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Title: Dissolved and particulate trace metals in the Forth and Tay estuaries
Author: Laslett, Rebekah E.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1993
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The estuarine biogeochemistries of Cd, Cu, Mn, Ni, Pb and Zn have been examined. Two adjacent, contrasting estuaries were selected to assess the effects of riverine discharge, hydrodynamic régime and particulate phase composition. Sampling throughout an annual cycle enabled seasonal differences in primary productivity and meteorological conditions to be included. Simultaneous nutrient determinations and fresh water flow measurements were used to assist in the interpretation of metal data. Dissolved Mn profiles in both estuaries are dominated by benthic inputs, a consequence of the reduction of Mn in sub-oxic sediments. Highest benthic fluxes occur in summer, and coincide with dissolved oxygen minima in the upper Forth. High wintertime fluxes are caused by the injection of porewater following sediment resuspension. Dissolved Ni and Zn are remobilised with Mn during summer in the Forth. Dissolved Cd concentrations in both estuaries increase with salinity as a result of chloro-complexation. Both Cd and Cu are remobilised during the breakdown of particulate material. Only about 5% of the Pb is in the dissolved phase. Suspended particulate trace element contents do not vary much within each estuary. The Ca contents, however, increase with distance seaward, since the coastal zone acts as a source of CaCO3 to the estuaries. Non-detrital Mn contents increase in the outer Forth during summer, a consequence of precipitative Mn oxidation. The behaviours of Ni and Zn mimic that of Mn, as they are scavenged from the dissolved phase by newly formed particulate Mn oxides. Particulate Mn contents are higher in summer than in winter, and higher in the well-oxygenated Tay than in the Forth. This is attributed to faster Mn oxidation rates at higher temperatures and dissolved oxygen concentrations. Suspended particulate Cd contents in both estuaries are highest in summer due to the binding of Cd to phytoplankton cells. Partition coefficients in the Forth and Tay follow the order Pb > Mn, Zn > Ni > Cu > Cd.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available