Thesis (Ph. D.)--University of Wisconsin--Madison, 1936. / Typescript. Includes abstract and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 86-98).

Hydrogen cyanide gas (HCN{g)) is formed during the process of extracting gold from ore and may pose a risk to the health of the workers at the gold refinery (Mill/plant), especially the risk of detrimental effects on the central nervous system and the cardiovascular system. The measurement of the personal airborne HCN(g) exposure of a worker using sorbent tubes, provides the concentration of the chemical that the worker breaths in. The measurement of the urinary thiocyanate (SCN~) concentration provides the total HCN exposure experience by the worker through all possible routes of exposure. The study's aim was to determine if the workers were exposed to HCN(g) concentrations that was higher than the occupational exposure limit (OEL) , which would mean that the workers are exposed to excessive and possibly harmful levels of HCN. The monitored workers were divided into three homogenous exposure groups or HEGs, according to the their potential level of exposure. The results were compared between the three HEGs and between three work description groups, namely the Mill/plant workers, SGS laboratory assistants and members of the environmental department. The study found that all the workers were exposed to personal airborne HCN(9) concentrations below the OEL. A statistical significant difference was found the personal airborne exposure experienced by the three HEGs and between the Mill/plant workers and the members of the environmental department. No statistical significant difference was found between the urinary SCN" concentration found in the three HEGs or the between the three work description groups. Confounding factors such as smoking, the consumption of cassava, the exposure to fire smoke and the amount of time worked at the mine did not influence the urinary SCN~ concentration. The implementation of a biological monitoring program would enable the identification of any worker that is exposed to excessive levels of HCN. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2009.

Hydrogen cyanide gas (HCN{g)) is formed during the process of extracting gold from ore and may pose a risk to the health of the workers at the gold refinery (Mill/plant), especially the risk of detrimental effects on the central nervous system and the cardiovascular system. The measurement of the personal airborne HCN(g) exposure of a worker using sorbent tubes, provides the concentration of the chemical that the worker breaths in. The measurement of the urinary thiocyanate (SCN~) concentration provides the total HCN exposure experience by the worker through all possible routes of exposure. The study's aim was to determine if the workers were exposed to HCN(g) concentrations that was higher than the occupational exposure limit (OEL) , which would mean that the workers are exposed to excessive and possibly harmful levels of HCN. The monitored workers were divided into three homogenous exposure groups or HEGs, according to the their potential level of exposure. The results were compared between the three HEGs and between three work description groups, namely the Mill/plant workers, SGS laboratory assistants and members of the environmental department. The study found that all the workers were exposed to personal airborne HCN(9) concentrations below the OEL. A statistical significant difference was found the personal airborne exposure experienced by the three HEGs and between the Mill/plant workers and the members of the environmental department. No statistical significant difference was found between the urinary SCN" concentration found in the three HEGs or the between the three work description groups. Confounding factors such as smoking, the consumption of cassava, the exposure to fire smoke and the amount of time worked at the mine did not influence the urinary SCN~ concentration. The implementation of a biological monitoring program would enable the identification of any worker that is exposed to excessive levels of HCN. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2009.

