published_or_final_version / Chemistry / Master / Master of Philosophy

Two perceived limitations of conventional atomic spectrometry were addressed in these studies. One limitation is that the time required for sample preparation can exceed the actual analysis time by two or more orders of magnitude. High pressure homogenization in combination with high speed blending was evaluated for the preparation of slurries which could be directly analyzed by graphite furnace atomic absorption spectrometry (GF-AAS). Cadmium, copper and lead concentrations were successfully determined in certified reference materials (CRMs) of biological origin and frozen cervine liver and kidney. By capping the flat valve head of the homogenizer with a ruby disc, metal contamination introduced by the processing was reduced appreciably (but not eliminated) and the procedure was extended to the determination of chromium, iron, manganese and nickel in botanical CRMs and air dried animal feeds. The one problematic analyte element proved to be selenium which was consistently underestimated with this procedure. However, the combination of high pressure homogenization and partial enzymatic digestion with a crude protease alone or admixed with lipase or cellulase, released Se-residues from zoological and botanical CRMs so that Se could be accurately determined by slurry introduction GF-AAS. This technique was also applied successfully to freeze-dried, fresh and boiled fish tissues. The principal advantages of the slurry preparation technique are its speed, simplicity and lack of operator intervention. / The second limitation involved the loss of chemical speciation information during analysis. To preserve this speciation information, individual chemical species were separated chromatographically then detected in the column eluate using a novel all silica T-tube interface coupled with AAS. The advantages of the current interface design over previous prototypes were the compatibility with both organic or aqueous mobile phases and the low limits of detection (LODs) for Ag, Cd, Cu or Zn. The feasibility of the approach was demonstrated by monitoring levels of metal analyte bound to individual metallothionein isoforms which had been partially resolved by size exclusion or ion exchange HPLC. Whereas the metallothionein-I (MT-I) isoform was enriched in Cu relative to the MT-II isoform, the reverse was true for Zn. Also, a Ag-saturation procedure rapidly and efficiently replaced the bound Cd, Cu and Zn in these polypeptides.

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Chapter 1 of this thesis is a general review of published work o_ the origins and distribution of Cd, Cu, Fe, Mn and Zn in soils and their uptake and functions in plants. Chapter 2 is a synopsis of the geological history of the Fayoum of relevance to the origins of sediments at the study sties. Previous fractionation procedures, and a proposed modification to improve the determination of carbonate-bound elements are discussed in Chapter 3, while other analytical procedures are described in Chapter 4. Results of general soil analyses, of the fractionation analyses and useful correlation matrices, are tabulated together (for convenience in Chapter 5) and are discussed in detail in the following chapter. Texture was a crucial factor, finer-textured soils generally having lower pH and higher organic matter contents, although the latter were generally greater closer to the surface. Clay and silt contents were highly correlated, probably reflecting water sorting in the Fayoum, which aided the texture/drainage effect. Drainage (i.e. texture) was apparently very important in the fractionation chemistry of elements influenced by redox-reactions, i.e. Fe and Mn, and elements for which distribution depended upon Fe and Mn oxides (e.g., Zn) to a significant extent. Clay was especially important to the concentration of crystalline and amorphous iron oxides. Cd and Cu showed marked surface accumulation, especially in the exchangeable fractions, for many profiles, probably through pollution. The Cu content of organic matter was strikingly uniform at the Fayoum. Amorphous and crystalline Fe oxides seem to be especially important in the distribution of Zn. Clay Cd, Fe and Zn and, to a lesser extent, Cu and Mn contents were relatively constant, suggesting uniform origins. Chapter 7 describes a pot experiment on the soils using barley as a test crop, aimed at relating uptake to the fractionation results. Interpretation was complicated by a dominant effect of soil salinity. Chapter 8 suggests future related research.

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Samples of suspended particulate matter (SPM) and sediment were collected from the Humber coastal zone during six seasonal and inter-annual surveys (November 1993 - July 1995) on board RRS Challenger as part of the NERC Land Ocean Interaction Study (LOIS) initiative. Concentrations of Ni, Zn, Fe and Mn, extracted using a 1M HCl digest, were determined by atomic absorption spectrometry techniques. Particulate Ni and Zn both exhibited a pronounced seasonal distribution in the Humber coastal zone. Significant metal-salinity relationships were obtained for both metals indicating the Humber Estuary to be a significant source of Nip and Znp to the region. Metal distributions in the coastal zone were influenced by residual flow and tidal range at the mouth of the estuary, as well as wind speed and direction. Estimated fluxes of dissolved and particulate Ni and Zn from the Humber mouth to the North Sea indicated significant seasonal variation for both metals (17-290 kg dayˉ¹ Ni; 34-1737 kg dayˉ¹ Zn) and identified transport in the particulate phase dominant in autumn/winter (61-82 % Ni; 68-92 % Zn) but less significant in spring/summer (2-41 % Ni; 15-72 % Zn). Comparison to estuarine inputs suggested retainment of Ni and Zn within the Estuary. In the Humber mouth and throughout the Plume Nip and Znp concentrations significantly correlated to Fep suggesting uptake onto Fe-oxyhydroxide phases was important. Trace metal settling velocities indicated a significant seasonal variation in the settling of Ni (<1-163 µm sˉ¹) and Zn (2-218 µm sˉ¹) with these metals generally settling slower than the average SPM in winter but at the same rate in spring. Particle-solute interactions of Ni and Zn, investigated using the radioisotopes ⁶³Ni and ⁶⁵zn, indicated significant variation in metal partitioning (Kd) for the SPM end-members of the Humber coastal zone with Ni Kd's varying from 6.7 x 10² for Holderness Cliff material, to 13.0 x 10² for estuarine SPM and up to a maximum of 22 x 10² during spring/summer phytoplankton blooms. These results provide the basis of a consistent seasonal data base of trace metal distributions within the Humber coastal Zone which will substantially contribute to the development and parameterization of a fine sediment transport model for trace metal contaminants in coastal zones.

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Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy) Bibliography: leaves 355-380.