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Title: U reduction and Hg methylation

Abstract

No abstract prepared.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »; ; ; ; ; ; « less
Publication Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
927511
Report Number(s):
CONF/ERSP2007-1029681
R&D Project: ERSD 1029681; TRN: US0803201
Resource Type:
Conference
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; MERCURY; METHYLATION; URANIUM; REDUCTION

Citation Formats

Anthony V. Palumbo, Craig C. Brandt, Lisa A. Fagan, Meghan S. McNeilly, Tatiana A, Vishnivetskaya, Andrew S. Madden, Tommy Phelps, Jack C. Schryver, Chris W. Schadt, Jana R. Tarver, Susan. M. Pfiffner, Sara Bottomly, Heath Mills, Denise M. Akob, Joel E. Kostka, Anthony V. Palumbo, Craig C. Brandt, Lisa A. Fagan, Meghan S. McNeilly, Tatiana A Vishnivetskaya, Steve Brown, George Southworth, F. Michael Saunders, Dwayne Elias, and Judy D. Wall. U reduction and Hg methylation. United States: N. p., 2007. Web.
Anthony V. Palumbo, Craig C. Brandt, Lisa A. Fagan, Meghan S. McNeilly, Tatiana A, Vishnivetskaya, Andrew S. Madden, Tommy Phelps, Jack C. Schryver, Chris W. Schadt, Jana R. Tarver, Susan. M. Pfiffner, Sara Bottomly, Heath Mills, Denise M. Akob, Joel E. Kostka, Anthony V. Palumbo, Craig C. Brandt, Lisa A. Fagan, Meghan S. McNeilly, Tatiana A Vishnivetskaya, Steve Brown, George Southworth, F. Michael Saunders, Dwayne Elias, & Judy D. Wall. U reduction and Hg methylation. United States.
Anthony V. Palumbo, Craig C. Brandt, Lisa A. Fagan, Meghan S. McNeilly, Tatiana A, Vishnivetskaya, Andrew S. Madden, Tommy Phelps, Jack C. Schryver, Chris W. Schadt, Jana R. Tarver, Susan. M. Pfiffner, Sara Bottomly, Heath Mills, Denise M. Akob, Joel E. Kostka, Anthony V. Palumbo, Craig C. Brandt, Lisa A. Fagan, Meghan S. McNeilly, Tatiana A Vishnivetskaya, Steve Brown, George Southworth, F. Michael Saunders, Dwayne Elias, and Judy D. Wall. Thu . "U reduction and Hg methylation". United States. doi:. https://www.osti.gov/servlets/purl/927511.
@article{osti_927511,
title = {U reduction and Hg methylation},
author = {Anthony V. Palumbo and Craig C. Brandt and Lisa A. Fagan and Meghan S. McNeilly and Tatiana A and Vishnivetskaya and Andrew S. Madden and Tommy Phelps and Jack C. Schryver and Chris W. Schadt and Jana R. Tarver and Susan. M. Pfiffner and Sara Bottomly and Heath Mills and Denise M. Akob and Joel E. Kostka and Anthony V. Palumbo and Craig C. Brandt and Lisa A. Fagan and Meghan S. McNeilly and Tatiana A Vishnivetskaya and Steve Brown and George Southworth and F. Michael Saunders and Dwayne Elias and Judy D. Wall},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Apr 19 00:00:00 EDT 2007},
month = {Thu Apr 19 00:00:00 EDT 2007}
}

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  • Short communication.
  • For the in situ reductive immobilization of U to be an acceptable strategy for the removal of that element from groundwater, the long-term stability of U(IV) must be determined. Rates of biotransformation of Fe species influence the mineralogy of the resulting products (Fredrickson et al., 2003; Senko et al., 2005), and we hypothesize that the rate of U(VI) reduction influences the mineralogy of resultant U(IV) precipitates. We hypothesize that slower rates of U(VI) reduction will yield U(IV) phases that are more resistant to reoxidation, and will therefore be more stable upon cessation of electron donor addition. U(IV) phases formed bymore » relatively slow reduction may be more crystalline or larger in comparison to their relatively rapidly-formed counterparts (Figure 1), thus limiting the reactivity of slowly-formed U(IV) phases toward various oxidants. The physical location of U(IV) precipitates relative to bacterial cells may also limit the reactivity of biogenic U(IV) phases. In this situation, we expect that precipitation of U(IV) within the bacterial cell may protect U(IV) from reoxidation by limiting physical contact between U(IV) and oxidants (Figure 1). We assessed the effect of U(VI) reduction rate on the subsequent reoxidation of biogenic U(IV) and are currently conducting column scale studies to determine whether U(VI) reduction rate can be manipulated by varying the electron donor concentration used to stimulate U(VI) reduction.« less
  • The purposes of this report are to: (1) to determine how flow and transport influence the distribution of U(VI) under field-relevant conditions and the transfer of reductive equivalents to the aqueous and solid phases by DMRB; and (2) to examine the solid-phase stability of bioreduced uranium phases--effects of mass transfer on reoxidation of U(IV) by O{sub 2} and other oxidants (e.g., NO{sub 3}{sup -}, denitrification products).
  • Atmospheric deposition of mercury (Hg) to surface water is one of the dominant sources of Hg in aquatic environments and ultimately drives methylmercury (MeHg) toxin accumulation in fish. It is known that freshly deposited Hg is more readily methylated by microorganisms than aged or preexisting Hg; however the underlying mechanism of this process is unclear. Here we report that Hg bioavailability is decreased by photochemical reactions between Hg and dissolved organic matter (DOM) in water. Photo-irradiation of Hg-DOM complexes results in loss of Sn(II)-reducible (i.e. reactive) Hg and up to an 80% decrease in MeHg production by the methylating bacteriummore » Geobacter sulfurreducens PCA. Loss of reactive Hg proceeded at a faster rate with a decrease in the Hg to DOM ratio and is attributed to the possible formation of mercury sulfide (HgS). Lastly, these results suggest a new pathway of abiotic photochemical formation of HgS in surface water and provide a mechanism whereby freshly deposited Hg is readily methylated but, over time, progressively becomes less available for microbial uptake and methylation.« less