As mandiocas utilizadas na produção da farinha contêm elevadas concentrações de glicosídeos cianogênicos, compostos que, após degradação, liberam cianeto na forma de ácido cianídrico (HCN) conferindo toxicidade à raiz. O processamento adequado da mandioca, para produção da farinha, resulta na degradação dos glicosídeos cianogênicos e na obtenção de um alimento com baixo teor de cianeto, o que gera a hipótese de liberação de HCN durante o processo. Neste contexto, o presente estudo objetivou avaliar a exposição de trabalhadores de casas-de-farinha ao HCN proveniente da mandioca, assim como identificar possíveis alterações clínicas e laboratoriais associadas a tal exposição. Foram incluídas no estudo 4 casa-de-farinha localizadas no Agreste Alagoano, microrregião de Arapiraca. A determinação de HCN em amostras de ar foi realizada de acordo com o método analítico 6010 recomendado pelo NIOSH. Cada casa foi monitorada em três pontos: dois em zona respiratória e um em ponto estático. Um total de 36 trabalhadores voluntários do sexo masculino distribuídos nas 4 casas-de-farinha foram selecionados para o estudo. Cada participante foi submetido à coleta de urina, sendo uma amostra pré-jornada e outra amostra pós-jornada e a uma coleta de sangue pré-jornada. O teor de tiocianato (SCN-) urinário foi quantificado espectrofotometricamente, enquanto que as outras avaliações bioquímicas foram realizadas em laboratório clínico. Os resultados indicam que os trabalhadores de casas-de-farinha estão expostos, cronicamente, a níveis atmosféricos de HCN dentro de um intervalo de 0,464±0,02 a 3,328±3,85 mg/m3 no ambiente de trabalho. A comparação entre os níveis atmosféricos determinados e os Limites de Exposição Ocupacional estabelecidos pelo NIOSH e ACGIH indica que trabalhadores de casas-de-farinha, podem estar expostos a níveis de HCN capazes de causar efeitos adversos à saúde. Os níveis médios de tiocianato urinário em mg/g de creatinina (10,62 - pré- jornada e 8,76 pós - jornada), foram significativamente superiores ao valor de referência para não fumantes e à média obtida no laboratório contratado para análise de SCN-, referente ao período de 2008 a 2010. Os resultados dos exames laboratoriais indicaram aumento nos níveis séricos de fosfatase alcalina nos trabalhadores de casas-de-farinha expostos ao HCN, com uma prevalência de 93,3%. Os trabalhadores foram submetidos ao exame clínico e não foram detectadas alterações características de exposição ao HCN. / Cassava used for flour production contains high amounts of cyanogenic glycosides, compounds that, after degradation, release hydrogen cyanide (HCN) which provide toxicity to these type of root. A suitable cassava processing results in the degradation of cyanogenic glycosides and in the production of a safety flour for consumption as food, which generates the hypothesis of HCN release during the process. In this context, the present study aimed to evaluate the HCN exposure of workers engaged in cassava processing, as well as, to identify possible clinical and laboratory alterations related to this exposure. It was included in the study 4 cassava processing facilities placed on Alagoas state, Brazil. It was conducted the determination of HCN in air samples according to the method 6010 proposed by NIOSH. Each industry was monitored in three points: two on workers respiratory zone and one static. A total of 36 male volunteers, distributed between the 4 facilities were included in the study. Each participant was submitted to urine sampling, been one before and other after work shift, and to one blood sampling before work shift. Urinary thiocyanate (SCN-) was spectrophotometrically determined, whereas the remaining biochemical evaluation was conducted in a commercial clinical laboratory. The results indicated that the cassava processors are chronically exposed to HCN at levels between 0,464±0,02 and 3,328±3,85 mg/m3, in the work environment. The comparison between the levels determined at the present study with the Occupational Exposure Limits (OEL) established by NIOSH and ACGIH indicated that cassava processors may be exposed to HCN levels capable of causing adverse health effects. The mean levels of urinary thiocyanate (10,62 - before shift and 8,76 - after shift), were significantly higher than the reference value for non smokers and also for the history mean obtained from the laboratory employed for SCN- analysis, during 2008-2010. The results of laboratorial evaluation indicated increase in the serum activity of alkaline phosphatase in cassava processors exposed to HCN, with a prevalence of 93,3%. The workers were submitted to clinical evaluation and it was not detected any alteration typical of HCN exposure.

