Distribution of Zinc, Copper, and Iron in the Tailings Dam of an Abandoned Mine in Shimokawa, Hokkaido, Japan

Abstract

This paper addresses the mechanism of acid mine drainage generation in tailings from an abandoned mine site and predicts the evolution of zinc (Zn), copper (Cu), and iron (Fe) concentrations. Batch leaching experiments and sequential extractions were conducted to investigate the leaching behavior of these contaminants from the tailings and to understand their solid-phase partitioning. Acid-base accounting and principal component analysis (PCA) were used to confirm factors affecting Zn, Cu, and Fe leaching and acid formation based on the leaching experiments. There were strong positive correlations between Zn, Fe, or EC and SO42−, indicating that pyrite and sphalerite are the major minerals releasing Zn and Fe. This aligns with the PCA results. In the upper part of the tailings, the water-soluble and sulfide fractions of Zn, Cu, and Fe were almost flushed out, whereas they remained high in the deeper tailings. This implies that the tailings will likely continue to release these contaminants (Zn > Cu > Fe) for a long time unless remedial measures are taken.