Small-scale heterogeneity in sediments:experimental and modelling investigations

Stockdale, Anthony (2008) Small-scale heterogeneity in sediments:experimental and modelling investigations. PhD thesis, UNSPECIFIED.

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This thesis consists of several studies relating to small-scale heterogeneity in sediments. The principal aim was to further our understanding of processes occurring at microniches. The individual studies consist of: 1) a critical review of previous studies of microniches that used probes with high spatial resolution and modelling approaches; 2) an experimental study of analysis of oxyanions in sediment at high resolution that applied a newly developed preparation method for a combined AgI/FeOOH binding phase, to investigating processes occurring at a sulphidic microniche within a freshwater sediment; 3) analysis of the relationship between trace metal (cobalt) and iron and manganese in a marine sediment using DGT, although this is not directly related to microniches, these data are useful in modelling the release of microniche trace metal from authigenic oxides; 4) the development and application of a three-dimensional diagenetic model to investigate conceptually the geochemical behaviour of microniches under different conditions, and to interpret modelled observations in terms of data from the literature and known trace element geochemistry. The key results/conclusions from both the laboratory and modelling studies are: 1) for a freshwater sediment, depletions in anions (of P, V, As) at a microniche of elevated sulphide were observed and the behaviour of phosphate at this niche was attributed to uptake associated with elevated activity of sulphate reducing bacteria; 2) modelled scenarios, with varying microniche properties, were shown to be relevant to experimental observations reported in the literature. The preferential deposition of FeS at the edge of microniches (with lifetimes of 2.5-5 days), forming ‘crustal’ deposits was demonstrated. The modelled data indicated that microniches may be significant in terms of the formation of some trace element sulphides. This thesis also contains an assessment of the significance of microniche processes and a discussion of priorities for future work.

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Thesis (PhD)
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Addendum to electronic version: This version contains unchanged introductory material from the print version of the thesis. The final print version of the thesis contained various version of papers depending on the stage reached in the publication process at the time of submission. All of the papers are now published so are not reproduced here. Paper 5 was changed substantially during the peer-review process, with the removal of a discussion of trace metals. For completeness the version submitted in the final thesis is included in this electronic version. The definitive version is housed at Lancaster University Library.
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12 Feb 2010 14:44
Last Modified:
12 Sep 2023 00:13