The Effects of gamma-Irradiation on the Fe(II)/Fe(III) Signatures in Iron Oxide and Iron Silicate Minerals
EMSL Project ID
25607
Abstract
In our previous study of the effects of gamma-irradiation (sterilization) on natural sediments containing Fe(III)-oxides, Mn-oxides, Fe-rich clay and quartz minerals, analyses showed that cation exchange capacity (CEC) and the sorption potential of soil changed considerably after exposure to ionizing radiation. Preliminary 57Fe transmission Mössbauer and electron paramagnetic resonance (EPR) studies suggested that the changes may be related to the reduction of Fe(III) to Fe(II) [and Mn(III)/(IV) to Mn(II)]. However, based on preliminary data we cannot unambiguously determine if iron reduction is occurring specifically in iron-containing clays or iron oxide minerals and to our knowledge there are no studies of gamma-induced reduction in iron oxide minerals. The objective of this study is to identify the effects of gamma-irradiation on the oxidation state of iron in four common iron-containing minerals with varying structural/surface water content: hematite (Fe2O3), goethite (FeO.OH), ferrihydrite [Fe2O3.½(H2O)], and nontronite [Na0.3Fe2(Si,Al)4O10(OH)2.n(H2O)]. Using these minerals will allow us to determine if the mechanism of iron reduction is related to free radicals produced by the radiolysis of water in the mineral structure or on the mineral surface. The changes in Fe-mineralogy [particularly the nature of sorbed Fe(II)] of these oxides will be studied after exposure to controlled doses of gamma-irradiation using wet chemistry techniques and 57Fe transmission Mössbauer spectroscopy. Mineral synthesis in our laboratory will ensure homogeneity of the samples and minimize trace element contamination, allowing for faster and better spectroscopy analyses. The proposed research is a fundamental study of the effects of ionizing radiation on common soil minerals which can be directly applied to understanding the effects of controlled (i.e. gamma-sterilization) and uncontrolled (i.e. nuclear waste storage) irradiation on heterogeneous sediment samples.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-06-25
End Date
2008-06-29
Status
Closed
Released Data Link
Team
Principal Investigator