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Title: Stable (Cu, Zn) and radiogenic (Pb) isotope geochemistry of airborne particulate matter
Author: Dong, Shuofei
ISNI:       0000 0004 2732 3811
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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The aim of the thesis was to test the isotope systematics of Cu, Zn and Pb in atmospheric particulate matter and potential source material in order to critically discuss its implications and applications to studies of global biogeochemical cycles and anthropogenic impact. Four specific objectives were addressed: First, we tailored existing analytical methods to enable for the first time accurate and precise Cu and Zn isotope ratio measurements in dust and aerosol samples with low element content. Second, we studied the Pb, Cu and Zn isotope composition in aerosols collected in London to test their potential to trace anthropogenic sources in the urban atmosphere. Third, we characterized the Cu and Zn isotope systematics of major Asian and African dust sources and constrained possible controls and implications on the marine isotope signature. Finally, we investigated the isotope fractionation of Zn during dissolution experiments with acidic solution of natural dust to test the possible effect of atmospheric processing on the isotope signature of deposited Zn. The conclusions from this work are: First, stable isotopes confirm that brake and tyre emissions are the likely dominant sources of Zn and Cu in urban aerosols and that recycled Pb deposited originally from leaded gasoline still contributes significantly to the burden of atmospheric Pb in London. Second, we show that the Cu and Zn isotope signatures vary significantly between the major Asian and African dust sources and we find a significant correlation between Cu isotope ratio and illite content. Mass balance calculation suggest that bulk samples record faithfully the isotope signature of the <4 μm fraction. Third, significant isotope fractionation of Zn is observed during dust dissolution suggesting that the isotope signature of Zn deposited in the surface ocean is not only controlled by source mixing but also by atmospheric processing during long range transportation. The work clearly supports the initial hypothesis that metal isotopes are powerful sources to study global and regional biogeochemical cycles.
Supervisor: Weiss, Dominik ; Spiro, Baruch Felix Sponsor: UK-China Scholarships for Excellence
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral