Proof-of-concept of polymetallic phyto-extraction of base metal mine tailings from Queensland, Australia

Abstract

Purpose The increasing volumes of mine tailings that are being generated globally because of the rise in metal demand, whilst ore-grades continue to decline, call for novel sustainable management options. Phytoextraction using hyperaccumulator plant species may be one of such strategies to deal with these large volumes of contaminated materials. However, base metals (such as zinc, lead, copper) mine tailings are inherently polymetallic that necessitate targeting multiple metal(loid)s simultaneously for effective phytoextraction. The aim of this study was to conduct a proof-of-concept experiment for polymetallic phytoextraction of base metal mine tailings. Methods Selected hyperaccumulator plants (Noccaea caerulescens targeting zinc, Biscutella laevigata and Silene latifolia targeting thallium, Phytolacca octandra targeting manganese, Pityrogramma calomelanos targeting arsenic) were grown in monocultures and mixed cultures for 12 weeks on tailings from the zinc-lead-copper Dugald River and Mt Isa Mines, Queensland, Australia. Results Noccaea caerulescens accumulated zinc and manganese (up to ~ 1 wt% and ~ 1.4 wt%, respectively) with zinc-manganese co-localization at the leaf apex and margins. The monocultured B. laevigata exhibited severe toxicity symptoms, which were alleviated when co-cultured with N. caerulescens. Trichomes were important storage sites for zinc and manganese in B. laevigata. Silene latifolia accumulated higher thallium than B. laevigata, whilst P. octandra promoted thallium accumulation in S. latifolia. Conclusions This proof-of-concept test of polymetallic phytoextraction provides a real-life demonstration of this innovative technology which could be adapted to further experiments at base metal mines around the world.