Chemische Charakterisierung eines Sedimentkerns aus dem Arabischen Meer


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Abstract

Sediments of the oceans arc a significant climate archive. Laminated sediments, in which the varve structure is preserved because of the absence of bioturbation, are especially interesting for high-resolution-analysis of the paleoclimate. Sediments from the Arabian Sea are formed within the oxygen minimum zone (<0,2 mg O2/L) and offer a high resolution climate archive in which e.g. variabilities of the indian monsoon intensity or the expansion of the oxygen minimum zone can be investigated in the course of time. In the Arabian Sea a broad oxygen minimum zone between 200-1200 m exists. Between the Asian massif and the Indian Ocean the monsoon strongly influences the life of people. It is seperated into the summer and winter monsoon. During summer nutrient rich water flows into the Arabian Sea resulting in high primary production and therefore in carbon-rich sediments. The northwest monsoon during winter lead to high terrigenous input into the Arabian Sea. To gain sub-mm scale information about the chemical signature of laminated sediments it is important to be sure that the used analysing method is precise and accurate. In this work parts of the sediment core GeoB12309-5 taken in the northern Arabian Sea, located south of the makran region out of 956 m of depth, were analysed by laser ablation inductively coupled plasma massspectrometry (LA-ICP-MS) and ICP-optical emission spectrometry (ICP-OES)/MS after a full acid digestion. The chosen parts are interesting because they contain turbidities and a preserved varve structure. In the geoscience community elemental or element ratio pattern are often analysed using the X-Ray-Fluorescence (XRF) core scanning technique. Therefore, results obtained in the presented study were also compared to XRF core scanner results. With this analytical approach it is possible to define the method which is best suitable to perform high resolution analysis. Results of this work have shown that the ICP-OES/MS-method after digestion is the most precise method to analyze soft sediment cores. The X-Ray-Fluorescence-method supplies only intensities and is strongly dependent on the water content, particle size distribution and surface conditions of the sediment core. In contrast to this, the LA-ICP-MS and ICP-OES/MS provides element concentrations, but these methods are more time consuming. The laser ablation system as it was used here shows problems with long term drift and calibration. During one measuring day (9 h) the cones of the ICP-MS device were plugged as a result of the ablated material. Due to the inhomogenity of sample material and least amounts taken for the analysis it is difficult to accuratly compare these three methods.



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Thesis (Diplom)
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Eprint ID
25100
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Römmermann, H. (2011): Chemische Charakterisierung eines Sedimentkerns aus dem Arabischen Meer , Diplom thesis, Fachbereich 2 (Biologie/Chemie) der Universität Bremen.


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