Thesis (M.S.)--The University of North Carolina at Greensboro, 2010. / Directed by Anne Hershey; submitted to the Dept. of Biology. Title from PDF t.p. (viewed Jul. 9, 2010). Includes bibliographical references (p. 29-34).

Thesis (M.S.)--Oregon Graduate Center, 1985.

Northern regions account for approximately 30% (1035 Pg) of the world’s soil organic carbon (SOC). Much of this carbon is currently stored in permafrost soils, which are vulnerable to increasing air and ground temperatures. Permafrost landscapes rich in ground ice, such as high-centred polygonal terrain, are likely to be highly vulnerable to thaw. Degradation of ice wedges in high-centred polygonal terrain causes increased moisture and ground temperatures. These environmental controls are likely to have a large impact on carbon cycling in this terrain type. My M.Sc. research combined both lab and field-based analyses to investigate current and potential carbon emissions from high-centred polygonal terrain in the Tuktoyaktuk Coastlands. To estimate the magnitude of future emissions from this terrain type I incubated six permafrost cores collected at two sites. Peat cores from four depths were each incubated under four conditions (cold anaerobic, warm anaerobic, cold aerobic, warm aerobic). The observation that carbon mineralization rates do not vary with depth demonstrates that the soil carbon liberated from permafrost in high-centred polygonal terrain will not be limited by SOC quality. This experiment also shows that emission rates will be moderated by temperature and moisture levels, and will be primarily in the form of CO2. To examine the impact of ice-wedge thaw on carbon emissions in high-centred polygonal terrain, we combined opaque chamber measurements of flux and estimates made from water samples using a gas diffusion model. Field sampling at two sites contrasted carbon emissions from polygon centres (n=18), wet troughs (n=18) and ponds (n=20). We also measured ground temperature and soil moisture using thermistors and a moisture sensor. Our field results demonstrate that ice-wedge degradation results in increased ground temperature, deeper active layers, and increased CO2 and CH4 emissions. Contrary to our expectations, CO2 emissions were not limited by waterlogged conditions, demonstrating the importance of anaerobic CO2 production. Our field measurements demonstrate that increasing temperatures are correlated with rising CO2 emissions in aerobic environments, and rising CO2 and CH4 emissions in anaerobic environments. Taken together, these two studies demonstrate that as ground temperatures increase in high-centred polygonal terrain, carbon emissions from ecosystem respiration are likely to increase. / Graduate / 0481 / 0425 / 0768

Northern peatlands occupy a very small proportion of the Earth’s surface but contain nearly a third of the world’s soil organic carbon. These wetland systems produce substantial fluxes of CH4, a potent greenhouse gas, and are expected to experience particularly high annual mean temperature increases as global climate change proceeds, which could result in a significant positive feedback. Using radioisotope labeling, we quantified the rates of two pathways of CH4 production in six sites in northern Michigan along a physiochemical and ecological gradient that characterizes northern peatlands. We found that the rates of these two pathways displayed markedly different dynamics in space and time and that the hydrogenotrophic pathway, previously presumed to be less significant in these systems, can increase substantially and become dominant across the landscape when water tables are high. Quantifying these two pathways provides critical insight into understanding dynamics of CH4 production in northern peatlands.

Orientador: Roberto Alves de Oliveira / Co-orientadora: Rose Maria Duda / Banca: Eduardo Cleto Pires / Banca: Valéria Del Nery / Resumo: Neste trabalho avaliou-se a conversão anaeróbia da vinhaça e melaço em metano, com aumento gradual da carga orgânica volumétrica (COV), em dois reatores UASB (R1 e R2) com volumes de 40,5 e 21,5 L, na faixa de temperatura mesofílica. Os reatores UASB foram operados durante 350 dias, dos quais de 01 a 230 dias utilizou-se a vinhaça como afluente, de 231 a 308 dias o melaço de cana-de-açúcar e de 309 a 350 dias novamente a vinhaça. Os reatores foram operados com tempo de detenção hidráulica (TDH) de 2,8 e 1,8 d e COV de 0,2 a 11,5 g DQOtotal (L d)-1 no R1 e R2, respectivamente. Durante os primeiros 230 dias de operação, com vinhaça da safra de 2012, a produção volumétrica de metano foi crescente com o aumento da COV, atingindo valores de até 0,8 L CH4 (L d)-1 no R1 e de 1,3 L CH4 (L d)-1 no R2. Após 140 dias de operação com a correção de pH do afluente com solução de NaOH, a produção específica de metano foi crescente no R1 de 0,133 a 0,181 L CH4 (g DQOtotal removida)-1, e no R2, de 0,145 a 0,185 L CH4 (g DQOtotal removida)-1. Os valores médios das eficiências de remoção de DQOtotal variaram de 49 a 82%. As porcentagens da DQO removida convertida em metano foram de 48 a 58% no R1 e de 39 a 65 % no R2. A recirculação do efluente foi utilizada para a COV acima de 6 g DQOtotal (L d)-1 no R1 e de 8 g DQOtotal (L d)-1 no R2 e permitiu a manutenção do pH do afluente do R1 e do R2 na faixa de 6,5 a 6,8, mas provocou a diminuição das conversões de DQO em metano no R2, de 53% para 42%, em virtude do aumento da fração de DQO de difícil degradação no afluente. Após 230 dias de operação, com o tratamento do melaço no período de entressafra, a produção volumétrica de metano nos reatores R1 e R2 diminuiu para 0,294 e 0,163 L CH4 (L d)-1, respectivamente... / Abstract: The purpose of this study was to evaluate the anaerobic conversion of vinasse in methane, increasing gradually the organic load rate (OLR) on two UASB reactors (R1 and R2), each with a volume of 40.5 and 21.5 L in mesophilic temperature range. The UASB reactors were operated for 350 days, of which 01-230 days used the vinasse as affluent, 231-308 days, the molasses cane sugar and 309-350 dias again stillage. The reactors were operated with a hydraulic retention time (HRT) of 2.8 and 1.8 and OLR of 0.2 to 11.5 g total COD (L d)-1 in R1 and R2, respectively. During the first 230 days of operation, with vinasse from 2012 harvest, the volumetric methane production increased with the increase of OLR, reaching values of up to 0.8 L CH4 (L d)-1 in R1 and 1.3 L CH4 (L d)-1 in R2. After 140 days of operation with correcting the pH of the effluent with NaOH solution, the specific methane production in R1 was increased from 0.133 to 0.181 L CH4 (g CODtotal removed)-1, and R2, 0.145 to 0.185 L CH4 (g CODtotal removed)-1. The average values of totalCOD removal efficiencies ranged 49-82%. The percentages of removed COD converted to methane were between 48 and 58% in R1 and 39 to 65% in R2. The recirculation of the effluent was used for OLR above 6 g total COD (L d)-1 in R1 and 8 g of totalCOD (L d)-1 for R2 and allowed to maintain the pH of the effluent of R1 and R2 in the range from 6.5 to 6.8, but caused a decrease in methane conversion of COD in R2, 53% to 42% due to the increase of the fraction of COD influent degradation difficult. After 230 days of operation, with the treatment of molasses in the off-season, the volumetric methane production in the reactors R1 and R2 decreased to 0.294 and 0.163 L CH4 (L d)-1, respectively... / Mestre

