No description available.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 176-203). Also available online.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 176-203). Also available in print.

Thesis (M. Sc.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 53-69).

No description available.

The adsorption of tributyltin onto materials commonly used for the construction of sampling and analytical equipment from aqueous solutions of varying ionic composition has been examined. The adsorption appears to be controlled by non-polar interactions between tributyltin and the surface involved. Since the speciation and hence polarity of tributyltin is affected by the ionic composition of the medium, the extent of adsorption is affected by the salinity and pH of a sample. The adsorption is rapid and, unless strategies are adopted to eliminate its effects, may render analytical results invalid. The electrochemistry of tributyltin, dibutyltin and monobutyltin, individually and in mixtures, has been investigated in aqueous media at mercury electrodes. The basic electrochemistry of each compound is summarised by the reaction BunSn (4-n)+ + (4-n)e- right left harpoons BunSn where n is the number of butyl groups attached to the tin atom. However, the electrochemistry of each compound is largely confined to the surface of the mercury electrode, and the simplicity of the above reaction is disrupted by polymerisation reactions and by butyl exchange processes occurring with the mercury electrode. When mixtures of butyltin compounds are present, the various processes that occur for each individual compound interfere with each other. A direct voltaminetric method for the determination of butyltin compounds in natural waters is therefore probably not possible.

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Igor Alabugin, Florida State University, College of Arts and Science, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Sept. 23, 2004). Includes bibliographical references.

An improved understanding of the geochemical partitioning of trace metals and tributyltin (TBT) in sediments is of great importance in risk assessment and remedial investigation. The aim of this thesis was to examine the distribution and partitioning behaviour of trace metals and TBT in benthic, estuarine sediments. This was achieved by a series of field- and laboratory-based studies investigating factors controlling the geochemical behaviour of trace metals and TBT in sediments from south-east Queensland, Australia. The distribution and enrichment of selected trace metals in benthic sediments of the Southport Broadwater (a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia) was studied. Sediment contamination for Cd, Cr, Cu, Ni, Pb, Sn and Zn was assessed by (1) comparison with Australian sediment quality guidelines, (2) calculation of the index of geoaccumulation based on regional background values, and (3) geochemical noi-malisation against Al (i.e. the abundance of alumino-silicate clay minerals). Based on this approach, several sites were found to be strongly enriched with Cu, Pb, Sn and Zn, arising from sources related to either urban runoff or vessel maintenance activities. The geochemical partitioning of Cu, Pb and Zn was examined in sediments collected from three of these sites of sediment contamination. Total Cu, Pb and Zn concentrations in coarse-textured (65 to 90 % sand sized particles), sub-oxic sediments (Eh + 120 to +260 mV) ranged from 8.3 to 194 mg/kg for Cu, 16.3 to 74.8 mg/kg for Pb and 30.1 to 220 mg/kg for Zn, and were related to vertical trends in sediment texture. The association of Cu, Pb and Zn with amorphous oxides, crystalline oxides and organic matter was linearly dependent on the abundance of each phase. For retention by amorphous oxide minerals, the trace metal retention ranged from 5.2 to 23.7 mgcjgFe oxide as Fe for Cu, 1 2.8 to 21 .5 mgpb/gFe oxide as Fe for Pb, and 23. I to 85.7 mgm/gFe oxide as Fe for Zn. Corresponding values for association with crystalline oxides were an order of magnitude less than those for amorphous oxides, indicating a weaker affinity of trace metals for crystalline oxides. The relationships describing association with organic matter ranged from 17.6 to 54.0 mgcu/gorg c for Cu, 6.1 to 9.6 mgpb/gorg c for Pb and 6.4 to 16.4 mgzn/gorg c for Zn. The in-situ solid/pore-water partitioning of TBT and the degradation products, dibutyltin (DBT) and monobutyltin (MBT), was determined for an estuarine sediment profile with previously identified elevated Sn concentrations. Total butyltin levels were (depending on depth) 220 to 8750 jig/kg for TBT, 150 to 5450 jig/kg for DBT and 130 to 4250 jig/kg for MBT. Pore-water butyltin concentrations ranged from 0.05 to 2.35 jig/L for TBT, 0.07 to 3.25 jiglL for DBT, and 0.05 to 0.53 J.tgIL for MBT. The organic carbon normalised distribution ratios (Doc) were similar for TBT, DBT and MBT, and were io to 106 L/kg. Values for the Butyltin Degradation Index (BDI) were larger than I at depths greater than 10 cm below the sediment/water-column interface, indicating that substantial TBT degradation has occurred in the sediments. This suggests that natural attenuation may be a viable sediment remediation strategy. Factors controlling the partitioning behaviour of Cu, Pb and Zn in nonsulfidic, estuarine sediments were examined in controlled laboratory-based studies with the use of combined sorption curve - sequential extraction analysis. This allowed determination of sorption parameters for Cu, Pb and Zn partitioning to individual geochemical fractions. Partitioning behaviour in sulfidic sediments was also determined by sequentially extracting Cu, Pb and Zn from synthetic sulfide minerals, and from natural sediment and pure quartz sand after spiking with acid-volatile sulfide (AVS). Trace metal sorption to the 'carbonate' fraction (pH 5, NaOAc extraction) increased with metal loading due to saturation of sorption sites associated with the 'Fe-oxide' (NH2OH.HCI extraction) and 'organic' (H202 extraction) fractions in non-sulfidic sediments. Freundlich isotherm parameters describing sorption to the 'Fe-oxide' and 'organic' fractions were dependent on the sediment Fe-oxide and organic carbon content, respectively. Sequential extraction of Cu from pure CuS, AVS-spiked sediment and AVS-spiked quartz sand showed that AVS-bound Cu was quantitatively recovered in association with the 'organic' fraction. However, some AVS-bound Pb and Zn were recovered by the NH2OH.HCI step (which has been previously interpreted as 'Fe-oxide' bound metals) in the sequential extraction procedure used in this study. This indicates that the sequential extraction of Pb and Zn in sulfidic sediments may lead to AVS-bound metals being mistaken as Fe-oxide bound species. Caution should therefore be exercised when interpreting sequential extraction results for Pb and Zn in anoxic sediments. Tributyltin (TBT) sorption to four natural sediment samples in artificial seawater was also examined under a range of modified pH and salinity conditions in controlled laboratory-based studies. Three of the sediment samples were relatively pristine with regard to TBT contamination, but the fourth was a TBT-contaminated sediment from a commercial marina. Sorption of TBT was described well by linear sorption isotherms, with distribution coefficients ranging from 6.1 to 5210 L/kg depending on pH and salinity. Sediment organic C content and particle size distribution were important determinants of sorption behaviour. The presence of resident TBT in the contaminated marina sediment caused a substantial reduction in TBT sorption due to satuaration of high selectivity sites. Desorption of TBT from the marina sediment was described by relatively large observed distribution coefficients ranging from 5100 to 9400 L/kg, suggesting that aging effects may reduce sorption reversibility. Increased artificial seawater salinity generally reduced TBT sorption at pH 4 and pH 6, but enhanced TBT sorption at pH 8. Regardless of salinity, maximum sorption of TBT was observed at pH 6, which is attributed to an optimal balance between abundance of the cationic TBT species and deprotonated surface ligands. Consideration of aqueous TBT speciation along with octanol-water partitioning behaviour suggest that hydrophobic partitioning of TBTCI to non-polar organic matter was important for pH (up to) 6, whilst partitioning of TBTOH was important at higher pH. The effect of aging on the solid/pore-water partitioning and desorption behaviour of TBT in sediments was examined. Three sediment samples with contrasting physical and chemical properties were spiked with 10 mg/kg TBT and aged under sterile conditions for periods of time ranging from I to 84 days. Aging had a negligible effect in a sandy sample with very low organic carbon content (0.2 % w/w). In contrast, for samples with larger amounts of organic carbon (2.6 and 4.8 % w/w), the effect of aging on the solid/pore-water partitioning behaviour was significant. For these samples, the apparent distribution coefficients (Ks) obtained from sequential two hour desorption experiments exhibited a two-fold increase between spiked sediments subjected to aging for 1 day and 84 days. This study demonstrates that aging effects may be an important aspect of TBT fate in contaminated sediments. Overall, the results described in this thesis demonstrate that environmental factors (i.e. pH, salinity, Eh, aging) and sediment composition (i.e. abundance of fine alumino-silicate minerals, organic matter, Fe-oxides, reactive sulfides) exert substantial effects on trace metal and TBT partitioning. The current reliance on measurement of total trace metal and TBT concentrations in contaminated sediment management may consequently lead to inaccurate estimates of environmental risk and inappropriate remediation measures if other factors regulating contaminant distribution and partitioning are ignored.

