## 3 Results and Discussion
### Partitioning of Cd, Pb, and Zn in Uncontaminated, Contaminated, and Remediated Soils  
Partitioning of Cd, Pb, and Zn was performed in uncontaminated, contaminated, and remediated soils by applying a modified [PERSON]'s sequential extraction procedure [24] (see sequential extraction procedure in Materials and methods). To find out whether sulfate, as present in the soil from \"Old Zinc-works\" site, has any effect on the remediation, sulfate-treated uncontaminated, contaminated, and remediated soils were also investigated (see Experimental design). The results of the partitioning of the Cd, Pb, and Zn in the uncontaminated, contaminated, and remediated soils are presented in Figures 3-5, while in sulfate-treated uncontaminated, contaminated, and remediated soils in the Supplementary Material (Figures S3-55). The related elemental concentrations in individual soil fractions of the extraction procedure related to data from Figures 3-5 and Figures S3-55 are provided in the Supplementary Material (Tables S4-S9). The concentrations of Cd, Pb, and Zn in steps I to VI were summed and compared to the total Cd, Pb, and Zn concentrations obtained by microwave-assisted digestion. The mass balance was agreed to within \(\pm\)5%, confirming the precision of the sequential extraction analysis. Figure 3: Partitioning of Cd in uncontaminated, contaminated, and remediated soil samples with time elapsed after the remediation. I water-soluble; II exchangeable; III bound to carbonates; IV bound to Fe/Mn oxides and hydroxides; V bound to organic matter; VI bound to silicate lattice. Figure 4: Partitioning of Pb in uncontaminated, contaminated, and remediated soil samples with time elapsed after the remediation. I water-soluble; II exchangeable; III bound to carbonates; IV bound to Fe/Mn oxides and hydroxodes; V bound to organic matter; VI bound to silicate lattice. Figure 5: Partitioning of Zn in uncontaminated, contaminated, and remediated soil samples with time elapsed after the remediation. I water-soluble; II exchangeable; III bound to carbonates; IV bound to Fe/Mn oxides and hydroxodes; V bound to organic matter; VI bound to silicate lattice. In the uncontaminated soils, Cd, Pb, and Zn were associated almost exclusively with the insoluble residual fraction, bound to the silicate lattice. Their concentrations in the water-soluble and exchangeable fractions, which are mobile in the environment, were negligible, not exceeding 0.0007, 0.0003, and 0.0025 mg/kg for the Cd, Pb, and Zn, respectively (see the data from Tables S4-S9). In the contaminated soils, the distribution of Cd, Pb, and Zn changed over time. After the contamination, the Cd was distributed mainly between the carbonate, exchangeable and residual fractions. In the water-soluble fraction, the Cd concentration exceeded the limiting value for inertness (0.04 mg/kg) [37; 38]. During the experiment, the sum of the Cd concentrations in highly the mobile water-soluble and exchangeable fractions was around 2-3 mg/kg. The Pb in the contaminated soils was associated with carbonate, Fe/Mn oxides and hydroxides, and the residual fractions. After the soil contamination, the Pb concentration in the water-soluble fraction was close to the limit value for inert materials (0.5 mg/kg) [37; 38], while its exchangeable concentrations were up to 30 times higher than in the water-soluble fraction (see data from Tables S4-S9). The Zn in the contaminated soils was distributed mainly in the carbonate fraction and, to a smaller extent, in the Fe/Mn oxides and hydroxides and residual fractions. In the water-soluble fraction of the contaminated soils, the Zn concentrations greatly exceeded (around 20 times) the criterion for inertness (4 mg/kg) [37; 38], whereas the exchangeable Zn contents were approximately 2-4 times lower than the water-soluble concentrations.