Made available in DSpace on 2014-06-11T19:23:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-12-12Bitstream added on 2014-06-13T20:10:31Z : No. of bitstreams: 1 000750657.pdf: 1145537 bytes, checksum: 727ac7d8b2d1fdff4c88f61aa7804e99 (MD5) / O objetivo deste estudo foi mensurar a quantidade de CH4, CO2, O2 e H2O no ar inspirado e expirado de forma simultânea em bovinos de corte, relacionando isto com a produção de calor metabólico e a perda de calor latente e sensível sob condições meteorológicas do ambiente natural. Foram avaliados cinco bovinos da raça Nelore em um delineamento experimental de quadrado latino ao sol e a sombra. A emissão de CH4, a produção de calor metabólico, a perda de calor latente por respiração foram determinadas usando um sistema de calorimetria indireta. Também foram determinados os fluxos de calor por radiação e convecção. Concomitantemente foram analisadas a temperatura retal (TR), temperatura da epiderme (TEP), temperatura do pelame (TP), temperatura do ar expirado (Texp), além de temperatura do ar (TA), umidade relativa (UR), radiação de ondas curtas (RC), e temperatura radiante média (TRM). A produção de calor metabólico apresentou média de 233,66±5,92 W m-2 e diferiu estatisticamente (P<0,05) entre si nos diferentes ambientes (sol e sombra), apresentando maior média à sombra (245,25±5,67 W m-2). Verificou-se que houve uma correlação positiva baixa entre a produção de calor metabólico (qmet) e a emissão de metano (ECH4). Este apresentou média de 7,68±0,46 L h-1 e diferiu estatisticamente em relação ao ambiente, apresentando maior média à sombra (8,85±0,39 L h-1). A evaporação respiratória (qER) pouco contribuiu para dissipação do calor produzido pelo metabolismo, apresentando média de 13,59±0,55 W m-2, o mesmo ocorreu com as perdas calor por mecanismos sensíveis. A perda de calor por evaporação da superfície (qes) foi a que mais contribuiu para perda de calor em bovinos da raça nelore (70,76±2,69 W m-2), porém esse mecanismo juntamente com os outros não foram suficientes para dissipar totalmente a energia térmica produzida... / The aim of this study was to measure the amount of CH4, CO2, O2 and H2O simultaneously in the air inhaled and exhaled in beef cattle. Relating this to the metabolic heat production and of latent and sensible heat loss under natural environment. Five Nelore cattle were evaluated in an experimental design of Latin square, exposed to sun and on shade. The CH4 emission, the metabolic heat production, latent heat loss by respiration and skin surface were determined using indirect calorimetry system were also determined the flow of heat by radiation and convection. Concomitantly rectal temperature (TR), hair coat temperature (TEP), skin temperature (TP), expired air temperature (TEXP) were analyzed, in addition to air temperature (TA), air humidity (UR) , short wave radiation (RC) and mean radiant temperature (TRM). The metabolic heat production had an average of 233,66 ± 5,92 W m-2 and statistically different (P< 0,05) from each other in different environments (sun and shade), with higher average on shade (245,25±5,67 W m-2). It was found that there was a low positive correlation between metabolic heat production (qmet) and methane emission (ECH4). This last one had an average of 7,68±0,46 L h-1 and was statistically different on environment, showing higher average in the shade (8,85±0,39 L h-1). The heat loss by cutaneous evaporation (qER) contributed a little to dissipate the heat produced by metabolism, with a mean of 13,59±0,55 W m-2, so did the same for heat loss by sensitive mechanisms. The qes was the largest contributor to heat loss in Nelore cattle (70,76±2,69 W m-2), but this mechanism along with others were not sufficient to fully dissipate the heat produced...

