## 3 Results
### Sequential Extraction of Cu  
Interestingly, the light soils had no content of the most bioavailable copper fraction I. Additionally, no Cu fraction II bound to iron and manganese oxides was found in the arable soil samples from Biala Podlaska, Lubartow, and Tarnobrzeg. In the garden soils from Tarnobrzeg, copper fraction II was present in the entire profile of the domestic garden soil and in the humus horizon of the allotment garden soil. The content of this fraction was in the range of 0.08-1.49 mg\(\cdot\)kg\({}^{-1}\) (Supplementary Materials Table S3), which accounted for 0.33 to 5.79% (Figure 2). In the sandy soils, humus-bound copper fraction III was detected only in the humus horizons of the garden soils from Biala Podlaska (the highest content: 11.69 mg\(\cdot\)kg\({}^{-1}\)) and Lubartow-0.87 and 0.16 mg\(\cdot\)kg\({}^{-1}\) (Supplementary Materials Table S3). In Tarnobrzeg, regardless of the mode of land use, the humus-associated fraction was present in the entire profiles and ranged from 1.12 to 5.08 mg\(\cdot\)kg\({}^{-1}\) (Supplementary Materials Table S3), constituting from 0% to 41.41% of the total copper content (Figure 2). The residual Cu fraction was the largest of all the fractions determined in the study. In the sandy garden soils, it was in the range of 5.60-38.74 mg\(\cdot\)kg\({}^{-1}\) (Supplementary Materials Table S3), which accounted for 58.59-100% of the total copper content (Figure 2). In turn, a narrower range of 2.02-10.58 mg\(\cdot\)kg\({}^{-1}\) (Supplementary Materials Table S3), which corresponded to 70.14-100% of the total copper content, was detected in the arable soils (Figure 2). In terms of the land use, the content of the residual copper fraction decreased with depth in the arable soils, while no such relationships were noted in the case of the garden soils (Supplementary Materials Table S3). The content of water-soluble copper fraction I in the silty soils ranged from 0.00 to 7.06 mg\(\cdot\)kg\({}^{-1}\) (Supplementary Materials Table S4) and its percentage proportion in the total content, regardless of the mode of land use, was in the range of 0.00-15.29% (Figure 3). This was the smallest fraction of all those analyzed in this study. The soil sampled in Zamosc exhibited an outstanding profile with the highest content of fraction I, which was found to  
Figure 2: Percentage content of Cu fractions in sandy soils. vary greatly with a tendency towards higher contents in the parent material. The humus horizons exhibited high levels of this fraction as well (Figure 3). Regardless of the mode of land use, the content of the copper fraction II bound to iron and manganese oxides in the soils ranged from 0.10 to 4.21 mg\(\cdot\)kg\({}^{-1}\) (Supplementary Materials Table S4), and its percentage proportion in the total content was in the range from 0.24 to 23.04% (Figure 3). The analysis of the content of this fraction in the analyzed cities revealed its highest levels in all genetic horizons in the soils sampled in Zamosc, irrespective of the mode of land use. It was impossible to assess whether the humus horizons had a greater proportion of this fraction; moreover, its distribution in the profile was highly variable. The difference in the content of copper fraction II between the field and garden soils was unclear (Figure 3). Regardless of the mode of land use, the content of humus-bound copper fraction III ranged from 0.91 to 9.42 mg\(\cdot\)kg\({}^{-1}\) (Supplementary Materials Table S4), which accounted for 2.17-45.92% of the total content (Figure 3). It was impossible to show unequivocally whether the content of this fraction was higher in the garden soil profiles, especially in the topsoil layer, as was the case of the sandy soils (Figure 3, Supplementary Materials Table S4). The percentage proportion of the residual fraction in the total Cu content in the silty soils ranged from 34.56% to 96.27%, which was lower than that in the sandy soils (Figure 3). Its content was in the range of 3.00-47.98 mg\(\cdot\)kg\({}^{-1}\) (Supplementary Materials Table S4).