Characterization of chromophoric dissolved organic matter with iron chelates in rain water
- UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
- Lorri Resetar (Creator)
- Institution
- The University of North Carolina Wilmington (UNCW )
- Web Site: http://library.uncw.edu/
- Advisor
- Robert Kieber
Abstract: The existence of Fe(II) and Fe(III) complexed CDOM has important ramifications
for the speciation of iron in atmospheric waters. The Fe(III)-CDOM complex is a
precursor to Fe(II) photochemical production where a ligand to metal charge transfer
(LMCT) leads to the production of the reduced iron. Fe(II) and Fe(III) were added to
Wilmington, NC rainwater containing chromophoric dissolved organic matter (CDOM).
In general Fe(II) enhanced the fluorescence of CDOM while Fe(III) quenched CDOM
fluorescence. The observation of fluorescence changes indicates complexation.
In authentic rain where Fe(II) and CDOM fluorescence were measured before and
after irradiation there was a significant correlation between the photoproduction of Fe(II)
and increased fluorescence. While in synthetic rainwater containing CDOM extracted
from rainwater and added Fe(III) irradiation for 2 hours photoproduced Fe(II). The
amount of Fe(II) produced was accurately predicted using a model calculation generated
for predicting changes of Fe(II) in authentic rainwater using starting Fe(II), Fe(III), and
H+ concentrations. The accuracy of this equation in both authentic and synthetic
rainwater with added rainwater CDOM demonstrates the importance of CDOM for Fe(II)
photoproduction. Once irradiation ceased Fe(II) oxidized slower in synthetic rainwater
containing CDOM relative to synthetic rainwater without CDOM with a rate constant of
1.66 nM h-1 which is similar to authentic rainwater oxidation studies where the rate of
oxidation range for was 0.9 – 7 nM h-1. After 22 hours the remaining Fe(II) was
protected against further oxidation by complexation with the extracted CDOM. The
reproducibility between authentic rainwater and synthetic rain with added CDOM
indicates that the ligand responsible for protecting Fe from oxidation is CDOM. A solution of CDOM extracted from rain with added Fe(II) remained stable in a
synthetic rainwater solution for 24 hours similar to observation in authentic rainwater;
however very different from synthetic rainwater without CDOM. A solution of CDOM
with Fe(II) had constant Fe(II) concentrations when mixed 1:1 with seawater for at least
four hours, however Fe(II) in synthetic rain with no added CDOM became undetectable
within three minutes of mixing with seawater. This stability of Fe(II) with added rain
CDOM suggests that CDOM is the organic ligand responsible for protected Fe(II) from
oxidation and its soluble form in natural waters.
Characterization of chromophoric dissolved organic matter with iron chelates in rain water
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Created on 1/1/2009
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Additional Information
- Publication
- Thesis
- A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
- Language: English
- Date: 2009
- Keywords
- Rain-water (Water-supply)--Iron content--Analysis, Rain-water (Water-supply)--Organic compound content--Analysis
- Subjects
- Rain-water (Water-supply) -- Organic compound content -- Analysis
- Rain-water (Water-supply) -- Iron content -- Analysis
Title | Location & Link | Type of Relationship |
Title Page, Table of Contents & Abstract | http://libres.uncg.edu/ir/uncw/f/resetarl2005-1.pdf | The described resource includes the related resource either physically or logically. |
References | http://libres.uncg.edu/ir/uncw/f/resetarl2005-3.pdf | The described resource includes the related resource either physically or logically. |