Tailings surface cover development through integration of reactive phosphate and organic matter

Abstract

In 1993, two 0.5 ha experimental plots were set up on inactive uranium tailings in Elliot Lake and on fresh pyrrhotite tailings at Copper Cliff, Ontari o. Phosphate rock and horse manure were mixed into the tailings surfaces by a roto-tiller. Field plots were investigated using electromagnetic resistivity measurements 39 months (Copper C liff) and 45 months (Elliot Lake) after set up. Resistivity measurements on the pyrrhotite tailings when modeled showed distinct differences between treatment plots, with phosphate treatments having the highest resistivity. At the same time, treatment plots were sampled both within and below the amended tailings surface stratum. The samples were stored for 5.5 years (Copper C liff) and 6.5 years (Elliot Lake), respectively, at room temperature in the dark. Slurries (1:5 w:v) to assess the chemistry, simulating pore water in the tailings layer were made. The supernatant was monitored for 22 months by periodically measuring pH, redox potential, electrical conductivity, and acidity . At the end of the monitoring period, the elemental composition of the supernatant was determined by ICP. Principal component analyses (PCA) were applied to parameters that were measured in the simulated pore water. With the PCA performed on the water quality data, differences in treatment conditions were determined within the uranium tailings and the base metal tailings plots. It was possible to discriminate between treatment conditions in term s of pore water characteristics in the uranium and the base metal pore water. The PCA indicated that the pyrrhotite tailings treatment with high horse manure and high phosphate generated distinct water quality conditions, but only in the amended surface layer at a depth of 7.5 cm. High horse manure and high phosphate improved the pore water quality in both tailings types.