# Spatial Mobility of U and Th in a U-enriched Area (Central Portugal)
## 3 Results and Discussion
### Contamination Indexes
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{3}{c}{**Mine Dumps**} & \multicolumn{3}{c}{**Stream Sediments**} \\  & **Min** & **Max** & **Med** & **Min** & **Max** & **Med** \\ \hline Fe & 0.9 & 2.3 & 1.4 & 0.7 & 1.1 & 0.9 \\ Mn & 0.5 & 1.7 & 1.0 & 0.4 & 1.4 & 0.7 \\ Ba & 0.2 & 0.8 & 0.5 & 0.4 & 1.6 & 1.0 \\ Cr & 0.3 & 0.9 & 0.6 & 0.2 & 1.7 & 1.0 \\ Zn & 0.7 & 1.6 & 1.1 & 0.6 & 2.8 & 1.7 \\ Pb & 0.6 & 3.9 & 1.0 & 0.5 & 1.8 & 1.2 \\ As & 1.3 & 9.3 & 3.6 & 0.2 & 2.0 & 0.8 \\ W & 0.9 & 16.1 & 5.3 & 0.4 & 3.8 & 1.5 \\ U & 1.0 & 34.4 & 17.6 & 0.1 & 3.4 & 0.7 \\ Th & 0.8 & 2.5 & 1.8 & 0.4 & 1.3 & 0.8 \\ CD & 11.6 & 54.1 & 34.7 & 8.7 & 14.5 & 11.4 \\ \hline \end{tabular} Min—minimum; Max—maximum, Med—median. Contamination factor: low contamination for CF \(<\) 1 (black color); moderate contamination for CF 1-3 (green color); high contamination for CF 3-6 (blue color); very high contamination for CF \(>\) 6 (red color). Contamination degree CD = sum of CF: low contamination degree with CD \(<\) 13; moderate contamination degree with CD 13-26; high contamination degree with CD 26-39; very high contamination degree with CD \(>\) 39.  
\end{table} 
Table 3: Values of contamination factor and contamination degree of mine dumps and stream sediments from Canto Lagar. Figure 3: Percentage of contamination factor classes in the Canto Lagar area. The background values from Portugal for Zn, As, U, and Th (Zn = 60 ppm; As = 6.0 ppm; U = 5 ppm, and Th = 18 ppm; [31]) were lower than background reference values considered for Canto Lagar, regarding the geological and mineralization settings of this U-enriched region. Almost all sediments from the Canto Lagar area showed an increase in the contamination index for Zn, As, U, and Th relative to Portuguese background values, which show moderate to very high contamination (Figure 4). The average contents of Cu, Zn, As, W, Pb, and U and maximum values of Zn, Th, and U (Table 4) exceeded the reference values from the European Geochemical Atlas [32]. In general, soils from the Canto Lagar area presented higher median values for Zn, As, Cs, W, Th, and U and higher values for U (Table 5) than the values included in the Geochemical Atlas of Europe [32]. There are no Portuguese-legislated standard values for soil contamination. Consequently, the soil standards from Ontario were applied in this study. The soil from the Canto Lagar uranium mine area was contaminated by As and U and cannot be used in agricultural or residential occupations (Table 5), \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Canto Lagar Area**} & \multicolumn{3}{c}{**Geochemical Atlas of Europe**} \\  & **Minimum** & **Maximum** & **Median** & **Minimum** & **Maximum** & **Median** \\ \hline Fe & 1.3 & 4.3 & 1.8 & 0.06 & 20.0 & 1.97 \\ Mn & 0.0 & 0.1 & 0.0 & 24.0 & 18900 & 452 \\ Cr & 3.1 & 13.8 & 5.2 & 2.0 & 1750 & 21.0 \\ Cu & 3.7 & 30.3 & 17.0 & 1.0 & 998 & 14.0 \\ Zn & 63.2 & 157.1 & 90.7 & 7.0 & 11.0 & 60.0 \\ As & 4.0 & 171.2 & 18.3 & \(<\)5 & 231.0 & 6.0 \\ W & 0.6 & 20.3 & 2.0 & \(<\)0.05 & 82.0 & 1.2 \\ Pb & 9.6 & 70.7 & 18.1 & \(<\)3 & 4880 & 14.0 \\ Th & 8.9 & 62.7 & 25.6 & \(<\)1 & 13.9 & 253 \\ U & 19.0 & 4540.1 & 131.9 & \(<\)1 & 98.0 & 2.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of Fe (%) and selected potential toxic element (mg/kg) contents from Canto Lagar sediments and Geochemical Atlas of Europe. Figure 4: Comparison of contamination factor classes percentage for Zn, As, U, and Th using Canto Lagar background values (CL) and Portuguese background values (Pt). in accordance with the soil standards from Ontario [33]. Moreover, roughly all soils could be applied in commercial and/or industrial occupations.