walkley-Black method, according to Ministerial Decree 13.09.1999, based on the oxidation to carbon dioxide of the organic carbon found in the examined sample, with a solution of 0.1667 mol/L of potassium dichromate in the presence of sulphuric acid, under standardized conditions. The speed of the reaction is promoted by the rise in temperature due to the rapid dilution of the acid. In a 500 mL Erlenmeyer conical flask, 1 g of each sediment sample, air-dried and sieved to 0.5 mm, 10 mL of potassium dichromate solution and 20 mL of sulfuric acid were poured into the flask. After a set time interval of 30 min, the reaction is stopped, then adding 200 mL of distilled water, previously chilled in the refrigerator at about 4 \({}^{\circ}\)C. The amount of potassium dichromate that has not reacted is determined by titration with an iron (II) sulfate heptahydrate solution (0.5 mol/L). The addition of 0.5 mL of a redox indicator, the ferroin, ascertains the end of the titration. At the same time, a blank test was performed with 10 mL dichromate, 20 mL sulfuric acid and 200 mL distilled water.