The trace metals zinc (Zn), cadmium (Cd), and copper (Cu) are vital micronutrients for
marine phytoplankton, but toxic at elevated concentrations. The predominant external sources
of these trace metals into the ocean are atmospheric and riverine fluxes. These fluxes, which
are dramatically perturbed by anthropogenic contributions, are the subject of this thesis. First,
the Zn and Cu isotope compositions of aerosols deposited into the tropical Atlantic Ocean are
presented. Second, the isotopic compositions of Zn, Cd and Cu within and around an estuary
of a highly metalliferous mining region are examined. The goal is to better constrain
anthropogenic influences on the fluxes of these trace metals to the oceans.
High-temperature industrial processes produce isotopically light Zn emissions.
Chapter 3 examines whether the Zn and Cu isotope compositions of aerosols can aid in
distinguishing anthropogenic and natural atmospheric inputs of these metals to the surface
ocean. The aerosols present Zn isotope compositions that demonstrate some potential for
tracing anthropogenic Zn, whilst the aerosol Cu isotope compositions are indistinct from the
lithogenic isotopic composition.
Chapters 4 and 5 focus on isotopic variations of Zn, Cd and Cu within the Ria of Huelva
estuary, which connect the acid mine drainage (AMD) impacted Tinto and Odiel Rivers in the
Iberian Pyrite Belt and the Gulf of Cadiz. The AMD carries remarkably high quantities of trace
metals, which are released into local watersheds and, ultimately, transported to the ocean.
Measurements of the trace metals in the estuary reveal dynamic biogeochemistry, including
significant removal of Zn and Cu to the particulate phase whilst Cd shows a conservative
distribution. The dissolved isotopic compositions of Zn, Cd and Cu do not demonstrate the
ability to trace specific AMD sources. Nevertheless, Zn and Cu show promise as tracers of
AMD in the eastern Atlantic Ocean and the Mediterranean Sea.