The continuous update of challenging emission legislations has renewed the interest for the use of alternative fuels. The low carbon content, the knocking resistance, and the abundance reserves, have classified natural gas as one of the most promising alternative fuels. The major constituent of natural gas is methane. Historically, the slow burning velocity of methane has been a major concern for its utilisation in energy efficient combustion applications. As emphasized in a limited body of experimental literature, a binary blend of methane and gasoline has the potential to accelerate the combustion process in an SI engine, resulting in a faster combustion even to that of gasoline. The mechanism of such effects remains unclear. This is partially owned to the inadequate prior scientific understanding of the fundamental combustion parameters, laminar burning velocity (Su0) and Markstein length (Lb), of a gasoline-natural gas Dual Fuel (DF) blend. The value of Lb characterises the sensitivity of the flame to stretch. The flame stretch is induced by aerodynamic straining and/or flame curvature. The current research study has therefore being concerned on understanding the combustion mechanism of premixed gasoline - natural gas DF blends both on a fundamental as well as practical SI engine level. The understanding on the contribution of Su0 and Lb to the velocity of a stretched laminar propagating flame has been extended through numerical analysis. A conceptual analysis of the laminar as compared to the SI engine combustion allowed further insights on the effect of turbulence to the mass burning rate of the base fuels. On a fundamental level, the research contribution is made through the quantification of the response of Su0 and Lb with the ratio of methane to PRF95 (95%volliq iso-octane and 5%volliq n-heptane) in a DF blend. Methane has been used as a surrogate for natural gas and PRF95 as a surrogate for gasoline. Constant volume laminar combustion experiments have been conducted in a cylindrical vessel at equivalence ratios of 0.8, 1, 1.2, initial pressures of 2.5, 5, 10 Bar, and a constant temperature of 373 K. Methane was added to PRF95 in three different energy ratios 25%, 50% and 75%. Spherically expanding flames visualised through schlieren photography were used to derive the values of Lb and Su0. It has been concluded that for pressures relevant to SI engine operation ( > 5bar) and stoichiometric to lean Air Fuel Ratios (AFRs), there is a positive synergy for blending methane to PRF95 due to the convergence of Lb of the blended fuel towards that of pure gas and Su0 towards that of pure liquid. In an SI engine environment, the research contribution is made through the characterisation and scientific understanding of the mechanism of DF combustion, and the importance of flame-stretch interactions at various engine operating conditions. Optical diagnostics have been integrated with in-cylinder pressure analysis to investigate the mechanism of flame velocity and stability with the addition of natural gas to gasoline in a DF blend, under a sweep of engine load (Manifold Absolute Pressure = 0.44, 0.51. 0.61 Bar), speed (1250, 2000, 2750 RPM) and equivalence ratio (0.8, 0.83, 1, 1.25). Consisted with the constant volume experiments, natural gas was added to gasoline in energy ratios of 25%, 50% and 75%. It has been concluded that within the flamelet combustion regime the effect of Lb is dominating the lean burn combustion process both from a flame stability and velocity prospective. The effect of Su0 on the combustion process gradually increases as the AFR shifts from stoichiometric to fuel rich values. For stoichiometric to fuel lean mixtures, the effect of turbulence on the increase of the mass burning rate is on average 13% higher for natural gas as compared to gasoline. The higher turbulence sensitivity of natural gas is attributed to its lower Lb value.

