CaltechTHESIS
  A Caltech Library Service

Processes controlling the fate and transport of trace metals in the subsurface during changing redox potential

Citation

Farnsworth, Claire (2011) Processes controlling the fate and transport of trace metals in the subsurface during changing redox potential. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:05132011-121157483

Abstract

This study investigated the cycling of Mn and Fe as oxic surface water entered shallow sediments and was reduced, and as reduced groundwater became exposed to oxygen and was oxidized. A Mn-oxide doped gel probe sampler was developed to study in situ rates of reductive dissolution and was validated with laboratory studies with ascorbic acid and Shewanella oneidensis MR-1 as model reductants. The sampler was deployed in the bank sediments of Lake Tegel, Berlin, Germany. Modeling of the diffusion-controlled reaction converted the mass loss from the gels in the sampler to a profile of pseudo-first-order rate constants as a function of depth. The rate constants were highest at depths with high dissolved Fe and low operationally defined fractions of reducible oxides of Fe and Mn in the sediments. A laboratory column experiment showed that 1.3-m water table fluctuations, as observed in bank filtration sites around Berlin, were able to provide sufficient dissolved oxygen delivery for Pseudomonas putida GB-1, an obligate aerobe, to oxidize Mn(II) in situ. Accumulation of Mn on the quartz sand in the column at the end of the experiment was limited to the top 60 cm, as measured with X-ray fluorescence (XRF), and X-ray absorption spectroscopy (XAS) analysis confirmed that the solid formed was a Mn(IV) oxide characteristic of biogenic origin. After a period of “filter ripening” in the column, rates of in situ oxidation were still lower than rates in engineered aerated sand filters. Adjacent to a production well with a water table that fluctuates up to 7 m annually at Lake Tegel, however, sediments collected from a borehole did not show any significant accumulation of Mn or Fe with depth, as measured by XRF; analysis of the speciation of Mn and Fe in the solid phase by XAS suggested a slight increase in the proportions of total Mn as Mn(II) and of total Fe as Fe(II) with depth. At this location, vertical zonation of groundwater may preclude the co-occurrence of reduced Mn and Fe with dissolved oxygen entrapped by water table fluctuations. Whether groundwater changes from oxidizing to reducing conditions or vice versa, the behavior of Mn and Fe reflects a complex interaction between sediments, solutes, microbial activity, and hydrology.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:manganese; iron; redox; groundwater
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Environmental Science and Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Hering, Janet G.
Thesis Committee:
  • Hering, Janet G. (chair)
  • Adkins, Jess F.
  • Hoffmann, Michael R.
  • Orphan, Victoria J.
Defense Date:10 May 2011
Funders:
Funding AgencyGrant Number
National Science Foundation Graduate Research FellowshipUNSPECIFIED
National Science FoundationEAR-0525387
Eawag, Swiss Federal Institute of Aquatic Science and TechnologyUNSPECIFIED
Record Number:CaltechTHESIS:05132011-121157483
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:05132011-121157483
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6392
Collection:CaltechTHESIS
Deposited By: Claire Farnsworth
Deposited On:17 May 2011 23:16
Last Modified:26 Dec 2012 04:35

Thesis Files

[img]
Preview
PDF (Front Material) - Final Version
See Usage Policy.

80Kb
[img]
Preview
PDF (Chapter 1: Introduction) - Final Version
See Usage Policy.

21Kb
[img]
Preview
PDF (Chapter 2) - Final Version
See Usage Policy.

347Kb
[img]
Preview
PDF (Chapter 3) - Final Version
See Usage Policy.

245Kb
[img]
Preview
PDF (Chapter 4) - Final Version
See Usage Policy.

273Kb
[img]
Preview
PDF (Chapter 5) - Final Version
See Usage Policy.

232Kb
[img]
Preview
PDF (Chapter 6) - Final Version
See Usage Policy.

262Kb
[img]
Preview
PDF (Chapter 7: Conclusions) - Final Version
See Usage Policy.

132Kb
[img]
Preview
PDF (Appendix A) - Final Version
See Usage Policy.

243Kb
[img]
Preview
PDF (Appendix B) - Final Version
See Usage Policy.

253Kb
[img]
Preview
PDF (Appendix C) - Final Version
See Usage Policy.

601Kb
[img]
Preview
PDF (References) - Final Version
See Usage Policy.

65Kb
[img]
Preview
PDF (Farnsworth thesis) - Final Version
See Usage Policy.

1561Kb

Repository Staff Only: item control page