Thesis (Ph. D.)--University of California, Santa Cruz, 1998. / Typescript. Includes bibliographical references.

Thesis (M.S.)--University of California, Santa Cruz, 1996. / Typescript. Includes bibliographical references.

No description available.

No description available.

No description available.

No description available.

No description available.

One of the prominent features in sediment sequences formed around the AllerOd-Younger Dryas transition (c. 12.9-12.8 ka bp) in North America is a dark layer of organic-rich material, i.e. the black mat. The black mat sequences in southeast Arizona contain a thin sandy basal layer corresponding to the lower Younger Dryas boundary. Trace element concentrations in the lower Younger Dryas boundary sediments, in the black mat, in the host sediments, and in charcoal from Western Europe and southeast Arizona were studied using LA-ICP-MS. The black mat samples and samples of the underlying host sediments display compositions similar to the average continental crust, while the sediments from the lower Younger Dryas boundary are enriched in rare earth elements, Ni, and Co whereas Ta, Nb, Zr, and Hf are depleted relative to the rare earth elements. Such a difference in compositions between the lower Younger Dryas boundary sediments and other sediments points to a short enigmatic event, which changed conditions of sedimentation just before the onset of the Younger Dryas cooling. The presence of products of biomass burning of still unknown origin is suggested on the basis of trace element features of sediments from the lower Younger Dryas boundary.

Digitized by Kansas Correctional Industries

by Oi-Ming Cheng. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 104-108). / Chapter 1 --- INTRODUCTION / Chapter A) --- Sources of zinc and its functional role --- p.10 / Chapter B) --- Effects of excessive zinc intake --- p.11 / Chapter (a) --- Human --- p.11 / Chapter (b) --- Animal --- p.11 / Chapter (c) --- Fish --- p.12 / Chapter C) --- Techniques in zinc determination --- p.12 / Chapter 2 --- ANODIC STRIPPING VOLTAMMETRY / Chapter A) --- Basic principles --- p.16 / Chapter (a) --- Cell --- p.16 / Chapter (b) --- Electrodeposition and stripping --- p.20 / Chapter B) --- Major interferences in anodic stripping and the common solutions to these problems --- p.25 / Chapter (a) --- Intermetallic compound formation --- p.25 / Chapter (b) --- Overlapping peaks --- p.26 / Chapter (c) --- Organic compounds adsorbed at the electrode --- p.28 / Chapter 3 --- MUTUAL INTERFERENCE FROM ZINC AND COPPER / Chapter A) --- Introduction --- p.30 / Chapter B) --- Review of reported methods to remove copper interference --- p.31 / Chapter (a) --- Dual-working electrode approach --- p.31 / Chapter (b) --- Adjustment of the deposition potential --- p.31 / Chapter (c) --- Standard addition --- p.33 / Chapter (d) --- Addition of a third element --- p.33 / Chapter C) --- The proposed solution --- p.35 / Chapter 4 --- EXPERIMENTAL / Chapter A) --- Proposed method --- p.37 / Chapter (a) --- Apparatus --- p.37 / Chapter (b) --- Reagents --- p.38 / Chapter (c) --- Procedure --- p.40 / Chapter B) --- Reference method --- p.45 / Chapter (a) --- Apparatus --- p.45 / Chapter (b) --- Reagents --- p.45 / Chapter (c) --- Procedure --- p.47 / Chapter 5 --- RESULTS AND DISCUSSION / Chapter A) --- Optimization of instrumental parameters and working conditions --- p.49 / Chapter (a) --- Effect of plating potential on zinc peak current --- p.49 / Chapter (b) --- Effect of plating time on zinc peak current --- p.53 / Chapter (c) --- Effect of holding time and holding potential on zinc peak current --- p.56 / Chapter (d) --- Effect of sweep rate on zinc peak current --- p.58 / Chapter (e) --- Effect of final potential and strip time on zinc peak current --- p.61 / Chapter (f) --- Effect of pH on the peak current and recovery of zinc in the presence of copper after the sulphide treatment --- p.63 / Chapter (g) --- Effect of the concentration of buffer on the peak current --- p.66 / Chapter (h) --- Effect of the reaction time of sulphide with copper on the zinc recovery --- p.68 / Chapter B) --- "Calibration graph, precision and detection limit" --- p.71 / Chapter C) --- Effect of copper on the zinc determination by the proposed method --- p.78 / Chapter D) --- Interference studies --- p.80 / Chapter E) --- Recovery tests --- p.84 / Chapter F) --- Determination of zinc in real samples using the proposed method --- p.86 / Chapter (a) --- Clean water samples such as sea water and tap water --- p.86 / Chapter (b) --- Contaminated natural water and domestic wastewater samples --- p.91 / Chapter (c) --- Air samples --- p.93 / Chapter (d) --- Oyster tissue samples --- p.96 / Chapter (e) --- Sewage sludge and sediment samples --- p.99 / Chapter 6 --- CONCLUSION --- p.102 / REFERENCES --- p.104