## 3 Results and Discussion
### Result of Dielectric Properties  
This section presents the dielectric constant and loss factor of both unsaturated and saturated contaminated soil before and after RF heating treatment, using various electric field intensities of 112.5 kV/m, 150 kV/m, 225 kV/m, and 450 kV/m. The experimental results were analyzed using the polynomial curve fitting method and the MATLAB software to find the most appropriate values for the fitting polynomial model parameters, in order to obtain values that closely match the measured data. Figure 5 displays the dielectric properties of all of the tested soil samples before and after RF heating treatment, as well as a reference line for soil without RF heating treatment. Additionally, the summary of the dielectric properties at significantly highlighted frequency is shown in Table 2.  
Figure 4: The difference between unsaturated contaminated soil and saturated contaminated soil based on the temperature profiles with time using various electric field intensities where (**a**) is based on RF heating treatment using 112.5 kV/m, (**b**) is obtained using 150 kV/m, (**c**) is derived from 225 kV/m, and (**d**) is based on RF heating treatment using 450 kV/m. As shown in Figure 5, the dielectric constant of the saturated contaminated soil samples was higher than that of the unsaturated contaminated soil samples and the uncontaminated soil samples, respectively. This is because the addition of commercial grade diesel B7 into the soil penetrates deep into the soil, replacing the air in the pore space and blocking air spaces with the diesel. As a result, the volumetric content of the diesel in the soil affects the dielectric constant of the uncontaminated soil samples, making it different from the dielectric constant of the unsaturated contaminated soil and more different than the saturated contaminated soil samples. It can also be seen that the unsaturated and saturated contaminated soil samples after RF heating treatment have a lower dielectric constant than the unsaturated and saturated contaminated soil samples before RF heating treatment, at all frequencies. This is because the evaporation of the commercial grade diesel B7 in the soil occurs during RF heating treatment, reducing the volumetric content of the diesel in the soil. Here, the RF heating system using an electric field intensity of 450 kV/m provided the highest reduction in the volumetric content of the diesel in the soil. This  
Figure 5: Dielectric properties of the unsaturated contaminated soil and the saturated contaminated soil samples before and after RF heating process compared with the soil without the commercial grade diesel B7 as the reference line where (**a**) is based on electric field of 112.5 kV/m; (**b**) is based on electric field of 150 kV/m; (**c**) is based on electric field of 225 kV/m; (**d**) is based on electric field of 450 kV/m. is because a higher electric field intensity leads to improved power absorbed per unit volume in the dielectric material, as previously discussed. Statistical analysis shows that the reduction in the volumetric content of the diesel in the soil was statistically significant (\(p\leq 0.05\)) when using the optimal electric field intensity for RF heating treatment. This result suggests that RF heating treatment is effective in reducing the volumetric content of diesel in soil. Additionally, it can be observed from Figure 5 that the dielectric loss factors are less pronounced beyond around 1 GHz, which may not be useful for the reader as this frequency range is not suitable for TDR, as summarized in [33]. To clearly see the signature of the unsaturated and saturated contaminated soil samples before and after RF heating process, Table 2 summarizes the comparison of the signature effect of the tested soil types and the volumetric content of the commercial grade diesel B7. As shown in Table 2, the difference in dielectric properties between the unheated and heated soils is noticeable and distinct.