As mandiocas utilizadas na produção da farinha contêm elevadas concentrações de glicosídeos cianogênicos, compostos que, após degradação, liberam cianeto na forma de ácido cianídrico (HCN) conferindo toxicidade à raiz. O processamento adequado da mandioca, para produção da farinha, resulta na degradação dos glicosídeos cianogênicos e na obtenção de um alimento com baixo teor de cianeto, o que gera a hipótese de liberação de HCN durante o processo. Neste contexto, o presente estudo objetivou avaliar a exposição de trabalhadores de casas-de-farinha ao HCN proveniente da mandioca, assim como identificar possíveis alterações clínicas e laboratoriais associadas a tal exposição. Foram incluídas no estudo 4 casa-de-farinha localizadas no Agreste Alagoano, microrregião de Arapiraca. A determinação de HCN em amostras de ar foi realizada de acordo com o método analítico 6010 recomendado pelo NIOSH. Cada casa foi monitorada em três pontos: dois em zona respiratória e um em ponto estático. Um total de 36 trabalhadores voluntários do sexo masculino distribuídos nas 4 casas-de-farinha foram selecionados para o estudo. Cada participante foi submetido à coleta de urina, sendo uma amostra pré-jornada e outra amostra pós-jornada e a uma coleta de sangue pré-jornada. O teor de tiocianato (SCN-) urinário foi quantificado espectrofotometricamente, enquanto que as outras avaliações bioquímicas foram realizadas em laboratório clínico. Os resultados indicam que os trabalhadores de casas-de-farinha estão expostos, cronicamente, a níveis atmosféricos de HCN dentro de um intervalo de 0,464±0,02 a 3,328±3,85 mg/m3 no ambiente de trabalho. A comparação entre os níveis atmosféricos determinados e os Limites de Exposição Ocupacional estabelecidos pelo NIOSH e ACGIH indica que trabalhadores de casas-de-farinha, podem estar expostos a níveis de HCN capazes de causar efeitos adversos à saúde. Os níveis médios de tiocianato urinário em mg/g de creatinina (10,62 - pré- jornada e 8,76 pós - jornada), foram significativamente superiores ao valor de referência para não fumantes e à média obtida no laboratório contratado para análise de SCN-, referente ao período de 2008 a 2010. Os resultados dos exames laboratoriais indicaram aumento nos níveis séricos de fosfatase alcalina nos trabalhadores de casas-de-farinha expostos ao HCN, com uma prevalência de 93,3%. Os trabalhadores foram submetidos ao exame clínico e não foram detectadas alterações características de exposição ao HCN. / Cassava used for flour production contains high amounts of cyanogenic glycosides, compounds that, after degradation, release hydrogen cyanide (HCN) which provide toxicity to these type of root. A suitable cassava processing results in the degradation of cyanogenic glycosides and in the production of a safety flour for consumption as food, which generates the hypothesis of HCN release during the process. In this context, the present study aimed to evaluate the HCN exposure of workers engaged in cassava processing, as well as, to identify possible clinical and laboratory alterations related to this exposure. It was included in the study 4 cassava processing facilities placed on Alagoas state, Brazil. It was conducted the determination of HCN in air samples according to the method 6010 proposed by NIOSH. Each industry was monitored in three points: two on workers respiratory zone and one static. A total of 36 male volunteers, distributed between the 4 facilities were included in the study. Each participant was submitted to urine sampling, been one before and other after work shift, and to one blood sampling before work shift. Urinary thiocyanate (SCN-) was spectrophotometrically determined, whereas the remaining biochemical evaluation was conducted in a commercial clinical laboratory. The results indicated that the cassava processors are chronically exposed to HCN at levels between 0,464±0,02 and 3,328±3,85 mg/m3, in the work environment. The comparison between the levels determined at the present study with the Occupational Exposure Limits (OEL) established by NIOSH and ACGIH indicated that cassava processors may be exposed to HCN levels capable of causing adverse health effects. The mean levels of urinary thiocyanate (10,62 - before shift and 8,76 - after shift), were significantly higher than the reference value for non smokers and also for the history mean obtained from the laboratory employed for SCN- analysis, during 2008-2010. The results of laboratorial evaluation indicated increase in the serum activity of alkaline phosphatase in cassava processors exposed to HCN, with a prevalence of 93,3%. The workers were submitted to clinical evaluation and it was not detected any alteration typical of HCN exposure.

