## 4 Discussion
### Evaluation of the Correlation Analyses  
The numerous positive correlations in the reservoir sediments between the metal(loid) concentrations themselves and between metal(loid)s and organic matter content may rely on the same source of the metal(loid)s investigated and/or preferential adsorption on organic matter [1; 2; 3; 4; 5]. The correlations between organic matter and metal(loid) concentrations were comparatively lower in the BSP sediments, probably due to the less intense adsorption of metal(loids) by organic compounds based on their lower content. While the forested and sloping catchment of the Einsied Reservoir provided high amounts of organic matter that was deposited into the reservoir, the comparatively lower organic matter contents in the BSP sediments can be explained by a high proportion of less organic-rich agricultural soils in the catchment. Negative correlations between sediment pH and metal(loid) concentrations varied between the Einsiedel Reservoir and BSP samples. As mentioned above (Section 3.2.3), the negative correlation between Fe and pH was interpreted as a result of the oxidation of Fe during sediment drying. In the Einsiedel Reservoir sediments, the negative correlations between pH and concentrations of Cr, Fe and V could be due to the preferential association of these lithogenic elements, which is at least supported by the fact that Fe, Cr and V were strongly positively correlated with each other. A primarily lithogenic origin of Cr and V was evidenced by the fact that the concentrations of both elements in the Einsiedel Reservoir samples fell below or only slightly exceeded their geogenic background. However, in the BSP sediments, Fe seemed to be more associated with Cd and As as indicated by the high positive correlations. On the one hand, this phenomenon can be explained by the ability of Fe compounds to preferentially adsorb high amounts of As and Cd [58; 59]. On the other hand, it also seems possible that these metal(loid)s rely on the same component of BSP sediments such as residues of Fe-, As- and Cd-rich ones.  
In contrast, the soil samples were more strongly characterised by soil profiling, which was expressed in less frequent correlations between the metal(loid)s themselves than found for the reservoir sediments. Horizon-specific differences were evident in the strong positive correlations between organic matter and As and Pb. This phenomenon relies on the accumulation of both elements in organic and fine-particle-rich toposils after atmospheric  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & **As** & **Cd** & **Cu** & **Cr** & **Hg** & **Ni** & **Pb** & **Zn** \\ \hline
**Precutionary values** for loam/silt & - & 1 & 40 & 60 & 0.5 & 50 & 70 & 150 \\
**Examination values** for the direct intake of pollutants & 125 & 50 & - & 1000 & 50 & 350 & 1000 & - \\ from park and leisure facilities (mg/kg) & & & & & & & & \\
**Action values** for the pathway soil-plant on & 50 & 20 & 1300 & - & 2 & 1900 & 1200 & - \\ grassland (mg/kg) & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 9: Legal guideline values according to Annex 2 of the Federal Soil Protection Ordinance [19].  
deposition [45] and has also been observed in catchment soils of the Klingenberg Reservoir [60]. In contrast, the fact that Co and Ni were negatively correlated with organic matter and clay content and positively correlated with soil pH proves the enrichment of both elements in the subsoil horizons. The lithogenic elements Cr and V were strongly positively correlated in catchment soils, indicating that no significant redistribution or separation of concentrations of the two elements occurred during erosion, transport and deposition as reservoir sediment. Oppositely, the soils showed no correlation between the concentrations of As and Co, which were strongly positively correlated in the Einsiedel Reservoir sediments, which could be due to the similar adsorption behaviour of both elements after deposition as reservoir sediment.