Origin of tungsten and geochemical controls on its occurrence and mobilization in shallow sediments from Fallon, Nevada, USA. (December 2020)

• Record Type: Journal Article
• Authors: Hobson, Chad; Kulkarni, Harshad V.; Johannesson, Karen H.; Bednar, Anthony; Tappero, Ryan; Mohajerin, T. Jade; Sheppard, Paul R.; Witten, Mark L.; Hettiarachchi, Ganga M.; Datta, Saugata
• Is Part Of: Chemosphere. Volume 260(2020)
• Publication Date: 2020-12
• Subjects: Tungsten -- Sediment-water interface -- Childhood leukemia -- μ-XRF mapping -- Water extractable tungsten; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2020.127577
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Tungsten (W) occurrence and speciation was investigated in sediments collected from Fallon, Nevada where previous studies have linked elevated W levels in human body fluids to an unusual cluster of childhood leukemia cases. The speciation of sedimentary W was determined by μ-XRF mapping and μ-XANES. The W content of the analyzed surface sediments ranged between 81 and 25, 908 mg/kg, which is significantly higher than the W content in deeper sediments which ranged from 37 to 373 mg/kg at 30 cm depth. The μ-XANES findings reveal that approximately 20–50% of the total W in the shallow sediment occurs in the metallic form (W 0 ); the rest occurs in the oxide form (W VI O3 ). Because W 0 does not occur naturally, its elevated concentrations in surface sediments point toward a possible local anthropogenic origin. The oxidation of metallic W 0 with meteoric waters likely leads to the formation of W VI O3 . The chief water-soluble W species was identified as WO4 2− by chromatographic separation and speciation modeling. These results led us to postulate that W 0 particles from a currently unknown but local source(s) is (are) deposited onto the soils and/or surface sediments. The W 0 in interaction with meteoric water is oxidized to W VI O3, and as these sediment-water interactions progress, WO4 2− is formed in the water at pH ∼7. Under pH < 7, and sufficient W concentrations, tungstate tends to polymerize, and polymerized species are less likely to adsorb onto sediments. Polymerized species have lower affinity than monomers, which leads to enhanced mobility of W. Graphical abstract: Image 1 Highlights: Tungsten (W) contents are elevated in surface sediments at Fallon, NV. Tungsten occurs in these sediments as two major species: metallic (W 0 ) and oxide species (W VI O3 ). Tungsten occurs in water as monomeric and polymeric tungstate (WO4 2− ) ions. Metallic W is oxidized into W VI O3 by interaction with meteoric water.