Particulate number (PN) standards in current and future emissions legislation pose a challenge for designers and calibrators during the warm-up phases of cold direct injection spark ignition (DISI) engines. To achieve catalyst light-off conditions in the shortest time, engine strategies are often employed that inherently use more fuel to attain higher exhaust temperatures. These can lead to the generation of locally fuel-rich regions within the combustion chamber and hence the formation and emission of particulates. To meet these emissions requirements, further understanding of the DISI in-cylinder processes during cold-start are required. This thesis investigates the effect of cooling an optical research engine to temperatures as low as -7°C, one of the legislative test conditions. A high-speed 9 kHz optical investigation of the in-cylinder combustion and fuel spray along with in-cylinder pressure measurements was completed with the engine motored and fired at 1500 rpm during combustion conditions that were essentially homogeneous and stoichiometric. Results showed significant differences between the flame growth structures at various operating temperature conditions with the notable presence of fuel-rich regions, which are understood to be prominent areas of particulate formation. Measured engine performance parameters such as indicated mean effective pressure (IMEP) and mass fraction burned (MFB) times correlated with the observed differences in combustion characteristics and flame growth speed. It was shown that flash boiling of the fuel spray was present in the fully heated engine case and significantly reduced the penetration of the spray plume and the likelihood of piston crown and cylinder liner impingement. The flow and combustion processes of a transient production cold start-up strategy were analysed using high-speed particle image velocimetry (HSPIV). Results highlighted a broad range of flame structures and contrasting flame stoichiometry occurring at different times in the start-up process. Turbulent flow structures were identified that have an effect on the fuel spray development and combustion process as well as providing a path for cold-start emissions reduction. PN and transient hydrocarbon (HC) emissions were measured at cold conditions to further elucidate the effect of operating temperature and correlate emissions data with in-cylinder measurements. A clear link between the quantity and size range of particulate and HC emissions and operating temperature was shown and the precise in-cylinder location of HC emissions, caused by fuel impingement, was inferred from the HC emissions data.

Chapter 1. This chapter aims to find the effects of financial point of sales incentives on the sales of electric vehicles across the Canadian provinces from September 2012 to December 2016. The findings of my study indicate that purchase incentives cause the sales of new electric vehicles to increase by 8 percent on average due to a $1000 increase in incentives. I find that 47% of electric vehicle sales across the rebating provinces (Ontario, Quebec, and British Columbia) are attributed to the purchase incentives. Results of my counter-factual simulations imply that the cost of eliminating one tonne of carbon emissions across the provinces that offer incentives over the years of my study is, on average, $216/tonne CO2. Chapter 2. In light of the rapid increase in Canadian gasoline prices from 2000 to 2010, this chapter focuses on the relationship between gasoline price and demand for vehicle fuel efficiency across the Canadian forward sortation areas (FSA) over this period. I find that consumers respond to variations in gasoline price when deciding the fuel efficiency of their new vehicle; increases in gasoline price result in shifts in demand for more fuel-efficient vehicles and therefore improve the average fuel efficiency of the new vehicle fleet. I find that the elasticity of fuel economy with respect to gasoline price for new vehicles sold across the Canadian forward sortation areas (FSA) from 2000 to 2010 is -0.06 to -0.16. Results of further analyses imply that consumer are more responsive to rising and constant gasoline prices than falling prices and that urban residents are slightly more responsive to variations in gasoline price compared to residents of suburb regions. Chapter 3. This chapter investigates the effect of the carbon tax policy implemented by the Canadian Province of British Columbia on households’ new vehicle purchase decisions. I dis-aggregate the effects of gasoline price into two effects: the carbon tax and carbon tax-exclusive gasoline price. These effects are both measured along the extensive margin of replacing a fuel inefficient vehicle with a fuel-efficient vehicle. The results indicate that there is a significant negative relationship between both effects and fuel efficiency substitutions. However, vehicle fuel economy is more sensitive to changes in the carbon tax than to equivalent changes in the carbon tax-exclusive gasoline price. I find that the elasticity of fleet fuel economy with respect to the carbon tax ranges from -0.22 to -0.26 whereas this elasticity changes between -0.1 and -0.15 with respect to gasoline price (net of the carbon tax). I obtain consistent results when estimating the effect of both factors on fleet fuel economy conditional on fleet composition, indicating that almost all vehicle segments respond more strongly to changes in the carbon tax component of gasoline price than other components. Results also imply that, among all segments, the fuel consumption of compact sport utility vehicles (SUVs), minivans, and luxury high-end cars respond the most to the carbon tax.

