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The global nitrogen cycle has been disrupted by large anthropogenic inputs of reactive nitrogen to the environment. Excess nitrogen underlies environmental problems such as eutrophication, and can negatively affect human health. Managing the natural microbial process of denitrification is advocated as a promising avenue to reduce excess nitrogen, and denitrifying bioreactors (DNBRs) are an emerging technology harnessing this biochemical process. Previous DNBR research has established successful nitrate removal, whereas this study examines the potential to expand DNBR functionality to address excess phosphorus and mitigate the production of nitrous oxide, a potent greenhouse gas. Results from a laboratory experiment supported the hypothesis that the addition of biochar, a charcoal-like soil amendment and novel organic carbon source in DNBR research, would increase nitrate and phosphorus removal as well as decrease the accumulation of nitrous oxide, an intermediate product of microbial denitrification. In order more closely examine the ratio of the products nitrous oxide and inert dinitrogen, development of a novel analytical method to quantify dissolved gases in environmental water samples using gas chromatography mass spectrometry was undertaken. Although static headspace analysis is a common technique for quantifying dissolved volatiles, the variation in sample preparation has recently been revealed to affect the determination of dissolved concentrations of permanent gases and convolute comparison between studies. This work demonstrates the viability of internal calibration with gaseous standard addition to make dissolved gas analysis more robust to variable sample processing and to correct for matrix effects on gas partitioning that may occur in environmental samples. / Master of Science

No / Improving the patient's experience of a bone marrow biopsy ¿ an RCT Aims. To compare nitrous oxide 50%/oxygen 50% (N2O/O2 ¿ entonox) plus local anaesthetic (LA) with placebo (oxygen) plus LA in the management of pain experienced by patients undergoing a bone marrow biopsy. . Bone marrow biopsies are a common procedure for many haematological conditions. Despite the use of a LA, pain during the procedure has frequently been reported by patients. Previous research in pain management of other invasive diagnostic procedures (e.g. sigmoidoscopy) has reported N2O/O2 as an effective alternative to LA. Design. Double-blind randomized controlled trial. Methods. Forty-eight patients requiring a bone marrow biopsy were randomized to receive either N2O/O2 or oxygen in addition to their LA. Participants were asked to complete a pain score and comment on their experience of the procedure. Results. Although the overall pain scores were moderate, there was a wide range of scores. N2O/O2 resulted in significantly less pain for men, but not for women. All patients who had had previous biopsies reported significantly more pain, regardless of the gas used. There were no significant adverse effects in either group. Conclusion. N2O/O2 is a safe, effective, easy-to-use analgesic which merits further investigation in potentially painful diagnostic (and other) interventions.

A better way to improve understanding and quantification of nitrous oxide (N₂O) emitted from intensive maize cropping systems is to develop an advanced emissions measurement method This study developed an open path (OP) method to measure N₂O emissions from four adjacent maize plots managed by tillage practices of no-till (NT) and chisel plow (ChP), and different nitrogen (N) treatments from 2014 to 2016. Anhydrous ammonia (220 kg NH₃-N ha^-1) was applied in once or equally split (full vs. split rate) and applied in different timing (Fall vs. Spring). The spring N application occurred either before planting (pre-plant) or in season (side-dress). Emissions measurements were conducted by using the OP method (the scanning OP Fourier transform infrared spectrometry (OP-FTIR) + the gas point-sampling system + a backward Lagrangian stochastic (bLS) dispersion model) and static closed chamber methods. The performance and feasibility of the OP measurements were assessed by a sensitivity analysis, starting with errors associated with the OP-FTIR for calculating N₂O concentrations, and then errors associated with the bLS model for estimating N₂O emissions. The quantification of N₂O concentrations using the OP-FTIR spectrum was influenced by ambient humidity, temperature, and the path length between a spectrometer and a retro-reflector. The optimal quantitative method mitigated these ambient interference effects on N₂O quantification. The averaged bias of the calculated N₂O concentrations from the spectra acquired from wide ranges of humidity (0.5 – 2.0 % water vapor content), temperature (10 – 35 °C), and path length (100 – 135 meters) was 1.4 %. The precision of the OP-FTIR N₂O concentrations was 5.4 part per billion(3σ) in a stationary flow condition for a 30-minute averaging period. The emissions measurement from multiple sources showed that the field of interest was likely interfered by adjacent fields. Fields with low emission rates were more sensitive to the adjacent fields with high emissions, resulting in substantial biases and uncertainties. The minimum detection limit of the N₂O emission rates was 1.2 µg m^-2 s^-1 (MDL; 3σ). The OP measurements showed that the NT practice potentially reduced N₂O emission compared with ChP. Under the long-term NT treatments, the split-N rate application (110 kg NH₃-N ha^-1 in the fall and spring) resulted in lower N₂O emissions than the full application (220 kg NH₃-N ha^-1 in the fall). The management of NT coupled with split-N rate application minimized N₂O emissions among treatments in this study, resulting in N₂O-N losses of 3.8, 13.2, and 6.6 N kg ha^-1 over 9-, 35-, and 20-days after the spring NH₃ application in 2014, 2015, and 2016, respectively. The spring pre-plant N application in 2015 also resulted in higher N₂O emissions than the spring side-dress application in 2016, and the increased N₂O-N loss was corresponding to lower N recovery efficiency in 2015 measurements. A comparison of chamber and OP measurements showed that soil N₂O emissions were likely underestimated by 10x without considering the wind-induced effect on gas transport at the ground-atmospheric interface. This study showed that the OP method provides a great opportunity to study agricultural N₂O emissions as well as management optimization for the sustainability of the agroecosystems.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Dale J. Bremer / Turfgrass covers 1.9% of the nation’s surface area and is the largest irrigated crop in the USA. Developed urbanized land is projected to double by 2025, which will increase turf’s environmental impact. Studies were conducted to evaluate environmental impacts by characterizing nitrogen, carbon, and water fluxes in turfgrass ecosystems. Emissions of nitrous oxide (N[subscript]2O), a major greenhouse gas and ozone depleter were measured from bermudagrass (Cynodon dactylon L. Pers. x C. transvaalensis Burtt-Davy) (bermuda), perennial ryegrass, (Lolium perenne L.) (rye), and zoysiagrass, (Zoysia japonica Steud.) (zoysia) under regional N management. In a separate study, N2O fluxes were measured from bermuda fertilized with controlled-release N fertilizers including polymer-coated and organic-N, and quick release urea. Emissions of N2O were measured using static surface chambers and gas chromatography. Zoysia, with less N requirements, had lower emissions than bermuda. Cumulative N[subscript]2O emissions were similar among N types. To measure water and carbon fluxes, a portable non-steady state chamber was designed and tested. The chamber had minimal affects to the canopy during field measurements: leak values averaged <1.5 micromol CO[subscript]2 m[superscript]-2 s[superscript]-1; average chamber pressure was 0.09 Pa ±0.01 Pa; temperature rise inside the chamber averaged 0.74C; and the chamber had 90% photosynthetically active radiation transmittance. Using the chamber, differences were detected in net photosynthesis (Pnet), gross photosynthesis (Pg), evapotranspiration (ET), canopy stomatal conductance (gc), and water use efficiency (WUE) in well-watered tall fescue (Festuca arundinacea Schreb.), Kentucky bluegrass (Poa pratensis L.) (KBG), zoysia, and bermuda. Irrigation requirements, visual quality ratings, and genetic rooting potential of 28 KBG cultivars and 2 Texas bluegrass hybrids (P. pratensis x P. arachnifera Torr.) were quantified in greenhouse and rainout facility studies. Average water applied ranged from 23.4 to 40.0 cm among cultivars. Bedazzled, Preakness, and Bartitia required less water and had higher average quality than other cultivars. Compact America and Mid-Atlantic phenotypes exhibited greatest potential for success in integrating reduced water inputs with maintenance of acceptable visual quality. Results indicated that turfgrass management could mitigate N[subscript]2O emissions and conserve water while maintaining healthy turfgrass, and the new chamber will enhance turfgrass studies by providing rapid measurements of photosynthesis.

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

Nos últimos anos, o Brasil tem liderado a produção e exportação mundial de cana-de-açúcar e seus derivados. Com isso, a produtividade agrícola aumenta necessitando-se ampliar as pesquisas de caráter sócio-ambiental, a fim de modelar um desenvolvimento tecnológico mais próximo do sustentável. Desta forma, torna-se necessário conhecer a contribuição do plantio da cana-de-açúcar com o aumento da concentração de gases de efeito estufa na atmosfera, especialmente no que se refere ao óxido nitroso (N2O), derivado do uso de fertilizantes nitrogenados. Sabe-se que na ausência de oxigênio, bactérias específicas passam a reduzir compostos nitrogenados, formando este poderoso gás de aquecimento global durante as etapas decorrentes de um processo conhecido como desnitrificação biológica. Através dos avanços nas áreas da biologia molecular, tornou-se possível conhecer os microorganismos não cultiváveis e suas respectivas funções em um determinado ambiente. Este trabalho teve como objetivo estimar as emissões de N-N2O nos solos de cana-de-açúcar derivadas da aplicação de fertilizantes nitrogenados durante um período de trinta dias, em duas situações de manejo da cultura: I- Sem queima: colheita mecanizada com a manutenção da palha da cana; II-Com queima: colheita manual precedida pela queima da palha da cana. Simultaneamente, os genes envolvidos na desnitrificação e produção de N2O no solo (norB, nirK, nirS e nosZ) foram quantificados por PCR quantitativo em tempo real em condições de laboratório e de campo. Sob condições de laboratório, pode-se observar que as emissões de NN2O atingiram 0,8 mg.m-2 h-1 em solos com a manutenção da palha, tanto com a aplicação de uréia quanto de nitrato de amônio. Os mesmos produtos, quando aplicados em solos sem a presença da palha emitiram 0,45 mg.m-2 h-1. No campo, os maiores fluxos de N-N2O foram encontrados no período de elevada precipitação pluviométrica, que ocorreu na primeira semana após a aplicação do fertilizante nitrato de amônio, chegando a 0,7 mg.m-2 h-1 nos solos com palha e 0,37 mg.m-2 h-1 nos solos sem a palha. Tanto no campo quanto no laboratório foram encontradas as maiores quantidades dos genes envolvidos na desnitrificação em solos com a permanência da palha, com valores próximos de 107 genes por grama de solo. A atual tendência a substituir a colheita manual da cana pela colheita mecanizada favorece a agregação do solo, diminui o grau de erosão e aumenta os estoques de carbono, mas também pode resultar em aumento das emissões de N-N2O e do fator de emissão dos fertilizantes nitrogenados, conforme encontrado para o nitrato de amônio aplicado no campo, onde o valor obtido foi de 0,3% para os solos sem a palha e 0,7% para solos com palha. Sendo assim, é fundamental estudar as melhores condições do uso da terra e o papel exercido pela microbiota que nela existe, proporcionando um tratamento mais adequado aos resíduos culturais, diminuindo assim as emissões de gases estufas. / In recent years, Brazil has led the production and worldwide export of sugarcane and its products. Thus, agricultural productivity increases need to expand research of socio-environmental, in order to model a technology development closer sustainable. Therefore, it is necessary to know the contribution of planting sugarcane with increasing concentration of greenhouse gases in the atmosphere, especially with regard to nitrous oxide (N2O), derived from nitrogenous fertilizer use. It is known that in the absence of oxygen, bacteria are specific to reduce nitrogen, forming this powerful global warming gas arising during the stages of a biological process known as denitrification. Through advances in molecular biology, it has become possible to know the non-cultivable micro-organisms and their functions in a given environment. This study aimed to measure the emissions of N-N2O in soils of sugarcane derived from the application of nitrogen fertilizers for a period of thirty days, in two situations crop management: I-No burning: mechanized harvesting with maintaining cane straw; II-With burning: manual harvest preceded by burning the straw. Simultaneously, the genes involved in denitrification and N2O production in soil (norB, nirS, nirK, and nosZ) were quantified by real-time quantitative PCR in the laboratory and the field. Under laboratory conditions, it can be seen that the N-N2O reached 0,8 mg.m-2 h-1 in soils with maintaining the straw, either with the application of urea and ammonium nitrate. The same products, when applied to soils without the presence of straw delivered 0,45 mg.m-2 h-1. In the field, the highest N-N2O fluxes were found in the period of high rainfall, which occurred in the first week after application of ammonium nitrate, reaching 0,7 mg.m-2 h-1 in soils with straw and 0,37 mg.m-2 h-1 in the soil without straw. Both in the field and in the laboratory were found greater amounts of genes involved in denitrification in soils fertilized with the permanence and straw, with values close to 107 per gram of soil. The current trend is to replace manual harvesting of sugarcane by mechanized harvesting promotes soil aggregation, decreases the degree of erosion and increases carbon stocks, but can also result in increased emission factor of nitrogen fertilizers, as found for nitrate applied in the field, where the value was 0,3% for the soil without straw and 0.7% for soils with straw. Therefore, it is essential to study the best conditions of land use and the role played by the microbiota that is therein, providing appropriate treatment to crop residues, thus reducing greenhouse gas emissions.

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.

Nos últimos anos, o Brasil tem liderado a produção e exportação mundial de cana-de-açúcar e seus derivados. Com isso, a produtividade agrícola aumenta necessitando-se ampliar as pesquisas de caráter sócio-ambiental, a fim de modelar um desenvolvimento tecnológico mais próximo do sustentável. Desta forma, torna-se necessário conhecer a contribuição do plantio da cana-de-açúcar com o aumento da concentração de gases de efeito estufa na atmosfera, especialmente no que se refere ao óxido nitroso (N2O), derivado do uso de fertilizantes nitrogenados. Sabe-se que na ausência de oxigênio, bactérias específicas passam a reduzir compostos nitrogenados, formando este poderoso gás de aquecimento global durante as etapas decorrentes de um processo conhecido como desnitrificação biológica. Através dos avanços nas áreas da biologia molecular, tornou-se possível conhecer os microorganismos não cultiváveis e suas respectivas funções em um determinado ambiente. Este trabalho teve como objetivo estimar as emissões de N-N2O nos solos de cana-de-açúcar derivadas da aplicação de fertilizantes nitrogenados durante um período de trinta dias, em duas situações de manejo da cultura: I- Sem queima: colheita mecanizada com a manutenção da palha da cana; II-Com queima: colheita manual precedida pela queima da palha da cana. Simultaneamente, os genes envolvidos na desnitrificação e produção de N2O no solo (norB, nirK, nirS e nosZ) foram quantificados por PCR quantitativo em tempo real em condições de laboratório e de campo. Sob condições de laboratório, pode-se observar que as emissões de NN2O atingiram 0,8 mg.m-2 h-1 em solos com a manutenção da palha, tanto com a aplicação de uréia quanto de nitrato de amônio. Os mesmos produtos, quando aplicados em solos sem a presença da palha emitiram 0,45 mg.m-2 h-1. No campo, os maiores fluxos de N-N2O foram encontrados no período de elevada precipitação pluviométrica, que ocorreu na primeira semana após a aplicação do fertilizante nitrato de amônio, chegando a 0,7 mg.m-2 h-1 nos solos com palha e 0,37 mg.m-2 h-1 nos solos sem a palha. Tanto no campo quanto no laboratório foram encontradas as maiores quantidades dos genes envolvidos na desnitrificação em solos com a permanência da palha, com valores próximos de 107 genes por grama de solo. A atual tendência a substituir a colheita manual da cana pela colheita mecanizada favorece a agregação do solo, diminui o grau de erosão e aumenta os estoques de carbono, mas também pode resultar em aumento das emissões de N-N2O e do fator de emissão dos fertilizantes nitrogenados, conforme encontrado para o nitrato de amônio aplicado no campo, onde o valor obtido foi de 0,3% para os solos sem a palha e 0,7% para solos com palha. Sendo assim, é fundamental estudar as melhores condições do uso da terra e o papel exercido pela microbiota que nela existe, proporcionando um tratamento mais adequado aos resíduos culturais, diminuindo assim as emissões de gases estufas. / In recent years, Brazil has led the production and worldwide export of sugarcane and its products. Thus, agricultural productivity increases need to expand research of socio-environmental, in order to model a technology development closer sustainable. Therefore, it is necessary to know the contribution of planting sugarcane with increasing concentration of greenhouse gases in the atmosphere, especially with regard to nitrous oxide (N2O), derived from nitrogenous fertilizer use. It is known that in the absence of oxygen, bacteria are specific to reduce nitrogen, forming this powerful global warming gas arising during the stages of a biological process known as denitrification. Through advances in molecular biology, it has become possible to know the non-cultivable micro-organisms and their functions in a given environment. This study aimed to measure the emissions of N-N2O in soils of sugarcane derived from the application of nitrogen fertilizers for a period of thirty days, in two situations crop management: I-No burning: mechanized harvesting with maintaining cane straw; II-With burning: manual harvest preceded by burning the straw. Simultaneously, the genes involved in denitrification and N2O production in soil (norB, nirS, nirK, and nosZ) were quantified by real-time quantitative PCR in the laboratory and the field. Under laboratory conditions, it can be seen that the N-N2O reached 0,8 mg.m-2 h-1 in soils with maintaining the straw, either with the application of urea and ammonium nitrate. The same products, when applied to soils without the presence of straw delivered 0,45 mg.m-2 h-1. In the field, the highest N-N2O fluxes were found in the period of high rainfall, which occurred in the first week after application of ammonium nitrate, reaching 0,7 mg.m-2 h-1 in soils with straw and 0,37 mg.m-2 h-1 in the soil without straw. Both in the field and in the laboratory were found greater amounts of genes involved in denitrification in soils fertilized with the permanence and straw, with values close to 107 per gram of soil. The current trend is to replace manual harvesting of sugarcane by mechanized harvesting promotes soil aggregation, decreases the degree of erosion and increases carbon stocks, but can also result in increased emission factor of nitrogen fertilizers, as found for nitrate applied in the field, where the value was 0,3% for the soil without straw and 0.7% for soils with straw. Therefore, it is essential to study the best conditions of land use and the role played by the microbiota that is therein, providing appropriate treatment to crop residues, thus reducing greenhouse gas emissions.

Submitted by Francine Silva (francine.silva@unipampa.edu.br) on 2019-03-27T14:45:02Z No. of bitstreams: 1 Fluxos de metano e óxido nitroso em solos sob coberturas vegetais e influência de aves em área de degelo em Rip Point, Ilha Nelson, Antártica.pdf: 910899 bytes, checksum: 0bd369223236893cb7d3f08d5b30fbfa (MD5) / Made available in DSpace on 2019-03-27T14:45:02Z (GMT). No. of bitstreams: 1 Fluxos de metano e óxido nitroso em solos sob coberturas vegetais e influência de aves em área de degelo em Rip Point, Ilha Nelson, Antártica.pdf: 910899 bytes, checksum: 0bd369223236893cb7d3f08d5b30fbfa (MD5) Previous issue date: 2012-12-12 / Atualmente é crescente a preocupação com a emissão de gases do efeito estufa (GEE) relacionada ao solo, sendo que dependendo do manejo adotado este pode ser fonte ou dreno de dióxido de carbono (CO2), óxido nitroso (N2O) e metano (CH4). Porém, sobre o comportamento destes gases em solos de ecossistemas naturais, como as áreas de degelo na Antártica Marítima, pouco se conhece. O presente trabalho objetivou avaliar os fluxos de GEE em solos sob degelo em Rip Point na Ilha Nelson, Antártica e verificar os aspectos no solo e clima que influenciam a emissão e absorção destes gases. Para tanto foram escolhidos cinco locais visando as diferentes coberturas vegetais e presença ou não de aves marinhas. A primeira foi de solo descoberto, a segunda com 100% de cobertura pelo musgo Sanionia uncinata e a terceira uma área coberta por líquens. As quarta e quinta áreas sofriam influencia direta da atividade de aves, sendo que uma era coberta pela alga Prasiola crispa e outra com a gramínea Deschampsia antarctica. A coleta dos gases se deu no período de seis dias no mês de fevereiro de 2012, pelo método de câmaras fechadas, foi coletado de solo para análises químicas e físicas, e monitorada a temperatura do solo e ar, teores de N mineral e umidade do solo. Para o período avaliado as taxas de fluxos de N2O variaram com média mais alta de 21,25±22,14 μg N2O m-2h-1 para área de P. crispa, e mais baixa de 0,11±1,93 μg N2O m-2h-1, na área de líquens. Para o CH4 somente a área de P. crispa apresentou, na taxa média, valores positivos de emissão, com 0,47±3,61 μg CH4 m-2h-1, sendo que a área de solo descoberto apresentou maior influxo, de -11,92±5,7 μg CH4 m-2h-1. Não foi observada correlação entre os fluxos de N2O e os atributos do solo. O fluxo acumulado de CH4 teve correlação com os estoques de Carbono (P<0.01) e Nitrogênio Total (P<0.01) do solo na camada de 0-10 cm. As áreas de solo descoberto e de S. uncinata tiveram emissão acumulada de N2O próximo à Zero, sendo que foram observados eventos de coleta com influxo do gás, podendo ter ocorrido redução do N2O. A área de solo descoberto teve o maior influxo acumulado de CH4 e a área de P. crispa foi a única a apresentar emissão acumulada para o período, observando-se que as taxas de fluxos do CH4 apresentaram relação direta e significativa (P<0,001) com os teores de amônio do solo. Assim, a influência da presença de aves parece ter maior efeito nos fluxos de CH4 e N2O do solo do que o tipo de vegetação presente. / Due to the problem of global warming is growing concern over the soil emission of greenhouse gases (GHG). It is known that the land use for agriculture and livestock, if managed incorrectly, cause severe impacts on the fluxes of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). But little is known about the behavior of these gases in soils of natural ecosystems. Analyzes of GHG emission or absorption in soil and edaphoclimatic factors that govern these fluxes are scarce in polar environments, such as defrost areas of maritime Antarctic. This study aimed to evaluate the GHG fluxes in soils in thaw areas in Rip Point, Nelson Island, Antarctica and check the soil and climate aspects that influence the emission and absorption of these gases. For both were selected five sites targeting the different vegetation cover and presence of sea birds. The first area was of bare ground, the second with 100% coverage by moss (Sanionia uncinata) and the third covered by lichens. The fourth and fifth areas suffered directly influences of the bird’s activity, one of which was covered by Prasiola crispa algae and other with Deschampsia Antarctica grass. The gases sampling occurred in the period of six days in February 2012, by the method of static chambers, and soil sampling was carried for chemical and physical analysis. For the evaluated period N2O fluxes varied with highest average 21.25±22.14 μg N2O m-2h-1 for P. crispa, and lowest at 0.11±1.93 μg N2O m-2h-1, in the Lichen soil. For CH4 only the area of P. crispa showed positive average, with 0.47±3.61 μg CH4 m-2h-1, and the area of bare soil showed greater influx of -11.92±5.7 μg CH4 m-2h-1. No correlation was observed between N2O fluxes and soil attributes. The accumulated CH4 flux correlated with stocks of Total Carbon (<0.01) and Total Nitrogen (<0.01) in the soil layer at 0.00-0.10 m. Areas of bare soil and S. uncinata showed accumulated N2O emission close to zero, and in some collection events were observed gas influx, which may have occurred N2O reduction. The area of bare soil had the highest cumulative CH4 influx and the area of P. crispa was the only to be presented cumulative emissions to the period, noting that the CH4 showed direct and significant relation with (p <0.001) whit the ammonium (NH4+) contents in the soil.