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In this work, a new approach to mercury speciation study on solid samples was tested and verified. This approach is different from commonly applied sequential extraction techniques. Mercury speciation was expressed as a stability constant K, describing the bonding equilibrium between mercury and solid. Stability constant K was measured on soil sample from Příbram, which was characterised in detail (chemical analysis, powder XRD diffraction, thermo desorption analyses). Using solution of potassium resp. ammonium bromide, iodide and thiocyanate the K value was quantified in a wide concentration range. We showed that in mercury in studied sample was present in a single specie with pK  36. We discussed the effect of extractant concentration and experimental setting on resulting K. The result of extraction experiments was in accordance with thermo desorption results confirming mercury present as one specie bound onto clay matrices. As a profound difference in approach to common speciation extraction techniques, in which a set of operationally defined mercury fractions is obtained, the K value obtained in this work represents a thermodynamical parameter feasible for further mathematical processing. Thiocyanate was identified as a useful anion for extraction studies of mercury speciation on solid...

Mercury is a well-known toxic element which can be taken up into the human body in different forms, causing particular harm to the nervous system. Despite this fact, it is still used widely in industrial processes, with chlor-alkali electrolysis one of the most extensive pollution sources of mercury. Though most industries today use mercury-free processes, some chlor-alkali factories still use the mercury process, especially in less developed countries. In addition, small-scale gold mining activity remains the largest global mercury consumer and continues to increase the use of mercury given the upward trend in the price of gold. The aim of this study is to investigate the level of mercury exposure to workers in chlor-alkali factories and a dental hospital in Pakistan. In addition, it is to investigate the level of mercury exposure to miners in small-scale gold mining areas (AGM) in Cambodia, Burkina Faso and Chile. Both investigations were undertaken within the United Nations Environment Programme (management of mercury waste). Within this study, the investigation of mercury exposure to miners was conducted in four small-scale gold mining areas in Sudan. A simple analytical digestion and extraction method for total mercury (T-Hg) analysis in biological and environmental samples with fast sample preparation procedure using CV-AFS and ICP-MS was developed. In addition, for SSIDMS-GC-ICP-MS analysis, the alkaline microwave assisted extract method and acid leaching assisted extract method for Me-Hg analysis in biological samples (hair samples) were developed. These developed analytical methods were used to evaluate the levels of occupational and environmental exposure in the selected areas with Hg hot spots. For Pakistan, to establish chlor-alkali workers' Hg exposure, hair and nail samples of 23 individuals were investigated for total mercury. Within this cohort, 15 individuals had hair total mercury levels above 100 μg g-1, thus exceeding the WHO regarded "safe limit" of 2 μg g-1 in hair Hg by a factor of 50. Several samples showed hair T-Hg levels above 1000 μg g-1, suggesting extreme exposure to Hg. These levels must be regarded as extremely toxic, assuming that these Hg levels in hair correspond to Hg ingestion. In the process of chlor-alkali electrolysis, volatile mercury compounds are formed, including Hg0 and other volatile mercury compounds. These volatile species can adsorb on surfaces, and it is suggested that besides uptake by inhalation, Hg compounds may be adsorbed on keratinous hair and nail material. The investigation of single hairs with synchrotron techniques showed that most of the mercury is found on the outside of the hair, but certain amounts were also metabolised. Adsorption experiments with Hg0 and HgCl2 were conducted to assess the sorption characteristics of these volatile Hg compounds. The results showed that both mercury species' vapour pressures are related to the adsorption of volatile mercury compounds. HgCl2 has a higher vapour pressure and is about two orders of magnitude higher in adsorption than Hg0, suggesting that the chlor- alkali workers have been exposed to HgCl2 in the chlor-alkali plant. Finally, mercury speciation was performed on the ICL chlor-alkali hair samples which showed that almost all mercury was in inorganic form. The source of Me-Hg in the hair seems to be dietary, as no correlation between inorganic and Me-Hg in the hair could be found. The highest value for Me-Hg is around 5.0 μg g-1, which is in the range of concentration found in communities with a high fish diet. Finally, the high mercury result suggests that the mercury (Hg) in the hair samples from workers in the ICL chlor-alkali is from external adsorption rather than from inhalation and was subsequently incorporated into the hair. Nevertheless, in the second chlor-alkali factory in Pakistan (SCL chlor-alkali factory), the average total mercury concentrations in hair and nails are low and almost at control level. However, in this factory, mercury cell technique was phased out a few years ago. This factory now uses membrane cell instead of mercury cell technology. For the dental hospital sector in Pakistan, inorganic mercury concentrations were 6 times higher than Me-Hg concentration in hair samples i.e. Me-Hg and In-Hg in hair accounted for, on average 14.13 % and 85.87 % of T-Hg respectively for these dental workers. However, the high mercury levels in hair could be due to exposure to amalgam. For AGM areas, the T- Hg concentration (μg g-1) in hair samples from AGM miners in Burkina Faso (mean, 3.80 μg g-1) were compared with Cambodian AGM miners and Sudan AGM miners (mean 5.78 and 5.04 μg g-1 respectively). This mean value was significantly lower than that found in the hair of miners in the Cambodia and Sudan AGM areas. This indicates that the AGM miners in these countries are exposed to mercury vapour during the AGM processes. Otherwise, the AGM workers in Cambodia are also exposed to considerable amounts of methylmercury (Me-Hg) through seafood consumption that is a more toxic Hg form. However, the long-term implications for water bodies such as River Nile and Red Sea ecosystems, fish as food and irrigation water use (e.g. for rice paddies) may be disastrous. Therefore, further investigation of Hg analysis in hair and soils should be conducted in these areas to analyse the risk of Hg contamination.

