## 4 Results and Discussion
### Metal(Oids) in Surface Sediments
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & & **As** & **Cd** & **Cr** & **Cu** & **Hg** & **Ni** & **Pb** & **Zn** \\ \hline \multirow{4}{*}{General} & Mean & 20.87 & 6.39 & 29.91 & 34.71 & 2.55 & 11.14 & 187.45 & 1042.12 \\  & Median & 16.60 & 1.25 & 10.00 & 12.50 & 0.57 & 8.60 & 63.90 & 319.00 \\  & Min & 6.00 & 0.04 & 3.00 & 2.10 & 0.05 & 3.30 & 8.90 & 49.00 \\  & Max & 56.40 & 32.80 & 248.00 & 152.00 & 18.35 & 83.40 & 806.00 & 6360.00 \\  & DVST & 13.69 & 9.21 & 45.88 & 39.48 & 3.81 & 9.43 & 223.22 & 1291.89 \\ \hline \multirow{4}{*}{Coastal} & Mean & 17.85 & 0.25 & 11.71 & 6.15 & 0.18 & 10.48 & 48.52 & 289.52 \\  & Median & 16.60 & 0.10 & 7.00 & 4.80 & 0.12 & 7.90 & 47.40 & 263.00 \\  & Min & 8.30 & 0.04 & 3.00 & 2.10 & 0.05 & 3.30 & 19.50 & 98.00 \\  & Max & 42.30 & 1.61 & 143.00 & 23.70 & 0.63 & 83.40 & 123.50 & 1070.00 \\  & DVST & 6.71 & 0.31 & 24.99 & 4.35 & 0.15 & 14.11 & 19.77 & 181.43 \\ \hline \multirow{4}{*}{Estuary} & Mean & 22.12 & 9.23 & 38.23 & 47.90 & 3.65 & 11.36 & 251.31 & 1387.55 \\  & Median & 13.80 & 3.89 & 16.00 & 38.20 & 1.42 & 10.00 & 147.00 & 761.00 \\ \cline{1-1}  & Min & 6.00 & 0.19 & 5.00 & 3.60 & 0.11 & 3.70 & 8.90 & 49.00 \\ \cline{1-1}  & Max & 56.40 & 32.80 & 248.00 & 152.00 & 18.35 & 25.70 & 806.00 & 6360.00 \\ \cline{1-1}  & DVST & 15.80 & 9.92 & 50.85 & 41.50 & 4.18 & 6.36 & 244.73 & 1432.70 \\ \hline \end{tabular}
\end{table} 
Table 1: Statistical summary of the metal(oid) concentrations in the study area. On the other hand, the rest of the elements presented coefficients of correlation with the concentration of fine sediments and TOC higher than 0.73 (\(p<0.05\)). While significant concentrations of Cd, Cu, Hg, Pb and Zn were not identified in the coastal zone, this  
Figure 3: Spatial distributions of the concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in surface sediments of the Aviles estuary and the nearby coastal area. is not the case for As. As previously mentioned, the general dynamics of the Aviles estuary result in the entry of material, and do not export potential contaminants out of it. Taking into account that the mean As concentration in the coastal sediments is higher than that in the port sediments (Table 1), it can be concluded that this anomaly of As in the adjacent coastal strip has a different origin. The previous works of [3; 17; 45; 46] and [47] indicate that the Nalon River is an important source of As and Hg in the coastal environment, and that its influence might reach the study area, thus relating it to the detected coastal anomaly. Finally, inside the port area, Cd, Cu, Hg, Pb and Zn presented similar dispersion patterns, with two preferential accumulation zones. On the one hand, in the area near the mouth, an isolated anomalous zone appears near the loading and unloading dock of a local zinc smelter industry. Secondly, the most extensive anomaly seen in the concentrations for these elements appears in the middle-internal zone. Since there seems to be no clear connection between the two areas, this indicates that both anomalies may have been generated by different sources or mechanisms. Previous studies in the estuary suggest that the main origin of the contaminants is dust dispersion from the discharge and storage of ore piles by the surrounding industries [27]. However, this potential mechanism is inconsistent with the anomaly found in the middle-inner part of the estuary. In this case, due to the correlations between metal(oids) and fine sediments and TOC, and given that this area had been subjected to continuous discharges of industrial water up until 2019 when they were discontinued, industrial wastewater discharge could be the origin of the anomalies. Checking the dispersion maps for Cd and Hg, the main anomalies of both seem to be associated mainly with the mouth of the Raices River, which has received industrial discharge from different factories on the left bank of the estuary (these are annually reported in the E-PRTR (Spanish Industrial Emissions Register) with concentrations of both elements).