## 3 Results and Discussion
### Surface Laaching  
Tables summarising the analysis of the leachate are presented in the Appendix. The analysis of the results of the surface leaching tests resulted in a lower values than the expected limits of contaminants, which is reported in the tests protocols see the Appendices A-C for full chemical protocols. In such cases, when the levels of pollutants are lower than the reported limits, it can be concluded that the leaching of the evaluated substance has a low level, and the soil is environmentally safe. Table 6 shows the distribution of values above or below the reporting limit for metals summarised in the additional Tables of Appendices A-C. Among the analysed heavy metals, arsenic (As) and nickel (Ni) demonstrated the levels of concentration above the detection limit for specimens treated during the entire period from 6 h to 64 days of leaching. Figure 5 shows the cumulative leaching of arsenic (As) over time where leaching can be considered as diffusion controlled, as shown in Figure 5. The lines on the graphs were interpolated as several segments of splines, separated by the Batches and Samples between each measurement and compared for average values, logarithm curve and standard deviation between the samples within the same time gap. The lines on the graph show the contamination level as curvatures for each Batch for evaluated specimens. A standard deviation of the leached As on day 16 was significantly higher, e.g., in sample No. 6. It may indicate a biased measurement in the laboratory on a given specific sample. Nevertheless, for the analysis of leaching, the data remain statistical unbiased, and were included in the calculation of the amount of the leached As. The average value of the three samples is used to visualise a statistical trend line. The equation from the trend line is calculated to estimated the expected leaching of As after one year. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample** & **As** & **Pb** & **Cd** & **Cr** & **Hg** & **Ni** & **Zn** \\ \hline B 1, S-6 & above & below & below & below & below & above & both \\ B 1, S-7 & above & below & below & below & below & above & below \\ B 1, S-8A & above & below & below & below & below & above & both \\ \hline \hline \end{tabular}  
* Notations for abbreviations in Table 6: Bl—Batch 1; 56—Sample 6; S7—Sample 7; S-8A—Sample 8A; As—Arsenic; Pb—Lead; Cd—Cadmium; Cr—Chromium; Hg—Mercury; Ni—Nickel; Zn—Zinc.  
\end{table} 
Table 6: Values of concentrations of leaching contaminants (mg/m\({}^{2}\)) from soil samples: above or below the reported limits. The intensive industrial development in the region of Kongshavn (Port of Oslo) in recent decades resulted in significant areas of degraded lands and contaminated soil. Therefore, the need for remediation of soil requires a comparison of data on the contamination level both in a retrospective mode and as a prognosis. The estimation of possible future leaching of the selected contaminants has been performed for arsenic (As), nickel (Ni), PAH-16, and TBT. Using the regression equation from Figure 5 and a time period of 365 days, the potential leaching amount was modelled per m\({}^{2}\) for one year, as shown in Equation (1). This gives an estimated leaching of arsenic (As) of 0.9153 mg/m\({}^{2}\) per year. \[y=0.128\ln(time)+0.161 \tag{1}\]  
Figure 6 shows a cumulative leaching of nickel (Ni) over time. The average value of the three samples is used to plot a statistical trend line showing general development and the interpolated trend in the increase in leaching of Ni. The equation from the trend line is used to calculate the expected leaching of Ni in one year. A trend of Ni leaching is based on the evaluated data from Batch 1 using Samples 6, 7, and 8A. For Ni, the results of estimated leaching look similar and in the same way as for As. Likewise, the regression equation was used from Figure 7 for modelling the data using a time span of 365 days to evaluate possible leaching of Ni per m\({}^{2}\) during one year by Equation (2).