The sedimentary sulfur cycle is one of the main components of estuarine
biogeochemical systems. It is initiated by the oxidation of organic matter via sulfate
reducing bacteria which produce hydrogen sulfide (H2S). The S(II) then reacts via both
abiotic and biotic pathways to form sulfur with other oxidation states. The three most
widely-studied “operationally”–defined components of the sedimentary sulfur system
are total reduced (inorganic) sulfur (TRS), acid volatile sulfide (AVS), and dissolved
(=filter-passing) sulfide.
This study focused on several parameters that are widely held to be important in
determining TRS in sediments and the relative proportions of TRS, AVS and dissolved
S(II) forms. The formation of iron sulfide minerals requires metabolizable organic
matter and SO4
2- to produce S(II) and “reactive”-Fe as a source for the iron in iron
sulfide minerals. One of these components is generally the limiting factor in TRS
formation (e.g., Berner 1970). Nine different sites from three locations on the Central
Texas coast were studied for a variety of parameters including organic matter, sulfate
concentrations, sulfate reduction rate, solid “reactive” and dissolved iron, and grain size,
as well as TRS, AVS, and ΣH2S. At each site five sediment cores were taken to a depth of 20 cm whenever possible. The cores were sectioned in 2 cm intervals. The porewater
was extracted and both solid and dissolved components were analyzed using a variety of
methods, including carbon and sulfur coulometry, acid extraction, chromium extraction,
and drying the sediment. The results of he analyses showed that the central Texas coast
is a widely diverse system. Some sites were very sandy while others were fine-grained.
This variety was especially true for the Nueces Bay and Baffin Bay sites. The East
Matagorda Bay sites showed more homogeneity in almost all analysis. While the
heterogeneity of locations along the Central Texas coast makes it difficult to make a
definitive statement about the controls on TRS in this area, most sites are controlled by
the low amounts of iron in the system, which limits the amount of iron sulfide that can
form. Low reactive iron concentrations and high degrees of pyritization (DOPs) support
this argument. Exceptions exist for low-salinity (sulfate-limited) or very fine-grained
(organic matter limited) sites.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1834 |
| Date | 02 June 2009 |
| Creators | Thomson, Heather |
| Contributors | Morse, John W. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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