Orientador: Alex Sandro Campos Maia / Co-orientadora: Telma Teresinha Berchielli / Banca: Evaldo Antônio Lencioni Titto / Banca: Márcia Helena Machado da Rocha Fernandes / Resumo: O objetivo deste estudo foi mensurar a quantidade de CH4, CO2, O2 e H2O no ar inspirado e expirado de forma simultânea em bovinos de corte, relacionando isto com a produção de calor metabólico e a perda de calor latente e sensível sob condições meteorológicas do ambiente natural. Foram avaliados cinco bovinos da raça Nelore em um delineamento experimental de quadrado latino ao sol e a sombra. A emissão de CH4, a produção de calor metabólico, a perda de calor latente por respiração foram determinadas usando um sistema de calorimetria indireta. Também foram determinados os fluxos de calor por radiação e convecção. Concomitantemente foram analisadas a temperatura retal (TR), temperatura da epiderme (TEP), temperatura do pelame (TP), temperatura do ar expirado (Texp), além de temperatura do ar (TA), umidade relativa (UR), radiação de ondas curtas (RC), e temperatura radiante média (TRM). A produção de calor metabólico apresentou média de 233,66±5,92 W m-2 e diferiu estatisticamente (P<0,05) entre si nos diferentes ambientes (sol e sombra), apresentando maior média à sombra (245,25±5,67 W m-2). Verificou-se que houve uma correlação positiva baixa entre a produção de calor metabólico (qmet) e a emissão de metano (ECH4). Este apresentou média de 7,68±0,46 L h-1 e diferiu estatisticamente em relação ao ambiente, apresentando maior média à sombra (8,85±0,39 L h-1). A evaporação respiratória (qER) pouco contribuiu para dissipação do calor produzido pelo metabolismo, apresentando média de 13,59±0,55 W m-2, o mesmo ocorreu com as perdas calor por mecanismos sensíveis. A perda de calor por evaporação da superfície (qes) foi a que mais contribuiu para perda de calor em bovinos da raça nelore (70,76±2,69 W m-2), porém esse mecanismo juntamente com os outros não foram suficientes para dissipar totalmente a energia térmica produzida... / Abstract: The aim of this study was to measure the amount of CH4, CO2, O2 and H2O simultaneously in the air inhaled and exhaled in beef cattle. Relating this to the metabolic heat production and of latent and sensible heat loss under natural environment. Five Nelore cattle were evaluated in an experimental design of Latin square, exposed to sun and on shade. The CH4 emission, the metabolic heat production, latent heat loss by respiration and skin surface were determined using indirect calorimetry system were also determined the flow of heat by radiation and convection. Concomitantly rectal temperature (TR), hair coat temperature (TEP), skin temperature (TP), expired air temperature (TEXP) were analyzed, in addition to air temperature (TA), air humidity (UR) , short wave radiation (RC) and mean radiant temperature (TRM). The metabolic heat production had an average of 233,66 ± 5,92 W m-2 and statistically different (P< 0,05) from each other in different environments (sun and shade), with higher average on shade (245,25±5,67 W m-2). It was found that there was a low positive correlation between metabolic heat production (qmet) and methane emission (ECH4). This last one had an average of 7,68±0,46 L h-1 and was statistically different on environment, showing higher average in the shade (8,85±0,39 L h-1). The heat loss by cutaneous evaporation (qER) contributed a little to dissipate the heat produced by metabolism, with a mean of 13,59±0,55 W m-2, so did the same for heat loss by sensitive mechanisms. The qes was the largest contributor to heat loss in Nelore cattle (70,76±2,69 W m-2), but this mechanism along with others were not sufficient to fully dissipate the heat produced... / Mestre

Made available in DSpace on 2014-06-11T19:30:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-30Bitstream added on 2014-06-13T20:00:05Z : No. of bitstreams: 1 000735909.pdf: 1783493 bytes, checksum: 98ce4905be3e5498b97253c684ce09a5 (MD5) / Neste trabalho avaliou-se a conversão anaeróbia da vinhaça e melaço em metano, com aumento gradual da carga orgânica volumétrica (COV), em dois reatores UASB (R1 e R2) com volumes de 40,5 e 21,5 L, na faixa de temperatura mesofílica. Os reatores UASB foram operados durante 350 dias, dos quais de 01 a 230 dias utilizou-se a vinhaça como afluente, de 231 a 308 dias o melaço de cana-de-açúcar e de 309 a 350 dias novamente a vinhaça. Os reatores foram operados com tempo de detenção hidráulica (TDH) de 2,8 e 1,8 d e COV de 0,2 a 11,5 g DQOtotal (L d)-1 no R1 e R2, respectivamente. Durante os primeiros 230 dias de operação, com vinhaça da safra de 2012, a produção volumétrica de metano foi crescente com o aumento da COV, atingindo valores de até 0,8 L CH4 (L d)-1 no R1 e de 1,3 L CH4 (L d)-1 no R2. Após 140 dias de operação com a correção de pH do afluente com solução de NaOH, a produção específica de metano foi crescente no R1 de 0,133 a 0,181 L CH4 (g DQOtotal removida)-1, e no R2, de 0,145 a 0,185 L CH4 (g DQOtotal removida)-1. Os valores médios das eficiências de remoção de DQOtotal variaram de 49 a 82%. As porcentagens da DQO removida convertida em metano foram de 48 a 58% no R1 e de 39 a 65 % no R2. A recirculação do efluente foi utilizada para a COV acima de 6 g DQOtotal (L d)-1 no R1 e de 8 g DQOtotal (L d)-1 no R2 e permitiu a manutenção do pH do afluente do R1 e do R2 na faixa de 6,5 a 6,8, mas provocou a diminuição das conversões de DQO em metano no R2, de 53% para 42%, em virtude do aumento da fração de DQO de difícil degradação no afluente. Após 230 dias de operação, com o tratamento do melaço no período de entressafra, a produção volumétrica de metano nos reatores R1 e R2 diminuiu para 0,294 e 0,163 L CH4 (L d)-1, respectivamente... / The purpose of this study was to evaluate the anaerobic conversion of vinasse in methane, increasing gradually the organic load rate (OLR) on two UASB reactors (R1 and R2), each with a volume of 40.5 and 21.5 L in mesophilic temperature range. The UASB reactors were operated for 350 days, of which 01-230 days used the vinasse as affluent, 231-308 days, the molasses cane sugar and 309-350 dias again stillage. The reactors were operated with a hydraulic retention time (HRT) of 2.8 and 1.8 and OLR of 0.2 to 11.5 g total COD (L d)-1 in R1 and R2, respectively. During the first 230 days of operation, with vinasse from 2012 harvest, the volumetric methane production increased with the increase of OLR, reaching values of up to 0.8 L CH4 (L d)-1 in R1 and 1.3 L CH4 (L d)-1 in R2. After 140 days of operation with correcting the pH of the effluent with NaOH solution, the specific methane production in R1 was increased from 0.133 to 0.181 L CH4 (g CODtotal removed)-1, and R2, 0.145 to 0.185 L CH4 (g CODtotal removed)-1. The average values of totalCOD removal efficiencies ranged 49-82%. The percentages of removed COD converted to methane were between 48 and 58% in R1 and 39 to 65% in R2. The recirculation of the effluent was used for OLR above 6 g total COD (L d)-1 in R1 and 8 g of totalCOD (L d)-1 for R2 and allowed to maintain the pH of the effluent of R1 and R2 in the range from 6.5 to 6.8, but caused a decrease in methane conversion of COD in R2, 53% to 42% due to the increase of the fraction of COD influent degradation difficult. After 230 days of operation, with the treatment of molasses in the off-season, the volumetric methane production in the reactors R1 and R2 decreased to 0.294 and 0.163 L CH4 (L d)-1, respectively...

