## 4 Results and Discussion
Being aware of the complexity of the processes, the ranges of concentrations of analysed metals in soils determined in the study were measured and are presented in Table 5.  
Graphical comparison of metal concentrations determined by individual methods and spectrometer types from soil samples prepared from both IUNG and two-stage decomposition is shown in Figure 4.  
It can be observed that both the type of decomposition method and laboratory determination methods noticeably affected the determined concentration value of almost all the analysed heavy metals. Generally, heavy metal concentrations were higher for the two-stage decomposition than for the IUNG method. The exception was Ni, where samples prepared by the IUNG method and determined by AAS were higher than in the other methods of preparation and/or laboratory determinations. In the case of Cu, sample preparation with both methods leads to practically the same results regardless of the method of laboratory determination. In order to confirm whether the variation in heavy metal concentrations in individual soil samples statistically significantly differs depending on the applied method of laboratory determinations and/or sample preparation, analysis of variance with repeated measurements (RMA) was applied. The results of normality tests (Shapiro-Wilk) indicate that in most cases (>92%), the analysed data are characterised by a distribution more or less deviating from normal. Therefore, an attempt was made to normalise the data using the Box-Cox transformation. Unfortunately, this did not give satisfactory results and only for two metals (Zn and Fe), a normal distribution was obtained for determinations performed \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{\begin{tabular}{c} **IUNG Distribution** \\ **Designation on the AAS** \\ **(AAS\({}_{1}\))** \\ \end{tabular} } & \begin{tabular}{c} **IUNG Distribution** \\ **Determination on** \\ **ICP-MS** \\ **(ICP-MS\({}_{1}\))** \\ \end{tabular} & \begin{tabular}{c} **Two-Step Decomposition** \\ **Determination on** \\ **ICP-MS** \\ **(ICP-MS\({}_{2}\))** \\ \end{tabular} & \
\begin{tabular}{c} **Geochemical Background** \\ **to Loess Soils** \\ **(According to** \\ **[PERSON], 1993)** \\ \hline Zn & 30.5–138 & 32.1–442 & 37.8–445 & 30–360 \\  & & & 65 on average \\ \hline Pb & 11.8–94 & 23.1–92.8 & 25.0–109 & 19–49 \\  & & & 25 on average \\ \hline Cu & 6–95 & 6.9–94.4 & 6.4–49.8 & 4.0–53.0 \\  & & & 19.0 on average \\ \hline Cr & 15.3–47.5 & 15.3–53.7 & 20.2–73.3 & 14.0–80.0 \\  & & & 38.0 on average \\ \hline Ni & 10.3–32.3 & 9.5–25.1 & 8.9–23.3 & 10–104 \\  & & & 25 on average \\ \hline Fe & 12,756–21,460 & 9510–20,055 & 11,771–24,854 &
\begin{tabular}{c} Fe (\%) \\ 0.8–2.78 \\ on average 1.2 \\ \end{tabular} \\ \hline Mn & 134–832 & 161–776 & 166–920 & 380–700 \\  & & & 560 on average \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Ranges of heavy metal concentrations in soils in the study area [mg/kg]. by all methods (AAS\({}_{1}\), ICP-MS\({}_{1}\) and ICP-MS\({}_{2}\)). At the same time, the results of [PERSON]'s test indicate a significant violation of sphericity for all analysed data and therefore further analysis was carried out using [PERSON], [PERSON] and [PERSON]'s multivariate tests. The results of these tests indicate statistically significant variation in the concentrations of all heavy metals depending on the analytical method and/or sample preparation used. For in-depth data analysis, conservative post-hoc tests ([PERSON]'s test) were additionally performed. These tests showed that Cu concentrations in soil samples do not differ significantly depending on the chosen laboratory test method and/or sample preparation. In contrast, the other results of the post-hoc tests are consistent with the results of the multivariate tests. This ambiguity in the results may be due to the fact that even if the multivariate tests are significant, this may only apply to a limited part of the data population.