The aim of this project was to enhance the current state of knowledge of the void structure of paper, and pigments used to coat paper. The porosities and pore size distributions of consolidated pigments were measured using mercury porosimetry. Prior to this work, mercury porosimetry was rarely used in this field due to problems associated with the conventional interpretation of mercury porosimetry data. These problems were examined and two limitations of mercury porosimetry were addressed. Firstly, the shrinkage of compressible samples causes an apparent increase in void volume and secondly, large void spaces shielded by smaller ones are not intruded until anomalously high applied pressures of mercury are reached. The first limitation was overcome by means of a new correction procedure which, uniquely, also allows the measurement of the bulk modulus of the continuous solid phase of a porous sample. Shielding effects have been taken into account by means of a software package known as Pore-Cor, which generates a three dimensional structure which has both a mercury intrusion curve and porosity in close agreement with experiment. It has also been possible to calculate the permeabilities and tortuosity of the simulated structure and this provides realistic and useful values, which may not be measured experimentally. Mercury porosimetry and a range of specialised absorption techniques, including liquid porosimetry, were used to characterise the porous structures of a highly filled paper which had been calendered using a range of different conditions. A unique feature of this work is that for the first time it has been shown that two porosimetric techniques which measure overlapping pore size distributions may be combined to give a better indication of the total pore size distribution.

