## 4 Discussion  
The literature describing the problem of soil contamination with heavy metals in gardens presents the opinion that these are soils contaminated by substances from neighboring houses, roads, urban, and possibly industrial, areas. Copper is one of the most common heavy metals, and its form in soils may be influenced by such physicochemical properties as: pH, content of organic matter, calcium carbonate, clay fraction. It is worth emphasizing that soils under horticultural use as compared to cultivated ones may be characterized by a higher content of organic matter, which predisposes them to retain heavy metals [5]. In the \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Statistic** & **Axis 1** & **Axis 2** & **Axis 3** & **Axis 4** \\ \hline Eigenvalues & 0.4018 & 0.2613 & 0.0955 & 0.0760 \\ Explained Variation (Cumulative) & 40.18 & 66.31 & 75.86 & 83.46 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of the Cu results in PCA. Figure 4: Principal component analysis (PCA) of two indices for the copper content and parameters. presented studies were higher content in humus horizons of C, N, and sorption capacity and some changes in the reaction. Taking into account the reaction of the analyzed soils and the proportion of the silt fraction, the total content of copper indicated natural levels of the element [22; 23], with the exception of the allotment garden and arable field in Przemysl and the domestic garden in Zamosc. The silty soils exhibited higher total Cu content than that in the sandy soils, which was similar in all types of land use. While its distribution in the garden soil profiles did not show any regularity, the arable soils exhibited a lower Cu level in the Et horizon and substantially higher content of the element in the Bt horizon, which indicates the dominance of natural soil-forming processes over anthropogenic factors. Investigations conducted by many authors have demonstrated a significant relationship of copper contents with the level of floatable parts and soil type, which was confirmed by the differences observed in the soils analyzed in this study [24; 25; 26; 27; 28; 29; 30; 31; 32; 33]. Nevertheless, the location of the site may significantly determine the copper content, as suggested by [PERSON] et al. [34]. The mode of land use differentiated the results. The profiles of the garden sandy soils had an evenly distributed two-fold higher level of copper than the arable soils. In turn, accumulation of this component and its systematic decline along the profile depth were observed in the humus horizons of the arable soils. The distribution of the total Cu content is reflected in concentration indices: the highest values were calculated for the humus horizons, irrespective of the mode of land use, and the sandy soils were characterized by higher values. In turn, in the group of the silty soils, a high index was calculated for the Bt horizon in the arable soils. The absence of differences in the copper content between silty soil horizons was confirmed by [PERSON] et al. [35]. The concentration of copper in the Ap horizon may be associated with copper binding to organic matter, which has been reported by many authors [1; 28; 33; 36; 37; 38; 39]. As underlined by [PERSON] et al. [40], the location of allotment gardens and cultivation treatments promote higher concentration of, e.g., Cu in the topsoil layers, compared to agricultural soils. In addition to the concentration index, the Igeo index presented here not only showed the high levels of the analyzed element in the soils, but also indicated anthropogenic effects. As reported by many authors, calculation of the Igeo index facilitates determination of the source of copper concentration, e.g., in garden soils [41; 42; 43]. Additionally, to demonstrate the relationship of copper with organic matter, a sequential analysis was performed using the BCR method. Very few of the numerous publications on the application of BCR sequential analysis describe the use of this method in analysis of horticultural soils.