title: Probing the biogeochemical behavior of technetium using a novel nuclear imaging approach.
abstract: Dynamic gamma-camera imaging of radiotracer technetium ((99m)Tc) was used to assess the impact of biostimulation of metal-reducing bacteria on technetium mobility at 10(-12) mol L(-1) concentrations in sediments. Addition of the electron donor acetate was used to stimulate a redox profile in sediment columns, from oxic to Fe(III)-reducing conditions. When (99m)Tc was pumped through the columns, real-time gamma-camera imaging combined with geochemical analyses showed technetium was localized in regions containing biogenic Fe(II). In parallel experiments, electron microscopy with energy-dispersive X-ray (EDX) mapping confirmed sediment-bound Tc was associated with iron, while X-ray absorption spectroscopy (XAS) confirmed reduction of Tc(VII) to poorly soluble Tc(IV). Molecular analyses of microbial communities in these experiments supported a direct link between biogenic Fe(II) accumulation and Tc(VII) reductive precipitation, with Fe(III)-reducing bacteria more abundant in technetium immobilization zones. This offers a novel approach to assessing radionuclide mobility at ultratrace concentrations in real-time biogeochemical experiments, and confirms the effectiveness of biostimulation of Fe(III)-reducing bacteria in immobilizing technetium.
authors.affiliation: Williamson Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, M13 9PL, UK.
authors.forename: Gavin
authors.initials: G
authors.lastname: Lear
authors.forename: Joyce M
authors.initials: JM
authors.lastname: McBeth
authors.forename: Christopher
authors.initials: C
authors.lastname: Boothman
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Gunning
authors.forename: Beverly L
authors.initials: BL
authors.lastname: Ellis
authors.forename: Richard S
authors.initials: RS
authors.lastname: Lawson
authors.forename: Katherine
authors.initials: K
authors.lastname: Morris
authors.forename: Ian T
authors.initials: IT
authors.lastname: Burke
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Bryan
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Brown
authors.forename: Francis R
authors.initials: FR
authors.lastname: Livens
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Lloyd
mesh_terms: D001671:Biochemistry; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D005844:Geology; D046529:Microscopy, Electron, Transmission; D013667:Technetium / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D013667:Technetium