## 3 Results and Discussion
### Effects of Aeration on the Pesticide Degradation Efficiency  
Aeration enhanced degradation rates of the pesticides in cocktail solution under VUV-TiO\({}_{2}\) (Figure 4). Mild aeration for 3 h degraded pesticides by 96.4%, 14.7%, 29.6%, and 63.5% for pyraclostrobin, boscalid, fluidoxonil, and azoxystrobin, respectively, indicating a better effect when compared to no aeration which degraded pesticide by 94.3%, 5.2%, 17.3%, and 55.8%. Extra aeration further enhanced the degradation efficiency with 100.0%, 21.1%, 56.9%, and 80.9% degradation for pyraclostrobin, boscalid, fluidoxonil, and azoxystrobin, respectively. These increased degradation percentages under extra aeration can be attributed to the reactor with an aeration system that supplied compressed air at a high flow rate through the stainless micropore mesh at the bottom of the vessel. Additionally, a fresh supply of oxygen in water through the pump might have enhanced the oxidation of organic compounds [47,48]. In addition, it is estimated that air bubbles in the pesticide solution also reduced the heterogeneity of photolysis by 185 nm light. In the VUV-TiO\({}_{2}\) treatment, the 185 nm light of the VUV lamp was emitted through the uncoated portion of the TiO\({}_{2}\) coated quartz tube, and the path that the 185 nm light that penetrated the water was very short due to a high absorption coefficient. Therefore, the intensity of 185 nm light was decreased nearly 90% in a 5.5 mm thickness of water. For this reason, under VUV-TiO\({}_{2}\) treatment, hydroxyl radicals (OH-) were only generated in a thin layer near the quartz tube [49,50]. It was estimated that 185 nm light penetrated air bubbles in contact with the TiO\({}_{2}\) coated tube, generating hydroxyl radicals (OH-) in the expanded layer, which contributes to an increase in the pesticide degradation efficiency by overcoming heterogeneous photolysis.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline  & \multicolumn{3}{c}{**Pyraclostrobin**} & \multicolumn{3}{c}{**Boscalid**} & \multicolumn{3}{c}{**Fludioxonil**} & \multicolumn{3}{c}{**Azoxystrobin**} \\ \cline{2-13}
**Rate** & \(\mathbf{K_{0}}\) & \(\mathbf{K_{1}}\) & \(\mathbf{K_{2}}\) & \(\mathbf{K_{0}}\) & \(\mathbf{K_{1}}\) & \(\mathbf{K_{2}}\) & \(\mathbf{K_{0}}\) & \(\mathbf{K_{1}}\) & \(\mathbf{K_{2}}\) & \(\mathbf{K_{0}}\) & \(\mathbf{K_{1}}\) & \(\mathbf{K_{2}}\) \\
**Constant** & **(R\({}^{2}\))** & **(R\({}^{2}\))** & **(R\({}^{2}\))** & **(R\({}^{2}\))** & **(R\({}^{2}\))** & **(R\({}^{2}\))** & **(R\({}^{2}\))** & **(R\({}^{2}\))** & **(R\({}^{2}\))** & **(R\({}^{2}\))** & **(R\({}^{2}\))** & **(R\({}^{2}\))** \\ \hline Single & 0.4888 & 1.8978 & 21.753 & 0.0775 & 0.0935 & 0.1141 & 0.213 & 0.4556 & 1.2681 & 0.1184 & 0.1719 & 0.2606 \\ solution & (0.8051) & (0.9809) & (0.9051) & (0.9560) & (0.9600) & (0.9590) & (0.9926) & (0.9092) & (0.7503) & (0.7920) & (0.8635) & (0.9263) \\ Cocktail & 0.2088 & 0.7035 & 4.2827 & 0.0014 & 0.0144 & 0.0148 & 0.0435 & 0.0480 & 0.0531 & 0.1278 & 0.1921 & 0.3043 \\ solution & (0.6975) & (0.9394) & (0.9787) & (0.9753) & (0.9759) & (0.9765) & (0.9650) & (0.9714) & (0.9763) & (0.8221) & (0.8992) & (0.9591) \\ \hline \end{tabular}
\end{table}
Table 2: Degradation rate constants in single solutions and in a cocktail solution. K\({}_{0}\) (mg L\({}^{-1}\) min\({}^{-1}\)), K\({}_{1}\) (min\({}^{-1}\)), K\({}_{2}\) (L mg\({}^{-1}\) min\({}^{-1}\)), and the corresponding R\({}^{2}\).