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The adsorption protection theory : an examination of two marine environments : the continental slope along southwestern Vancouver Island, British Columbia and the continental shelf and slope of the Makran area along the coast of Pakistan Mackin, Jonathan Patrick

Abstract

The model of adsorption of organic matter onto sediment surfaces is increasingly being used to explain enhanced preservation of organic matter in marine sediments. While recent studies have shown that there is strong evidence that sediment surfaces play a role in protecting organic matter from microbial degradation, these same studies have looked primarily at marine environments that could be considered "ideal," whereby there exists plenty of organic matter production, consistent sedimentary inorganic material input and no post-depositional disturbance of the sediment and organic material. The continental slope along the southwestern coast of Vancouver Island, British Columbia, and the continental shelf and slope of Makran area of the Arabian Sea, along the coast of Pakistan, are regions in which there is moderate to high primary productivity and varying sediment input and redistribution regimes. The continental slope of the southwestern coast of Vancouver Island can be characterized as sediment starved region, the majority of riverine sediments are captured in the coastal fjord system and there is very little aeolian input. The sediments that are deposited along the coast of Vancouver Island have been classified as relict deposits and undergo re-suspension and redistribution events as a result of both tectonism and interactions with bottom water currents. The continental shelf and slope of the Makran area of the Arabian Sea varies from the continental slope of Vancouver Island in that there is plenty of sediments supplied via rivers along the coast of Pakistan, India, and Iran. Furthermore, the Makran area is subject to inputs of aeolian deposits from the surrounding deserts. Similar to the coast of Vancouver Island, the Makran area is subject to tectonism and bottom water and storm currents re-suspending and re-distributing sediment. Organic matter production along the coast of Vancouver Island ranges from 150 -200 g C m⁻² year⁻¹, while organic matter production in the Makran area of the Arabian Sea ranges from 200-400 g C m⁻² year⁻¹. The percentage of organic matter preserved on the continental slope of the southwestern coast of Vancouver Island and the continental shelf and slope of the Makran area ranges from 0.36 - 0.77% and 0.50 - 2.48%, respectively. Bulk sediment surface area for samples from the continental slope of the southwestern coast of Vancouver Island and the continental shelf and slope of the Makran area range from 11.6 - 24.6 m²/g and 10.0 - 24.8 m²/g, respectively. There is no correlation between surface area and organic carbon concentrations for either region. Samples from the continental slope of the southwestern coast of Vancouver Island have surface area to organic carbon concentration ratios that fail to meet the limits set for monolayer equivalence. Samples from the continental shelf and slope of the Makran area of the Arabian Sea, on the other hand, have surface area to organic carbon concentration ratios that fall within the limits set for monolayer coverage of the individual sediment grains by organic matter, however when their fractional coverage was calculated the majority of samples were

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