Title page for ETD etd-08172004-131546


Type of Document Master's Thesis
Author Roller, Jonathan William
Author's Email Address jorolle1@vt.edu
URN etd-08172004-131546
Title Arsenic mobilization through bioreduction of iron oxide nanoparticles
Degree Master of Science
Department Geosciences
Advisory Committee
Advisor Name Title
Schreiber, Madeline E. Committee Co-Chair
Tadanier, Christopher J. Committee Co-Chair
Rimstidt, james Donald Committee Member
Keywords
  • Geobacter metallireducens
  • Fe(III) reduction
  • arsenic
Date of Defense 2004-08-12
Availability unrestricted
Abstract
Arsenic sorbs strongly to the surfaces of Fe(III) (hydr)oxides. Under aerobic conditions, oxygen acts as the terminal electron acceptor in microbial respiration and Fe(III) (hydr)oxides are highly insoluble, thus arsenic remains associated with Fe(III) (hydr)oxide phases. However, under anaerobic conditions Fe(III)-reducing microorganisms can couple the reduction of solid phase Fe(III) (hydr)oxides with the oxidation of organic carbon. When ferric iron is reduced to ferrous iron, arsenic is mobilized into groundwater. Although this process has been documented in a variety of pristine and contaminated environments, minimal information exists on the mechanisms causing this arsenic mobilization.

Arsenic mobilization was studied by conducting controlled microcosm experiments containing an arsenic-bearing ferrihydrite and an Fe(III)-reducing microorganism, Geobacter metallireducens. Results show that arsenic mobility is strongly controlled by microbially-mediated disaggregation of arsenic-bearing iron nanoparticles. The most likely controlling mechanism of this disaggregation of iron oxide nanoparticles is a change in mineral phase from ferrihydrite to magnetite, a mixed Fe(III) and Fe(II) mineral, due to the microbially-mediated reduction of Fe(III). Although arsenic remained associated with the iron oxide nanoparticles and was not released as a hydrated oxyanion, the arsenic-bearing nanoparticles could be readily mobilized in aquifers. These results have significant implications for understanding arsenic behavior in aquifers with Fe(III) reducing conditions, and may aid in improving remediation of arsenic-contaminated waters.

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