# Determining Effective Threshold Range of Image Pixel Values for Municipal Waste-Contaminated Clay
## 2 Materials and Methods
### Sample Preparation  
Seeing municipal waste-contaminated soil was obtained by extracting six sets of contaminated clay samples at different seepage depths from six sampling holes of the seepage municipal waste-contaminated soil preparation test device, while uncontaminated clay samples were also prepared as a control. The clay properties at the different seepage depths are listed in Table 3. Soaking municipal waste-contaminated soil was obtained by preparing six groups of CaCO\({}_{3}\) and CH\({}_{3}\)COOH-contaminated clay samples with concentrations of 0.2, 0.4 and 0.6 mol/L, and the chemical elements are listed in Table 4. The samples for SEM analysis were prepared in accordance with the specifications of the adopted SEM with as little disturbance as possible. The clay was sliced and trimmed into samples with measurements of 1 cm by 1 cm by 1 cm. The samples were then dried in an oven at 65 \({}^{\circ}\)C. After the samples were dried, tape was used to remove any loose clay particles from the cross section of the sample until a completely smooth surface was obtained.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample** & **Na\({}_{2}\)O (\%)** & **MgO (\%)** & **Al\({}_{2}\)O\({}_{3}\) (\%)** & **SiO\({}_{2}\) (\%)** & **K\({}_{2}\)O (\%)** & **CaO (\%)** & **Fe\({}_{2}\)O\({}_{3}\) (\%)** \\ \hline Uncontaminated clay & 0.60 & 1.35 & 15.48 & 62.93 & 1.88 & 2.18 & 5.77 \\
0.2 mol/LCaCO\({}_{3}\)-contaminated clay & 1.28 & 1.41 & 14.72 & 60.67 & 1.84 & 2.79 & 5.70 \\
0.4 mol/L CaCO\({}_{3}\)-contaminated clay & 1.22 & 1.39 & 14.74 & 60.43 & 1.85 & 2.80 & 5.64 \\
0.6 mol/L CaCO\({}_{3}\)-contaminated clay & 1.95 & 1.39 & 13.96 & 59.83 & 1.83 & 3.04 & 5.65 \\
0.2 mol/L CH\({}_{3}\)COOH-contaminated clay & 0.45 & 1.29 & 13.83 & 59.56 & 1.83 & 2.05 & 5.63 \\
0.4 mol/L CH\({}_{3}\)COOH-contaminated clay & 0.46 & 1.28 & 13.64 & 59.55 & 1.84 & 2.08 & 5.58 \\
0.6 mol/L CH\({}_{3}\)COOH-contaminated clay & 0.44 & 1.27 & 13.67 & 59.61 & 1.83 & 2.05 & 5.56 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Chemical elements of soaking municipal waste-contaminated soil.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameters** & **Parameters** & **Parameters** & **Parameters** \\ \hline COD (mg/L) & 19,500 & Mg (ug/g) & 414 & Mn (ug/g) & 0.3734 \\ BOD (mg/L) & 9833 & K (ug/g) & 1639 & Pb (ug/g) & 0.0289 \\ TSS (mg/L) & 1334.59 & Na (ug/g) & 3319 & Cu (ug/g) & 0.0253 \\ VSS (mg/L) & 576.89 & As (ug/g) & 0.0855 & Si (ug/g) & 8.7 \\ NH\({}_{4}^{+}\)-N (mg/L) & 1701.8 & B (ug/g) & 3.88 & Al (ug/g) & 2.3 \\ Ca (ug/g) & 186 & Cd (ug/g) & 0.0005 & Total hardness (mg/L) & 1746.455 \\ pH & 6.57 & Hg (ug/g) & 0.0049 & Total alkalinity (mg/L) & 12,410.09 \\ TVFA (mmol/L) & 63 & Ni (ug/g) & 0.2306 & \\ Fe (ug/g) & 20 & Zn (ug/g) & 0.6148 & \\ \hline COD = chemical oxygen demand, BOD = biochemical oxygen demand, TSS = total suspended solids, VSS = volatile suspended solids, TVFA = total volatile fatty acids. & \\ \end{tabular}
\end{table}
Table 2: Water quality of leachate in simulating landfill experiment.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline Depth of Sampling Hole (cm) & 3.1 & 17.3 & 36.8 & 48.5 & 56.3 & 75.8 \\ \hline Dry density (g/cm\({}^{3}\)) & 1.55 & 1.55 & 1.5 & 1.53 & 1.53 & 1.56 \\ Void ratio & 0.34 & 0.64 & 0.73 & 0.79 & 0.81 & 0.83 \\ Saturated water content (\%) & 28.38 & 29.12 & 28.42 & 28.02 & 27.78 & 26.52 \\ Organic slit produced per kg of clay (\%) & 13.85 & 12.37 & 8.81 & 7.12 & 6.33 & 4.61 \\ Calcium carbonate produced & 5.68 & 4.98 & 4.49 & 4.38 & 3.78 & 2.24 \\ per kg of clay (g) & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Physical parameters of contaminated clay samples at different depths of the column after seepage.