Tellurium (Te) is a rare metalloid with an average crustal abundance of 3 µg kg-1. However, Te can be enriched up to hundreds of parts per million in Au/Ag deposits. Since it is generally not recovered, significant amounts of Te remain in mine tailings exposed to the environment. Tellurium is toxic to humans; TeIV is more toxic than TeVI, SeIV, or AsIII. Chemically, it behaves similarly to Se, so the effects of Te deposition on the ecosystem may similarly be of concern. The weathering of Te-bearing mine tailings in surficial environments can transform Te and have implications for human and environmental health. Our goal is to determine whether Te-rich historic mine tailings pose a health risk to surrounding ecosystems and communities. The historic Delamar mining district, located in semi-arid Lincoln County, NV, was mined for Au from 1891 to 1938 and produced at least 450,000 tons of mine tailings containing elevated concentrations of Te (up to 267 mg kg-1). Circum-neutral (pH 7.4-8.3) tailings piles were sampled as a function of depth. Bulk fits modeling Te speciation via X-ray absorption spectroscopy suggest the predominance of TeVI, the less toxic form of Te. Micro-focused X-ray fluorescence mapping and electron microscopy indicate the enrichment of Te in small particles associated with S and Fe (oxy)hydroxides. Tellurium and other toxic metal(loid)s (e.g. Pb, Bi, Cu, and As) are enriched in surficial tailings, likely present as bioaccessible efflorescent salts, and may be susceptible to dispersion by wind or surface water erosion. Strong semi-arid wind and rainfall events can greatly impact metal transport. Roughly 50% of particles by weight have diameters below the wind transportable threshold of 37 µm, indicating these tailings may be dispersed to population centers supported by HYSPLIT modeling. Taken together, these results lend insight into the potential health and environmental impacts of Te.

Assessment of tellurium in semi-arid mine tailings at Delamar, Nevada: Implications for human and ecosystem health

249th National Meeting (2015)

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