Hartmann, Katharina (2014) N2O-Messungen im Auftriebsgebiet vor Namibia. (Bachelor thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 61 pp.

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Abstract

N2O is a gas which has a global warming potential that is 300 times more effective than CO2. Additionally, N2O is a precursor for NO-radicals that deplete the ozone layer. Therefore, it is highly relevant for the earth´s climate. There are two known natural processes that are mainly responsible for the production of N2O: nitrification and denitrification. The global oceans are main sources of N2O, especially the Eastern Upwellung Systems (EBUS). One of these EBUS is the Benguela system off Namibia. There have only been a few measurements in this area. During two cruises (M 98 and M 99) in 2013, samples were taken from the Benguela upwelling system. For this bachelor´s thesis the N2O concentrations have been measured to determine the distribution of N2O in the Benguela upwelling system off Namiba. The concentrations have been compared to the relevant literature. The main process for building N2O in this area has been identified as nitrification. The N2O saturation of the surface was up to 240 % which indentifies the Benguela upwelling system as a source of atmospheric N2O. Depth profiles show that the concentration of N2O increases with increasing depth while the concentration of oyxgen decreases. This inverse correlation identifies nitrification as the main process of building N2O in the water column. This finding is supported by a positive correlation of nitrate and N2O. The stations on the shelf show a less obvious correlation of N2O and oxygen. The depth profiles from these stations show higher variability. This variability may be a consequence of denitrification in the sediment which influences the concentration of N2O in the water column. Plots of DN2O vs AOU show positive correlations. This also indicates that N2O is produced mainly by nitrification. The plot of M 99 shows more dispersion than the plot of M 98. In the case of M 98 the slope of the line regression was 0,0406 nmol/μmol and in the case of M 99 0,0650 nmol/μmol. In comparison with the findings in the literature (0,1nmol/μmol) the above montioned results are minor. This thesis assumes that the reason for the minor slopes is that a lot of the stations were situated on the shelf.

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