Morphological and Chemical Characteristics of Airborne Tungsten Particles of Fallon, Nevada

Abstract

Morphological and chemical characteristics were determined for airborne tungsten particles in Fallon, Nevada, a town that is distinguishable environmentally by elevated airborne tungsten and cobalt. From samples of airborne dust collected previously at six different places in Fallon, tungsten-rich dust particles were isolated and analyzed with automated electron microprobe and wavelength-dispersive spectrometry. Representative W particles were further analyzed using transmission electron microscopy. Morphologically, Fallon W particles are angular and small, with minimum and maximum sizes of < or = 1 microm and 5.9 microm in diameter, respectively. The number and size of tungsten-rich particles decrease in Fallon with distance from a hard-metal facility located near the center of town. Chemically, Fallon airborne W particles include mixtures of tungsten with cobalt plus other metals such as chromium, iron, and copper. No W-rich particles were identifiable as CaWO4 (scheelite) or MnWO4 (huebnerite). From d-spacings, Fallon particles are most consistent with identification as tungsten carbide. Based on these multiple lines of evidence, airborne W particles in Fallon are anthropogenic in origin, not natural. The hard-metal facility in Fallon processes finely powdered W and W-Co, and further investigation using tracer particles is recommended to definitively identify the source of Fallon's airborne tungsten.

Saharan dust events in the European Alps: role in snowmelt and geochemical characterization

“…The role of black carbon in Alpine snow still represents a great uncertainty in snow modelling and climate prediction in the Alps. While the role of industrial black carbon on post-industrial glacier retreat has been debated (Painter et al, 2013b;Sigl et al, 2018), its role in seasonal snow melting has not been studied in the European Alps. Hereafter we focus on the season 2015-2016, since Crocus simulations with impurities resulted in a 38 d advancement of the snow melt-out date compared to the corresponding simulations without impurities.…”

Comparison of Size and Geography of Airborne Tungsten Particles in Fallon, Nevada, and Sweet Home, Oregon, with Implications for Public Health

“…The bottom methyl iodide layer was filtered on 25-millimeter polyester membrane filters and mounted onto aluminum stubs for automated analysis. This method recovers a representative sample for particle sizing and chemical analysis and has worked specifically with tungsten particles in prior work [19]. …”

“…This hard-metal facility was named by the Nevada State Health Division as a candidate source of tungsten in Fallon [18]. Morphological and chemical characteristics of airborne tungsten particles in Fallon indicate that they are anthropogenic in origin, not natural [19]. …”

Erratum

“…These indicators incorporate environmental conditions differently from one another, yet they have corroborated one another in showing that airborne tungsten is elevated in Fallon relative to other towns of west-central Nevada or the surrounding desert. Additionally, airborne tungsten particles in Fallon have been identified as anthropogenic in origin, and not natural (Sheppard et al 2007e).…”