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SUMMARY:EESS talk on "Tungsten isotopes as a probe of reactions governing 
 environmental transport of a toxic heavy metal"
DTSTART:20170425T121500
DTEND:20170425T131500
DTSTAMP:20260916T085836Z
UID:b4813f6e845c2a7bf0b3f2625e5f6eb26f7c6fd3bd3d0c18f7ae8f2f
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Laura Wasylenki\, associate professor (visiting professor @
 EML-EPFL)\, Sesame Lab\, Dept. Geological Sciences Biogeochemistry of Meta
 ls\, Indiana University Bloomington (USA)\nShort biography:\nDr. Wasylenki
  received her bachelor’s degree in Geology from Stanford and a PhD degre
 e from Caltech. She was formerly a specialist in igneous petrology and a p
 rofessor at a small liberal arts college in the US. Dr. Wasylenki became a
  low-temperature geochemist during a postdoctoral position at Virginia Tec
 h in 2002-2004 and began working with metal isotopes as a Research Scienti
 st at Arizona State University in 2005-2010. She has been at Indiana Unive
 rsity for almost seven years. Her primary interests are biogeochemistry of
  transition metals in the modern and ancient oceans and environmental tran
 sport of heavy metal contaminants in soils and sediments. \nAbstract:\nMi
 ning\, smelting\, and use of tungsten (W) have increased rapidly in the pa
 st few decades\, but recently the US EPA declared this element an “emerg
 ing contaminant of concern\,” because it is likely a carcinogen. Despite
  the health concerns\, remarkably little research has yet addressed the en
 vironmental transport and fate of tungsten.\nAs dissolved tungsten moves i
 n soils or oxidizing groundwater\, its mobility is likely governed primari
 ly by adsorption to particles of Mn\, Fe\, and Al oxyhydroxides. In additi
 on to how much tungsten adsorbs\, crucial questions are how exactly tungst
 en 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 c
 oncentrations of tungsten\, especially at environmentally relevant pH\, an
 d chemical speciation of tungsten is known to vary strongly with concentra
 tion. Hence we propose a new approach to constraining speciation and adsor
 ption mechanisms at field-relevant concentrations.\nTungsten stable isotop
 e 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 adso
 rption to synthetic Mn and Fe oxyhydroxides\, beginning at concentrations 
 where adsorption mechanisms can be examined directly using X-ray absorptio
 n spectroscopy. Initial experiments with Fe and Mn oxyhydroxides have prod
 uced easily resolvable fractionations\, with lighter isotopes preferential
 ly 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 t
 o field-relevant levels\, since only 50 nanograms of W are needed for anal
 ysis. Eventually we hope to apply W isotopes as a tool for tracking the ex
 tent to which adsorption reactions are attenuating migration of W in conta
 minated settings.\n 
LOCATION:GR C0 01 https://plan.epfl.ch/theme/generalite_thm_v2?room=GR%20C
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STATUS:CONFIRMED
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