## 3 Results
### Spatial Concentration Mapping Using NN-PSO + EBK  
The NN-PSO simulation was applied to accelerate the performance of the prediction capability of the EBK method. The simulation showed an excellent result as evident to the mean squared error (MSE) and correlation coefficient (R) values wherein the ideal value is 0 and 1, respectively. The NN-PSO simulation performed for the physicochemical parameters and heavy metal concentrations are presented in Table 5. Correlation plots of the R (validation) and R (testing) for the governing NN-PSO models of physicochemical parameters and heavy metals concentration are illustrated as Figure A1 of Appendix B. The relationship between the number of neurons ranging from 1 to 30 and the corresponding AIC (Akaike Information Criterion) values obtained for the physicochemical parameters (temperature, pH, EC, and TDS) as well as the heavy metal concentrations are exhibited in Figures 8 and 9, respectively. These figures represent the AIC values of all NN-PSO models for each hidden neuron that was simulated in this study. It was observed that the best models for the physicochemical parameters were determined from the 25, 29, 30, and 27 hidden neurons (HN) for temperature, pH, EC and TDS, respectively. The best models for Ba, Cu, Fe, Mn, and Zn were observed in 29, 29, 28, 29, 30 HN, respectively, for the hea \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Metal** & **Ba** & **Cu** & **Fe** & **Mn** & **Zn** \\ \hline Ba & 1 & & & & \\ Cu & 0.055 & 1 & & & \\ Fe & \(-\)0.136 & \(-\)0.001 & 1 & & \\ Mn & \(-\)0.235 & 0.072 & 0.320 & 1 & \\ Zn & \(-\)0.089 & 0.013 & 0.870 ** & 0.190 & 1 \\ \hline \hline \end{tabular}  
* Correlation is significant at the 0.01 level (2-tailed).  
\end{table} 
Table 4: Correlation matrix for the heavy metal concentration of groundwater samples. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Hidden** & **No. of** & **No. of** & **Elapsed** & & & **R** \\  & **Neurons** & **Particles** & **Iterations** & **Time (sec)** & **MSE** & & **Validation** & **Testing** \\ \hline Temp & 25 & 3 & 2000 & 180.38559 & 0.01204 & 0.99878 & 0.99656 \\ pH & 29 & 10 & 2000 & 119.16085 & 0.00434 & 0.99078 & 0.99039 \\ EC & 30 & 1 & 2000 & 163.34882 & 0.00155 & 0.99851 & 0.99966 \\ TDS & 27 & 3 & 2000 & 337.90592 & 0.00032 & 0.99925 & 0.99981 \\ Ba & 29 & 1 & 2000 & 172.62202 & 2.44 \(\times\)\(10^{-6}\) & 0.98838 & 0.99286 \\ Cu & 29 & 3 & 2000 & 366.12861 & 1.64 \(\times\)\(10^{-7}\) & 0.99826 & 0.99636 \\ Fe & 28 & 3 & 2000 & 139.78693 & 0.00091 & 0.999010 & 0.99951 \\ Mn & 29 & 5 & 2000 & 115.26285 & 1.34 \(\times\)\(10^{-7}\) & 0.98252 & 0.99725 \\ Zn & 30 & 1 & 2000 & 142.60618 & 1.08 \(\times\)\(10^{-5}\) & 0.97945 & 0.99580 \\ \hline \hline \end{tabular}  
\end{table} 
Table 5: NN-PSO Simulation Results. The spatial concentration of the physicochemical parameters of GW in Calapan City, Oriental Mindoro was mapped using NN-PSO+EBK interpolation method. The highest temperature for GW recorded in the study area was 33.6 \({}^{\circ}\)C which was observed in Brgy. Parang. While the least temperature was observed in Brgy. Biga with recorded temperature of 26.2 \({}^{\circ}\)C. The highest pH for GW was observed at Brgy. Canubing I, with pH equal to 8.8. The lowest pH was detected at Brgy. Sto. Nino with pH of 6.7. The highest EC and TDS observed in Brgy. Ibaba West with EC and TDS value of 1820 \(\upmu\)S/cm and 900 ppm, respectively. The least observed EC and TDS concentration was 100 \(\upmu\)S/cm and 40 ppm, respectively which was recorded in Brgy. Sta. Rita. The spatial concentration of the physicochemical parameters of GW is shown in Figure 10.  
Figure 8: The AIC Values for Physicochemical Parameters. Figure 9: The AIC Values for Heavy Metals. The spatial concentration of the heavy metals of GW in Calapan City, Oriental Mindoro including Ba, Cu, Fe, Mn, and Zn was also mapped using the NN-PSO+EBK interpolation method. The heavy metal concentration maps generated using the NN-PSO+EBK method was presented in Figure 11.  
Figure 11: Cont.