Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman Research article Blended pulp mill, forest humus and mine residual material Technosols for mine reclamation: A growth-chamber study to explore the role of physiochemical properties of substrates and microbial inoculation on plant growth Asma Asemaninejad a,* , Jessica Arteaga a , Graeme Spiers a,b , Peter Beckett a,c , Samantha McGarry d , Nadia Mykytczuk a,b , Nathan Basiliko a,c a Laurentian University, Vale Living with Lakes Centre, 935 Ramsey Lake Road, Sudbury, Ontario, P3E 2C6, Canada b Laurentian University School of the Environment, Canada c Laurentian University Department of Biology, Canada d Sudbury Integrated Nickel Operations, A Glencore Company, Canada ARTICLE INFO Keywords: Bacteria Metals Germination Ryegrass Reclamation Sludge ABSTRACT A growth chamber trial was conducted to investigate the effects of blends of pulp and paper mill residuals and forest humus on soil properties, microbial communities and germination rate and biomass production of annual ryegrass (Lolium multiflorum) in both acid-producing and neutral to mildly alkaline mine tailings in a mine reclamation context. The organic residual amendments improved the nutritional status of the tailings substrates, and increased pH in acid-generating tailings, leading to higher germination rates and improved plant growth. A trace addition (< 0.02% of sludge by dry weight) of natural forest floor material as a microbial inoculum 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 copper (Cu) and nickel (Ni) increasing in some of the substrates following organic amendments. Addition of paper mill residuals to mine tailings modified the microbial com- munities 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 rather than the chemolithotrophic communities that dominate tailings environments. 1. Introduction Mine tailings, the principal solid residuals generated from metalli- ferous mining activities (Santibáñez et al., 2008), are prone to high concentrations of heavy metals that are potentially toxic to plants and soil biota (Hue, 1995). Vast volumes of these tailings are disposed on mining sites, and depending on the effluent containment and processing controls in place, can pose several threats to the environment (Dudka and Adriano, 1997). The exposure of sulphide minerals such as pyrite and pyrrhotite to atmospheric oxygen triggers the production of sul- phuric acid-containing mine drainage that can significantly reduce soil pH leading to mobilization of heavy metals at toxic concentrations (Akcil and Koldas, 2006; Kuyucak, 2006). Additionally, the absence of organic matter and nutrients, low water holding capacity, and high bulk density of mine tailings (Hue, 1995; Wong et al., 1998; Ye et al., 2002) interactively suppress seed germination and successful establishment of vegetative caps (Mendez et al., 2007) that play an important role in the containment of mine tailings (Brooks, 1998). As a result, water erosion and aeolian dispersion of tailings off the sites can lead to the con- tamination of adjacent ecosystems and food webs (Johnson et al., 1977; Dudka and Adriano, 1997; Green and Renault, 2008). Amongst most reclamation strategies where the primary aim is the prevention of the exposure of metal-rich sulphidic mineral wastes to air and water (Feasby et al., 1997), the addition of organic residual ma- terials either by mixing or usage as covers has proven a useful and more cost-effective method compared to other approaches (Tordoff et al., 2000; Watkinson et al., 2017). The organic amendments can stimulate soil formation and improve fertility and water holding capacity, pro- viding a suitable growth matrix for revegetation (Beauchamp et al., 2006). They can also alter the structure of microbial communities, causing a shift from potentially acid-generating chemolitoautotrophs, that are the dominant microbes in the mine wastes, to more soil-like https://doi.org/10.1016/j.jenvman.2018.08.114 Received 28 April 2018; Received in revised form 24 August 2018; Accepted 31 August 2018 * Corresponding author. E-mail address: aasemaninejad@laurentian.ca (A. Asemaninejad). Journal of Environmental Management 228 (2018) 93–102 0301-4797/ © 2018 Elsevier Ltd. All rights reserved. T