# Assessment and Review of Heavy Metals Pollution in Sediments of the Mediterranean Sea
## 3 Results and Discussion
### Suitable Sea to Detect Relationship Pollution between Mediterranean Regions  
The correlation matrices (Figure 2) reveal predominantly positive relationships among heavy metals, with specific exceptions like As-Cr in the M-A limit (southeast of Spain) and Hg-Zn in the south of Italy (Gulf of Taranto). However, Mallorca (southwest of Spain) exhibits a unique pattern with positive correlations among As and V but negative correlations with other heavy metals. The enrichment of As and V may be linked to nitrogenous fertilizer discharges and coastal aquifer pumping systems. Matrices compare study areas, excluding anomalous values from punctual discharges in northern Greece and southern Italy.  
The Igeo index distribution, shown in Figure 3, varies significantly between heavy metals but reveals similar contamination patterns in marine sediments. The percentage distribution of Igeo index classes indicates contamination levels for each heavy metal in different regions.  
Mallorca stands out for Ba, Cr, Pb, and Zn; Greece for Cr, Ni, Pb, and Zn; M-A limit for Cu, Ni, Pb, and Zn; southern Italy for Cr, Cu, Ni, Pb, and Zn. The pollution ranking, based on Igeo classes, is as follows:  
SE Spain (Mallorca): Cu > Zn > Pb > Ni > Hg > Ba > Cr > As > Cd > V  
SW Spain (M-A limit): Hg > Ni > Cd > Cu > Pb > Zn > As  
SW Italy (Gulf of Taranto): Hg > Cr > Zn > Cu > Pb > Ni  
S Italy (Sicily) (north (a) and south (b)): (a) Hg > Ba, and (b) Cu > Zn > Pb > Cr > Hg  
Greece: Ni > Cu > Cr > Zn > Pb > As  
The contamination levels of heavy metals, assessed by the Igeo index, show similarities across regions, which are directly related to their discharge sources. In Sicily (a), the index is influenced by industrial lixiviate discharge, while in Sicily (b), it is associated with diverse anthropic activities linked to tourism.  
Figure 1: Wastewater discharge volumes in the north-central Mediterranean Sea. Estimates have been calculated with data provided by the Public Institutions from different countries. Subsequently, a weighting has been carried out between the volume of water (hm\({}^{3}\)/year) and the resident and floating population (\(\alpha\)\(r_{p}\) + \(f_{p}\)).  
Figure 3: Results of the Igeo index in sites from central-north of Mediterranean Sea. Dates are show in class of percentage of pollution in relation to the Igeo method.  
Figure 2: Correlation matrix in each area considered. Relationship between west and east of the Mediterranean Sea.  
Figure 4 shows the analysis using PCA principal components corresponding to the heavy metal concentration of the analyzed samples. As can be seen, the PCA does not separate different families of concentrations between the regions studied. The PCA suggests randomness in the presence of metals analyzed because the origin of the wide variability of percentage concentrations is related to the discharge of untreated wastewater. This masks certain concentrations that may be significant if studied in isolation. However, what the global PCA analysis shows is that the concentration and type of heavy metals in discharged wastewater is so broad that it is not possible to classify it.