The primary goal of the research studies conducted was to apply statistical mechanical and computer simulation methods to describe the equilibrium behavior of hazardous dipolar/quadru-polar single-gases and mixtures confined in micro porous adsorbents. Statistical mechanical models capable of handling the energetic heterogeneity by complex electrostatic interactions between adsorbate-adsorbent and adsorbate-adsorbate electrostatic interactions were developed and studied. The heterogeneous pore shape and size of different adsorbents were taken into account by two different approaches described in the following paragraphs. Under certain conditions, the use of Mean Field Perturbation Theories (MFPTs) is more attractive than Monte-Carlo (MC) simulations because of the enhanced physical insights that they offer, as well as very low computational times required. Existing literature shows that the applications of MFPTs for studying adsorption of polar molecules were limited due to the orientation dependency of the intermolecular potentials for electrostatic interactions, that in turn poses the challenging problem of seeking analytical expressions for the various thermodynamic functions involved. Furthermore, other existing approaches of accounting for complex electrostatic interactions through hydrogen bonding have limitations due to the requirement of parameter estimation related to radial distribution functions and the critical orientation values of molecules for hydrogen bonds, which are generally obtained through MC simulations and X-ray scattering techniques. In the first stage of research efforts, an attempt was made to express angle-dependent intermolecular potentials in the form of angle-independent intermolecular potential terms by employing statistical averaging methods. In particular, the permanent dipole-dipole and permanent dipole-induced dipole intermolecular potentials were expressed as angle-averaged intermolecular potentials. Then, angle-averaged intermolecular potentials were used to predict water isotherms in nano-slit pores. Furthermore, the angle-averaged intermolecular potentials were used for a binary mixture of polar molecules (water-methanol) to predict the adsorption behavior in nano-slit pores. However, significant limitations of MFPTs arise when they are used for the study of adsorption in zeolites that exhibit irregular shaped cavities with surface heterogeneities. The latter certainly represent a future meaningful research direction. It should be pointed out, that the mean field approach allows us to predict equilibrium sorption properties in homogeneous adsorbents like graphitic carbon (slit), carbon nano tubes (cylinder) and highly siliceous faujasites (spherical) as they have regular shaped cavities. The applications of such kinds of theory remained limited due to the (generally) unknown distribution of functional sites on adsorbents of interests (mainly activated carbons and zeolites) and their locations in the adsorbent framework. The second stage of research efforts focused on models capable of incorporating surface heterogeneities and addressing complex pore geometries. The models developed relied on Grand Canonical Monte-Carlo (GCMC) simulations. In particular, two types of GCMC simulations were carried out, namely molecular and atomistic MC simulations. Both techniques were applied to simulate sorption isotherms on zeolites and activated carbon to remove mercury chloride (quadrupole), hydrogen cyanide (HCN, dipole) and methyl ethyl ketone (MEK, dipole) from air. The molecular based MC technique utilized molecular properties of the molecules namely dipole, quadrupole moments, molecular polarizability and molecule size (kinetic diameter). The molecule was considered to be a spherical shaped particle. The dispersion interactions were calculated using Vaan der Waals equation and electrostatic interactions were quantified through the multi-pole expansion method. This approach was used to simulate adsorption of HgCl2, HCN and MEK in zeolite NaX and activated carbon with functional sites namely carbonyl, hydroxyl and carboxyls. Simulation results indicated that HgCl2 sorption could be attributed to charge-induced dipole interactions for activated carbon, suggesting that sorbents with more number surface charges can be useful except for the case of carbonyls in which quadrupole moments plays a crucial role in reducing sorbent capacities, in turn implying that relative positions of positively and negatively charged cations are indeed important. However, for zeolite NaX, performance characteristics were primarily attributed to charge-quadrupole interactions and dispersion interactions. Moreover, zeolite-NaX performance characteristics for capturing HCN and MEK were attributed to dipole-Na interactions due to the relatively large dipole moments of the molecules under consideration. In the case of activated carbon, HCN sorption was governed by mainly charge-dipole and charge-induced dipole interactions, and hence, carbons with carboxyls seemed to perform better than hydroxyls and carbonyls. MEK sorption was influenced by dispersion interactions (due to the large polarizability of MEK) and charge-dipole interactions, which makes carbon with carbonyls more efficient rather than carbons with hydroxyls