# Preliminary Analysis of the Water Quality Status in an Urban Mediterranean River
## 4 Discussion  
As demonstrated by other researchers [3; 8], the quality of recreational water must be of prescribed standards for both physicochemical and microbial quality. According to similar \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Site/r** & **T** & **EC** & & \\  & (°C) & (\(\mu\)S/cm) & **pH** & **DO (mg/L)** \\ \hline K Ekv & \(0.1\) & \(0.1\) & \(0.2\) & \(0.0\) \\ K 5 & \(-0.2\) & \(-0.2\) & \(0.1\) & \(-0.2\) \\ K 12 & \(-0.3\) & \(\mathbf{-0.8}\) & \(0.0\) & \(-0.1\) \\ K 17 & \(-0.3\) & \(-0.1\) & \(0.1\) & \(0.2\) \\ K MD & \(-0.1\) & \(\mathbf{-0.8}\) & \(-0.3\) & \(0.0\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Pearson correlation coefficient (r) per site between _E. coli_ and the physicochemical parameters (bold values are statistically significant with \(p\) < 0.01). \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **TPAHs (ng/L)** & \multicolumn{2}{c}{**THS (ng/L)**} \\ \hline
**Site** & **September** & **February** & **September** & **February** \\  & **2021** & **2022** & **2021** & **2022** \\ \hline K Ekv & \(1272.0\) & \(112.7\) & \(382.8\) & \(20.4\) \\ K 5 & \(4541.6\) & \(402.8\) & \(1050\) & \(84.2\) \\ K 12 & \(147.5\) & \(168.9\) & \(91.2\) & \(54.1\) \\ K 17 & \(106.8\) & \(728.0\) & \(924\) & \(468.0\) \\ K MD & \(145.7\) & \(17.2\) & \(55.2\) & \(8.1\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Total polycyclic aromatic hydrocarbons (TPAHs) and total hydrocarbons (THs) concentrations. Figure 7: Black lines show the medians; white lines represent individual data points, while the gray area shows the distributions. Green line indicates the good quality threshold according to the EU Directive 2006/7/EC. studies for urban rivers, Kifisos is not bathing water. However, it is used for recreational and commercial activities, where users can get in direct contact with the water via several activities (rowing, boating, kayaking, fishing and activities on the banks), making the Water Framework (2000/60/EC) as well as the bathing water (2006/7/EC) directives appropriate reference for risk assessment [7; 24]. Additionally, the physicochemical water quality status of all five study locations during the sampling period was always below good threshold according to the WFD standards. Similar water quality conditions were estimated in previous studies for the Kifisos river [15]. Analysis with [PERSON]'s correlation demonstrated that the physicochemical water quality index (HWQI) was significantly correlated with NO\({}_{2}\)\({}^{-}\)-N and NH4\({}^{+}\)-N and to a lesser degree PO4-P, which implies the substantial presence of human sewage in the river system. This is attributed to the very high levels of _E. coli_, for which the maximum admissible _E. coli_ concentration, as set by the EU directives, was exceeded on all occasions. EC can indirectly influence the presence and behavior of _E. coli_ since it is often associated with the concentration of dissolved ions in water, including nutrients like phosphates and nitrates, which may support the growth and survival of _E. coli_ bacteria. These contaminants could originate from various sources, such as industrial discharges or agricultural runoff, and can affect the viability of _E. coli_ populations. However, EC is not a direct measure of _E. coli_ presence or concentration. A coefficient of determination R-squared (R\({}^{2}\)) of 0.63 for the K MD site indicated that the two variables are likely related to each other. However, more data are necessary for decisive validation of the relationships illuminated in this study. Pollution of the Kifisos river with human sewage likely occurs when the sewer system gets overloaded during heavy rainfall events, during illegal disposal of industrial and domestic waste, livestock farming effluents and other illegal point pollution sources. Other studies [25; 26] found similar causes that led to water quality deterioration in urban rivers.