This work describes several thiophene-based molecular sensors and various modifications aimed to improve and understand the photophysical and supramolecular properties, such as the association constant (Ka) and selectivity, towards the development of a selective mercury(II) sensor. From the first generation of sensors containing pyridine and thiophene groups, it was determined that thiophene can offer good selectivity for mercury(II) against other transition metal ions, and provide a ratiometric absorption and fluorescent response. The projects following this focused on improving the Ka of the first generation of sensors through several different strategies. Substitution of thiophene for dibenzothiophene was shown to improve the Ka however this resulted in less than ideal photophysics of the dibenzothiophene sensors with absorption and emission in the UV-region. In addition to the effect of the chelating group was examined by incorporating imidazole, and thiazole rings, to compare to the original pyridyl chelating group employed. From this it was determined that pyridine offered the greatest Ka and selectivity for mercury(II). Following this electron-donating groups, including alcohol, octaethyleneglycol monomethyl ether, and amine, were added to a sensor, 2,5-bis(2-pyridyl)thiophene, as an alternative strategy to improving the Ka. Initially these functional groups were placed on the pyridine ring which caused a great increase in affinity for transition metal ions such as iron(II) and copper(II), however this translated to a loss in selectivity. In the final project I functionalized the thiophene ring with the same electron-donating groups which resulted in an increased Ka and maintained good selectivity for the mercury(II) ion, though iron(III) was still a competitive binder. In addition to this one of these thiophene functionalized sensors, 2,5-di(pyridin-2-yl)thiophene-3,4-diol, was shown to have a specific response to copper(II), iron(III), lead(II) and mercury(II) suggesting it could be used as a model for the development of a small-molecule multiplex sensor. Herein I will describe this work in greater detail and focus on the effects the modifications discussed had on the Ka and selectivity for the mercury(II) ion.

Relative lifetimes, and the closely related quadrupole moments (Q[subscript]i values), of the six superdeformed (SD) bands in �������Hg and the yrast SD band in �������Hg were determined by a Doppler-shift attenuation method measurement. The experiment was performed using the Gammasphere array and Lawrence Berkeley National Laboratory's 88-inch Cyclotron. The Q[subscript]i values, which are a sensitive probe of the nuclear shape, of all the �������Hg SD bands were found to be similar. This is the first accurate determination of the Q, values of SD bands in an odd-A nucleus in the mass-190 region. Additionally, evidence is presented for an unexpected difference in the Q[subscript]i values of the �������Hg and �������Hg SD bands. There is an indication that the Q[subscript]i value of the �������Hg yrast SD band is approximately 15 percent greater that the Q[subscript]i values of the �������Hg SD bands. The results provide information on the shape-driving effects of orbitals in the mass-190 region and imply that the deformations of bands with identical transition energies are not necessarily the same. / Graduation date: 1997

Thesis (M.S.)--University of Wisconsin -- La Crosse, 1983. / Includes bibliographical references (leaves 99-108).

Mass-independent fractionation (MIF) of Hg isotopes has the potential to track the environmental transport and fate of Hg. Herein we demonstrate that reducing both the frequency and intensity of light have a large effect on the expression and magnitude of MIF. This strongly supports the magnetic isotope effect as the mechanism behind MIF observed during aqueous photo-reduction of Hg(II) and MeHg. The ratios of MIF, KapDelta199Hg/KapDelta201Hg, were 1.00 ± 0.04 (2SE) for Hg(II) and 1.35 ± 0.16 (2SE) for MeHg respectively and did not change as incident radiation energy and magnitude of MIF diminished, suggesting the respective MIF pathways remained constant regardless of experimental conditions. Comparable amounts of total photo-reduction were shown to coincide with different magnitudes of MIF depending the wavelength light available for photo-reduction. This confirms there are multiple pathways for photo-reduction in freshwater reservoirs and indicates that quantitatively relating photo-reduction and MIF will be challenging.

Mass-independent fractionation (MIF) of Hg isotopes has the potential to track the environmental transport and fate of Hg. Herein we demonstrate that reducing both the frequency and intensity of light have a large effect on the expression and magnitude of MIF. This strongly supports the magnetic isotope effect as the mechanism behind MIF observed during aqueous photo-reduction of Hg(II) and MeHg. The ratios of MIF, KapDelta199Hg/KapDelta201Hg, were 1.00 ± 0.04 (2SE) for Hg(II) and 1.35 ± 0.16 (2SE) for MeHg respectively and did not change as incident radiation energy and magnitude of MIF diminished, suggesting the respective MIF pathways remained constant regardless of experimental conditions. Comparable amounts of total photo-reduction were shown to coincide with different magnitudes of MIF depending the wavelength light available for photo-reduction. This confirms there are multiple pathways for photo-reduction in freshwater reservoirs and indicates that quantitatively relating photo-reduction and MIF will be challenging.