# Heavy Metals in Post-Exploitation Reservoirs--The Bagry Lake Case Study (Poland)
## 3 Results  
### Sediment  
A mineral fraction in the sediment ranges from 0.812 to 0.987 g/g dry matter (d.m.) (0.9142 \(\pm\) 0.0456 g/g d.m.) with an average of 91.4% d.m. while the volatile organic fraction is definitely lower and varies from 0.013 to 0.188 g/g d.m. (0.0858 \(\pm\) 0.456 g/g d.m. ), with an average of 8.58% d.m. Moreover, the fractions with a diameter \(\geq\) 0.06 mm (sand fraction) and \(<\)0.06 mm (fine fraction with silty clay and clay fractions) were analyzed in the sediment. Particles with a diameter \(\geq\) 0.06 mm predominate in the dry mass of the sample; they vary from 60.64 to 94.60% (79.38 \(\pm\) 9.39%). The mass fraction of particles with a diameter \(<\) 0.06 mm is smaller and ranges from 5.40 to 39.36% (20.62 \(\pm\) 9.39%). It was noticed that the volatile fraction (\(1-y\)) decreases with a higher concentration U\({}_{\rm d}\) of particles \(\geq\)0.06 mm and increases along with U\({}_{\rm d}\) for particles \(<\)0.06 mm (Figure 2). Additionally, a mineral fraction \(y\) gets smaller when the fine fraction U\({}_{\rm d}\) (\(<\)0.06 mm) increases; it increases along with U\({}_{\rm d}\) for particles \(\geq\)0.06 mm (Figure 2). The above observations indicate that the mineral fraction is mainly associated with a sand fraction while the volatile fraction is mainly associated with a fine silty clay and clay fractions. Figure 2: Mineral and volatile fractions vs. particles of different diameters in the sediment. Table 1 summarizes the average metal concentration in the dry sediment mass, standard deviations and the minimum and maximum values calculated on the basis of the analysis results for the whole lake. A negative correlation between the sediment mineral fraction and its metals concentration is observed for Fe, Mn, Cu, Pb, Zn and Ca (Figure 3); such correlation is not true in case of Cd (positive correlation). Therefore, a high mineral fraction will be followed by a generally lower concentration of Fe, Mn, Cu, Pb, Zn and Ca in the sediment, except for Cd (Figure 3). Mostly, it means that metals tend to accumulate in the volatile fraction while cadmium, on the other hand, will accumulate in mineral matter. A positive correlation between the fine particles (<0.06 mm) and the metals in the sediment is observed for Fe, Mn, Cu, Pb, Zn and Ca (Figure 4); only for Cd the correlation is negative. Since the fine fraction (<0.06 mm) comprises both mineral and organic matter it means that fine particles predominate in accumulation of metals, except for Cd. An increase in the fine fraction <0.06 mm (Figure 4) is followed by higher metal concentration in the sediment, again except for Cd. For the fraction \(\geq\)0.06 mm (Figure 4), the opposite is true: its higher concentration in the sediment results in a lower metal concentration, except for Cd (Figure 4). Therefore, looking at the line (Figure 4) in Figure 3, it can be assumed that metals accumulate in the fine volatile fraction (<0.06 mm, Figure 4) of the sediment but not in the fine mineral fraction (see a blue line in Figure 3). In the case of Cd, the opposite it true: Cd accumulates mainly in the mineral fraction (Figure 3) with particles \(\geq\) 0.06 mm (Figure 4). \begin{table}
\begin{tabular}{c c c c c c c} \hline  & **Fe** & **Mn** & **Cu** & **Pb** & **Zn** & **Cd** & **Ca** \\  & **[g Fe/kg d.m.]** & **[mg Mn/kg d.m.]** & **[mg Cu/kg d.m.]** & **[mg Pb/kg d.m.]** & **[mg Zn/kg d.m.]** & **[mg Ca/kg d.m.]** & **[g Ca/kg d.m.]** \\ \hline Average & 16.04 & 292.7 & 65.53 & 24.33 & 122.9 & 0.7709 & 64.45 \\ \hline Standard deviation & 9.803 & 159.4 & 42.06 & 13.65 & 84.48 & 0.5845 & 32.27 \\ \hline Min= & 3.162 & 61.60 & 2.113 & 1.962 & 25.35 & 0.1592 & 28.70 \\ \hline Max= & 36.03 & 566.4 & 161.0 & 54.11 & 321.0 & 1.831 & 144.8 \\ \hline \end{tabular}
\end{table} 
Table 1: Metals concentrations in the sediment (d.m.—dry matter). Figure 3: Correlation R between different fraction of the sediment and a metal’s concentrations. Figures 5-10 show the metal concentration maps for Fe, Mn, Cu, Pb, Zn and Cd in the lake sediment.