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This study investigated trace essential metals (Cu, Zn and Cr) and non-essential metals (Pb, Cd and Hg) in water, sediment and tissues of water spinach, snake head fish and swamp eel from the Saigon River. Sampling was conducted from January to December 2004 at three sites. Three water and sediment samples, edible parts of twenty water spinach (Ipomea aquatica) samples (leaves and stems), twenty snake head fish (Channa striata) and twenty swamp eels (Monopterus albus) were collected at each site. Water, sediment and biota tissues were analysed for Cu, Zn, Cr, Pb, Cd and Hg following the method of USEPA, AOAC and NFTA. Results showed that Cu, Zn, Cr, Cd and Hg in water from the river was not higher than the maximum permitted level for protection of aquatic life by the national standards while the average Cu concentration in sediment was found to be close to the Effects range- low value and within the slightly polluted range (25- 50 ìg.g-1 dry weight). The results also showed that the river sediment was considered to be contaminated by Zn and Hg in comparison with contaminated sites in Australia and in Thailand. In water spinach, no Cu deficiency was found but Zn was accumulated. No accumulation of Cr, Cd and Hg was revealed but Pb was detectable. The results indicated that snake head and eel may have Cu deficiencies. Pb and Hg were found to be bioaccumulated in the muscle of snake head and eel at some sites on some occasions, but the levels were small. The results showed that metal in sediment liver of snake head muscle of snake head and eel water. The metals in water spinach decreased in the order Zn Cu Cr Pb Cd and Hg; in snake head the metal concentrations decreased in the order Zn Cu Cr PbHgCd and in eel as Zn Cu Cr PbCd and Hg. The ANOVA test showed no significant relationship between metals in the water and sediment and biota. Therefore it was concluded that the metals in the selected biota samples did not reflect the metals in the environment. The essential metals Cu, Zn and Cr were found to decrease at the end of the dry season and then increase at the end of the rainy season. The seasonal variations of metals in the river and biota maybe a result of the change of temperature in the area and the need for essential metals in the reproduction of fish. The results of this study clearly demonstrates that water spinach, snake head fish and swamp eel are not potential bio-indicators for metals in the Saigon River since they did not reflect concentrations of metals in their environment. It was also concluded based on consumption rates that water spinach, snake headfish and eel from the Saigon River do not present any potential health risk to consumers. However, attention should be paid to controlling the load of pollutants entering the river to avoid such risks and future problems.

Graduation date: 1995

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references. Also available in print.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also in a digital version from Dissertation Abstracts.

Thesis (M. Phil.)--University of Hong Kong, 1988.

Thesis (M. Phil.)--University of Hong Kong, 1979.

Let S2k(N) be the space of cusp forms of weight 2k and level N. Atkin-Lehner theory shows that S2k(N) can be decomposed into the oldspace and its orthogonal complement newspace. Again, from Atkin-Lehner theory, it follows that there exists a basis of newspace whose elements are simultaneous eigenforms of all the Hecke operators. Such eigenforms when normalized are called primitive forms. In 1932, Petersson introduced a harmonic weighted sum of the Fourier coefficients of an orthogonal basis B2k(N) for S2k(N), denoted by _2k;N . Petersson connected _2k;N to Kloosterman sums and Bessel functions, which is now known as the Petersson trace formula. The Petersson trace formula shows that _2k;N is independent of the choice of orthogonal basis. It is known that the oldspace decomposes into the images of newspaces of different levels under the scaling operator Bd where d is a proper divisor of N. It is of interest to derive a Petersson-type trace formula for primitive forms. In 2001, H. Iwaniec, W. Luo and P. Sarnak obtained an expression of Petersson-type trace formula for primitive forms in terms of _2k;N , when the level N is squarefree. Their method is to construct a special orthogonal basis for S2k(N). Using their approach, D. Rouymi has extended similar results to the case of prime power level in 2011. In this thesis, the case of arbitrary levels is investigated. Analogously, a special orthogonal basis is constructed and a Petersson-type trace formula for primitive forms in terms of _2k;N is found. The result established in this thesis recovers the results of H. Iwaniec, W. Luo and P. Sarnak, and D. Rouymi respectively for the cases of squarefree and prime power levels. / published_or_final_version / Mathematics / Master / Master of Philosophy

The overall goal of this study is to determine the resolution and type of proxy that any one drip site can provide for the determination of past climate. The study examines surface conditions (effective rainfall, temperature, PDSI), cave characteristics (cave geometry, cave air CO2, location), drip site characteristics (drip rate, drip rate response to rainfall), and drip water characteristics (pH, trace element ratios, alkalinity, temperature). The study encompasses two distinctly different caves, Inner Space Cavern (Chapter 2) and Westcave (Chapter 3). A goal of Chapter 2 is to identify drip sites where there is an intra-annual climate signal, which can assist with high resolution paleo-drought reconstructions when extended to speleothem studies. To be considered an intra-annual climate sensitive drip site, a site should display statistically significant correlations between (1) effective rainfall and drip rate; (2) effective rainfall and Mg/Ca; (3) drip rate and Mg/Ca; (4) Palmer Drought Severity Index (PDSI) and drip rate; and (5) PDSI and Mg/Ca. These relationships can be explained by the extent to which water flux in the karst overburden influences flow path characteristics, water residence time, and water-rock interactions. The data in Chapter 3 will indicate that (1) variations in trace element/Ca values in cave drip waters are temperature dependent and vary on a seasonal time scale, (2) the standardization of trace element/Ca values allows for between drip site comparisons, (3) the standardization of trace element/Ca values can add statistical power to statistical analyses by increasing the sample size, (4) calcite growth rates follow a seasonal pattern based on variations in surface temperature, (5) a regional drought indicator provides correlation with trace element/Ca values at some drip sites and this relationship is most likely dependent upon temperature. / text