Assessing metal transfer to vegetation and grazers on reclaimed pyritic Zn and Pb tailings

Abstract

A study of the concentrations of zinc and lead in an engineered soil capping system overlying sulphide mine tailings was undertaken. Tailings geochemistry, soil cover and vegetation were monitored over a 4-year period, and a cattle grazing demonstration exercise was conducted over a 1-year period. Whilst the tailings had a relatively high pyrite content and demonstrated oxidation, a circum neutral pH was observed for the duration of the study period due to the high dolomitic content. No evidence of metal mobility into the soil cover and vegetation was observed over the monitoring period. Relatively high Zn herbage content is attributed to the glacial till component of the soil cover. Similarly, no evidence of metal transfer to grazing cattle was observed through blood and tissue analysis with Zn content not significantly different from control animals. Pb tissue content was below limit of detection.

Initiation of soil formation in weathered sulfidic Cu-Pb-Zn tailings under subtropical and semi-arid climatic conditions

“…Sulfidic metal mine tailings (e.g., Cu, Pb-Zn, Fe ore) are mineralogicallly and chemically different from natural soil, which are much more abundant in primary minerals (e.g., pyrite, chalcopyrites) with unstable geochemistry and inherent extreme toxicity (Li and Huang, 2015). Natural weathering of these primary minerals, especially pyrite is shown to be relatively rapid even in arid area and controls the levels of acidity and solubility of toxic metals and saline ions (Gleisner and Herbert, 2002;Hayes et al, 2011), which are fundamental causes for WC: woodchips OC: organic carbon OA: organic amendments MIM: Mount Isa Mines TD5: Tailings dam 5 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 4 phytotoxicity and rehabilitation failure (Callery and Courtney, 2015). After an extensive weathering of sulfidic tailings over decades (>e.g., about 30 years) under semi-arid climatic conditions, the relative hydro-geochemical stability resulted from the oxidation and depletion of large amounts of sulphides (<8 wt.%) compared to the freshly deposited sulfidic tailings (>30 wt.%) (Forsyth, 2014), providing the opportunity to rehabilitate physical structure (e.g., water-stable aggregates) and soil biological properties towards functional technosols and the colonization of target plant communities (Huang et al, 2012;Huang et al, 2014).…”