Adding Agricultural Topsoil and Growing Perennial Ryegrass (Lolium perenne L.) Enhanced the Rehabilitation of Metal/loids Enriched Iron Ore Mine Tailings

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Abstract

Revegetating iron-ore mine tailings is difficult due to their poor physicochemical and microbial properties. This experiment aimed to improve tailings properties for better plant growth and rhizosphere activities. First, a pot experiment was
conducted to assess the influence of topsoil amendment on the remediation of tailings collected from two sites (coded A
and B) in Western Australia to promote the growth of perennial ryegrass (Lolium perenne L. cv Ausvic). Each pot was
filled with pre-defined ratios of topsoil to mine tailings (0, 10, 20, 30, 50 and 100% w/w). Perennial ryegrass was harvested 60 days after sowing and analysed for plant growth, root morphological characteristics and metal uptake by shoots.
Second, a study on biological attributes and an incubation study over 84 days were carried out. The addition of topsoil
significantly decreased pH, but EC and total organic carbon (TOC) increased with an increased proportion of topsoil. Total
concentrations of As, Co, Cr, Cu, Ni, Pb, Zn, Fe and Mn decreased with an increased ratio of topsoil in growth medium.
The highest root dry biomass was observed in the treatments with 30% and 50% topsoil addition to tailings, whereas shoot
dry biomass only increased with 50% topsoil. Total root length increased significantly with 50% topsoil addition to site A
tailings. A significant increase in microbial biomass carbon (MBC) was found with 50% addition of topsoil compared with
the control. Microbial quotient (MBC/TOC) decreased significantly with the addition of topsoil to both types of tailings.
Metal contents in perennial ryegrass shoots decreased with the increasing rate of topsoil, but perennial ryegrass was an
effective phytoextractor of Cu, Zn and Mn. Further, the incubation study revealed that 50% topsoil application increased
cumulative respiration emissions in both A and B tailings after 42 days. Iron ore mine tailings can be improved in terms
of physicochemical and biological attributes by adding topsoil. However, further investigation should be carried out to
determine the speciation of metal/loids in amended iron ore tailings
Original languageEnglish
JournalJournal of Soil Science and Plant Nutrition
DOIs
Publication statusE-pub ahead of print - 18 Mar 2024

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