The atmosphere is an important pathway of particulate matter and their associated trace elements to the ocean and can play vital roles in marine bio-geochemical cycles. Factors that control trace element inputs from the atmosphere (e.g. solubility, sources) are not well understood, in particular for the South Atlantic Ocean. In this thesis, select major, trace and rare earth elements and the isotopes of two of the elements, lead (Pb) and neodymium (Nd), were investigated in potential sources of aerosols, and aerosol samples, from over the South Atlantic Ocean. Chapter 2 of this thesis presents new element concentration and isotopic compositions of potential source areas from South America and southern Africa, combined with previously published data to represent an up-to-date characterisation of natural and anthropogenic aerosol source areas in South America and southern Africa. Chapters 3 and 4 of this thesis present new element concentration and isotopic compositions of aerosol samples from across the 40°S transect of the South Atlantic Ocean (from the UK GEOTRACES GA10 transect). The results provide the first constraints on the elemental and isotopic composition of total and soluble fraction of aerosol samples across a zonal transect of the South Atlantic Ocean. By comparing the element and isotopic compositions of the aerosol samples to the potential source areas from South America we demonstrate that natural and anthropogenic sources from South America and southern Africa are major sources of atmospheric particulates, but of varied contribution, across the South Atlantic. Elemental and isotopic compositions of the aerosols suggest there is a strong impact of anthropogenic sources from South America on atmospheric particles delivered to the western South Atlantic and a strong influence of natural sources from South America on atmospheric particles delivered to the middle of the South Atlantic. We further demonstrate that there is an importance of anthropogenic southern African sources on aerosol composition over eastern South Atlantic as well as South American source inputs. In Chapter 4 we reveal that large ranges in trace element solubility (between < 5 and > 95%, generally above 40% across the ocean) in aerosols carried to the South Atlantic may be available for seawater dissolution and may have implications on marine biogeochemical cycles. Overall the present thesis underlines the important role that anthropogenic source areas can play on atmospheric composition, and provide for the first time measurements of major, trace and rare earth element availability to the surface ocean of the South Atlantic. The thesis also highlights the key role that multi-element concentrations and Pb and Nd isotopic compositions can play in deciphering the provenance of aerosols and element seawater supply.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:721542 |
| Date | January 2014 |
| Creators | Khondoker, Roulin |
| Contributors | Weiss, Dominik ; van de Flierdt, Tina ; Rehkamper, Mark |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/49778 |
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