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Vaisanen U.,Ulpu Vaisanen Geologian tutkimuskeskus | Hirvasniemi H.,Ulpu Vaisanen Geologian tutkimuskeskus | Kouri P.,Ulpu Vaisanen Geologian tutkimuskeskus | Kupila J.,Ulpu Vaisanen Geologian tutkimuskeskus | And 2 more authors.
Tutkimusraportti - Geologian Tutkimuskeskus | Year: 2015

In this report, the results of geochemical studies in the Kemi Mine area as a part of the mining environmental project of ENVIMINE are presented. The project was carried out in 2012–2014, in cooperation between the Geological Survey of Finland (GTK), Luleå University of Technology (LTU), Sweden, and the Mining Institute, Kola Science Centre, Russian Academy of Sciences (MI KSC RAS), Russia. The study area in Russia was the closed mine of Umbozero and in Sweden the closed mine of Laver. The Kemi Mine was chosen as the study area of Finland due to the abundance of monitoring data on its environmental impacts, and information on the present state. The mine provides an example of what type of data is collected during mining, and how it can be exploited during mine closure. One aim of the project was to update the database on the mine site by means of previous and new research data. New research included mapping of surficial deposits, fieldwork and geochemical sampling. Geochemical studies were conducted by analysing organic bottom sediments in the tailings and streams and surface waters in the mine sites and reference areas. Based on water analyses at the Kemi Mine, indicative elements for tailings water contamination were nitrate (NO3), sodium (Na) and chromium (Cr). The concentrations of the effluents markedly decreased in downstream waters of the mine. Cr was mainly bound to solid particles in waters of the facility and downstream creek waters. Therefore, Cr in downstream waters does not cause toxic impacts on the biota. The chemical behaviour of the several trace metals, especially manganese (Mn), zinc (Zn) and lead (Pb), but also copper (Cu), molybdenum (Mo), arsenic (As) and selenium (Se), suggests that they could originate from peat in the neighbouring bog rather than from the tailings facility. This argument is based on their mobility (acetate extractability) in peat next to the facility. The results demonstrated that most of the phosphorus (P) in the stream sediments is discharged from the drained bogs next to the facility. The occasional increase in P concentrations in the settling pond and seepage well waters originated from the pad peat sediments rather than from the tailings fines. Overall, it can be concluded that the potential impact of tailings effluents on watercourses is more connected with turbidity (fine solids, salinity), despite the NO3 effluent. Cr effluents into downstream watercourses consist of Cr-bearing solid particles, which appear to be inert in the neutral creek waters. © 2015, Geological Survey of Finland. All rights reserved.

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