## 3 Results
### Comparison of the HCF Obtained by the Simulated and the Filter Paper Method  
The \(\psi_{d}\) used to adjust the SWRC with [PERSON] model was obtained by using the filter paper method at a high saturation rate (i.e., \(\psi_{d}\) = 4000 kPa). The saturated hydraulic conductivity used were 5.3 \(\times\) 10\({}^{-10}\) m/s \(\pm\) 6.2 \(\times\) 10\({}^{-11}\) m/s for the natural soil, 2.5 \(\times\) 10\({}^{-8}\) m/s \(\pm\) 4.7 \(\times\) 10\({}^{-9}\) m/s for the 25 mg/kg arsenic-concentration, and 1.2 \(\times\) 10\({}^{-8}\) m/s \(\pm\) 1.4 \(\times\) 10\({}^{-7}\) m/s for the 50 mg/kg arsenic-concentration. Figure 3 shows the HCF of the arsenic-contaminated soils for the filter paper and the simulated conditions. It is worth noting that both of these methods used [PERSON]'s restrictions. For clarity, the analysis was divided into two phases: (i) the SWRC of the natural soil and (ii) the comparison of the simulated SWRC with the filter paper SWRC.  
In the first phase, the comparison of the HCF shows that there was no significant variation between the simulated SWRC and those of the filter paper SWRC under natural conditions with the [PERSON] model. However, at high suction values, the hydraulic conductivity value (\(k\)) of the simulated SWRC does not correspond to that of the filter paper due to the van Genuchten fit, where the parameter \(n\) value controls the slope of the SWRC and, therefore, the \(\psi_{m}\) value.  
In the second phase, the comparison of the HCF for the 25 mg/kg shows a great variation in the shape of the HCF curve, which is affected by the parameter value in the van Genuchten method (\(m\) = 0.43 \(\pm\) 0.03 and \(m\) = 0.16 \(\pm\) 0.00 for the simulated and the filter paper method curves, respectively). Even when the results are in the same order of magnitude, the simulated curves give higher \(k\) values than those of the filter paper method. At \(s_{r}\) = 90%, the \(k\) value for the simulated SWRC is about 18 times smaller than that of the filter paper method. For the 50 mg/kg condition, similar results were obtained (\(m\) = 0.47 \(\pm\) 0.01 and \(m\) = 0.15 \(\pm\) 0.01 for the simulated and the filter paper method curves, respectively).  
Both methods (simulated and filter paper) provided similar HCF curves. However, the estimated data are higher than those obtained through the filter paper. This indicates that the retention potential does not reflect the behavior of the evaluated soils. Specifically, the HCF of the soil is modified due to the arsenic contamination, which, in turn, increases the permeability coefficient by increasing the specific surface and pore-size distribution [29], indicating a modification of the soil's structure. In contrast, the simulated HCF for the contaminated soils does not reflect that change either by the SWRC or the HCF.  
The available SWRCs of the contaminated soils [24; 29] showed an oddly shaped curve when evaluated using the filter paper method. This has significant repercussions when the data are fitted to [PERSON]'s model. Consequently, its use may result in inadequate hydraulic analysis, that is, HCF. Furthermore, although it would be risky to indicate that [PERSON] model does not represent the contaminated soil condition, the results provided by this model should be interpreted with caution, nevertheless. Thus, further investigation needs to be conducted to verify the applicability of such models to other contaminated soils.