Pulp mill and mine residual materials blended to manufacture techno sols for mine reclamation: a growth-chamber study to explore the role of substrates and microbial inoculation on plant growth and microbial communities. Mine tailings reclamation

A growth chamber trial was conducted to investigate blends of pulp and paper mill residuals with mine tailings seeded with annual ryegrass (Lolium multiflorum) in a mine reclamation context. The organic residual amendments improved the nutritional status of the tailings substrates, specifically increasing pH in acid-generating tailings, with higher germination rates and improved plant growth, and a trace addition (<0.02% of sludge by dry weight) of natural forest floor material as a microbial inoculum added to the sludge could increase plant biomass up to four-fold. The effects of sludge application on bioavailability of metals were variable, with the concentration of soluble Cu and Ni increasing following organic amendments addition. Addition of paper mill residuals to mine tailings modified the microbial communities observed in the oligotrophic tailings with the majority of DNA sequences in the sludge amended substrates being found to be closely related to heterotrophic bacterial species.