title: Characterization of interlayer Cs+ in clay samples using secondary ion mass spectrometry with laser sample modification.
abstract: Ultraviolet laser irradiation was used to greatly enhance the secondary ion mass spectrometry (SIMS) detection of Cs(+) adsorbed to soil consisting of clay and quartz. Imaging SIMS showed that the enhancement of the Cs(+) signal was spatially heterogeneous: the intensity of the Cs(+) peak was increased by factors up to 100 for some particles but not at all for others. Analysis of standard clay samples exposed to Cs(+) showed a variable response to laser irradiation depending on the type of clay analyzed. The Cs(+) abundance was significantly enhanced when Cs(+)-exposed montmorillonite was irradiated and then analyzed using SIMS, which contrasted with the behavior of Cs(+)-exposed kaolinite, which displayed no Cs(+) enhancement. Exposed illitic clays displayed modest enhancement of Cs(+) upon laser irradiation, intermediate between that of kaolinite and montmorillonite. The results for Cs(+) were rationalized in terms of adsorption to interlayer sites within the montmorillonite, which is an expandable phyllosilicate. In these locations, Cs(+) was not initially detectable using SIMS. Upon irradiation, Cs(+) was thermally redistributed, which enabled detection using SIMS. Since neither the illite nor the kaolinite is an expandable clay, adsorption to inner-layer sites does not occur, and either modest or no laser enhancement of the Cs(+) signal is observed. Laser irradiation also produced unexpected enhancement of Ti(+) from illite and kaolinite clays that contained small quantities of Ti, which indicates the presence of microscopic titanium oxide phases in the clay materials.
authors.affiliation: Idaho National Engineering and Environmental Laboratory, Idaho Falls, Idaho 83415, USA. gsg@inel.gov
authors.forename: G S
authors.initials: GS
authors.lastname: Groenewold
authors.forename: R
authors.initials: R
authors.lastname: Avci
authors.forename: C
authors.initials: C
authors.lastname: Karahan
authors.forename: K
authors.initials: K
authors.lastname: Lefebre
authors.forename: R V
authors.initials: RV
authors.lastname: Fox
authors.forename: M M
authors.initials: MM
authors.lastname: Cortez
authors.forename: A K
authors.initials: AK
authors.lastname: Gianotto
authors.forename: J
authors.initials: J
authors.lastname: Sunner
authors.forename: W L
authors.initials: WL
authors.lastname: Manner