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Title: Magnesium isotope fractionation during shale weathering in the Shale Hills Critical Zone Observatory: Accumulation of light Mg isotopes in soils by clay mineral transformation

Authors:
; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1249670
Grant/Contract Number:
FG02-05ER15675
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Chemical Geology
Additional Journal Information:
Journal Volume: 397; Journal Issue: C; Related Information: CHORUS Timestamp: 2016-09-06 05:26:52; Journal ID: ISSN 0009-2541
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English

Citation Formats

Ma, Lin, Teng, Fang-Zhen, Jin, Lixin, Ke, Shan, Yang, Wei, Gu, Hai-Ou, and Brantley, Susan L. Magnesium isotope fractionation during shale weathering in the Shale Hills Critical Zone Observatory: Accumulation of light Mg isotopes in soils by clay mineral transformation. Netherlands: N. p., 2015. Web. doi:10.1016/j.chemgeo.2015.01.010.
Ma, Lin, Teng, Fang-Zhen, Jin, Lixin, Ke, Shan, Yang, Wei, Gu, Hai-Ou, & Brantley, Susan L. Magnesium isotope fractionation during shale weathering in the Shale Hills Critical Zone Observatory: Accumulation of light Mg isotopes in soils by clay mineral transformation. Netherlands. doi:10.1016/j.chemgeo.2015.01.010.
Ma, Lin, Teng, Fang-Zhen, Jin, Lixin, Ke, Shan, Yang, Wei, Gu, Hai-Ou, and Brantley, Susan L. Sun . "Magnesium isotope fractionation during shale weathering in the Shale Hills Critical Zone Observatory: Accumulation of light Mg isotopes in soils by clay mineral transformation". Netherlands. doi:10.1016/j.chemgeo.2015.01.010.
@article{osti_1249670,
title = {Magnesium isotope fractionation during shale weathering in the Shale Hills Critical Zone Observatory: Accumulation of light Mg isotopes in soils by clay mineral transformation},
author = {Ma, Lin and Teng, Fang-Zhen and Jin, Lixin and Ke, Shan and Yang, Wei and Gu, Hai-Ou and Brantley, Susan L.},
abstractNote = {},
doi = {10.1016/j.chemgeo.2015.01.010},
journal = {Chemical Geology},
number = C,
volume = 397,
place = {Netherlands},
year = {Sun Mar 01 00:00:00 EST 2015},
month = {Sun Mar 01 00:00:00 EST 2015}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.chemgeo.2015.01.010

Citation Metrics:
Cited by: 12works
Citation information provided by
Web of Science

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  • Microscopic and spectroscopic studies were conducted to assess mineral transformation processes in aqueous suspensions of illite (Il), vermiculite (Vm) and montmorillonite (Mt) that were subjected to weathering in a simulated high-level radioactive tank waste leachate (0.05 m AlT, 2 m Na*, 1 m NO3 *, pH *14, Cs* and Sr2* present as co-contaminants). Time series (0 to 369 d) experiments were conducted at 298 K, with initial [Cs]0 and [Sr]0 concentrations from 10*5 to 10* mol kg*. Incongruent clay dissolution resulted in an accumulation of secondary aluminosilicate precipitates identified as nitrate-sodalite, nitrate-cancrinite and zeolite X, by molecular spectroscopy and electronmore » microscopy (XRD, IR, NMR, SEM-EDS and TEM-EDS). Contaminant fate was dependent on competing uptake to parent clays and weathering products. TEM-EDS results indicated that high Il affinity for Cs was due to adsorption at frayed edge sites. The Il system also comprised Sr-rich aluminous precipitates after 369 d reaction time. In Mt systems, Cs and Sr were co-precipitated into increasingly recalcitrant spheroidal precipitates over the course of the experiment, whereas contaminant association with montmorillonite platelets was less prevalent. In contrast, Cs and Sr were found in association with weathered Vm particles despite the formation of spheroidal aluminosilicate precipitates that were comparable to those formed from Mt dissolution.« less
  • The formation of transition-metal surface precipitates may occur during sorption to clay minerals under ambient soil conditions. This process may lead to significant long-term stabilization of the metal within the soil profile. However, the rates and mechanisms controlling surface precipitate formation are poorly understood. The authors monitored changes in the reversibility of Ni sorbed to a clay mineral, pyrophyllite, in model batch experiments maintained at pH 7.5 for up to 1 year. The macroscopic sorption and dissolution study was complemented by a time-resolved characterization of the sorbed phase via spectroscopic and thermal methods. They found that nickel became increasingly resistant,more » over time, to extraction with EDTA. Initially, the sorbed phase consisted of a Ni-Al layered double hydroxide (LDH). With time, the anionic species in the interlayer space of the LDH changed from nitrate to silica polymers transforming the LDH gradually into a precursor Ni-Al phyllosilicate. The authors believe that this phase transformation is responsible for a substantial part of the observed increase in dissolution resistance. Thus, clay mineral weathering and the time-dependent release of Al and Si ions controlled Ni precipitate nucleation and transformation. The results suggest a potential pathway for long-term Ni stabilization in soil.« less
  • Caustic high level radioactive waste induces mineral weathering reactions that can influence the fate of radionuclides released in the vicinity of leaking storage tanks. The uptake and release of CsI and SrII were studied in batch reactors of 2:1 layer-type silicates?illite (Il), vermiculite (Vm) and montmorillonite (Mt)?under geochemical conditions characteristic of leaking tank waste at the Hanford Site in WA (0.05 mAlT, 2 m Na*, 1 m NO3 *, pH *14, Cs and Sr present as co-contaminants). Time series (0 to 369 d) experiments were conducted at 298 K, with initial [Cs]0 and [Sr]0 concentrations from 10*5 to 10*3 molmore » kg*1. Clay mineral type affected the rates of (1) hydroxide promoted dissolution of Si, Al and Fe, (2) precipitation of secondary solids and (3) uptake of Cs and Sr. Initial Si release to solution followed the order Mt * Vm * Il. An abrupt decrease in soluble Si and/or Al after 33 d for Mt and Vm systems, and after 190 d for Il suspensions was concurrent with accumulation of secondary aluminosilicate precipitates. Strontium uptake exceeded that of Cs in both rate and extent, although sorbed Cs was generally more recalcitrant to subsequent desorption and dissolution. After 369 d reaction time, reacted Il, Vm and Mt solids retained up to 17, 47 and 14 mmol kg*1 (0.18, 0.24 and 0.02 *mol m*2) of Cs, and 0, 27 and 22 mmol kg*1 (0, 0.14 and 0.03 *molm*2) Sr, respectively, which were not removed in subsequent Mg exchange or oxalic acid dissolution reactions. Solubility of Al and Si decreased with initial Cs and Sr concentration in Mt and Il, but not in Vm. High co-contaminant sorption to the Vm clay, therefore, appears to diminish the influence of those ions on mineral transformation rates.« less