Details
| Original language | English |
|---|---|
| Pages (from-to) | 1370-1375 |
| Number of pages | 6 |
| Journal | Environmental Science and Technology |
| Volume | 45 |
| Issue number | 4 |
| Publication status | Published - 15 Feb 2011 |
Abstract
Previous work has shown uranium (U) isotope fractionation between natural ferromanganese crusts and seawater. Understanding the mechanism that causes 238U/235U fractionation during adsorption to ferromanganese oxides is a critical step in the utilization of 238U/235U as a tracer of U adsorption reactions in groundwater as well as a potential marine paleoredox proxy. We conducted U adsorption experiments using synthetic K-birnessite and U-bearing solutions. These experiments revealed a fractionation matching that observed between seawater and natural ferromanganese sediments: adsorbed U is isotopically lighter by ∼0.2‰ (δ238/235U) than dissolved U. As the redox state of U does not change during adsorption, a difference in the coordination environment between dissolved and adsorbed U is likely responsible for this effect. To test this hypothesis, we analyzed U adsorbed to K-birnessite in our experimental study using extended X-ray absorption fine structure (EXAFS) spectroscopy, to obtain information about U coordination in the adsorbed complex. Comparison of our EXAFS spectra with those for aqueous U species reveals subtle, but important, differences in the U-O coordination shell between dissolved and adsorbed U. We hypothesize that these differences are responsible for the fractionation observed in our experiments as well as for some U isotope variations in nature.
ASJC Scopus subject areas
- Chemistry(all)
- General Chemistry
- Environmental Science(all)
- Environmental Chemistry
Sustainable Development Goals
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In: Environmental Science and Technology, Vol. 45, No. 4, 15.02.2011, p. 1370-1375.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Uranium isotope fractionation during adsorption to Mn-oxyhydroxides
AU - Brennecka, Gregory A.
AU - Wasylenki, Laura E.
AU - Bargar, John R.
AU - Weyer, Stefan
AU - Anbar, Ariel D.
PY - 2011/2/15
Y1 - 2011/2/15
N2 - Previous work has shown uranium (U) isotope fractionation between natural ferromanganese crusts and seawater. Understanding the mechanism that causes 238U/235U fractionation during adsorption to ferromanganese oxides is a critical step in the utilization of 238U/235U as a tracer of U adsorption reactions in groundwater as well as a potential marine paleoredox proxy. We conducted U adsorption experiments using synthetic K-birnessite and U-bearing solutions. These experiments revealed a fractionation matching that observed between seawater and natural ferromanganese sediments: adsorbed U is isotopically lighter by ∼0.2‰ (δ238/235U) than dissolved U. As the redox state of U does not change during adsorption, a difference in the coordination environment between dissolved and adsorbed U is likely responsible for this effect. To test this hypothesis, we analyzed U adsorbed to K-birnessite in our experimental study using extended X-ray absorption fine structure (EXAFS) spectroscopy, to obtain information about U coordination in the adsorbed complex. Comparison of our EXAFS spectra with those for aqueous U species reveals subtle, but important, differences in the U-O coordination shell between dissolved and adsorbed U. We hypothesize that these differences are responsible for the fractionation observed in our experiments as well as for some U isotope variations in nature.
AB - Previous work has shown uranium (U) isotope fractionation between natural ferromanganese crusts and seawater. Understanding the mechanism that causes 238U/235U fractionation during adsorption to ferromanganese oxides is a critical step in the utilization of 238U/235U as a tracer of U adsorption reactions in groundwater as well as a potential marine paleoredox proxy. We conducted U adsorption experiments using synthetic K-birnessite and U-bearing solutions. These experiments revealed a fractionation matching that observed between seawater and natural ferromanganese sediments: adsorbed U is isotopically lighter by ∼0.2‰ (δ238/235U) than dissolved U. As the redox state of U does not change during adsorption, a difference in the coordination environment between dissolved and adsorbed U is likely responsible for this effect. To test this hypothesis, we analyzed U adsorbed to K-birnessite in our experimental study using extended X-ray absorption fine structure (EXAFS) spectroscopy, to obtain information about U coordination in the adsorbed complex. Comparison of our EXAFS spectra with those for aqueous U species reveals subtle, but important, differences in the U-O coordination shell between dissolved and adsorbed U. We hypothesize that these differences are responsible for the fractionation observed in our experiments as well as for some U isotope variations in nature.
UR - http://www.scopus.com/inward/record.url?scp=79951667925&partnerID=8YFLogxK
U2 - 10.1021/es103061v
DO - 10.1021/es103061v
M3 - Article
C2 - 21250673
AN - SCOPUS:79951667925
VL - 45
SP - 1370
EP - 1375
JO - Environmental Science and Technology
JF - Environmental Science and Technology
SN - 0013-936X
IS - 4
ER -