Estuarine environments are threatened by the synergistic effects of anthropogenic disturbance and bioinvasion. The construction of artificial structures (such as pilings and pontoons) provides a habitat resource in close proximity to vessel hulls that may be carrying a wide range of non-indigenous fouling species. In addition, the release and accumulation of toxicants from antifouling (AF) paints on vessel hulls creates a chemical disturbance that may reduce the invasion resistance of native communities. This thesis examines how shipping-related disturbances affect sessile communities, and in particular what role AF paints and artificial structures play in the invasion of estuaries. Using a series of field-based experiments, I found that copper and tributyltin have the potential to influence both the transport of species to a new region, via the application of AF paints on vessel hulls, and their subsequent establishment, via the accumulation of AF biocides in estuaries. Temperature, pH, salinity and turbidity were also related to species distributions. During subtidal surveys of artificial and natural structures I found more non-indigenous species (NIS) on pilings and pontoons than on rocky reef, and shallow floating structures were identified as hotspots for invaders. These findings suggest that artificial structures play an important role in the initial establishment of sessile non-indigenous species in new regions. A subset of NIS were also present on the reefs sampled during the survey and I conducted manipulative experiments to determine factors affecting the invasibility of turf and canopy-forming algal assemblages. The resident assemblage provided a barrier to most invaders, particularly when light and sedimentation levels were also high (i.e. on horizontal substrate). My results suggest that the areas of reef most susceptible to invasion are vertical rock walls and those subjected to disturbances that release space. In summary, this is the first study to relate copper and tributyltin contamination in the field to NIS distributions. My research has also highlighted the potential role of artificial structures in facilitating the establishment of NIS in estuaries and identified invasion threats to rock wall communities and disturbed reefs in estuarine systems.

Thesis (M.S.)--Florida State University, 2005. / Advisor: Dr. Igor Alabugin, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Sept. 19, 2005). Document formatted into pages; contains xv, 123 pages. Includes bibliographical references.