Submitted by Daniel Augusto Ferrari (nielferrari@hotmail.com) on 2018-07-31T14:15:53Z No. of bitstreams: 1 TESE-DANIEL-REVISADA-POS-DEFESA-2.pdf: 15259575 bytes, checksum: 976e1aed6cc90cbbcc4d3cdf30ede87e (MD5) / Approved for entry into archive by Minervina Teixeira Lopes null (vina_lopes@bauru.unesp.br) on 2018-08-02T17:51:15Z (GMT) No. of bitstreams: 1 ferrari_da_dr_bauru.pdf: 14918488 bytes, checksum: 5d274321a9c8304b2e99a5b5a326d818 (MD5) / Made available in DSpace on 2018-08-02T17:51:15Z (GMT). No. of bitstreams: 1 ferrari_da_dr_bauru.pdf: 14918488 bytes, checksum: 5d274321a9c8304b2e99a5b5a326d818 (MD5) Previous issue date: 2018-07-06 / Uma Roçadeira Lateral Motorizada (RLM) consiste num equipamento manual destinado ao corte de vegetações. Entretanto, alguns desses equipamentos oferecidos no mercado não atendem aos requisitos de conforto e usabilidade em seus sistemas de sustentação, o que pode ocasionar problemas posturais aos utilizadores. O objetivo deste estudo foi investigar as relações entre a usabilidade de sistemas de RLMs com possíveis percepções de desconforto, geradas por montagens inadequadas, bem como projetar e avaliar um novo design do sistema, fundamentado em parâmetros ergonômicos. Para os registros de percepção de desconforto, foram utilizados protocolos de percepção subjetiva de desconforto; para os dados de satistação, foram utilizados protocolos específicos de usabilidade, além de questionários específicos. Para os registros objetivos, realizou-se a análise das tarefas, cronometragem de tempos, bem como outras tecnologias, como: Captura por inércia 3D, eletromiografia e dinamômetros (dispositivo de mensuração). A coleta de dados ocorreu em fases experimentais: 1° – análise postural da atividade e utilização de captura por inércia 3D (n=1); 2° – Construção e validação de um dispositivo de mensuração de forças atuantes em usuários de RLMs (n=8); 3° – Análise da eficiência, eficácia, satisfação e níveis de percepção de desconforto no uso de sistemas de sustentação (n=50); 4° – Mensuração de forças atuantes em sistemas de sustentação de RMLs (n=50); 5° – Análise da percepção de desconforto no uso de cintos de sustentação (n=10); Design ergonômico (projeto de um novo sistema) (n=1); 6° – Análise da percepção de desconforto no uso de cintos de sustentação (Experimento com novo cinto) (n=10); 7° – Análise da eficiência, eficácia e satisfação no uso de sistemas de sustentação (Experimento com novo sistema) (n=30); 8° – Avaliação eletromiográfica aplicada à verificação dos níveis de atividade muscular através das simulações de movimentos com RLMs (n=3). Os resultados apontaram que dois sistemas de sustentação de RLMs oferecem interfaces que induzem seus usuários a empunharem a máquina de forma inadequada, ocasionando cargas assimétricas sobre o corpo. Também foram constatadas relações entre o aumento das impressões subjetivas de conforto, apresentadas nos questionários específicos, e a diminuição da percepção de desconforto, relatada nos diagramas de percepção subjetiva de desconforto, especialmente na região lombar, onde houve reduções significativas de apontamentos de desconforto. Assim, foi constatado que os sujeitos expressam menor percepção de desconforto e maior segurança quando se utilizam de cintos de sustentação providos de apoio para os quadris. / A Gasoline Brush Cutter (GBC) consists of a manual motorized equipment for vegetation cutting. However, some of these equipments offered in the market do not meet the requirements