Isotope-Resolved Mapping of Fe(II)/Fe(III)-Oxide Redox Exchange Interfaces
EMSL Project ID
48629
Abstract
In subsurface redox microenvironments, as an outcome of essential microbial activity, interaction of aqueous Fe(II) with Fe(III)-(oxyhydr)oxide minerals such as goethite and hematite yields a catalytically reactive "sorbed Fe(II)" species. Despite its widespread relevance to biogeochemical carbon and nitrogen cycling and pollutant degradation processes, the products of this interaction remain poorly understood at a fundamental level. Our team has a DOE-funded world-leading experimental research campaign underway on understanding this interaction through isotopic labelling and tracking of the Fe(III)(56Fe dominant) and Fe(II)(57Fe dominant) pools upon contact and mixing. Mossbauer, aqueous analytical Fe isotopic analyses, and bulk solids characterization suggest that Fe(II) adsorbs to and exchanges electron density with structural Fe(III) in goethite and hematite without significant phase change, a fraction of which may be stabilized by association with defects. However, these studies have been limited to bulk characterization. EMSL's mass- and spatially resolved microscopies such as APT and nanoSIMS will provide critical and unique mechanistic insight into this interaction by first-ever examination of the Fe isotope distribution throughout these exchanged mineral solids.
Project Details
Project type
Special Science
Start Date
2015-02-10
End Date
2015-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members