Surficial geochemistry and bioaccessibility of tellurium in semiarid mine tailings

Abstract

Environmental contextTellurium can be more toxic than arsenic, but its fate in the surficial environment is poorly understood. We studied tellurium behaviour in semiarid mine tailings and found that most tellurium is associated with iron (oxy)hydroxides as tellurate (TeVI), the less toxic oxidation state. Iron (oxy)hydroxides are likely to control the fate of Te in the surficial environment and may effectively sequester Te oxyanions released by oxidative weathering. AbstractTellurium (Te) is a critical element owing to its use in solar technology. However, some forms are highly toxic. Few studies have examined Te behaviour in the surficial environment, thus little is known about its potential human and environmental health impacts. This study characterises two physicochemically distinct Te-enriched mine tailings piles (big and flat tailings) deposited by historic gold (Au) mining in the semiarid Delamar mining district, Nevada, USA. The big tailings are characterised by smaller particle size and higher concentrations of potentially toxic elements (up to 290mgTekg−1), which are enriched at the tailings surface. In contrast, the flat tailings have larger particle size and properties that are relatively invariant with depth. Based on the sulfate to sulfide ratio, the tailings were determined to be sulfate dominated, which suggested a high degree of weathering, although the flat tailings did contain significant amounts of sulfides (~40%). Tellurium X-ray absorption spectroscopy of the big tailings indicates that tellurate, the less toxic Te species, is the principal form of Te. Electron microscopy indicates that most of the Te present at the site is associated with iron (oxy)hydroxides, and sometimes with other potentially toxic elements, especially lead and antimony. Physiologically-based extraction tests indicate that substantially more Te is solubilised in synthetic stomach fluids than in lung fluids, with gastric bioaccessibility ranging from 13 to 31% of total Te. This points to low to medium bioaccessibility, which is common for iron (oxy)hydroxide-associated elements. Together, these results represent a preliminary assessment of Te surficial behaviour in a semiarid environment and indicate that Te in these tailings represent a moderate health concern.

Occurrence and Geochemistry of Lead-210 and Polonium-210 Radionuclides in Public-Drinking-Water Supplies from Principal Aquifers of the United States

“…Although experimental data on Po –2 species are lacking, , the Po speciation indicated in Figures and SI-7A is consistent with analogous Te species (H 2 TeO 3 , TeO 3 –2 , and HTeO – , and HTe – ; Figure SI-7B). ,,, …”

Natural Nanoparticles of the Critical Element Tellurium

“…At the Kawazu mine, Japan, Qin et al (2017) showed that Te was present as a mixture of Te IV and Te VI species; Fe III hydroxides were the host phases for Te IV and Te VI , but some Te VI was also associated with illite. In contrast, Hayes and Ramos (2019) found that Te was present as Te VI and associated with Fe III hydroxides within the Delamar mine tailings, Nevada, USA. Both studies used synchrotron-based X-ray Absorption Spectroscopy (XAS) to decipher the nature of Te (µ-XAS in Qin et al, 2017;bulk XAS in Hayes and Ramos, 2019).…”

Development of a Tellurium Speciation Study Using IC-ICP-MS on Soil Samples Taken from an Area Associated with the Storage, Processing, and Recovery of Electrowaste

“…Except from samples collected close to sources of contamination, tellurium concentrations in soils and sediments are normally at the low ppb (μg/g) level [ 5 ]. Te is generally bound by sorption onto clay-sized soil particles rather than in minerals [ 49 ]. In particular, a strong association has been observed between Fe 3+ oxide minerals and tellurium.…”