Conferences - Seminars
EESS talk on "Tungsten isotopes as a probe of reactions governing environmental transport of a toxic heavy metal"
By Dr Laura Wasylenki, associate professor (visiting professor @EML-EPFL), Sesame Lab, Dept. Geological Sciences Biogeochemistry of Metals, Indiana University Bloomington (USA)
Dr. Wasylenki received her bachelor’s degree in Geology from Stanford and a PhD degree from Caltech. She was formerly a specialist in igneous petrology and a professor at a small liberal arts college in the US. Dr. Wasylenki became a low-temperature geochemist during a postdoctoral position at Virginia Tech in 2002-2004 and began working with metal isotopes as a Research Scientist at Arizona State University in 2005-2010. She has been at Indiana University for almost seven years. Her primary interests are biogeochemistry of transition metals in the modern and ancient oceans and environmental transport of heavy metal contaminants in soils and sediments.
Mining, smelting, and use of tungsten (W) have increased rapidly in the past few decades, but recently the US EPA declared this element an “emerging contaminant of concern,” because it is likely a carcinogen. Despite the health concerns, remarkably little research has yet addressed the environmental transport and fate of tungsten.
As dissolved tungsten moves in soils or oxidizing groundwater, its mobility is likely governed primarily by adsorption to particles of Mn, Fe, and Al oxyhydroxides. In addition to how much tungsten adsorbs, crucial questions are how exactly tungsten bonds to particle surfaces and how stable it is in those chemical forms. A few researchers have employed X-ray absorption spectroscopy to examine W sorption complexes, but that technique requires unrealistically high concentrations of tungsten, especially at environmentally relevant pH, and chemical speciation of tungsten is known to vary strongly with concentration. Hence we propose a new approach to constraining speciation and adsorption mechanisms at field-relevant concentrations.
Tungsten stable isotope ratios are likely highly sensitive to changes in coordination number and W-O and W-metal bond distances that occur during adsorption reactions. We are conducting experiments to determine W isotope systematics during adsorption to synthetic Mn and Fe oxyhydroxides, beginning at concentrations where adsorption mechanisms can be examined directly using X-ray absorption spectroscopy. Initial experiments with Fe and Mn oxyhydroxides have produced easily resolvable fractionations, with lighter isotopes preferentially sorbed, and systematic patterns as a function of surface loading. Once the relationships between isotope behavior and adsorption mechanisms are established at higher concentrations, we can extend isotope experiments to field-relevant levels, since only 50 nanograms of W are needed for analysis. Eventually we hope to apply W isotopes as a tool for tracking the extent to which adsorption reactions are attenuating migration of W in contaminated settings.
Organization EESS - IIE
Accessibility General public
This event is internal