of comfort and usability in their support systems, which can lead to postural problems for the users. The purpose of this study was to investigate the relationships between the usability of GBC systems with possible perceptions of discomfort generated by inadequate assemblies. Then, develop and evaluate a new design system, based on ergonomic parameters. For the subjective records of discomfort perception, the Corllet and Manenica (1980) diagram was used; for the satisfaction data, it was used the SUS protocol (BROOKE, 1996), as well as specific questionnaires. For the objective records, it was performed tasks analysis, time timing, as well as other technologies such as: 3D inertial capture, electromyography and dynamometers (measurement device). The data collection occurred in experimental phases: 1 - postural analysis of the activity and the use of 3D movement tracking (n = 1); 2 - Construction and validation of a device to measure forces acting on GBC users (n = 8); 3 - Analysis of the efficiency, effectiveness, satisfaction and levels of perception of discomfort in the use of support systems (n = 50); 4 - Measurement of forces acting on GBC support systems; 5 - Analysis of the perception of discomfort in the use of support belts (n = 10); Ergonomic design (design of a new system) (n=1); 6 - Analysis of the perception of discomfort in the use of support belts (Experiment with new belt) (n = 10); 7 ° - Analysis of efficiency, effectiveness and satisfaction in the use of support systems (Experiment with new system) (n = 30); 8 - Electromyographic evaluation applied to the verification of muscular activity levels through the simulations of movements with GBC (n = 3). The results pointed out that some GBC support systems offer interfaces that induce their users to handle the machine improperly, causing asymmetric loads on the body. It was also observed relationships between the increase of the subjective impressions of comfort, presented in the specific questionnaires, and the decrease of the perception of discomfort, reported in the Corllet and Manenica diagrams. Especially in the lumbar region, where there were significant reductions in the observation of discomfort. Finally, it was observed that the users express lower perception of discomfort and greater safety when using support belts provided with support for the hips.

Public transit, an important mobility service for many, has incurred ridership decline in the U.S. for the past three years. In 2014, U.S. transit ridership was 10.74 billion unlinked passenger trips. In 2015, total ridership was 1.0 percent fewer, and the 2016 decrease was 2.2 percent from 2015. The consistent abandonment of transit in the U.S. does not seem to be ending. In 2017, ridership predicted from year-to-date data is 2.4 percent less than 2016. Furthermore, per capita ridership has decreased 17 percent since 1980. Both the short-term ridership trend and long-term per capita ridership trend is concerning given the increased spending and service provision during the same periods. In seeking to understand the many factors that influence transit ridership trends, it is important to analyze each so that policymakers and practitioners can respond and position transit accordingly. Numerous demographic and economic phenomena help explain this decline in transit use. This research focuses on five of these considerations – age, vehicle availability, telecommuting, fuel price, and geographical distribution of the population.

Esta tese buscou como tema de pesquisa a defesa da concorrência no mercado varejista de combustível líquido, cujo enfoque principal foi o desenvolvimento de um filtro georreferenciado, como ferramenta de auxílio na detecção de indícios de cartel, aplicado ao combustível gasolina comum. O problema de práticas anticoncorrencias em mercados que operem sob livre concorrência tem sido discutido ao longo do tempo tanto pela literatura quanto pelos operadores de política antitruste. No Brasil, a defesa da concorrência, no âmbito administrativo, está sob a responsabilidade do Sistema Brasileiro de Defesa da Concorrência – SBDC, o qual utiliza um filtro nas investigações sobre denúncias de cartel no mercado varejista de combustível líquido, através de averiguação preliminar, a fim de identificar indícios de evidências econômicas sobre a prática de cartel. A tese abordou três pontos principais. O primeiro envolveu a formação de uma base de dados, através das averiguações preliminares disponibilizadas pelo SBDC, com o intuito de analisar os critérios que compõem o filtro. Sugere-se que este filtro seja reavaliado, devido à falta de hierarquia entre os critérios que o compõem, bem como a alteração da periodicidade dos dados. O segundo diz respeito à aplicação, com base na Teoria dos Jogos, de um jogo sequencial de interação estratégica entre o revendedor varejista, o consumidor e o SBDC. O resultado do jogo mostrou que o revendedor ficará desmotivado a formar um cartel se a chance de ser pego e punido realmente existir. Por fim, o terceiro, consistiu na inclusão do georreferenciamento aos filtros utilizados na literatura para detectar cartéis. Isso foi realizado através de uma análise comparativa do filtro atual com o filtro georreferenciado para o município de Porto Alegre, durante o período de março de 2007 a março de 2008. Ambos filtros indicaram indício de cartel. No entanto, o filtro georreferenciado mostrou um melhor refinamento sobre o comportamento dos revendedores, ao indicar indício de cartel na área de maior densidade urbana do município, assim como gerar um ranking dos revendedores. / This thesis research the defense of competition among fuel retail market and had like objective the development of georeference screen to be used like aid tool to detect vestige of cartel. The problem of anticompetition practices had been discussed by the time even in literature like the antitruste authorits. In Brazil, Brazilian System of Competition Defense (SBDC) are responsable about defense of competition, in administration ambict, and in initial investigation used a filter to detect vestiges of cartels. This tool search economic evidences to find out cartel. This proposition studied three points. First we organized data basis considering preliminary inquiry made by SBDC to study the rules that form this screen. We suggest that this screen had to be revisal due lack of hierarchy in your rules such as period data. Second we proposed a strategic interaction in sequential game between gasoline retail market, consumer and SBDC, based in Games Theory. The result of this game showed that gasoline retail market will not be motivated to organize cartel if he knows that this pratice could be detected and punished. Finally we included in filter used in literature the georeferencing through comparision among screen actually used and georeference screen applied to Porto Alegre, in period of march 2007 to march 2008. Both indicate vestiges of cartel. Nevertheless, the georeference one showed best refinement about behaviour gasoline retail market to indicate collusion in areas of higher density population in the city just as form a ranking of retailers.

Quando dois ou mais mercados, anteriormente separados, começam a apresentar certa convergência de preços, diz-se que eles estão integrados. Geralmente, os pesquisadores têm objetivado o estudo da integração entre mercados externos e internos (integração espacial) ou entre os diferentes elos de uma cadeia produtiva (integração vertical), mas de um único produto. Após uma importante mudança na tecnologia, concretizada através do lançamento dos motores flex-fuel no Brasil, a presente pesquisa teve por desafio analisar a existência de integração entre os mercados da gasolina e do etanol, dita como "integração de mercados por substituição". Para tal fim, e depois de filtradas as séries de preços mediante os testes de estacionariedade (Dickey-Fuller Aumentado e Phillips-Perron), foi feito uso de modelos de transmissão de preços, mais especificamente os testes de Cointegração, o do Mecanismo de Correção de Erro (MCE) e o da Causalidade. No período em análise (de março de 2003 até julho de 2008), foi constatada a presença de cointegração entre os dois mercados. Também foi observado que um incremento de 1% no preço da gasolina é responsável por um incremento de 2,74% no preço do etanol. Ainda que tenha sido pequeno o parâmetro do Mecanismo de Correção de Erro obtido, ele indica que é possível relacionar o comportamento de curto com o de longo prazo, nas séries analisadas. Dos resultados obtidos, pode-se concluir que os mercados do etanol e da gasolina estão integrados a longo prazo, onde variações no preço da gasolina causam variações no do etanol (GRANGER, 1969). / When two or more markets, previously separated, start showing a price convergence, it is possible to say that they are integrated. Usually, the researchers have focused the integration study between external and internal market (spatial integration) or between the different links of a productive chain (vertical integration), but just of an unique product. After an important technological change, materialized in the releasing of flex-fuel motors in Brazil, this work had as a challenge analyze the existence of the integration between the gasoline and ethanol markets, referred as "integration of substitution markets". Therefore, after filtering the prices series through stationary tests (Augmented Dickey-Fuller and Phillips-Perron), it was made the use of price transmission models, specifically the cointegration tests, and the Error Correction Mechanism (ECM) and the causality. In the analyzed period (from March 2003 to July 2008), it was verified the existence of cointegration between the two markets. Also it was observed that an increase of 1% in the gasoline price is responsible for the increase in 2.74% of the ethanol price. Although it was small the parameter of the correction mechanism in the obtained error, it points out that is possible to relate the behavior in the short and long term, in the analyzed series. Taking in consideration the obtained results, we arrived to the conclusion that the ethanol and gasoline markets are integrated in the long term, where variations in the gasoline price cause variations in the ethanol market.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-09-13T16:59:06Z No. of bitstreams: 1 Dissertação Edvaldo Pereira Queiroz Junior.pdf: 2104197 bytes, checksum: 0367d064454d2d944933b51a88e4e20d (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-14T10:38:40Z (GMT) No. of bitstreams: 1 Dissertação Edvaldo Pereira Queiroz Junior.pdf: 2104197 bytes, checksum: 0367d064454d2d944933b51a88e4e20d (MD5) / Made available in DSpace on 2016-09-14T10:38:40Z (GMT). No. of bitstreams: 1 Dissertação Edvaldo Pereira Queiroz Junior.pdf: 2104197 bytes, checksum: 0367d064454d2d944933b51a88e4e20d (MD5) / Neste trabalho, avaliou-se a influência da umidade, temperatura e tipos de recipientes na integridade das amostras de combustíveis. A avaliação foi feita através de caracterização físico-química das amostras no período de oito meses de armazenagem. Para isto, amostras de gasolina, óleo diesel e álcool hidratado combustível foram acondicionadas em garrafas PET âmbar, PET incolor e em frasco de vidro, num número suficiente para que a cada mês fossem realizadas as análises de caracterização. Escolheu-se três locais para a estocagem dos combustíveis, onde acompanhou-se a temperatura e umidade diariamente: sala de armazenagem, com temperaturas máximas na faixa 27,3-32,8 oC; laboratório (LAB), com temperaturas máximas na faixa 24,5-29,6 oC; e refrigerador, com temperaturas máximas na faixa 6,8-12,8 oC. As análises realizadas para as amostras de gasolina foram: aspecto, destilação, massa específica, teor de benzeno e teor de álcool anidro. Para as amostras de álcool, realizaram-se as seguintes análises: pH, condutividade, massa específica e teor alcoólico; enquanto que para as amostras de óleo diesel, acompanhou-se o aspecto, massa específica, destilação, teor de enxofre e ponto de fulgor. No momento da preparação das amostras, foram tiradas alíquotas de cada combustível e realizados os ensaios e análises do ponto inicial, mês zero. A partir daí, repetiu-se determinações mensalmente, até o oitavo mês, utilizando-se de métodos analíticos oficiais e validados para acompanhar o comportamento de cada parâmetro. Com os resultados obtidos, verificou-se que tanto os frascos de vidro como as garrafas PET podem ser utilizadas como embalagens para os combustíveis, principalmente para gasolina e diesel, para períodos longos, mesmo em locais de temperatura mais alta ou mais baixa, apenas com algumas considerações quanto a massa específica para o diesel nas garrafas PET, onde observou-se um acréscimo de cerca de 0,0010 g/cm3, com uma incerteza de medição de 0,0005 g/cm3 . Contudo, observaram-se restrições quanto ao uso das garrafas PET para o armazenamento do álcool, principalmente com relação ao pH, onde observou-se um decréscimo de cerca de 2 unidades, com incerteza de medição de 0,06 pH, e teor alcoólico (massa específica), onde observou-se um acréscimo de cerca de 0,0015 g/cm3, com uma incerteza de medição de 0,0006 g/cm3. O frasco de vidro se apresentou mais adequado para o armazenamento de álcool. / This work evaluates the influences of moisture, temperature and type of the bottles in the fuel samples integrity, during the time of storage (8 months), through the physical- chemistry analysis. Samples of gasoline, diesel oil and alcohol were prepared, and the bottles (amber PET, colourless PET, and amber glass) had been filled with respective fuels, in amount enough, considering to each month (duplicate) and to each place (three).These bottles were placed in three different places, where was noted dayly the temperature and humidity: in the storage room, where the maxims temperatures varied by 27,3-32,8 oC; in the laboratory, where the maxims temperatures varied by 24,5-29,6 oC; and in the refrigerator, where the maxims temperatures varied by 6,8-12,8 oC. The analysis for gasoline samples was: aspect, destilation, especific mass, benzene content and alcohol content. For alcohol samples, the analysis was: pH, condutivity, especific mass and alcohol content. For diesel oil samples, was: aspect, especific mass, destilation, sulfur content and flash point. The initial samples were withdrawed, as the zero point, before to fill the bottles, of each fuel, and maked the official phisycal-chemistry analysis. Monthly, until the eighth month, these analysis had been done, of the each bottle to each fuel, to each place, to monitor the behaviour of each analytical parameter. In agreement with the analytical results, both the glass and PET botlles had good performance as preservactive bottles and they can be used as recipient for the fuels to long time, mainly for gasoline and diesel oil, even in place with high or down temperatures, with some considerations for the PET bottles about the especific mass to diesel oil, where was observed an increase of 0,0010 g/cm3 with an uncertainty of 0,0005 g/cm3. However, was observed restrictions to use PET bottles to storage alcohol, mainly to pH, where was detected a reduction of 2 unities of pH, with an uncertainty of 0,06 pH, and to alcoholic content (especific mass) parameters, where was detected an increase of 0,0015 g/cm3, with an uncertainty of 0,0006 g/cm3. The glass bottle presented itself the best bottle to storage alcohol.

[pt] Os hidrocarbonetos monoaromáticos constituintes da gasolina (BTEX) têm sido encontrados em aquiferos devido aos vazamentos de tanques de armazenamento e sua consequente dissolução na água subterrânea. No Brasil existe ainda um agravante: o etanol é utilizado como aditivo à gasolina, o que promove um aumento na profundidade de percolação dos poluentes, já que atua como cossolvente e possui degradação preferencial. Alterações nas condições químicas do meio ambiente proporcionam, por conseqüência, adaptações na dinâmica de sobrevivência da microbiota residente. Em um ambiente redutor com baixo nível de manganês, ausência de nitratos e presença significativa de óxidos de ferro, o Fe(III) passa a ser o receptor de elétrons preferencial para a biodegradação anaeróbia da matéria orgânica. Com o objetivo de avaliar a biodegradação anaeróbia da mistura BTEX-Etanol em aquífero tropical, mediada pela redução de Fe(III), foram desenvolvidos microcosmos anaeróbios, envolvendo solo homogêneo saturado com água não contaminada e água contaminada com mistura de BTEX-Etanol. A partir da quantificação e análise da atividade microbiana degradadora, dos resíduos da contaminação e do teor de Fe(+2), foi possível verificar o aumento da disponibilização de ferro oriundo dos respectivos óxidos e também da produção de Fe(+2) durante o tempo de incubação, bem como o período de adaptação dos microorganismos, variação de sua atividade e a queda dos níveis dos BTEX-Etanol. Estes resultados podem ser um indicativo da ocorrência de uma atenuação natural, porém, estudos mais extensos são necessários, incluindo uma metodologia mais adequada para medir as especiações do ferro. / [en] Gasoline monoaromatic hydrocarbons (BTEX) have been detected in aquifers due to storage tank spills from gas stations that lead to their consequent dissolution on groundwater. An aggravating factor in Brazil is ethanol being used as additive to gasoline, promoting an increase on pollutants percolation in soil since it works as co-solvent and is preferentially degraded. Therefore, changes on environmental chemical conditions promote adaptations of the survival dynamic of native microorganisms. In a reducing environment with low levels of manganese, absence of nitrate and significant presence of iron oxides, Fe(III) becomes the preferential electron acceptor for anaerobic biodegradation of organic matter. In order to evaluate this anaerobic biodegradation of BTEXEthanol mixture in a tropical aquifer, mediated by Fe(III) reduction, anaerobic microcosms were developed involving homogeneous soil saturated with noncontaminated and BTEX-Ethanol contaminated water. Quantifying and analyzing microbial activity, contamination residues and Fe(+2) contents allowed to verify increases of iron availability from the respective oxides and Fe(+2) production throughout the assay, as well as the period of microbial adaptation, the variation of microbial activity and the decrease of BTEX-Ethanol levels. These results may be indicative of the occurrence of natural attenuation. However, more studies are needed, including a better methodology to measure iron speciation in these experimental conditions.

Este estudo tem como objetivo identificar evidências empíricas sobre os determinantes do desempenho dos postos de combustíveis urbanos brasileiros, em termos do volume mensal de vendas de gasolina comum. Para tanto, com base numa amostra de 372 postos de combustíveis, operando sob a bandeira da Petrobras Distribuidora, para os quais foram amostradas observações sobre o volume mensal de gasolina comum comercializado e seu respectivo preço de venda, o preço de venda do álcool combustível, a renda do consumidor e o estoque da frota de veículos leves, compondo um painel completo de dados, para o período compreendido entre janeiro de 2010 a dezembro de 2012. Assim, utilizando as ferramentas econométricas para dados em painel, concluiu-se que a abordagem dos efeitos fixos é a que melhor se adequa aos dados da amostra, evidenciando que há influência de efeitos específicos (heterogeneidade não observável) inerentes a cada unidade de corte transversal sobre o respectivo volume de vendas de gasolina. Além disso, foram estimadas as elasticidades da demanda em relação ao preço, à renda e ao estoque da frota de veículos, bem como a elasticidade-preço cruzada em relação aoálcool combustível.A demanda por gasolina comum mostrou-se elástica com relação ao seu preço. Foi confirmado o corretoemprego do etanol como um substituto imperfeito da gasolina. Constatou-se que, o estoque da frota de veículos tende a ter influênciasignificativa e positiva sobre a demanda de gasolina. Entretanto, contrariando a teoria econômica, foi rejeitada a hipótese de influência da variável renda sobre as vendas de gasolina comum. / This study aims to identify empirical evidence on the determinants of the performance of the Brazilian urban fuel stations, in terms of monthly sales of gasoline. Therefore, based on a sample of 372 gas stations operating under the banner of PetrobrasDistribuidora, for which were sampled observations on the monthly volume of traded gasoline and its respective saleprice, the sale price of ethanol, consumer income and the stock of the light vehicle fleet, composing a complete panel data for the period from January 2010 to December 2012. Thus, using econometric tools to panel data, it was concluded that the approach the fixed effects is the best suited to the sample data, evidencing the influence of specific effects (unobservable heterogeneity) inherent in every cross-section unit on the respective volume of gas sales. Moreover, the demand elasticities were estimated in relation to price, income and stock of the vehicle fleet, as well as the cross-price elasticity in relation to ethanol. Demand for regular gasoline was shown to be elastic with respect to its price. It was confirmed the use of ethanol as an imperfect substitute for gasoline. It was found that the stock of vehicle fleet tends to have significant and positive influence on the demand for gasoline. However, contrary to economic theory, the hypothesis of the influence of variable income on sales of gasoline was rejected.