Stable carbon isotope analysis of seawater samples: a new approach to assess CO2 effects on the marine carbon cycle
Stable isotope ratio analyses offer a unique opportunity to obtain information about ecosystem dynamics, patterns and processes. The anthropogenic contribution to the global atmospheric CO2 rise through fossil fuel combustion, deforestation and other related human activities has changed the stable c...
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| Format: | Thesis |
| Language: | English |
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University of Southampton
2017
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| Online Access: | https://eprints.soton.ac.uk/412277/ https://eprints.soton.ac.uk/412277/1/Esposito_Mario_PhD_Thesis_June_17.pdf |
| Summary: | Stable isotope ratio analyses offer a unique opportunity to obtain information about ecosystem dynamics, patterns and processes. The anthropogenic contribution to the global atmospheric CO2 rise through fossil fuel combustion, deforestation and other related human activities has changed the stable carbon isotope composition (δ13C) of the atmosphere over the past 200 years. Changes in the carbon isotopic patterns of terrestrial biosphere, lithosphere and oceans are also expected. The global ocean has been acting as a net sink for CO2 emissions and although it moderates the climate, it is currently in a critical state of health. While the physico-chemical consequences (ocean acidification) of the increasing CO2 uptake by the ocean are fairly well known, the perturbation to marine ecosystems and the related effects on biota still entail large uncertainties. This thesis investigates the feasibility of using measurements of δ13C of seawater samples to increase our understanding of the biogeochemical responses of marine ecosystems to human CO2 perturbation. The isotopic composition of all the individual inorganic and organic carbon species from three long term mesocosm experiments (Sweden 2013, Gran Canaria 2014, Norway 2015) was determined. To have accurate and precise isotopic measurements, mass spectrometry instrument calibrations and method validation procedures were performed. Universal and inter-laboratory accuracy of the analysis was assessed by running standard materials provided by the International Atomic Energy Agency (IAEA, Vienna) and by the Scottish Universities Environmental Research Centre (SUERC) stable isotope laboratory, respectively. Precision and internal consistency was assessed from isotopic measurements of seawater reference materials from A.G. Dickson and D. Hansell for dissolved inorganic and organic carbon, respectively. A novel accurate, precise and rapid method, coupling a Shimadzu 5000A total organic carbon (TOC) analyser to an isotope ratio mass spectrometer (Thermo Scientific Delta V ... |
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