Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-10-03T16:31:46Z No. of bitstreams: 1 _Dissertação-1.pdf: 1765644 bytes, checksum: 7e195b49bdd27dff996d76e75bbb6210 (MD5) / Made available in DSpace on 2017-10-03T16:31:46Z (GMT). No. of bitstreams: 1 _Dissertação-1.pdf: 1765644 bytes, checksum: 7e195b49bdd27dff996d76e75bbb6210 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / O aquecimento global provocado por gases como CO2, N2O e o CH4 resultantes de atividades agrícolas e por solos alagados tem motivado inúmeros estudos em diversos países, procurando quantificar a contribuição de diferentes sistemas na emissão desses gases. Os objetivos desse estudo foram elucidar o mecanismo de produção do gás do efeito estufa, óxido nitroso (N2O) em uma área de floresta secundária baixa localizada em Manguariba - Rio de Janeiro e determinar se estas emissões ocorrem acompanhadas por processos de nitrificação ou desnitrificação. Para que isso fosse possível, foram realizadas quatro campanhas de amostragens seguidas de experimentos de incubação do solo em laboratório e análises químicas deste solo antes e após as incubações. Medidas de variação de pressão em câmaras sob condições controladas de temperatura foram realizadas empregando-se um manômetro tubo em “U” em quatro experimentos e um barômetro/sensor/datalogger em outros dois experimentos. As concentrações de N2O, bem como as de CH4 no solo, foram determinadas antes e após as incubações por cromatografia gasosa. Na primeira campanha de amostragem foram coletadas também amostras de água em um curso de água que pode ser uma fonte de nitrogênio para este solo, pois em época de chuvas a água poluída com esgoto doméstico, deste riacho chega até os pontos de amostragem. Foram determinadas as concentrações de amônio e nitrato em amostras do solo, antes e após incubações, e na água do riacho. Através dos dados gerados pelas análises químicas determinamos as taxas líquidas de nitrificação, mineralização/assimilação ocorridas durante o período de incubação do solo e correlacionamos essas taxas com a produção de óxido nitroso. A nitrificação a uma taxa constante se mostrou dominante no experimento onde houve a maior produção de N2O. Nos demais experimentos a nitrificação permaneceu dominante, porém seguida por desnitrificação em outros dois experimentos, nos quais a produção do gás foi muito pequena e até mesmo nula, indicando a redução do óxido nitroso a N2. A desnitrificação ocorreu de forma dominante em apenas um dos experimentos e possivelmente foi seguida por nitrificação, pois houve uma pequena produção de N2O durante esta incubação. / The global warming caused by greenhouse gases like CO2, CH4 and N2O resulting from agricultural activities and flooded soils has motivated numerous studies in many countries, seeking to quantify the contribution of different systems on greenhouse gas emissions. The objectives of this study were to elucidate the mechanism of production of greenhouse gas, nitrous oxide (N2O) in a secondary forest area located in downtown Manguariba (Rio de Janeiro) and determines if these emissions occur accompanied by processes of nitrification and denitrification. To make this possible, there were four sampling campaigns followed by incubation experiments of soil in the laboratory and chemical analyses of soil before and after incubations. Measures of barometric pressure variation in PVC chambers under controlled temperature were carried out using a variation of a pressure gauge manometer tube into "U" for four incubation experiments and a sensor which measures the pressure variation barometer / sensor / datalogger (Baro Diver) during the third and fourth experiments. N2O concentrations were determined by gas chromatography. In the first year of sampling, samples of water were taken from a tributary of the Rio Guandu, which can be a source of sewage pollution for this soil, because in the rainy season the water in this tributary reaches the sampling points. Chemical analysis was performed for determination of NH4 + and for analysis of nitrate ions. Data generated by the chemical analysis determined the rate of net nitrification, mineralization / assimilation which occurred during the incubation periods and correlated these rates with the production of nitrous oxide. Nitrification at a constant rate proved to be dominant in the experiment where there was a greater production of N2O. In other experiments, however, nitrification remained dominant followed by denitrification in two other experiments, in which gas production was very small and even zero, indicating the reduction of nitrous oxide to N2. Denitrification was very dominant in only one experiment and was followed by nitrification possibly because there was a small N2O production during this incubation. The experiment with the barometer / sensor / datalogger (Baro Diver) was carried out to confirm what would be the dominant process along these incubations. With this sensor we observed nitrification-dominant production of nitrous oxide. There were no correlations between the flow of N2O emitting in situ and flow generated during the incubation periods. We also observed that the effluent water from the Rio Guandu sample showed high concentrations of nitrate and ammonia and can be considered as a source of inorganic N to this soil

