# Characteristics and Causes of Coastal Water Chemistry in Qionghai City, China
## 3 Results
### Analysis of Major Ion Sources and Control Factors  
The Gibbs diagram is a graphical method that can describe the source of water chemical components. By analyzing the distribution of each ion in the Gibbs diagram, it is possible to qualitatively determine the influence of factors such as atmospheric rainfall, rock weathering, and evaporation concentration on the source of ions in the surface water [31]. In the Gibbs plot of the coastal zone area of Qionghai City (Figure 6), it can be seen that the cation Na\({}^{+}\)/(Na\({}^{+}\) + Ca\({}^{2+}\)) was mainly between 8% and 60%, and the anion Cl\({}^{-}\)/(Cl\({}^{-}\) + HCO\({}_{3}\)\({}^{-}\)) was mainly between 9% and 50%. This indicates that the main sources of ions in surface water in the region are atmospheric precipitation and seawater, while the contribution of rock weathering is small. In this region, the influence of seawater was high, so the proportion of Na\({}^{+}\)/(Na\({}^{+}\) + Ca\({}^{2+}\)) was relatively high, while the influence of evaporation concentration was relatively small, so the proportion of Cl\({}^{-}\)/(Cl\({}^{-}\) + HCO\({}_{3}\)\({}^{-}\)) was also not high.  
According to the results of the Pearson correlation coefficient analysis in Table 2, it can be seen that there was a significant correlation (\(p<0.05\)) between TDS and Na\({}^{+}\), Ca\({}^{2+}\), Cl\({}^{-}\), and SO\({}_{4}\)\({}^{2-}\) in the surface water of the coastal zone of Qionghai City, indicating that there is a significant linear relationship between the content of these ions in surface water and the content of the total dissolved solids (TDS). Thus, both Na\({}^{+}\) and Cl\({}^{-}\) are major contributors of ions to the water of this region. In addition, there was a significant correlation between Na\({}^{+}\) and Cl\({}^{-}\), suggesting that these two ions have the same source and may be influenced by seawater. In addition, Table 2 showed a significance of 0.14 between Ca\({}^{2+}\) and HCO\({}_{3}\)\({}^{-}\), probably because Ca\({}^{2+}\) was derived from rock weathering processes, while HCO\({}_{3}\)\({}^{-}\) was mainly derived from atmospheric precipitation and evaporative concentration. It can be further speculated that the sources of surface water ions in the coastal zone of Qionghai City are mainly seawater, rock weathering, atmospheric precipitation, and evaporation concentration, and other factors [32; 33; 34; 35; 36].  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & **Ca\({}^{2+}\)** & **Mg\({}^{2+}\)** & **Na\({}^{+}\)** & **K\({}^{+}\)** & **Cl\({}^{-}\)** & **SO\({}_{4}\)\({}^{2-}\)** & **HCO\({}_{3}\)\({}^{-}\)** & **CO\({}_{3}\)\({}^{2-}\)** & **TDS** \\ \hline Ca\({}^{2+}\) & 1 & & & & & & & \\ Mg\({}^{2+}\) & 0.526 ** & 1 & & & & & & \\ Na\({}^{+}\) & 0.887 ** & 0.536 * & 1 & & & & & \\ K\({}^{+}\) & 0.125 & 0.524 * & 0.128 & 1 & & & & \\ Cl\({}^{-}\) & 0.791 ** & 0.619 * & 0.844 ** & 0.116 & 1 & & & \\ SO\({}_{4}\)\({}^{2-}\) & 0.689 & 0.199 & 0.743 ** & 0.147 & 0.674 ** & 1 & & \\ HCO\({}_{3}\)\({}^{-}\) & 0.140 & 0.635 * & 0.535 ** & 0.141 & 0.450 * & 0.507 ** & 1 & \\ CO\({}_{3}\)\({}^{2-}\) & 0.296 & 0.133 & 0.372 & 0.117 & 0.161 & 0.136 & 0.140 & 1 & \\ TDS & 0.712 ** & 0.569 * & 0.897 ** & 0.327 & 0.830 ** & 0.730 ** & 0.568 ** & 0.177 & 1 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Correlations between conventional indicators.  
Figure 6: Qionghai Coastal Water Quality Gibbs Chart.