having the same charge densities. However, application of the aforementioned molecular approaches was limited to sorbents with regular shape cavities having some surface heterogeneity such as activated carbons. Finally, in order to account for sorbents with irregular shaped cavities, such as silicalite and mordenite, one needs to use atomistic MC simulations. The atomistic MC technique utilizes appropriate atomic sizes and charges for the molecules under consideration to quantify intermolecular forces among the adsorbate molecules and the atoms of the zeolite framework as well as activated carbon. The dispersion interactions were calculated using the Van-Der Waals equation and electrostatic interactions were quantified through a standard Coulombic equation. The bond distances among atoms were kept fixed but variations in angular movement and dihedral/torsional movements were considered, and appropriate harmonic potentials were used to account for angle bending and torsional effects. The sorption performance was evaluated for mordenite, silicalite and zeolite beta for a Si/Al ratio of 47-197 for both an HCN and MEK system. The results of HCN/MEK sorption suggested that silicalite has greater capacity than that of mordenites .In the case of MEK Zeolite beta with sodium cations, performance was better than that of mordenites and silicalites. Sorption of HCN in silicalite was observed in straight and zigzag channels, and mainly attributable to hydrogen bonding among HCN molecules. The increase in sodium cations however decreases the capacity of silicalite, zeolite beta and mordenite slightly. The sorption of MEK in mordenite was mainly observed in an 12- and 8-member ring channel. It was found that an increase in sodium cations did not increase the sorption capacity of mordenite significantly as most of the cations in mordenite were located in an 8-member ring channel where MEK molecules can not be accommodated properly due to steric effects. However, the sorption of MEK in zeolite beta seemed to be influenced by the presence of sodium cations as most of the cations are at the intersection of two 12 member rings which provide sufficient space to orient MEK molecules at the intersection and maximize electrostatic interactions. The sorption of MEK in silicalite exhibited similar trends as in the case of mordenite, as all cations were at the intersection of straight and zigzag channels . Finally, in the last Section of the Thesis, a comparative assessment was made of all three approaches in terms of their significance in applications and the ease in applying them.

A chemical ionisation mass spectrometer (CIMS) was developed and utilised for measurements onboard the Facility for Atmospheric Airborne Measurements (FAAM) BAe-146 aircraft. The I- ionisation scheme was implemented to detect nitric acid (HNO3), formic acid (HC(O)OH), hydrogen cyanide (HCN) and dinitrogen pentoxide (N2O5) simultaneously at a sampling frequency of 1 Hz. Sensitivities ranged from 35±6 ion counts pptv-1 s-1 for HC(O)OH to 4±0.9 ion counts pptv-1 s-1 for HCN and limits of detection from 37 ppt for HNO3 and 5 ppt for HCN. Trace gas concentrations of species such as HC(O)OH are currently under predicted in global models. In order to understand their role in controlling air quality, it is crucial that their production pathways and abundance are accurately measured and constrained. To date, airborne measurements of these trace gases have been difficult as a result of instrumental limitations on an aircraft such as limit of detection and sampling frequency. The first UK airborne measurements of HC(O)OH and HNO3 confirmed that HC(O)OH is under predicted by up to a factor of 2 in a trajectory model that implements the full Master Chemical Mechanism (MCM) and Common Representative Intermediate Scheme (CRI). The inclusion of a primary vehicle source enabled the model to reproduce the concentrations observed; verifying that direct sources are under represented. Secondary formation of HC(O)OH was observed through its correlation with HNO3 and ozone (O3), indicating a strong photochemical production source. Hydroxyl (OH) concentrations were estimated for the first time in a flight around the UK using the HC(O)OH and HNO3 measurements. A biomass burning (BB) plume identification technique is applied to data obtained from Canadian biomass fires using HCN as a marker. A 6 sigma above background approach to defining a plume resulted in a higher R2 correlating value for the normalised excess mixing ratio (NEMR) to carbon monoxide (CO) when compared to current methods in the literature. The NEMR obtained from this work; 3.76±0.02 pptv ppbv-1, lies within the range found in the literature. This NEMR is then used to calculate a global emission total for HCN of 0.92 Tg (N) yr-1 when incorporated into the global tropospheric model STOCHEM CRI. The first direct N2O5 airborne measurements on an aircraft at night are compared to indirect measurements taken by a broadband cavity enhancement absorption spectrometer. An average R2 correlation coefficient of 0.87 observed over 8 flights for 1 Hz measurements indicates the selectiveness of the I- ionisation scheme to detect N2O5 directly, without nitrate (NO3) interference.

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