## 4 Discussion  
The CCS technologies may cause punctual potential acidification events due to CO\({}_{2}\) enrichment in the marine environment caused by leakages. These CO\({}_{2}\) leakages may occur over time during some steps of operations technology [31]. In this context, studies of environmental risk characterization in the areas nearby CCS operations are highlighted [2]. In Brazil there are projects with operating status of CCS system in Rio de Janeiro and Bahia [32]. The sediment stations selected for this study are located in the Santos estuary and Bay; this zone is considered relatively close to Rio de Janeiro and with tropical characteristics as well. Moreover, both sediment stations selected for this study are areas usually known to receive large quantities of organic matter from the surrounding mangrove and urban activities. According to the report on coastal waters quality of the State of Sao Paulo [33], the pH value found in the areas selected in this study varies between a pH of 6.5 and 8.5. Furthermore, a previous study has shown a value of 2.2% and 7.5% of total organic carbon (TOC) in the PAI and CPI stations, respectively [16]. Therefore, studies of the impact  
Figure 5: Estimated factor scores for each sediment sampling sites used in this study (PAI and CPI). The factor scores quantify the prevalence of every component for each sediment site in relation to the pH levels and are used to confirm the factor description (Table 4). caused by enrichment of CO\({}_{2}\) in areas that present tropical characteristics as Brazil and with organic carbon concentrations in sediments are also highlighted. The results found in the study were expressed using the WoE approach, based on different lines of evidence, to characterize the environmental degradation associated with the enrichment of CO\({}_{2}\) in the coastal zones. The use of this integrated approach has been widely indicated as an efficient method to identify and distinguish the origin of contamination and provide a better monitoring and protection of the marine environment [6; 15; 25; 27; 34]. Previous studies have characterized the sediment contamination by means of metals, PAHs and PCB concentrations in the Santos Estuary [16; 27; 35]). These authors and their results agree with our study showing that the lowest metal concentrations were found for the control sediment station (PAI). The concentrations obtained in the other station (CPI) were also in agreement with previous studies showing the sediments at this station as an intermediate contamination. Besides, sediment quality guidelines based on _Tiburonella viscana_[23] determined no pollution for concentrations below 63 mg kg\({}^{-1}\) Cu, 73.3 for Zn, below 0.5 for \(\Sigma\)PAHs and 4 ug.kg\({}^{-1}\) EPCBs. However, no significant differences were showed in the concentration of metals in the sediment between the reference case, and all pH treatments tested for both stations when using the tabular matrix and pie charts. Additionally, the concentration of metals found in both stations were below limit values defined by [36] (used in Brazil to classify the levels of metal concentrations in dredged sediment). The results from the multivariate analysis showed no correlation between the biological indexes of macro-benthic communities and pH reduction (#2, Table 3). The diversity and richness of the macro-benthic communities were associated with concentrations of Zn in seawater (#3), while the total abundance of the organisms was associated with the sediment contamination and the mobility of Cu, Zn, and Ni (#1). These results can explain those demonstrated in the tabular matrix and pie charts that were found a significant difference (\(p<0.05\)) in the ecological integrity in all pH treatments when using the CPI sediment station. Moreover, these findings may indicate the contamination and bioavailability of elements present in this station, which was confirmed with the estimated factor scores (Figure 5).