Airborne dust and methane are common problems in the underground coalmines. They pose health and safety risk to mining personnel, and a safety risk to mining equipment as well. In order to prevent these risks air borne dust and methane concentrations must be reduced to within the acceptable levels. In South Africa, the dust and methane concentration in coalmines should not exceed 2.0 mg/m³ and 0.5% per volume, respectively. Mine ventilation is one of the popular ways of controlling both dust and methane. Different ventilation systems have been designed since the history of underground coal mining. Unfortunately, none provides ultimate solution to the dust and methane problem, especially in the most critical areas of the underground coalmine, like blind-end of the heading and last through road. By changing airflow patterns and air velocity, it is possible to obtain an optimum ventilation design that can keep dust and methane within the acceptable levels. Since it is very difficult to conduct experiments in the underground coalmine due to harsh environmental conditions and tight production schedules, the designer made use of the Computational Fluid Dynamics (CFD) modelling technique. The models were then experimentally verified and validated using a scaled down model at University of Pretoria. After verification further numerical analysis was done to in order to device a method for determining optimum fan positions for different heading dimensions. This study proves that CFD can be used to model ventilation system of a scaled down coalmine model. Therefore chances that this might be true for the actual mine are very high but it needs to be investigated. If this is found to be true then CFD modelling will be a very useful tool in coalmine ventilation system research and development. / Dissertation (MSc)--University of Pretoria, 2011. / Mechanical and Aeronautical Engineering / unrestricted

Relaxation properties of the deuteron spin system in CD₄ and CD₃H were studied in the temperature range from 105°K - 57°K. These results show that the intra-molecular quadrupole interactions dominate and the relaxation occurs through the molecular reorientations of the molecule. The deuteron spin-lattice relaxation times are approximately temperature independent, except for a small contribution from the magnetic dipolar interactions near the melting point in CD₃H. From this data it is concluded that the reorientatlonal correlation time is temperature independent. The deuteron T₂ shows the same temperature dependence as the proton T₂; the deuteron T₂ can be accounted for on the basis of magnetic dipolar interactions alone. / Science, Faculty of / Physics and Astronomy, Department of / Graduate