## 3 Results and Discussion  
### Solid Phase  
#### 3.1.1 Sediment Geochemistry and Enrichment Factor (EF) of Metal(loid)  
Based on the grain-size data, sediments of both cores were rather homogeneous with depth. According to [PERSON]'s classification [32], both sediments were prevalently silty (average 74% at VN1 and 69% at VN3), followed by sandy and clay fractions, on average 18% and 7% at VN1 and 25% and 5% at VN3, respectively [12]. The total carbon (C\({}_{\text{tot}}\)) profiles showed a decreasing trend with depth, from 6.16 to 5.59% at VN1, and from 7.42 to 5.77% at VN3, whereas the organic carbon (C\({}_{\text{org}}\)) contents varied in a narrow range (1.85-2.57% at VN1 and 1.85-3.99% at VN3) [12]. Total nitrogen (N\({}_{\text{tot}}\)) decreased with depth only at VN3 (from 0.51% to 0.18%) [12]. The C\({}_{\text{org}}\)/N\({}_{\text{tot}}\) molar ratio >14 is characteristic for organic matter of terrestrial origin [33], which is typically depleted in nitrogen and enriched in carbon. Conversely, the molar ratio <10 is associated with marine-derived organic matter, characterized by higher nitrogen contents [34]. In this study, C\({}_{\text{org}}\)/N\({}_{\text{tot}}\) was usually <10, thus indicating the marine origin of the organic matter. Only the last two levels at VN3 showed higher C\({}_{\text{org}}\)/N\({}_{\text{tot}}\) values of 10.2 and 17.4, respectively [12]. As an additional chemometric support to the traditional data interpretation, PCA was performed on total and labile metal(loid) concentrations in sediments to better underline differences between the two investigated sites and among depth levels (Figure 2). The two investigated sites are clearly distinguished in the PCA output, and, generally, slightly higher concentrations of metal(loid)s were found at site VN3 where Cd, Cr, Cu, Fe, Ni, Pb, V and Zn reached maximum values in the first level of sediments (Figure 2 and Table 1). The vertical profiles of Cd, Cu, Cr, Fe, Mn, Ni, Pb, V and Zn contents at VN1 showed rather constant values with increasing depth, thus suggesting a common source of these metal(loid)s (Supplementary Materials Figure S1). Arsenic and Hg varied in a relatively narrow range decreasing with depth. Moreover, at site VN3, the metal(loid) trends were pretty constant with depth, and only As, Hg and Mn showed increasing values (Table 1). To assess whether \"anomalous\" metal(loid) contributions are present in the sediments, metal(loid) concentrations (M) were normalized to a grain-size proxy, i.e., a normalizing element (N), and compared to the same ratio from the local baseline, to obtain the Enrichment Factor (EF = [M/N]\({}_{\text{sample}}\)/[M/N]\({}_{\text{baseline}}\)). In this study, Al was chosen as the normalizing element, since it has been proved that it is essentially lithogenic in the sediments of the Northern Adriatic [35]. The M/N ratio for the baseline was calculated from the average concentrations obtained from the deepest three levels (49-50, 69-70 and 95-96 cm) of a 1 m-long sediment core collected in the Grado Lagoon (G4, [36]) near the Val Noghera fish farm. A value of unity denotes no enrichment or depletion relative to the local background. According to the five degrees of contamination proposed by [PERSON] [37], the highest EF values were found at site VN3 (Supplementary Materials Table S1), especially for Cd and Hg, which showed a significant enrichment (EF = 5-20), and for Fe, which showed a moderate enrichment (EF = 2-5), but only in the 0-1 cm level (2.27). Cadmium and Hg were significantly enriched also in core VN1, but with EF values lower than VN3. The significant enrichment of Hg is due to the legacy of 500 years of the historical mining activity at Idrija (NW Slovenia) [38], whereas Cd, as well as the minimal enrichment (EF <2) observed for Fe, Pb and Zn at both sites, could be associated with the more recent anthropogenic inputs from several local sources, mainly industrial and agricultural activities located inland.