## 4 Results and Discussion
### Evaluation of the Contamination and Ecotoxicological Risks  
#### 4.2.1 Contamination Assessment  
Only elements with Cf higher than one in some samples are herein considered. As. Arsenic mean values are in the order of 9 ppm (Table 3) that are slightly lower than the average marine shale composition (Table 2) and are in line with the local background value (Table 2) of the southern Marche Holocene peiltic wedge (10 ppm at \(-\)105 cm). The spatial distribution indicates the occurrence of relatively high concentrations (up to 31 ppm) in the northern area (Figure 7a).These data suggest that this area has, on average, high As values likely related to the composition of the source rocks coming from North [4]. Arsenic was included in the multivariate analysis but shows a good affinity with elements of the BSFI. In two sandy areas located inshorse in front of the Chienti and Ete Vivo river mouths, as well as in a peiltic belt directed north-south, in front of the Chienti River (Figure 7a), the As values are equal to or higher than the Italian thresholds (Table 2), its C\({}_{f}\) is higher than 1 and the EF and I\({}_{geo}\) fall in the second class (Table 4).The mainly sandy sites, located inshorse, in front of the Chienti River (station 101) and of the Ete Vivo River (station 303) fall in the moderate enrichment class (2-5) for EF index and unpolluted to moderately polluted (0-1) for I\({}_{geo}\), respectively. Furthermore, the concentration of As at station 303 is over the second threshold of the Italian legislation (20 ppm, Table 2). In addition, the station 106, in the peiltic belt in front of the Chienti River, is moderately polluted (1-2) for I\({}_{geo}\) and shows a concentration over the second threshold of the Italian legislation (20 ppm, Table 2). Unpolluted to moderately polluted (0-1) I\({}_{geo}\) values are also recorded offshore and to the Southeast of the study area, in correspondence with mainly clayey sediment, but in this case the high values are due to the inputs of fine materials coming from North, that however influence also other proximal areas, further south [73]. The As pollution in the north-western area could be ascribed to local discharges of waste of fertilizer productions along the southern Marche coast in the past decades. Figure 8: Areal distribution of the elements in surface sediments with C\({}_{f}\) < 1 in all samples. (**a**) Co, (**b**) Cr, (**c**) Cu, (**d**) Ni, (**e**) Sc, (**f**) V, (**g**) Y, and (**h**) Zr. Ba. The average concentrations of barium are around 270 ppm (Table 3) reaching a maximum of 329 ppm, far below the average marine shale composition and in line with local background (Table 2). The highest values of Ba are found near the coast between the Chienti and Aso Rivers and in a belt along the central area that mainly corresponds to the BSF3 (Figure 7b). In some stations of these areas, the EF of Ba slightly exceeds 2, resulting in the moderate enrichment class, while the absolute concentrations (average 272.8 ppm; Table 2) are higher than the background value of 295 ppm in the high Al content stations (Table 2). The high Ba concentrations near the coast and in the BSF3 _facies_, particularly in the northern side of the study area, suggest a provenance of Ba from North. It also suggests a scavenging process, due to high specific weight of the barium sulphate, a heavy mineral that tends to remain in situ after reworking processes. The barium sulphate is a component of the drilling muds so that the high Ba concentrations could be due to discharges into the sea in the past of these drilling muds from hydrocarbon platform perforation as reported for other areas [2, 46, 80]. Ga. The values of Ga in the whole area (average 12.3 ppm, Table 3) with a maximum of 22 ppm are in line with average marine shale and with local background concentrations (16.2 ppm, Table 2) even if some stations show values of C\({}_{f}\) slightly above 1. The EF and I\({}_{geo}\) indexes are constantly lower than the minimum threshold values.