Atualmente a questão das mudanças climáticas causada por gases do efeito estufa (GEE), desperta grande interesse. Diante dos possíveis impactos que tais mudanças podem causar, buscam-se alternativas visando diminuir as emissões desses gases associadas a atividades antrópicas. Entre essas alternativas está a utilização de biocombustíveis, que no caso do Brasil é representado pelo etanol proveniente da cana-de-açúcar. Existe um debate sobre a magnitude da redução de emissões de GEE que tal opção de combustível representa. Fatores como mudança do uso da terra e fluxos de óxido nitroso (N2O) e metano (CH4) nas plantações de cana-de-açúcar, ainda estão sendo estudados. O propósito deste trabalho foi avaliar, com auxílio de modelagem computacional e sistemas de informações geográficas (SIG), as emissões de GEE associadas ao cultivo da cana-de-açúcar no estado de São Paulo, nos anos de 2003 e 2010, comparando os resultados com os obtidos a partir das diretrizes do \"Intergovernmental Panel on Climate Change\" (IPCC). Também foi avaliada a influência nos resultados quando os dois métodos são utilizados em diferentes escalas espaciais. O programa computacional de emissões utilizado foi o \"Denitrification Decomposition\" - DNDC. Inicialmente foram comparados valores de emissão simulados pelo programa com valores de um experimento com medição contínua desses gases numa plantação de cana-deaçúcar na região de Quensland - Austrália. Os resultados da simulação foram quantitativamente semelhantes aos obtidos no experimento no caso dos fluxos de N2O, e qualitativamente satisfatórios com relação aos fluxos CH4. As estimativas estaduais de emissões de N2O, obtidas através do programa DNDC foram significativamente maiores do que as obtidas pelas diretrizes do IPCC, em todas as escalas consideradas. Também foram observadas variações significativas entre as estimativas nas diversas escalas espaciais quando utilizado o programa computacional, o mesmo não sendo verificado quando utilizados os algoritmos do IPCC. Em ambos os casos também se notou um aumento na estimativa de emissões de N2O para o ano de 2010 em relação a 2003. A simulação computacional indicou que os fluxos de N2O e CH4 na cultura da cana-de-açúcar, são influenciados pelo tipo de solo e condições climáticas, sendo que tais fatores não são levados em consideração quando as estimativas são baseadas nos algoritmos do IPCC. / Currently the climate change issue caused by greenhouse gases (GHG) attracts great interest. Given the potential impacts that such changes might cause, option aiming to reduce emissions of these gases associated with anthropogenic activities are currently being sought. Among these options is the use of biofuels, which in the case of Brazil is represented by sugarcane ethanol. There is a debate about the magnitude of GHG emission reduction that this option represents. Issues like land use change and fluxes of nitrous oxide (N2O) and methane (CH4) on sugarcane plantations are still being investigated. The purpose of this work is to evaluate, with the assistance of computational modeling and geographic information systems (GIS), greenhouse gases emissions associated with the cultivation of sugarcane in the state of São Paulo, in the years 2003 e 2010, comparing the results with the ones obtained by the International Panel on Climate Change (IPCC) guidelines. The influence on the results when both methods are used at different spatial scales was also evaluated. The computer program used to simulate GHG emissions was the \"Denitrification Decomposition\" - DNDC. Initially, emissions values simulated by the computer program were compared with values obtained in an experiment with continuous measurements of such gases in a plantation of sugarcane in the region of Queensland-Australia. The simulation results were quantitatively similar to those obtained in the experiment in the case of N2O fluxes, and of a satisfactory quality with respect to CH4 fluxes. The statewide estimates for N2O emissions, obtained through the DNDC program were significantly greater than the ones obtained by the IPCC guidelines, at all scales considered. Significant variations between estimates were also observed at different spatial scales when using the computer program, the same thing was not observed when using IPCC algorithms. In both cases it was also notice an increase on the estimates of N2O emissions for the year 2010 compared to 2003. The computer simulation indicated that the flows of N2O and CH4 in sugarcane crops are influenced by soil types and climatic conditions, and these factors are not taken into account when estimates are based on the IPCC algorithms.

Solos de ecossistemas tropicais são considerados maiores emissores naturais de óxido nitroso (N2O) para a atmosfera. Grande parte do N2O produzido a partir destes solos é originada por dois processos microbiológicos, desnitrificação e nitrificação. A dinâmica de produção e decomposição de raízes e de serapilheira também contribuem para os estoques de carbono e nitrogênio no solo e para a produção de N2O e outros gases de efeito estufa. Diante do exposto e da grande importância, produtividade e extensão da Mata Atlântica, o presente estudo apresenta como objetivo principal investigar se as perdas de nitrogênio (N) pela emissão de N2O é um componente importante no ciclo do N na Mata Atlântica e se há uma variação nesses fluxos em relação às diferentes altitudes (100, 400 e 1000 m) e em relação a outros parâmetros (sazonalidade, temperatura, umidade do solo, dinâmica de produção e decomposição de serapilheira e raízes, e razão C:N da serapilheira). Não houve diferença na quantidade de chuva entre as áreas estudadas. A temperatura diminuiu com a altitude e foi significativamente mais baixa na altitude 1000 m. A umidade do solo determinada através dos espaços porosos do solo preenchidos por água diminuiu com a altitude. As áreas localizadas a 100 m apresentaram maior produção de serapilheira e entre as demais altitudes não houve diferença significativa na produção. Ao contrário da produção, o estoque de serapilheira e o tempo para decomposição também aumentou com as altitudes. O solo das parcelas localizados a 1000 m apresentaram biomassa de raízes vivas e mortas significativamente maior (P<0,05) e a razão C:N das raízes foi similar para todas as áreas. Os fluxos médios anuais encontrados para cada altitude durante o ano desta pesquisa foram: 3,2 kg-N ha-1 ano-1, 1,3 kg-N ha-1 ano-1 e 0,6 kg-N ha-1 ano-1 para as altitudes 100, 400 e 1000m, respectivamente. As emissões de N2O foram fortemente influenciadas pela umidade do solo e pela temperatura e diminuíram significativamente com a altitude. Os baixos fluxos de N2O a 1000 m são decorrentes da baixa disponibilidade de NO3- que viabiliza os processo de geração de N2O, que é produzido por desnitrificação.Com base nestes resultados, a Floresta de Mata Atlântica apresenta um ciclo de N mais conservador em relação às florestas da região Amazônica tanto pelas diferenças físico-químicas do solo como temperatura e regimes pluviométricos / Soils of tropical ecosystems are considered one of the major natural sources of nitrous oxide (N2O) to the atmosphere. Most of the N2O in soils is produced by two microbial processes, denitrification and nitrification. Litterfall and fine root dynamics are believed to contribute to the labile carbon (C) and nitrogen (N) and also contribute to the production greenhouse gases. According to these assumptions and regarding to the magnitude of the Brazilian Atlantic Forest this study aimed to investigate the losses of N by the emission of N2O along an altitudinal gradient and the relation between these fluxes and other climatic and edaphic parameters (precipitation, temperature, soil moisture, litterfall and fine roots dynamics). There was no difference in precipitation among the studied areas. Temperature and soil moisture decreased with altitude. Lower altitudes showed high litter production and low stock of soil litter. Root mass was significantly higher at altitude 1000m but root C:N ratio showed no difference among the altitudes. N2O annual soil fluxes were 3,2 kg-N ha-1yr-1, 1,3 kg-N ha-1yr-1, and 0,6 kg-N ha-1yr-1 at 100, 400 and 1000m, respectively. N2O fluxes were significantly influenced by soil moisture and temperature and decreased with altitude. Lower fluxes at 1000m are due to low NO3- availability and thus low N2O production. According to these results, The Atlantic Forest is considered to have a more conservative N cycle related to the Amazon forests due to the differences of soil chemical and physical properties and pluviometric conditions

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-05-05T18:01:27Z No. of bitstreams: 1 2013 - Silvio da Silva Santos.pdf: 1585710 bytes, checksum: 55512544fcf22f1d09c9080258d4c607 (MD5) / Made available in DSpace on 2017-05-05T18:01:27Z (GMT). No. of bitstreams: 1 2013 - Silvio da Silva Santos.pdf: 1585710 bytes, checksum: 55512544fcf22f1d09c9080258d4c607 (MD5) Previous issue date: 2013-04-30 / CAPES / There is a growing demand for organic fertilizers in Brazil, mainly for growing vegetables. Composting is a technique that can be used as an alternative to increase the availability and quality of organic fertilizers. During the composting process, there is emission gases such as carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), which contribute to the greenhouse effect in the planet, also of ammonia (NH3), which reduces the efficiency of the composting process. Emissions of N2O and NH3 to the atmosphere has been attributed in part to the decomposition of organic matter from crop residues that are used in soil management systems. Thus, Chapter I aimed to characterize mixtures of elephant grass (Pennisetum purpureum) with different materials in order to produce an organic fertilizer rich in nutrients and can be used in the cultivation of sugar beets. The treatments were: (i) elephant grass + cattle manure;(ii) elephant grass + gliricidia; and (iii) elephant grass + castor cake. The evaluations were performed for 120 days. In this study, the compound formulated with a mixture of elephant grass and gliricidia resulted in higher concentrations of N, which shows the high potential of the material to be used as organic fertilizer for crops with high nutritional requirements. The N losses by volatilization were not relevant in the composting process. In the Chapter II it was evaluated the emissions of N2O and NH3 in the compost and other organic N sources used in the production of beet and lettuce. The treatments consisted of: (i) organic compound, prepared from the mixture of elephant grass with gliricidia (Gliricidia sepium) + fertilization coverage with castor bean; (ii) green manure dwarf mucuna (Mucuna deeringiana) + fertilization coverage with castor bean; (iii) cattle manure + fertilizer topdressing with chicken manure tanned; (iv) urea in planting and coverage; and (v) the control treatment (without nitrogen). Considering these results, the N2O emissions from the soil ranged from 7.37 and 2699.62 ?g N2O-N-1. The volatilization losses of ammonia ranged from 9.5 to 30% of the N applied. The application of cattle manure + chicken manure management proved to be environmentally more suitable for growing vegetables, since it resulted in lowest flow of nitrous oxide from the soil and ammonia volatilization. Moreover, urea is the N source that causes most losses by volatilization of ammonia, with zero residual effect for the next crop, in this case for the production of lettuce. The highest emissions were observed after rainfall, regardless of treatment, highlighting the importance of presence of water in the environment for the emissions of N2O to occur. / ? crescente a demanda por adubos org?nicos no Brasil, principalmente para o cultivo de hortali?as. A compostagem ? uma t?cnica que pode ser utilizada como alternativa para aumentar a disponibilidade e a qualidade dos fertilizantes org?nicos. Durante o processo de compostagem, h? emiss?o de gases, como g?s carb?nico (CO2), ?xido nitroso (N2O) e metano (CH4), que contribuem para o efeito estufa no planeta, al?m de am?nia (NH3), que reduz a efici?ncia do processo de compostagem. As emiss?es de N2O e NH3 para atmosfera tem sido atribu?das, em parte, ? decomposi??o da mat?ria org?nica proveniente dos res?duos vegetais que s?o empregados nos sistemas de manejo do solo. Dessa maneira, o Cap?tulo I teve como objetivo caracterizar misturas de capim-elefante (Pennisetum purpureum) com diferentes mat?rias-primas, visando produzir um adubo org?nico rico em nutrientes e capaz de ser usado no cultivo de hortali?as. Os tratamentos foram os seguintes: (i) capim-elefante + esterco bovino curtido; (ii) capim-elefante + gliricidia (Gliricidia sepium); e (iii) capim-elefante + torta de mamona. As avalia??es foram realizadas durante 120 dias. Neste estudo, o composto formulado com a mistura de capim-elefante e gliricidia resultou em maior teor de N, o que mostra o elevado potencial do material para ser usado como adubo org?nico em culturas com elevada exig?ncia nutricional. As perdas de N por volatiliza??o de am?nia n?o foram relevantes at? 34 dias de compostagem. O Cap?tulo II teve como objetivo avaliar as emiss?es de N2O e NH3 em composto org?nico e outras fontes de N usadas na produ??o de hortali?as. Os tratamentos consistiram da aplica??o de: (i) composto org?nico, preparado da mistura de capim elefante com gliricidia (Gliricidia sepium) + fertiliza??o em cobertura com torta de mamona; (ii) aduba??o verde com mucuna an? (Mucuna deeringiana) + fertiliza??o em cobertura com torta de mamona; (iii) esterco bovino curtido + fertiliza??o em cobertura com esterco de ave curtido; (iv) ureia em plantio e cobertura; e (v) tratamento controle (sem aplica??o de N). Considerando os resultados obtidos neste estudo, as emiss?es de N2O do solo variaram de 7,37 e 2699,62 ?g N-N2O m2h-1. As perdas por volatiliza??o de am?nia variaram de 9,5 e 30% do N aplicado. A aplica??o de esterco bovino curtido + esterco de ave curtido mostra ser um manejo ambientalmente mais adequado para o cultivo de hortali?as, por resultar em menores fluxos de ?xido nitroso do solo e volatiliza??o de am?nia. Por outro lado, a ureia ? a fonte de N que provoca as maiores perdas de N por volatiliza??o de am?nia com efeito residual nulo para a cultura seguinte, neste caso para produ??o de alface. As maiores emiss?es foram observadas ap?s precipita??es, independente do tratamento, destacando a necessidade da presen?a de ?gua no ambiente para que ocorram as emiss?es de N2O.

O Pantanal é a maior área úmida do planeta e considerada uma das maiores fontes naturais de gases de efeito estufa (GEE). A sub-região da Nhecolândia, um dos maiores ecossistemas do Pantanal, possui o sistema lêntico mais diverso, onde lagoas de água doce coexistem com salinas, apesar das condições climáticas regionais não explicarem totalmente esta alta salinidade. As salinas são permanentes e funcionam de maneira diversa, sendo assim, subdivididas em tipologias verde e preta. As salinas verdes e pretas diferem tanto pela composição e funcionamento biogeoquímico, quanto pela abundância de espécies extremófilas. Tal distinção pode afetar o balanço regional de GEE, e assim, reduzir a confiabilidade das estimativas regionais das emissões gasosas. As estimativas de emissões de GEE obtidas anteriormente no Pantanal representaram principalmente ecossistemas de água doce, desconsiderando, portanto, a transferência de massa a partir das lagoas salinas. As lagoas de água doce, porém, podem ser permanentes ou temporárias, dependo da intensidade das inundações anuais. Estas lagoas concentram grande quantidade de matéria orgânica e vegetação aquática que aumenta este aporte orgânico. Devido a diversidade química das águas superiores na Nhecolândia, buscou-se quantificar os fluxos de GEE em lagoas salinas dos tipos verde e preta, e lagoas de água doce. O monitoramento destes corpos d\'água ocorreram nas duas estações climáticas comuns do Pantanal, seca e úmida, quando as alterações climáticas e químicas das águas são marcantes. Deste modo, foi possível retratar o efeito das variáveis abióticas sobre o balanço de massa no sistema água-atmosfera da segunda maior sub-região pantaneira. Duas metodologias distintas foram utilizadas para indicar a variabilidade espacial entre lagoas análogas, como as salinas, e variações específicas em cada lagoa. Os resultados indicaram que houve grande variabilidade espaço-temporal na dinâmica dos GEE entre os ecossistemas estudados, de maneira que, uma mesma lagoa que atuou como fonte em uma estação, comportou-se como sumidouro em outro período. Houve intensa variabilidade espacial, ainda, entre salinas de mesma tipologia, quando no mesmo período, umas podem ser fonte e outras sumidouros para determinados gases. As maiores emissões de metano e gás carbônico ocorreram na lagoa de água doce, porém, salinas verdes apresentaram valores próximos na mesma estação. Isto aponta a necessidade de aumentar as amostragens diretas visando incorporar a variabilidade espacial e temporal aos modelos climáticos regionais. As medidas in situ podem, assim, caracterizar as contribuições individuais no sistema lêntico e aumentar a confiança nas estimativas de emissões gasosas atribuídas ao Pantanal. / The Pantanal is the largest wetland on the planet and considered one of the largest natural sources of greenhouse gases (GHG). The sub-region of Nhecolândia, one of the largest ecosystems in the Pantanal, has the most diverse lentic system, where freshwater lagoons coexist with saline, although regional climatic conditions do not fully explain this high salinity. The salinas are permanent and function in a different way, being thus subdivided into green and black typologies. The green and black salinas differ as much by the composition and biogeochemical functioning, as by the abundance of extremófilas species. Such a distinction may affect the regional GHG balance sheet, and thus reduce the reliability of regional estimates of gaseous emissions. Estimates of GHG emissions previously obtained in the Pantanal represented mainly freshwater ecosystems, thus disregarding the mass transfer from saline lagoons. Freshwater ponds, however, can be permanent or temporary depending on the intensity of annual floods. These ponds concentrate a great amount of organic matter and aquatic vegetation that increases this organic contribution. Due to the chemical diversity of the upper waters in Nhecolândia, it was sought to quantify GHG flows in saline lagoons of the green and black types, and freshwater lagoons. The monitoring of these bodies of water occurred in the two common wetland climate seasons, when the climatic and chemical changes of the waters are remarkable. In this way, it was possible to portray the effect of the abiotic variables on the mass balance in the water-atmosphere system of the second largest sub-region of the Pantanal. Two different methodologies were used to indicate the spatial variability between analogous lagoons, such as salinas, and specific variations in each lagoon. The results indicated that there was great space-time variability in the GHG dynamics among the studied ecosystems, so that the same lagoon that acted as a source in one season, behaved as a sink in another period. There was intense spatial variability, also, between salinas of the same typology, when in the same period, some can be source and other sinks for certain gases. The highest emissions of methane and carbon dioxide occurred in the freshwater lagoon, however, green salinas presented close values in the same season. This points to the need to increase direct sampling to incorporate spatial and temporal variability into regional climate models. In situ measurements can thus characterize individual contributions in the lentic system and increase confidence in the gaseous emissions estimates attributed to the Pantanal.

Existe uma preocupação mundial com as mudanças climáticas causadas pelo aumento da concentração de gases do efeito estufa (GEE) e consequente acréscimo na temperatura média da superfície terrestre. A queima de combustíveis fósseis é a maior causadora do aquecimento global e responsável por danos à saúde humana. É notável o esforço global em diversificar a matriz mundial de combustíveis líquidos, priorizando a substituição de fontes fósseis por renováveis. Tal substituição reforça a necessidade de avaliações de todas as emissões de GEE na cadeia produtiva da cana-de-açúcar. O Brasil é o maior produtor de etanol proveniente de cana-de-açúcar. Um importante co-produto deste processo produtivo é a vinhaça, sendo produzida em elevadas quantidades e constituída por uma expressiva carga orgânica. Esta é comumente aplicada ao solo por fertirrigação. Apesar de atuar beneficamente no solo, pouco se sabe sobre a capacidade deste co-produto de aumentar as emissões de GEE no solo. Assim, o objetivo foi avaliar o efeito da aplicação da vinhaça nas emissões de N2O e CH4 e na comunidade de bactérias desnitrificantes e metanogênicas do solo. As amostragens de GEE e solo foram em áreas de cana sem queima a partir da aplicação de doses vinhaça (0, 150, 300 e 450 m3 ha-1). O delineamento experimental realizado foi em cinco blocos casualizados, totalizando 25 câmaras de coleta de gases do efeito estufa. Amostras de solo foram coletadas em quatro períodos de amostragem após aplicação de vinhaça (0, 7, 15 e 30 dias), em dois anos consecutivos. Foram analisados os GEE, N2O e CH4, além da abundancia de genes por meio da técnica de qPCR. A fertirrigação via aplicação de vinhaça no solo, nos dois anos, proporcionou aumento nas emissões de N-N2O, principalmente nos primeiros dias após a aplicação. Contudo os fluxos de C-CH4 oscilaram indicando a capacidade do solo de servir ora como fonte ora como sumidouro deste GEE. Os fatores de emissão obtidos para aplicação de N na forma de vinhaça, dose de 300 m3 ha-1, foram de 0,08% para o primeiro ano e 0,07% para o segundo ano. A partir da técnica de qPCR, a abundância dos genes indicou que a introdução deste resíduo ao solo pode aumentar significativamente o total de bactérias no solo e a atividade do gene nosZ, contudo o mesmo não ocorre com o potencial de desnitrificação biológica (gene nirK) e nem com o gene mcrA (redução de CH4). Os resultados demonstram que a aplicação da vinhaça no solo influencia as emissões de GEE, assim como a comunidade microbiana do solo / There is a global concern with climate change caused by increased concentration of greenhouse gases (GHG) and consequent increase in the average temperature of the Earth surface. Fossil fuels burning is the major cause of global warming and it is responsible for damages to human health. Remarkable global efforts in diversifying liquid fuels have been attempted, giving priority to the replacement of fossil fuels to renewables. Such substitution reinforces the need of an evaluation of all GHG emissions in the production chain of sugarcane. Brazil is the largest producer of ethanol with source from sugarcane. An important co-product of the production process is vinasse, which is being produced in large quantities comprising a significant organic load. This is commonly applied over the ground by fertigation. Despite being good for the soil, little is known about the ability of this co-product of increasing GHG emissions. This work aimed to evaluate the effect of the application of vinasse in the emissions of N2O and CH4 and in the soil community of denitrifying and methanogenic bacteria. Sampling of GHG and soil were performed in areas of sugarcane without burning with the application of different vinasse doses (0, 150, 300 and 450 m3 ha-1). The experiment was conducted in five blocks, totaling 25 collection chambers of greenhouse gases. Soil samples were collected in four sampling periods after application of vinasse (0, 7, 15 and 30 days), in two consecutive years. We analyzed the GHG, N2O and CH4, and the abundance of genes by qPCR technique. The fertigation via vinasse application on the ground in two years provided an increase in emissions of N-N2O, especially in the first couple of days after application. However the flow of C-CH4 was variable indicating the ability of the soil to serve either as source or as sink of this GHG. The emission factor obtained for N application in the form of vinasse dose of 300 m3 ha-1 was 0.08% for the first year and 0.07% for the second year. By qPCR technique, the abundance of the genes indicated that the use of this residue to the soil can significantly increase the amount of bacteria in the soil and nosZ gene activity. However it does not occur with the potential for biological denitrification (nirK gene) or with the gene mcrA (reduction of CH4). These results demonstrate that the application of vinasse in the soil influences GHG emissions as well as the soil microbial community

New Zealand is dominated by its agricultural industry with one of the most intensive farming practices being that of intensive dairying. New Zealand currently has approximately 5.3 million dairy cows that excrete up to 2.2 L of urine, per urination event, up to 12 times per day. This equates to 5.1 x10¹⁰ L per year or enough urine to fill over 1.2 million milk tankers. This sheer volume of urine and its associated N content has implications for the cycling of N within the pasture soils utilised, and New Zealand’s greenhouse gas budget due to the emission of N₂O from urine affected areas. The emission of nitric oxide (NO) from agricultural systems is also receiving increasing attention due to concerns about alterations in the balance of atmospheric trace gases and sinks. Worldwide there is a dearth of information with respect to the emissions of NO from urine-N deposition onto soils with only two in situ studies and no studies on the effects of soil pH, environmental variables or urine-N rate on NO fluxes. This present study has provided some fundamental information on the factors and processes affecting the emission of NO from bovine urine applied to pasture soils. Five experiments were performed in total; three laboratory experiments and two field experiments. The first laboratory experiment (chapter 4) examined the effect of the initial soil pH on NOx emissions from urine-N applied at 500 kg N ha⁻¹. Soil was treated to alter the initial soil pH over the range of 4.4 to 7.6. Initial soil pH affected rates of nitrification which in turn affected the decline in soil pH. Emissions of NO increased with increasing soil pH. However, a strong positive linear relationship was established between the NO-N flux, expressed as a percentage of the net NH4⁺-N depletion rate, and the level of soil acidity. The NO-N fluxes were higher under the more acidic soil conditions where N turnover was lower. The fluxes of N₂O did not follow the same pattern and were attributed to biological mechanisms. In experiment two (chapter 5) the objectives were to concurrently examine the effects of varying the soil temperature and the water-filled pore space (WFPS) on NOx emissions from urine-N. In this experiment increasing the soil temperature enhanced both the rate of nitrification and the rate of decrease in soil pH. The relationship between the net NO-N flux, expressed as a percentage of the net NH4⁺-N depletion rate, and the level of soil acidity was again demonstrated at the warmest soil temperature (22°C) where soil acidification had progressed sufficiently to enable abiotic NO formation. The NO-N fluxes increased with decreasing soil moisture and increasing soil acidity indicating abiotic factors were responsible for NO production. The Q10 response of the NO flux between 5 to 15°C decreased from 4.3 to 1.5 as WFPS increased from 11% to 87% respectively. Fluxes of N₂O increased with increasing WFPS and temperature indicating that denitrification was the dominant process. Results from experiments 2 and 3 indicated that the rate of nitrification had a direct bearing on the ensuing soil acidity and that it was this in conjunction with the available inorganic-N pools that affected NOx production. Therefore the third experiment examined the effect of urine-N rate on NOx emissions, with urine-N rate varied over 5 levels from 0 to 1000 kg N ha⁻¹, the highest rate being that found under maximal urine-N inputs to pasture. Rates of nitrification were diminished at the highest rates of urine-N applied and decreases in soil acidity were not as rapid due to this. Again significant but separate linear relationships were developed, for each urine-N rate used, between the NO-N flux, expressed as a percentage of the net NH4⁺-N depletion rate, and the level of soil acidity. The slope of these relationships increased with increasing urine-N rate. The NO-N flux, expressed as a percentage of the net NH4⁺-N depletion rate, versus soil acidity was higher under 1000 kg N ha⁻¹, despite the lower soil acidity in this treatment. This indicated that the enhanced inorganic-N pool was also playing a role in increasing the NO flux. The N₂O fluxes were of limited duration in this experiment possibly due to conditions being disadvantageous for denitrification. In the field experiments two urine-N rates were examined under both summer and winter conditions at two urine-N rates. The emission factors after 71 days for NO-N in the summer were 0.15 and 0.20% of the urine-N applied for the 500 and 1000 kg N ha⁻¹ rates respectively while the respective N₂O-N fluxes were 0.14 and 0.16%. Under winter conditions the emission factors after 42 days for NO-N were <0.001% of the urine-N applied regardless of urine-N rate while the N₂O-N fluxes were 0.05 and 0.09% for the 500 and 1000 kg N ha⁻¹ urine-N rates respectively. The relationships and predictors of NO-N flux determined in the laboratory studies did not serve as strong indicators of the NO-N flux under summer conditions. Low emissions from urine-N over winter were due to the low soil temperatures and high WFPS. These studies have demonstrated that soil chemical and environmental variables influence the production of NOx and N₂O emissions from urine-N applied to soil and that seasonal effects have a significant impact on the relative amounts of NO-N and N₂O-N emitted from urine patches. Suggestions for future work are also made.

