# Spatial Mobility of U and Th in a U-enriched Area (Central Portugal)
## 4 Conclusions  
The spatial variation in the concentration of potentially toxic elements in mine dumps, stream sediments, and soils from a U-enriched area was studied, and the potential contamination degree was evaluated according to international contamination indexes and contamination soil guide values.  
The mobility of elements from mine dumps to stream sediments was relatively low. However, some sediments and soils from the area were contaminated. Considering the reference values for remediation purposes, the area is an appropriate subject for improvement and remediation proposals. The mine dumps represent an environmental risk because they can promote contamination with spatial mobility and dispersion of potentially toxic elements from the dumps to the sediments and soils, as well as by surface runoff and wind. The obtained results suggest that remediation must be done in the whole area, including the cover of mine dumps. The application of adequate remediation processes must be undertaken in the soils and sediments.  
Future work requires an exhaustive, well-defined spatial design campaign that could be applied to understand the dynamic processes of potentially toxic elements and to identify the main sources for these elements and the local enrichment around the uranium mine area. The future application of multivariate and geostatistical methodologies will promote reconnaissance and consequently will allow adequate monitoring procedures to be defined in this area or similar ones.  
All authors have contributed extensively to the work presented in the paper. [PERSON] and [PERSON] were involved in fieldwork design, sampling, and laboratory analysis. All were involved in results, evaluation, and discussion. [PERSON] wrote the manuscript with the contribution and editing of all the co-authors. All authors have read and agreed to the published version of the manuscript.  
This research was funded by FCT--Fundacao para a Ciencia e a Tecnologia, I.P., grant number FCT-SFRH/BPD/64921/2009 and Nano-MINENV PTDC/CTA-AMB/29259/2017.  
The authors thank FCT--Fundacao para a Ciencia e a Tecnologia, I.P., through the project's reference SFRH/BPD/64921/2009, UIDB/04683/2020, UIDP/04683/2020, and reference Nano-MINENV PTDC/CTA-AMB/29259/2017.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Canto Lagar**} & \multicolumn{3}{c}{**Geochemical Atlas of Europe**} & \multicolumn{3}{c}{**Canadian Soil Guidelines**} \\ \cline{2-9}  & **Minimum** & **Maximum** & **Median** & **Minimum** & **Maximum** & **Median** & **Agricultural** & **Residential** \\  & & & & & & & & **Parkland** \\ \hline Fe & 1.51 & 2.53 & 1.96 & 0.1 & 15.2 & 1.96 & - & - \\ Mn & 0.02 & 0.08 & 0.04 & \textless{}10 & 6480 & 382 & - & - \\ Cr & 3.38 & 13.36 & 6.30 & 1 & 2340 & 22 & 64 & 64 \\ Cu & 3.07 & 171.41 & 21.06 & \textless{}1 & 118 & 13 & 63 & 63 \\ Zn & 57.97 & 134.86 & 86.04 & 4 & 2270 & 48 & 200 & 200 \\ As & 4.68 & 60.48 & 20.11 & 5 & 220 & 6 & 12 & 12 \\ Cs & 3.49 & 61.53 & 19.03 & \textless{}0.5 & 69.1 & 3.71 & - & - \\ Zr & 0.23 & 9.55 & 1.09 & 5 & 1060 & 231 & - & - \\ Ba & 12.97 & 59.72 & 34.29 & 10 & 1700 & 65 & 750 & 500 \\ W & 0.54 & 2.93 & 1.13 & \textless{}5 & 14 & \textless{}5 & - & - \\ Pb & 9.08 & 32.8 & 18.71 & \textless{}3 & 15 & 886 & 70 & 140 \\ Th & 15.81 & 54.8 & 34.24 & 0.3 & 75.9 & 7.24 & - & - \\ U & - & 1561.06 & 109.2 & 0.2 & 53.2 & 2.03 & 23 & 23 \\ \hline \hline \end{tabular} All soil concentrations are in mg/kg, while Fe and Mn are expressed in percent.  
\end{table}
Table 5: Comparison of potentially toxic elements values of soil from Canto Lagar area with European values and reference values of Canadian guidelines.