The evolution of the sulphur content of humic substances extracted from a near-shore sediment core was investigated. Special attention was taken to avoid S contamination of the humic materials during sample handling and extraction. The S/C ratios increased continuously with depth to values which strongly suggest S addition to the humic matrix during early diagenesis by reactions between organic matter and H₂S or its oxidation products. The light isotopic composition of this organic sulphur supports this view; however, subsequent isotopic exchange has obscured the mechanism initially involved. Since a large fraction of the enrichment occurred above the sulphidic zone, redox boundaries, such as the interface of anoxic microniches within the more oxidized zones, or the sulphidic/suboxic boundary of the sediment column, must have been important sites for S addition. The influence of sulphur enrichment on the complexing capacity of humic materials was also investigated, and it was shown that S-addition increases significantly the number of sites on which Cu is irreversibly bound. Iodine is characteristically enriched at the surface of hemipelagic and nearshore sediments deposited under oxygenated conditions. In such sediments, bulk I/Corg ratios usually decrease with depth to values which are characteristic of anoxic sediments, reflecting a preferential release of iodine during early diagenesis. There is some debate as to whether sedimentary iodine is associated with the iron oxyhydroxide phase or with the organic fraction, and whether the decrease in I/Corg with depth is due to the dissolution of the iron oxyhydroxides or the decomposition of labile organic matter. In this study, it is shown that in a surficial hemipelagic sediment sample and in a nearshore sediment core iodine is mainly associated with the organic fraction and, moreover, that humic substances are involved in the surficial iodine enrichment. Laboratory experiments on the uptake and release of iodine by and from sedimentary humic substances also suggest a mechanism whereby humic materials reduce iodate at the sediment/water interface to an electrophilic iodine species which further reacts with the organic matter to produce iodinated organic molecules. During burial, this excess iodine could be displaced from the organic matrix by nucleophiles such as sulphide ions or thiosulphate, thus providing a possible explanation for the decrease in I/corg ratio with depth observed in many nearshore and hemipelagic sediments. Bulk metal concentrations were measured in the sediments of Saanich Inlet in an attempt to establish the occurrence of trace metal enrichments in the anoxic central basin. Ba, Ni, V, Cr, Zn, Pb, Cu, and Mo were found to be enriched in the anoxic ooze over the possible contributions from lithogenous sources. Spatial and seasonal variations in the chemical composition of the settling particulates collected with interceptor traps gave further indications of the mode of incorporation of these metals. Biogenic Ba and Cr appeared to be associated with opaline silica, although alternative explanations are also possible, particularly for Ba. Zinc seemed to be added to the sediment essentially in association with planktonic materials, while Cu required an additional source directly linked to the anoxic environment. Similarly, Ni, V, and Mo were added to the anoxic sediments by reactions occurring at the sediment-water interface. In the nearshore environment studied here, these metals were not associated to any significant extent with planktonic materials, particularly Ni and Mo. Of all the elements analyzed, Mo showed the largest enrichment in the anoxic sediments of Saanich Inlet. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The study of suspended sediment provides insights into the transport and accumulation of sediment in depositional basins. Past investigations have suffered, however, from a lack of methodology that can deal with the low concentrations of suspended sediment. The theory and method of three techniques to be used in the analysis of suspended sediment have been outlined. 1) VSA, provides a rapid, accurate and precise method of determining grain size distributions of low weight samples. The method is based on the solution to a set of equations that discretely define the increasing volume of a homogeneous sediment sample settling in an enclosed volume of water. The results are in terms of sedimentation diameters, a hydrodynamically sensitive property. 2) The Ag filter mount provides a fast technique for a low sample weight random oriented mount to be used in quantitative XRD analysis. The method has excellent precision and does not fractionate the mineral component due to their settling velocity. 