Sweden's rare earth mine tailings pose long-term water contamination risk
Swedish researchers have mapped toxic elements lurking in tailings from the Kiirunavaara iron ore mine, finding high concentrations of rare earth elements and sulfates that could leach into groundwater for decades. The findings highlight a blind spot in mining regulation: neutral drainage conditions were thought safe, but may pose serious risks to water supplies and downstream ecosystems.
Originaltitel: Geochemical characterisation of AIO mine tailings enriched in REE influenced by neutral mine drainage environment, Northern Sweden
Kiruna-gruvan i Sverige lagrar tailings rika på sällsynta jordartsmetaller under neutrala dräneringförhållanden – en miljökontext som tidigare ignorerats trots riskerna för spridning av spårämnen. Luleå tekniska universitet och LKAB kartlade geokemiken i tio meter djupa kärnprov och grundvattnet från apatit-järnmalms-tailings. Materialet består huvudsakligen av silikater (74 %), tillsammans med mindre mängder sulfider och sulfater. Sällsynta jordartsmetaller lagras primärt i oförändrad apatit (1100 ppm lätta, 180 ppm tunga element). Trots höga halt i mineralet är REE-mobiliteten låg i grundvattnet – genomsnittligt endast 0,29 µg/L – eftersom miljön är cirkumneutral till alkalisk och mestadels anaerob. Sulfidmineraler oxideras minimalt, men gips och anhidrit löses upp gradvis, vilket höjer sulfat- och kalciumkoncentrationer vid snösmältning. Resultaten är relevanta för långsiktiga tipphanteringsstandarder och för att bedöma miljörisker vid malmbrytning av REE-innehållande förekomster.
<p>Tailings affected by neutral mine drainage (NMD) have received comparatively little attention despite their potential to release trace elements, including rare earth elements (REE) and sulphate to downstream hydrological systems. This study presents a comprehensive geochemical characterisation of apatite iron ore (AIO) tailings from Kiirunavaara mine in northern Sweden, providing baseline geochemical and mineralogical data needed to evaluate the long-term stability of REE and other elements of potential concern in NMD conditions. Three vertical cores (KI_01, KI_02, and KI_03; up to 10 m deep) and groundwater samples were examined. The tailings were dominated by silicate minerals (ca. 74 wt%, albite, biotite, quartz, actinolite) with smaller amounts of carbonates (calcite, dolomite), sulphides (pyrite, chalcopyrite) and sulphates (gypsum, anhydrite). Hydraulic sorting during deposition created clear textural and compositional differences, with coarser material near the discharge points and finer material further away. The tailings contained average light REE and heavy REE content of 1100 ppm and 180 ppm, respectively, hosted in primarily unaltered apatite with minor monazite and allanite. This is supported by strong correlations between REE, P, F and As, and by intact grain boundaries in mineral analyses. The groundwater in the tailings was circumneutral to alkaline (pH 6.8–9.7) and mostly anoxic. Dissolved REE concentrations in groundwater were low, with ΣREE average value of 0.29 µg/L, showing that REE mobility is limited under current conditions. Sulphide minerals displayed minimal oxidation, reflected by low dissolved O2 and the absence of secondary iron phases, suggesting restricted oxygen ingress. In contrast, gypsum and anhydrite showed signs of dissolution, contributing to elevated sulphate and calcium in groundwater, especially during spring melt. </p>