A series of laboratory and field investigations were carried out to elucidate the
importance of natural organic matter in aquatic systems, i.e., trace element scavenging
(e.g., 234Th) by exopolymeric substances (EPS), formation of biofilms, as well as
interactions with 129I.
A method involving cross flow ultrafiltration, followed by a three-step cartridge
soaking and stirred-cell diafiltration, was developed for isolating EPS from
phytoplankton cultures, especially in seawater media. EPS isolated from a marine diatom,
Amphora sp. was then subjected to semi-quantitative (e.g., carbohydrate, proteins) and
quantitative analysis (e.g., neutral sugars, acidic sugars, sulfate). It appeared that Th (IV)
binding by EPS was dominated by the acidic polysaccharides of fraction.
For EPS of biofilms collected from polluted streams, hydrophobic proteins were the
most abundant components in EPS, followed by more hydrophilic carbohydrates.
However, chemical composition of carbohydrates or proteins, i.e., monosaccharides and amino acids, respectively, varied with environmental conditions and substrata applied,
which suggests that the formation of biofilms on different substrates is regulated by
specific properties of microorganisms, environmental conditions and nature of
substratum. No correlation between relative hydrophobicity of substratum and
development of biofilm was found in this study.
A sensitive and rapid GC-MS method was developed to enable the determination of
isotopic ratios (129I/127I) of speciated iodine in natural waters. At the F-area of the
Savannah River Site (SRS), iodine species in the groundwater consisted of 48.8 percent iodide,
27.3 percent iodate and 23.9 percent organo-iodine. Each of these iodine species exhibited vastly
different transport behavior in the column experiments using surface soil from the SRS.
Results demonstrated that mobility of iodine species depended greatly on the iodine
concentration, mostly due to the limited sorptive capacity for anions of the soil. EPS,
especially enzymes (e.g., haloperoxidases) could facilitate the incorporation of iodide to
natural organic carbon. At high input concentrations of iodate (78.7 μM), iodate was
found to be completely reduced and subsequently followed the transport behavior of
iodide. The marked reduction of iodate was probably associated with natural organic
carbon and facilitated by bacteria, besides inorganic reductants (e.g., Fe2 ) in sediments
and pore water.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-08-8432 |
| Date | 2010 August 1900 |
| Creators | Zhang, Saijin |
| Contributors | Santschi, Peter H., Brinkmeyer, Robin |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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