## 3 Results and Discussion  
### Initial Agronomic and Contamination Characteristics of the Site  
The agronomic parameters and the total TE concentration in the sediment (Table 1) of the three areas were already presented and discussed in earlier research [18]. The agronomic parameters showed a fine sediment texture on the three areas, with a pH of around 8. The organic matter and C/N were high due to the matrix origin, i.e., dredged sediment. Concerning the characterization of the total TE concentration in the sediment, our results were compared to the threshold values (S1, Table 1) defined in the French law (French Environmental code, article R214-1, rubrique 3.2.1.0) [41]. For all of the areas, the Cd, Pb, and Zn concentrations were 3-4 times, 7-10 times, and 20-30 times higher than the legal threshold values, respectively. This proves the high degree of contamination of our site and confirms the need for adapted management. Moreover, the TE contamination was heterogeneous on the site, with the highest contamination in Area 3 and the lowest in Area 2. In addition, the Cd, Cu, Pb, and Zn concentrations in the extractable solution were superior to the values that are frequently retrieved in extractable solutions that are reported in the standard ISO 19730:2008 (E) (Cd: 0.005 \(\mu\)g g\({}^{-1}\); Cu: 0.25 \(\mu\)g g\({}^{-1}\); Pb: 0.02 \(\mu\)g g\({}^{-1}\); Zn: 0.25 \(\mu\)g g\({}^{-1}\)) [39]. The sediment's total and extractable TE concentration evidenced that Cd, Cu, Pb, and Zn were the cause of the most concern due to their potential environmental risks.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameters** & **Area 1** & **Area 2** & **Area 3** & **S1 \({}^{*}\)** \\ \hline Clay (\%) & _7.7_ & 10.7 & 11.69 & - \\ \hline Slit (\%) & 69 & 70.5 & 78.52 & - \\ \hline Sand (\%) & 23.3 & 18.8 & 9.79 & - \\ \hline Sediment texture (USDA texture triangle) & Fine silt & Fine silt & Fine silt & - \\ \hline Carbon (g kg\({}^{-1}\)) & 76.3 & 82.4 & 96.8 & - \\ \hline Organic matter (g kg\({}^{-1}\)) & 131.3 & 141.7 & 166.5 & - \\ \hline C/N \({}^{**}\) & 28.4 & 28 & 31.5 & - \\ \hline CEC (meq 100 g\({}^{-1}\)) \({}^{*}\) & 17.6 & 17.9 & 21.2 & - \\ \hline CaO g kg\({}^{-1}\) & 11.7 & 11.5 & 12.5 & - \\ \hline TRN (g kg\({}^{-1}\)) \({}^{**}\) & 2.69 & 2.94 & 3.07 & - \\ \hline Phosphorus Olsen (g kg\({}^{-1}\)) P\({}_{2}\)O\({}_{5}\) & 0.216 & 0.259 & 0.258 & - \\ \hline pH-H\({}_{2}\)O & 8.08 & 8.06 & 8.12 & - \\ \hline \multirow{6}{*}{Total TE (mg kg\({}^{-1}\))} & \multirow{2}{*}{Pb} & 6685 \(\pm\) 509 & 6084 \(\pm\) 132 & 8980 \(\pm\) 340 \\  & & (3.86 \(\pm\) 0.39) & (5.66 \(\pm\) 0.59) & (7.32 \(\pm\) 1.46) \\ \cline{1-1}  & & 774 \(\pm\) 18 & 592 \(\pm\) 12 & 1043 \(\pm\) 12 & \\ \cline{1-1}  & & (0.05 \(\pm\) 0.02) & (0.04 \(\pm\) 0.008) & (0.06 \(\pm\) 0.03) & \\ \cline{1-1}  & & 6.3 \(\pm\) 0.14 & 5 \(\pm\) 0.08 & 9 \(\pm\) 0.13 & \\ \cline{1-1}  & & (0.03 \(\pm\) 0.005) & (0.04 \(\pm\) 0.003) & (0.05 \(\pm\) 0.008) & \\ \cline{1-1}  & & 87 \(\pm\) 2.3 & 76 \(\pm\) 1.5 & 101 \(\pm\) 1.3 & \\ \cline{1-1}  & & (0.41 \(\pm\) 0.06) & (0.52 \(\pm\) 0.08) & (0.48 \(\pm\) 0.07) & \\ \hline \hline \end{tabular} \({}^{*}\): [41], **: carbon/nitrogen, \({}^{*}\): cationic exchange capacity, \({}^{**}\): total Keldahl nitrogen.  
\end{table}
Table 1: Main physico-chemical properties, total and NH\({}_{4}\)NO\({}_{3}\) extractable (between parenthesis) concentrations of TE in the sediment of the field site for each area, and TE threshold values (S1) for sediment management. TE are expressed in mg Kg\({}^{-1}\) DW. With the exception of the sediment parameters (\(n=1\)), values are means \(\pm\) standard deviation (SD) (\(n=5\) for total TE; \(n=3\) for NH\({}_{4}\)NO\({}_{3}\) extractable).