This thesis carefully investigates some of the limitations of existing methods for atomic spectroscopic determination of mercury, selenium and arsenic in biological and environmental materials. In particular the need for adequate sample preparation to ensure reliable atomic spectroscopic determination of these metalloids was demonstrated extensively. The thesis evaluates four most commonly used wet digestion methods for the accurate determination of mercury in biological and environmental materials by cold vapour atomic absorption spectroscopy. Excellent recovery efficiencies were obtained with this digestion mixture in fish homogenate, horse kidney, soil, canned fish and hair samples for inorganic and organic mercury. The suitability of the digestion method for the reliable determination of mercury in soil, hair and canned fish samples was also demonstrated. Mercury levels in these samples were found within normal acceptable range. The thesis outlines a new simple procedure for overcoming the loss of mercury due to sample charring. It also described a new sample ultrasound low temperature wet digestion method for biological and environmental materials. The main advantage of this approach over other conventional methods is its ability to release all mercury in inorganic form from biological and environmental samples at much lower temperatures than reported earlier / Doctor of Philosophy (PhD)

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (M.S.)--University of Nevada, Reno, 2005. / "December, 2005." Includes bibliographical references (leaves 80-85). Online version available on the World Wide Web.

Weathered waterborne treated wood is believed to behave differently than new wood during service regarding the loss of its metallic-based preservatives. Also, weathered preserved wood should be separated from the unpreserved wood upon recycle. The first objective of this dissertation was to evaluate losses from weathered CCA-treated wood samples at different retention levels under normal field conditions and to compare leaching to new ACQ (as alternative to CCA). Results showed that arsenic leached at a higher rate than chromium and copper in all CCA treated wood samples, while copper leached the highest from the ACQ sample. Overall results suggest that the leaching rate of metals on a percent basis from in-service pressure treated wood may increase as the wood weathers; however due to lower retention levels of the metals in the wood as it ages the yearly mass of metals lost would be at similar or at lower quantities in comparison to new treated wood. The second objective was to evaluate the use of automated X-ray fluorescence (XRF) systems for identifying and removing As-based and Cu-based treated wood within the recovered wood waste stream. A full-scale online automated XRF-detection, conveyance and diversion system was used for experimentation. At the different applied feeding rates and belt speeds, online sorting efficiencies of waste wood by XRF technology were high (>70% for both treated wood and untreated wood). The incorrectly diverted pieces of wood were attributed to deficiencies in the wood conveyance systems and not to deficiencies in the XRF-based detection. Online sorting was shown to sort wood which would meet the residential soil cleanup target levels in Florida when an infeed is composed of 5% of treated wood pieces. Comparisons with other sorting methods show that XRF technology can potentially fulfill the need for cost-effective processing at large wood recycling facilities (> 30 tons per day). Management of weathered CCA-preserved wood, due to its continuity of leaching metals and the need to remove it upon the recycle of wood, will likely continue until complete banning and removal from the environment, a process that may extend up to the next century.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Also available online.

Chronic arsenic poisoning due to arsenic contamination of groundwater is a serious public health problem in Bangladesh and neighboring countries. Severe health effects associated with chronic exposure to arsenic include melanosis and several kinds of cancer. It is now generally agreed that the arsenic contamination of groundwater in Bangladesh is of geological origin. Arsenic naturally present in aquifers may be mobilized into drinking water by microbial action.<p> The formation of a novel arsenic-selenium compound: seleno-bis (S-glutathionyl) arsinium ion, [(GS)2AsSe]-, and its subsequent excretion in rabbit bile has been demonstrated previously. This molecular basis for the in vivo antagonism between arsenic and selenium was discovered using X-ray absorption spectroscopy. There is growing evidence that, in Bangladeshi people who are suffering long term chronic lowlevel arsenic poisoning, this antagonism is causing a selenium deficiency. Administering selenium supplements might provide a simple but highly effective treatment of the Bangladeshi arsenic poisoning.<p> In order to examine the disposition of [(GS)2AsSe]-, a set of rabbits were intravenously injected with selenite, arsenite or both. Whole blood, red blood cell and plasma samples were collected at different time intervals within 2hrs after injection and cecotrope samples 24hr after injection. Samples were examined using X-ray absorption spectroscopy and both arsenic and selenium K-near edge spectra were recorded.<p> iii Speciation of arsenic and selenium will be discussed in this thesis. Results indicate that [(GS)2AsSe]- is formed in blood very rapidly after injection of both arsenite and selenite, and then is removed from blood stream within 2hrs post injection. Results also show that [(GS)2AsSe]- is assembled in red blood cells, with no [(GS)2AsSe]- detected in plasma samples. [(GS)2AsSe]- is also found in cecotrope samples after injection of both arsenite and selenite.<p> The results of this study in rabbits will contribute to the understanding of chronic arsenic poisoning in humans.

Mining for silver, lead, zinc, and copper in Zimapan, Hidalgo State, Mexico has been ongoing since 1576. Unsecured tailings heaps and associated acid mine drainage have presented problems related to soil quality, water quality, and dust emission control in the Zimapan area. Objectives of the study of the mine tailings are (1) to determine mineralogy of the tailings in order to identify acid-producing minerals and heavy metals at risk for release in acidic conditions, and (2) to quantify carbonate minerals and (3) to determine heavy metal content that may be released by the products of sulfide mineral weathering. Representative mine tailings have been sampled from a site located north of Zimapan. Mineralogical characterization has been conducted with X-ray diffraction (XRD), and scanning and transmission electron microscopes (SEM and TEM). Total carbonates have been determined the Chittick procedure. X-Ray Fluorescence (XRF) has been utilized to determine total elemental composition. XRD and SEM analyses have confirmed the presence of pyrite and arsenopyrite indicating a potential for acid mine drainage. Calcite has been confirmed to have a significant presence in the unweathered samples by XRD and the Chittick procedure, with some samples containing an average of 19.4% calcite. NAA and XRF have revealed significant concentrations of toxic elements such as As, Pb and Zn in both the oxidized and unoxidized samples.

Graduation date: 1992

Chronic arsenic poisoning due to arsenic contamination of groundwater is a serious public health problem in Bangladesh and neighboring countries. Severe health effects associated with chronic exposure to arsenic include melanosis and several kinds of cancer. It is now generally agreed that the arsenic contamination of groundwater in Bangladesh is of geological origin. Arsenic naturally present in aquifers may be mobilized into drinking water by microbial action.<p> The formation of a novel arsenic-selenium compound: seleno-bis (S-glutathionyl) arsinium ion, [(GS)2AsSe]-, and its subsequent excretion in rabbit bile has been demonstrated previously. This molecular basis for the in vivo antagonism between arsenic and selenium was discovered using X-ray absorption spectroscopy. There is growing evidence that, in Bangladeshi people who are suffering long term chronic lowlevel arsenic poisoning, this antagonism is causing a selenium deficiency. Administering selenium supplements might provide a simple but highly effective treatment of the Bangladeshi arsenic poisoning.<p> In order to examine the disposition of [(GS)2AsSe]-, a set of rabbits were intravenously injected with selenite, arsenite or both. Whole blood, red blood cell and plasma samples were collected at different time intervals within 2hrs after injection and cecotrope samples 24hr after injection. Samples were examined using X-ray absorption spectroscopy and both arsenic and selenium K-near edge spectra were recorded.<p> iii Speciation of arsenic and selenium will be discussed in this thesis. Results indicate that [(GS)2AsSe]- is formed in blood very rapidly after injection of both arsenite and selenite, and then is removed from blood stream within 2hrs post injection. Results also show that [(GS)2AsSe]- is assembled in red blood cells, with no [(GS)2AsSe]- detected in plasma samples. [(GS)2AsSe]- is also found in cecotrope samples after injection of both arsenite and selenite.<p> The results of this study in rabbits will contribute to the understanding of chronic arsenic poisoning in humans.

<p>This dissertation examines the potential of information-provision in motivating behavior that reduces human exposure to arsenic in drinking-water in Bangladesh. In chapter 2, the longer-term effects of the countrywide arsenic-testing and information-program are examined by tracking tube-well switching behavior of households over a five-year period. Chapter 3 focuses on the effects of arsenic information communication formats on tube-well switching behavior, by employing a randomized field experiment. In chapter 4, an instrumental variables approach is used to understand whether a household's decision to switch sources is affected by its proximate neighbors' decisions to switch sources. To answer these questions, primary data was collected by the researchers through field-work in Bangladesh. The results suggest that arsenic-testing and information-provision programs produce persistent behavioral changes that reduce exposure to arsenic, with their impact increasing over time. Comparing the impacts of risk-communication formats, we find that quantitative formats do not significantly increase source-switching behavior, in comparison to that generated by qualitative formats. Lastly, despite econometric identification issues, our data suggest that households gather information about source-switching by observing the actions of their neighbors. In sum, the results presented in this dissertation suggest that the provision of information to rural households can motivate health-improving behavior that reduces households' exposure to arsenic in Bangladesh. This dissertation contributes to the use of information disclosure as a policy instrument to reduce exposure to environmental contaminants.</p> / Dissertation