## 4 Results and Discussion
### Evaluation of the Contamination and Ecotoxicological Risks
#### 4.2.1 Contamination Assessment
Many of the observations are above the L1 threshold level of the Italian legislation (50 ppm, Table 2). It should however be considered that, both for Cr and all the other considered elements, the values of the national legislation refer to an aqua regia digestion and not to a multi-acid digestion including HF, as the one applied in the present study. Cu. Copper concentrations have a mean value of 14.4 ppm and a maximum value of 32 ppm Cu (Table 3), the latter is lower than the average marine shale (45 ppm) and the local background (40 ppm) ones. (Table 2). This element does not, therefore, represent an important issue for this area. This is further confirmed by the C\({}_{f}\) values of Cu (Table 4) constantly lower than 1 as well as by the values of the EF and I\({}_{geo}\) indexes, permanently lower than the minimum threshold values (Table 4). Considering this, there has not been any enrichment with respect to the pre-industrial periods. Indeed, the weak decrease in the last decades could be related to the reduction of northern rivering inputs. Ni. Nickel has an average concentration of 32.7 ppm and a maximum of 63 ppm, which are both lower than the average marine shale and the local background. Despite of it, many stations show values above the L1 threshold level of the Italian legislation (30 ppm, Table 2). The comparison between the average values and the background data in the study area suggests that L1 threshold level of the Ni could be underestimated for this area, likely due to the different analytical method. A support is given by the C\({}_{f}\) values always below 1 and by the EF and I\({}_{geo}\) indexes constantly lower than the minimum threshold values (Table 4). Figure 9: Areal distribution of the PLI values. Sc. Scandium has an average concentration of 6.8 ppm and a maximum of 12 ppm (Table 3) against an average marine shale concentration of 13 ppm and a local background of 29 ppm (Table 2). It is not an element considered by the legislative side, and its C\({}_{f}\) values are constantly less than 1 as well as the EF ER and I\({}_{geo}\) indexes are permanently lower than minimum threshold values (Table 4). These data indicate that there is not Sc enrichments respect to the pre-industrial period and its decrease in the last decades could reflect the decrease of northern riverine inputs. V. Vanadium has an average concentration of 49 ppm and a maximum value of 105 ppm. Its spatial distribution displays a clear seaward increase (Figure 8f). The values are below the average marine shale and the local background values (Table 2), likely for the diluting effect of the carbonate fraction and the relative importance of sandy sediments, both causing a general depletion of V. The C\({}_{f}\) value are always lower and the EF and I\({}_{geo}\) indexes and lower than the minimum threshold values (Table 4). This indicates that there are no enrichments of V respect to the pre-industrial period but an overall decrease. These decreases could be due to the decrease of northern riverine inputs in the last decades. Y. Yttrium concentrations have an average concentration of 13.7 ppm and a maximum of 16 ppm, all values are well below the global reference and the local background (Table 2). The dilution effect of carbonate material is the likely explanation for this difference. The C\({}_{f}\) values are always lower than 1; similarly, EF and I\({}_{geo}\) indexes are constantly lower than the minimum threshold values (Table 4). All these evidence points to a lack of t enrichments of this element with respect to the pre-industrial period. Zr. Zirconium has average value of 35 ppm Zr and a maximum value of 65 ppm that are well below the average marine shale (160 ppm, Table 2) and the local background (97 ppm, Table 2). The values of C\({}_{f}\) value are always \(<\)1, and EF and I\({}_{geo}\) indexes are permanently lower than minimum threshold values (Table 4). This decrease respect to the pre-industrial period is attributed to the decrease of northern riverine inputs in the last decades.