Amendment-assisted revegetation of mine tailings: improvement of tailings quality and biomass production

Abstract

Mining activities have left a legacy of metals containing tailings impoundments. After mine closure, reclamation of mine wastes can be achieved by restoration of a vegetation cover. This study investigated the impact of biochar (BC), biosolids (BS), humic substances (HS), and mycorrhizal fungi (MF) for improving mine tailings fertility and hydraulic properties, supporting plant establishment, tailings revegetation, and enabling growth of energy crops. We conducted a pot trial by growing willow, poplar, and miscanthus in Pb/Zn/Cu mine tailings untreated or amended with two rates of amendments (low or high input). Biosolids resulted in the most significant changes in tailings properties, neutralizing pH and increasing organic carbon, nutrient concentrations, cation exchange capacity, water retention, and saturated hydraulic conductivity. The greatest increase in energy crops production was also observed in BS treatments enabling the financial viability of mine reclamation. Although BC resulted in significant improvements in tailings fertility and hydraulic properties, its impact on biomass was less pronounced, most likely due to lower N and P available concentrations. Increases in willow and miscanthus biomass were observed in HS and MF treatments in spite of their lower nutrient content. A pot experiment is underway to assess synergistic effects of combining BS with BC, HS, or MF.

Keywords:

• Mine tailings
• mycorrhizal fungi
• nutrient
• organic amendments
• revegetation

Acknowledgments

Assistance from Mr. Chris Neaville and Genevieve Sutton at Doe Run for facilitating tailings collection is gratefully acknowledged. TerraPro and MycoMaxima Professional products, used for humic substances and mycorrhiza inoculum, were provided by the Soil Secret Company. The authors would like to thank Paul Manley who has provided valuable edits to our manuscript and also Dr. Mark Fitch, Dr. Matt Limmer, and Dr. Honglan Shi for experimental design insight and analytic assistance, Dr. Xiong Zhang and his group in Geotechnical Laboratory were of great assistance with hydraulic tests, and fellow students Cory Pollpeter and Jenna Gruner for helping with the experiments and greenhouse operations.

Additional information

Funding

This study was funded in part by the Doe Run Company.