## 3 Results and Discussion
### Targeted Analysis of Emerging Contaminants  
In addition to the evaluation of major volatile and semi-volatile compounds, the second monitoring (sampling III) involved a further investigation on the presence of emerging contaminants (ECs) in aquarium waters (supply and treated). The selected target analytes belong to different classes (pharmacicals, UV filters, hormones and perfluorinated compounds); therefore, an LC-MS/MS multi-residual analysis method was used for their determination. The concentration of the analytes was expressed as the amount of analyte per POCIS (ng/POCIS) to obtain a quantitative comparison between supply and treated waters. Thirteen analytes were identified in POCIS deployed in supply and treated waters (results in Table 2), although many of them were simply detected but not quantifiable. Sampling rates (Rs) of some of the considered chemicals are present in the literature, thus theoretically allowing the estimation of the time-weighted average (TWA) concentration of the contaminants in supply and treated waters. However, the Rs from the literature are generally affected by high variability; thus, analogously to the detected volatile compounds, the TWA concentrations of most ECs were not calculated. The data obtained exhibit a general decrease in concentration after treatments, confirming the good performance of filtration and disinfection systems. The presence of different contaminants in the samples, even though at low concentrations, confirms that these compounds may be considered as semi-persistent in the environment. In fact, they are continuously released from wastewater treatment plants due to incomplete removal [1; 15]. The most concentrated chemicals in the supply water were BPA and the UV-filters OC and EHMC. BPA is an intermediate in the production of epoxy resins and polycarbonate plastics [29]. It is used in many plastic products [30] and is ubiquitous due to its frequent release [31]. BPA represents a potential concern for aquatic organisms, with reproductive and developmental effects on aquatic species [32]. In order to assess the risk for marine organisms, the Risk Characterization Ratio is used, which is the ratio between the Predicted Environmental Concentration (PEC) in water and the provisional predicted no-effect concentration (PNEC). A PNEC value of 0.15 \(\upmu\)g L\({}^{-1}\) for BPA has been proposed for marine waters by the European Union [33]. Considering the literature sampling rate for BPA obtained in seawater of 0.288 L day\({}^{-1}\)[16], the TWA concentration in water results in 0.0015 \(\upmu\)g L\({}^{-1}\). By assuming TWA as an acceptable approximation of PEC, the Risk Characterization Ratio (PEC/PNEC) should be below 1 in the analyzed waters. This result suggests that adverse effects are not expected on seawater organisms for this substance [34]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Compound** & **Supply Water (ng/POCIS)** & **Treated Water (ng/POCIS)** \\ \hline CAF & \textless{LOQ} & \textless{LOQ} \\ CBZ & 0.51 \(\pm\) 0.12 & \textless{LOQ} \\ BP-3 & \textless{LOQ} & \textless{LOQ} \\ DIC & \textless{LOQ} & \textless{LOQ} \\ OD-PABA & \textless{LOQ} & \textless{LOQ} \\ EHMC & 15.28 \(\pm\) 0.13 & 7.31 \(\pm\) 0.32 \\ OC & 17.92 \(\pm\) 1.05 & 5.44 \(\pm\) 0.41 \\ PFOA & \textless{LOQ} & \textless{LOQ} \\ PFOS & \textless{LOQ} & \textless{LOQ} \\ BPA & 5.97 \(\pm\) 0.86 & \textless{LOQ} \\ MEF & \textless{LOQ} & \textless{LOQ} \\ GBZ & 1.58 \(\pm\) 0.01 & 0.322 \(\pm\) 0.004 \\ TCS & \textless{LOQ} & \textless{LOQ} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Measured mean concentrations (\(\pm\)standard deviation) of the emerging pollutants detected in supply (S3, S4 and S5) and treated (T5, T6 and T7) water (ng/POCIS). UV filter compounds are integrated in many cosmetic formulations and can reach surface waters through the release from the skin during recreational activity or through wastewater [35]. Relatively high levels of EHMC and OC and the presence of BP-3 and OD-PABA were detected in POCIS extracts.