Microscale measurements of oxygen diffusion and consumption in subaqueous sulfide tailings

The disposal of sulfide mine tailings in an environmentally sound, yet cost -effective, manner is an issue facing most metal mines. Subaqueous tailing disposal is considered an attractive option for disposal that limits oxygen (O-2) availability within sulfide mine tailings and controlling sulfide ox idation and the resultant acid mine drainage (AMD). Assuming that O-2 profi les represent steady-state conditions, we aim to evaluate the depth-depende nt and temperature-dependent rates of O-2 consumption in saturated mine tai lings. Measurements include microscale O-2 gradients and diffusivity profil es within columns representing undisturbed mine tailing profiles from an im poundment near Nanisivik Mine in northern Canada. Measurements were made ac ross the diffusive boundary layer (DBL) above the tailing-water interface a s well as in the tailings below. Laboratory measurements of O-2 profiles ar e compared to in situ profiles. From the laboratory results it is possible to evaluate the O-2 flux across the DBL and the depth-integrated O-2 uptake . The results are compared with the average sulfate production rate over 3 months. O-2 uptake in saturated tailings is discussed in relation to O-2 up take measured in columns after free drainage. The methods applied provide c onsistent O-2 consumption rates as well as reliable predictions for control ling AMD by keeping tailings under water. Copyright (C) 2001 Elsevier Scien ce Ltd.