3) Suspended sediment collectors have been used to measure the downward flux of sediment in the fjord environment. The traps have also provided a means to calculate the natural settling velocity of flocculated or otherwise enhanced particle settlement. Laboratory and field studies have dealt with the interaction of zooplankton with suspended sediment. Marine zooplankton ingest suspended sediment at a rate dependent on sediment concentration and mineralogy. Ingested mineral particles undergo chemical and mineral transformations which are functions of mineralogy, cation exchange capacity and residence time in the digestive tract. Zooplankton fecal pellets have a much larger settling velocity than their component particles. This increased settling rate allows clay to be deposited where the hydrodynamic nature of the environment would only allow coarse silt to fine sand deposition. Glacial flour (feldspar, quartz, trioctahedral mica, chlorite, amphibole, tourmaline, and vermiculite) enters the surface-layer of the Howe Sound fjord as a sediment plume which moves quickly down inlet while slowly mixing with the marine water. Although flocculation occurs in the lower brackish water of the surface-layer, mixing and diffusion are the dominant means for sediment to enter the lower-marine-water. Once in the lower-marine-water, zooplankton pelletization and biologic agglomeration of inorganic floccules takes place. These processes that enhance the individual particle settlement, generate a fast response time between the surface-layer and the lower-marine-layer in terms of sedimentation of particulate matter. Settling velocities of particles less than 1 μm have been enhanced over 1400 times. Size distributions of sediment deposited on the sea-bed are a function of variable multimodal and/or non log-normal size distributions from sub-laminae falling through the water column. The increase in deviation away from log-normality down inlet, for size distributions of both suspended and deposited sediment, is an artifact of the size analytical method. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The purpose of the study was to examine the distributional patterns of diatoms in the surface sediments of ten southern British Columbia inlets with respect to oceanographic and hydrographic setting, and phytoplankton distribution and productivity. The study area was divided on the basis of inlet type (high, medium, and low runoff), within-inlet gradients, and zones (northern, central, and southern). A small group of species dominated the 95 sediment assemblages. There was a fairly good correlation between the biocoenoses and the thanatocoenoses in the sense that most of those species reported as dominants in the phytoplankton were also dominants in the sediment assemblages. However, there were discrepancies and these could not be explained on the basis of the relative silicification of the diatom valves. Skeletonema costatum, usually considered a weakly-silicified, dissolution-sensitive species, was abundant in British Columbia sediments. Both the pacifica and the aestivalis forms of Thalassiosira aestivalis were abundant in the phytoplankton, but only the pacifica form was preserved well in the sediments. Thalassiosira nordenskioeldii, which is found in other sediment assemblages, was rare in most British Columbia sediments. The distributional patterns of freshwater and marine littoral species appeared to be indicative of river sources entering the estuarine system. The absolute abundance of diatoms in the sediment assemblages increased from the northern to the southern zone. Within the inlets, both absolute abundance and primary productivity increased toward the mouth. Estuarine circulation did not appear to alter substantially the spatial relationship between the biocoenoses and the thanatocoenoses. In general, individual species and species-groups often exhibited distinct distributional patterns which could be related to inlet type, zonal, and within-inlet patterns. In particular, the principal coordinate analysis showed a zonal correlation between the dominant species in the sediment assemblages, and primary productivity, salinity, and temperature in the surface waters. / Science, Faculty of / Botany, Department of / Graduate

Varved, anoxic sediments in Saanich Inlet, British Columbia, are formed by the annual cycle of summer deposition of diatom frustules and winter inputs of terrigenous material derived from land runoff. The objective of this study was to sample the varve record in order to develop a palaeoceanographic history of the Inlet. Box-cores of varved sediments were collected from Finlayson Arm, Saanich Inlet. The cores were quick, frozen upon recovery, to preserve the laminae, were subsequently sectioned and X-radiographs of the sections prepared. The varves were individually sampled and analysed for their diatom assemblages together with carbon, carbonate, major and minor element concentrations and ²¹⁰Pb activity. The chronology of a representative core determined by ²¹⁰Pb was inconsistent with that determined by varve counting. The geochemical data indicated that the upper 15cm of the core had a distinct elemental composition and a lower porosity that indicated a changed sedimentation rate. It also appeared that around 20 years of sediment had been lost from the core-top. The upper sediment contains a carbonate increase linked to a dust dump from a local cement plant which occurred between 1960-1963. In the lower section of the core, both the diatom and the geochemical data indicate seasonal variation expected from the formation of annual varves. However, a well constrained chronology cannot be obtained for this core because of the non-steady state sedimentation. This makes the interpretation of inter-varve variations in the light of regional climatic records impossible. Nevertheless, a change in production on a cycle of approximately 10-15 years is evident and this study provides conclusions that will be useful to future palaeoceanographic investigations on longer cores from a part of the Inlet where sedimentation is more constant. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate