This pioneering investigation focused on the mercury bioaccumulation relationship of bats and insects. Identifying biomarkers that can be extrapolated to humans is necessary. Radio-transmitter-fitted bats were tracked to identify five of their preferred feeding sites within and outside the Cornwall Area of Concern. Bats, insects and guano were collected from the five sites. High THg levels in bats (N= 80) were noted among species and locations but these levels were not correlated with insects. Some individual Myotis lucifugus and Eptesicus fuscus bats had concentrations (10 - 12 ppm and 15 - 26 ppm) that exceeded those from previous studies (7.6 ppm and 1.5 ppm) (Hickey et al., 2001). One-way ANOVA and t-test (two-tailed) established statistical significance among caddisflies by location (p= 0.0013), insect taxa (p <0.001), bat species (p =0.001) and Eptesicus fuscus by location (p= 0.004). Caddisflies were sampled for MeHg (> 50% Hg was MeHg).

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This work presents a study of the character and distribution of structural defects in (00l)CdTe buffer layers grown on GaAs substrates by metal organic vapour phase epitaxy (MOVPE). These are of importance as hybrid substrates for the growth of Cd(_x)Hg(1-x)Te (CMT), a prominent infrared detector material. The 14.5% mismatch between CdTe and GaAs leads to a high-density of dislocations at the CdTe/GaAs interface, and threading through the layer. The presence of linear and planar defects is detrimental to the performance of CMT devices and it is desirable to reduce the density of dislocations to below l0(^5)cm(^-2). Results of high resolution X-ray diffraction (HRXRD) studies on a series of MOVPE grown CdTe/GaAs epilayers of different thickness and on a single thick layer which was repeatedly etched and remeasured are reported. Threading dislocation density was estimated from HRXRD full width at half maximum (FWHM) using a relationship proposed by Gay, Hirsch and Kelly and was found to decrease rapidly in the initial stages of layer growth. An optimum buffer layer thickness of 8µm is proposed for the subsequent growth of CMT. Rocking curves were recorded from a single thick CdTe/GaAs epilayer for wavelengths in the range 0.69-1.95A at the Daresbury SRS, and this data is extrapolated to infinite absorption to obtain an estimate of the rocking curve width representative of the surface of a thick layer. A number of models which attempt to describe the reduction in threading dislocation density with increasing thickness are reviewed and a new model based on the coalescence of like dislocations is developed. The models are compared to published data for layers with misfit in the range 0.23-14.6%. The models previously developed by Tachikawa and Yamaguchi and by Durose and Tatsuoka are shown to be the more appropriate for describing the dislocation density distribution in highly mismatched layers. Results of the transmission electron microscopy of CdTe/GaAs epilayers, both in plan view and cross-section, showing the character of dislocations threading through thick CdTe buffer layers are presented. Many dipoles composed of 30º type dislocations with Burgers vectors parallel to the interface were observed and found to adopt an orientation whereby the component dislocations had no effect on misfit strain. In cross-section, 30º type dislocations with Burgers vectors inclined to the interface were found to be numerous, 60º and screw type threading dislocations were also observed, but the cross-section projection axis made analysis of these types difficult. The screw and edge components of 30º , 60º and screw type threading dislocations are compared and it is found that the Burgers vector component causing layer tilt is of magnitude (a(_o)/2) for each type. Annealing of CdTe/GaAs epilayers under di-methyl cadmium flow was found to have no deleterious effect on layer morphology but did not result in a narrower X-ray rocking curve. Based upon HRXRD FWHM, 8µm thick CdTe buffer layers grown by MOVPE are estimated to have a dislocation density of about 3xl0(^8)cm(^-2). Even after many of the threading dislocations have been bent over at the CdTe/CMT interface, their density in MOVPE grown CMT/CdTe/GaAs is still greatly in excess of the l0(^5)cm(^-2) desired. The issues discussed and conclusions drawn in this thesis represent a thorough study of the continuing progress towards high quality MOVPE growth of CMT.

The presence of ultra-trace levels of mercury in industrial gas and condensate streams is a cause of both environmental and production concern. The toxic nature of the element, in all forms, together with its ability to shut-down large processing plants dictates a need for its accurate and precise measurement. The study which investigated the recovery of various mercury species, spiked into synthetic and real condensate samples using conventional and new digestion and/or extraction techniques showed recovery was dependent upon the speciation. Using the most efficient technique, L-cysteine with persulphate, recoveries of over 90 % were obtained for diphenyl mercury, ethyl and phenyl mercury chlorides and mercury chloride. The recovery of 15% for the important dimethyl mercury species limits the use of this technique. A novel technique has been developed for the determination of total mercury in complex liquid hydrocarbons. Samples (up to 1.0 ml) were vaporised (400°C) and swept through a gold-coated silica trap maintained at 200°C, which retained all mercury species and discarded the matrix. The trap when heated to 900°C released the mercury for measurement by atomic fluorescence spectrometry (AFS). The recoveries for eight mercury species spiked (10 to 50 ng ml -1) into toluene and condensate were generally over 90 %. The instrumental limit of detection (LOD) was 11 pg. The total mercury content of gas condensates, gasolines and heavy oils were determined. Gas chromatography coupled, via a pyrolysis interface, with AF detection was able to determine mercury species in gas condensate, at picogram levels (LOD: 2.5 to 7 pg) using a direct sample injection procedure. For a given column system the positive identification and quantification of up to eight mercury species was obtained. A maximum injector temperature of 125 °C was recommended, to avoid the conversion of species. Mass balance calculations show a strong correlation between the total mercury content and the sum of the lower diallcyl mercury species, for all condensate samples studied. Three commercially available mercury removal systems, A, B and C produced a reduction in the mercury content of hydrocarbon streams under pilot plant conditions. The two stage system, 'A', produced a minimum of 30 % conversion from organomercury to elemental mercury after the hydrogenation reaction in stage 1. While elemental mercury was adsorbed by the stage 2 reactor, the organomercury species were not removed. The single stage adsorber 'B' showed 100 % removal efficiency for three dialkyl mercury species in liquid hydrocarbon streams. The removal efficiency for adsorber 'C' was species dependent. Two common condensate species gave values of 50 to 80 % removal efficiency while the third species showed time-dependent bleed-off.

Thesis--University of Missouri, School of Mines and Metallurgy, 1916. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed April 30, 2009) Includes bibliographical references (p. 31).

Thesis (M.S.)--University of North Carolina Wilmington, 2008. / Title from PDF title page (viewed May 27, 2009) Includes bibliographical references (69-71)

Thesis (Master)--İzmir Institute of Technology, İzmir, 2005. / Keywords: Mercury, atomic absorption spectrometry, gold, amalgamation, cold vapor. Includes bibliographical references (leaves 48-51).