Natural radioactivity and element characterization in pit lakes in Northern Sweden

• Published in: PLOS ONE
• Main Authors: Thomas, R., Mantero, J., Ruiz Cánovas, Carlos, Holm, E., García-Tenorio, R., Forssell-Aronsson, Eva, Isaksson, Mats
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2022
• Subjects: 2506 Geología; Northern Sweden
• Online Access: https://hdl.handle.net/10272/21946; https://doi.org/10.1371/journal.pone.0266002

Northern Sweden has been the object of intense metal mining in the last decades producing several water-filled open-pits, or pit lakes. Most of these pit lakes have been limed to maintain a good water quality and to prevent generation of acidic water that could leach the exposed rocks and release metals into water. The aim of this work was to examine the concentration of stable elements and naturally occurring radionuclides in water and sediment samples from pit lakes originating from non-uranium mining activities in Northern Sweden. Surface water and surface sediments were collected from 27 pit lakes in Northern Sweden. Water quality parameters, concentration of stable elements and radionuclides were measured by a water probe, ICP-MS and XRF, and alpha and gamma spectrometry, respectively. Furthermore, a multivariate statistical analysis (PCA) was performed on the water samples and sediments. In general, the quality of the surface water was good, but some lakes had low pH values (2.5–5.7), and high concentrations of Fe (up to 200 mg/L) and other metals (e.g. Zn, Cu). When relating the metal concentrations in sediments in pit lakes with the concentration found in natural lakes, some sites had relatively high levels of Cu, As, Cr and Pb. The activity concentration of 210Po, and U and Th isotopes in water and sediment samples were at environmental levels, as was the ambient dose equivalent rate at these sites (range 0.08–0.14 μSv/h). Financial support was granted by the Swedish Radiation Safety Authority (SSM2014-3485). The authors acknowledge the support from the X-Ray Laboratory staff (XRF measurements) placed at CITIUS facilities at University of Seville. Furthermore, we are grateful to the Applied Nuclear Physics Group, University of Seville, for its continuous technical support during the different stages of this project. We also thank Boliden AB and LKAB for giving access to several of the mining sites and for providing details on the closed mines. One of the authors (JM) acknowledges the support to this ...