Molybdenum
contamination is a concern in mining regions worldwide.
Better understanding of processes controlling Mo mobility in mine
wastes is critical for assessing potential impacts and developing
water-quality management strategies associated with this element.
Here, we used Mo stable isotope (δ98/95Mo) analyses
to investigate geochemical controls on Mo mobility within a tailings
management facility (TMF) featuring oxic and anoxic environments.
These isotopic analyses were integrated with X-ray absorption spectroscopy,
X-ray diffraction, Raman spectroscopy, transmission electron microscopy,
and aqueous chemical data. Dissolved Mo concentrations were inversely
correlated with δ98/95Mo values such that enrichment
of heavy Mo isotopes in solution reflected attenuation processes.
Inner-sphere complexation of Mo(VI) with ferrihydrite was the primary
driver of Mo removal and was accompanied by a ca. 1‰ isotope
fractionation. Limited Mo attenuation and isotope fractionation were
observed in Fe(II)- and Mo-rich anoxic TMF seepage, while attenuation
and isotope fractionation were greatest during discharge and oxidation
of this seepage after discharge into a pond where Fe-(oxyhydr)oxide
precipitation promoted Mo sorption. Overall, this study highlights
the role of sorption onto Fe-(oxyhydr)oxides in attenuating Mo in
oxic environments, a process which can be traced by Mo isotope analyses.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.