## 3 Results  
### Inorganic Pollutants  
Compared to the Germany-wide NFSI data, the peak values of inorganic pollutants in Brandenburg are far below those in other regions in Germany due to the low geogenic base concentrations [17; 35]. For the levels of inorganic pollutants found in the mineral topsoil, in addition to the atmospheric pollution from supra-regional and local emitters, the current chemical soil condition also plays a decisive role. The scatter diagrams in Figure 2 exemplify the univariate dependencies of the element concentration on the \(\text{CEC}_{\text{eff}}\). Of all the potentially influencing variables considered, \(\text{CEC}_{\text{eff}}\) shows the closest relationship to the concentrations of the examined trace elements. The \(\text{CEC}_{\text{eff}}\) expresses the quantity of clay minerals, hydroxides and oxides, the content of organic soil colloids and--due to the partially pH-dependent charges--also the soil reaction. These soil properties are crucial for the binding of heavy metals in the mineral topsoil and delay their leaching into subsoil. This also applies to the partially anionically bound trace elements such as As and Cr, although in these cases the relationship to the \(\text{CEC}_{\text{eff}}\) is of an indirect nature, because top soils with high anion exchange capacity usually also have high cation exchange capacity. For each element, two regression models were calculated. The pH value is considered in both models. In addition, the logarithmized organic carbon content and the clay content were considered in the first model approach and the logarithmized effective cation exchange capacity in the second approach. For the logarithmized \(\text{CEC}_{\text{eff}}\) or \(\text{C}_{\text{org}}\) content values, the correlations were somewhat better than using the non-logarithmic values, so that a non-linear relationship was generally assumed here. The results of the regression analyses are shown in Table 1.  
\[Trace\;element[mg/kg]=a*log(CEC_{\text{eff}})[molc/kg]+b*pH(KCl)+c \tag{1}\]  
\[Trace\;element[mg/kg]=a*log(C_{\text{org}})[\%_{\infty}]+b*clay\;content[\% ]+c*pH(KCl)+d \tag{2}\] \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{5}{c}{**Equation (1)**} \\ \hline  & **a** & **b** & **c** & **R** & **F** \\ \hline As & 2.120 \({}^{**}\) & - & \(-\)0.798 \({}^{*}\) & 0.34\({}^{**}\) & 50.0 \\ Cd & 0.160 \({}^{**}\) & 0.054 \({}^{**}\) & \(-\)0.369 \({}^{**}\) & 0.65 \({}^{**}\) & 105.0 \\ Cr & 3.280 \({}^{**}\) & 0.873 \({}^{**}\) & \(-\)3.866 \({}^{**}\) & 0.49\({}^{**}\) & 44.8 \\ Cu & 4.394 \({}^{**}\) & 0.489 \({}^{**}\) & \(-\)6.121 \({}^{**}\) & 0.62 \({}^{**}\) & 179.0 \\ Ni & 2.325 \({}^{**}\) & 0.929 \({}^{**}\) & \(-\)4.406 \({}^{**}\) & 0.49 \({}^{**}\) & 45.7 \\ Pb & 24.197 \({}^{**}\) & \(-\)2.054 \({}^{**}\) & \(-\)13.334 \({}^{**}\) & 0.65 \({}^{**}\) & 207.2 \\ Zn & 18.633 \({}^{**}\) & 7.126 \({}^{**}\) & \(-\)40.608 \({}^{**}\) & 0.60 \({}^{**}\) & 155.9 \\ \hline \multicolumn{5}{c}{**Equation (2)**} \\ \hline  & **a** & **b** & **c** & **d** & **R** & **F** \\ \hline As & 1.191 \({}^{**}\) & 0.096 \({}^{*}\) & - & 0.598 \({}^{*}\) & 0.38 \({}^{**}\) & 24.0 \\ Cd & 0.091 \({}^{**}\) & 0.0035 \({}^{**}\) & 0.061 \({}^{*}\) & \(-\)0.278 \({}^{**}\) & 0.64 \({}^{**}\) & 65.8 \\ Cr & 1.336 \({}^{**}\) & 0.342 \({}^{**}\) & 0.787 \({}^{**}\) & \(-\)1.369 \({}^{*}\) & 0.50 \({}^{**}\) & 30.5 \\ Cu & 2.566 \({}^{**}\) & 0.093 \({}^{**}\) & 0.453 \({}^{**}\) & \(-\)2.741 \({}^{**}\) & 0.62 \({}^{**}\) & 119.2 \\ Ni & 0.998 \({}^{**}\) & 0.222 \({}^{**}\) & 0.833 \({}^{**}\) & \(-\)2.541 \({}^{**}\) & 0.54 \({}^{**}\) & 37.6 \\ Pb & 15.56 \({}^{**}\) & 0.692 \({}^{**}\) & \(-\)1.344 \({}^{*}\) & \(-\)0.150 & 0.70 \({}^{**}\) & 174.3 \\ Zn & 9.778 \({}^{**}\) & 0.911 \({}^{**}\) & 6.448 \({}^{**}\) & \(-\)24.513 \({}^{**}\) & 0.61 \({}^{**}\) & 107.7 \\ \hline \hline \end{tabular}
\end{table}