Physisorption of CO and N2O on surfaces of ceria (CeO2) was investigated by means of high-level quantum-mechanical embedded cluster calculations. Both systems have high relevance in the field of environmental chemistry and heterogeneous catalysis. The CO/CeO2 system, has been investigated in a couple of both experimental and theoretical studies, but for the N2O/CeO2 system, this is the first study in the literature, experimental or theoretical. In physisorption, the interaction relies entirely on classical electrostatic interactions and electron dispersion forces. No covalent bond is formed between the molecule and the surface. A proper description of the dispersion requires some of the most accurate quantum-mechanical methods available, such as MP2 or CCSD(T). Moreover, even the most sophisticated methods cannot heal errors anywhere else in the theoretical treatment. Standard periodic models cannot be used with methods such as CCSD(T), but embedded cluster models can, and have been thoroughly explored in this thesis. In this thesis, embedded cluster models were constructed for the CeO2(110) and (111) surfaces. Using a range of assessment tests, it was verified that the electronic structure of the central region of a large and fully embedded surface cluster agrees well with the corresponding region in a periodic system. CO physisorption was investigated at the CCSD(T) level. Due to the prohibitively large expenses (in computer time) for standard CCSD(T) calculations, the method of increments, previously used in the literature for bulk systems, was extended to adsorption problems. It was found that, electron correlation contributes by 30 - 80% to the molecule-surface interaction and that the contribution depends on the topology of the surface. The calculated CO-ceria interaction energy is 20 kJ/mol for the (111) surface and 27 kJ/mol for the (110) surface. In low temperature TPD experiments for the N2O/CeO2(111) system, one surface species was found with an adsorption energy of about 29 kJ/mol. IR measurements showed stretching frequencies that are typically assigned to N2O adsorption with the O-end directed towards surface cations. However, theoretical calculations up to the MP2 level predicted two equally favorable adsorption species. Improvements in the structural model (larger clusters, consideration of molecule-induced relaxation) or the computational method (larger basis sets) did not affect this result. Only at the CCSD(T) level was one dominating surface species found, namely N2O adsorbed over a Ce ion, with the O-end of the molecule directed towards the surface. The calculated stretching vibrational frequency shifts (with respect to the gas phase) for this adsorbed species agree well with the measured IR spectra.

Soil N2O flux is sensitive to soil moisture content and soil temperature, which are in turn sensitive to changes in climate and topography. Thus, N2O flux measurements exhibit a high degree of spatial and temporal variability. Knowing how the spatial distribution of soil N2O flux changes over time in a hummocky, agricultural landscape will identify measurement scales appropriate for estimates of N2O emissions from these types of terrains. As well, little is known about N2O emissions from uncultivated, ephemeral wetlands in agricultural landscapes, but this information is needed for accurate inventories of N2O emissions. The objectives of this study were to describe the spatial and temporal distribution of soil N2O flux in a hummocky agricultural landscape, and to understand how soil water and soil temperature control the spatial and temporal patterns of N2O flux. For a hummocky, agricultural landscape in the Dark Brown soil zone of Saskatchewan, N2O flux and related soil variables were measured along a 128-point transect multiple times over two years and concurrently from a 50 point, stratified design over three years. The spatial and temporal variation in N2O flux followed an event-based / background emission pattern. High flux events were triggered by precipitation events and recession of water from wetlands following spring snowmelt. Days with high mean flux were characterized by highly skewed (reverse J-shaped) distributions. High variance and coherency was observed at cultivated wetland elements during emission events. Strong location-dependent positive relationships were found between soil N2O flux and water-filled pore space or soil temperature, related to specific landscape elements. Background emissions were characterized by random variation or cyclic behavior that ranged in scale from 20 to 60 m. Cumulative emissions were highest from cultivated wetlands and basin centers of uncultivated wetlands, although emissions from cultivated wetlands were much more important to total cumulative emissions on an area basis. The results indicate that models intended to estimate N2O flux from these landscapes cannot rely on a single predictive relationship, but will have to incorporate predictive relationships localized at specific landscape elements depending on the time of year. At certain times predictive relationships cannot be used and up-scaled estimates will have to rely on direct measurement of emissions.

This study was conducted to obtain landscape- and regional-scale estimates of N₂O emissions for a representative part of the Black soil zone of Saskatchewan. A 4318-km² study region was stratified based on soil texture and land use. At the regional scale, soil texture was the proxy variable used to represent the differences in soil moisture regimes and soil fertility, whereas land use was the surrogate variable used to reflect the differences in N and C cycling. Soil landscapes were selected to cover the range of soil texture and land use characteristics in the study region. At the landscape level, shoulder and footslope complexes were used as the spatial sampling units to cover the range of topographical and soil characteristics within the landscape. At the landform complex level, soil moisture (as assessed by volumetric moisture content and water-filled pore space) was the most important factor controlling N₂O emission. At the landscape scale, soil moisture was, in turn, influenced by topography, and on the seasonal scale it was affected by climatic factor(s) (e.g., precipitation). The annual N₂O emissions were calculated as the sum of the spring and the summer to fall fluxes. The spring emission was estimated by interpolating the N₂O fluxes measured on discrete sampling days, whereas the summer to fall emission was estimated by establishing regression models that related N₂O fluxes to water-filled pore space. Regional estimates of N₂O emissions were obtained using the GIS database of soil texture and land use types. The average annual fluxes for fertilized cropped, fallow, pasture, and forest areas, weighted by their areal extent in the different textural areas of the study region, were 2.01, 0.12, 0.04, and 0.02 kg N₂O-N ha^-1 yr^-1 respectively. The weighted-average annual fluxes for the medium- to fine-textured and sandy-textured areas were 1.31 and 0.04 kg N₂O-N ha^-1 yr$\sp{-1},$ respectively. For the study region, the weighted-average annual flux was 0.90 kg N₂O-N ha^-1 yr$\sp{-1}.$