[pt] O presente trabalho apresenta estudos de simulações dos processos de transporte e atenuação do derramamento de gasolina nas condições encontradas em postos de gasolina. Estas simulações são realizadas através da aplicação de métodos numéricos para análise de transporte de multicompostos em meios porosos. Na simulação são utilizados programas para análise tridimensional de fluxo e transporte de contaminantes, bem como um programa de pré- e pós-processamento gráfico utilizado na definição da geometria, geração da malha de diferenças finitas, definição dos parâmetros adotados e visualização dos resultados. Um estudo detalhado dos programas utilizados nas análises é realizado. Este estudo inclui um teste para validar os dados fornecidos pelo programa de análise de transporte de contaminantes, bem como, a implementação numérica de uma nova reação química (reação do BTEX com o reagente de Fenton). Como aplicação dos procedimentos estudados, foi utilizado um caso de derramamento de gasolina em um posto na cidade do Rio de Janeiro-RJ. Para representar este derramamento, a simulação foi dividida em três etapas. A primeira refere-se à tentativa de reproduzir as condições de fluxo e contaminação do BTEX, medidos no campo, até o instante de retirada dos tanques. A segunda etapa da simulação corresponde ao período após a substituição dos tanques. A última etapa da simulação, corresponde ao início da injeção de oxigênio usado para bioremediação da área contaminada. O trabalho apresenta uma descrição dos programas utilizados e sua formulação. Apresenta e comenta também os resultados das análises e implementação efetuada. / [en] The present work presents studies related to the simulation of transport and attenuation processes of gasoline spills in conditions normally encountered in petrol stations. These studies are carried out through the application of numerical methods for the analysis of transport of multicomponents in porous media. Computer programs for 3D analysis of flow and transport of contaminants were used as well as graphics routines for the visualization of results. A detailed study of the programs used was carried out. Validation tests were performed as well as an external implementation of a new routine to simulate a particular chemical reaction (reaction of BTEX with Fenton`s reagent) related to a special remediation technique. As application of the studied procedures, a case related to the gasoline spill in a petrol station located in the city of Rio de Janeiro-RJ was focused. In order to represent as close as possible the gasoline spill the simulation was divided into three stages. The first one, refers to an attempt to reproduce the flow and contamination conditions of BTEX compounds formed in situ until the removal of the underground tanks. The second stage corresponds to a period just after the replacement of the damaged tanks. Finally, the last stage consisted in the injection of oxygen used for bioremediation of the contaminated area. The present work describes the overall methodology used, the obtained results and pertinent comments. / [es] EL presente trabajo presenta estudios de simulación de los procesos de transporte y atenuación del derrame de gasolina en las condiciones encontradas en los puestos de gasolina. Estas simulaciones son realizadas aplicando métodos numéricos para el análisis de transporte de multicompuestos en medios porosos. En la simulación se utilizan programas par el análisis tridimensional de flujo y transporte de contaminantes, así como un programa de pré y postprocesamiento gráfico utilizado en la definición de la geometría, generación de la malla de diferencias finitas, definición de los parámetros adoptados y visualización de los resultados. Se incluye un detallado estudio de los programas utilizados en el análisis. Este estudio incluye una prueba para validar los datos suministrados por el programa de análisis de transporte de contaminantes, así como, la implementación numérica de una nueva reacción química (reacción del BTEX con el reagente de Fenton). Como aplicación de los procedimentos estudiados, fue utilizado un caso de derramamiento de gasolina en un puesto de la ciudad del Rio de Janeiro RJ. Para representar este derramamento, la simulación fue dividida en tres etapas. La primera intenta reproduzir las condiciones de flujo y contaminación del BTEX, medidos en el campo, hasta el instante de retirada de los tanques. La segunda etapa de la simulación corresponde al período después la substituición de los tanques. La última etapa, corresponde al início de la inyeción de oxígeno usado para biocuración de la área contaminada. EL trabajo presenta una descripción de los programas utilizados, de su formulación y los resultados del análisis son comentados.

Orientador: Jarbas José Rodrigues Rohwedder / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T15:32:58Z (GMT). No. of bitstreams: 1 Santos_LiviaMartinsdos_D.pdf: 6212654 bytes, checksum: f20eb97ce2aae510654340b401468dd2 (MD5) Previous issue date: 2015 / Resumo: A contaminação de solos oriundos de derrames de compostos derivados do petróleo é um problema que representa riscos ao meio ambiente e a população. Dentre os constituintes do petróleo, os BTEX são os mais tóxicos. O uso da espectroscopia no infravermelho próximo (NIR) foi empregado como uma ferramenta analítica visando a determinação de BTEX em amostras de solo. À um espectrofotômetro construído no laboratório foi adaptado uma célula de medida, uma célula de amostra e uma válvula esfera responsável pela conexão entre essas duas células. Uma bomba de vácuo foi adaptada ao instrumento visando facilitar o enriquecimento da fase vapor dos hidrocarbonetos voláteis na célula de medida, a qual operou com uma pressão de 29,0 inHg abaixo da pressão do laboratório (APL). Os espectros obtidos da fase vapor contendo os hidrocarbonetos aromáticos apresentaram sobreposição de bandas de absorção. Desta forma, foi necessária a construção de modelos de calibração multivariados empregando Regressão por Mínimos Quadrados Parciais (PLS). Os resultados do melhor modelo de regressão obtidos a melhores condições experimentais mostraram que os valores de RMSECV foram de 12,4 mg kg-1, 47,3 mg kg-1, 72,4 mg kg-1 e 58,6 mg kg-1, respectivamente, para benzeno, tolueno, etilbenzeno e xilenos. Esses valores estão de acordo com os valores orientadores para solo da CETESB de 2005, com exceção para o benzeno que encontra-se acima do valor permitido. Para cada tipo de solo é necessário a construção de modelos de calibração, pois a composição do solo influencia na determinação dos hidrocarbonetos / Abstract: The contamination of soils due to petroleum compounds spills is a problem that represents risks to environment and population. Among petroleum constituents, the volatile aromatic hydrocarbons known as BTEX are toxic. This study aims to evaluate the use of near infrared spectroscopy as an analytical tool for determination of volatile hydrocarbons in soil samples. Spectra were obtained in a spectrophotometer built in the laboratory. It is also part of the instrument, a measuring cell with 540 mm of optical path, a sample cell and a valve which allows connection between the two cells. A vacuum pump was adapted to the instrument in order to facilitate enrichment of the vapor phase of the volatile hydrocarbons in the measuring cell, which operated at a pressure of 29.0 inHg below of the laboratory pressure (BLP). Spectra of the vapor phase containing aromatic hydrocarbons exhibited overlapping of absorption bands. Thus, it was necessary to construct multivariate calibration models using Partial Least Squares Regression (PLS). The results obtained for the calibration model provided values of RMSECV of 12.4 mg Kg¬-1, 47.3 mg Kg¬-1, 72.4 mg Kg¬-1 and 58.6 mg Kg¬-1 for benzene, toluene, ethylbenzene and xylenes, respectively. These values are in agreement with the 2005 CETESB guiding values for soil, except for benzene that is above the allowed value. For each type of soil, it was needed to build calibration models because soil composition affects the determination of hydrocarbons. The developed method is promising and may be used as a screening method to determine the occurrence of contamination in soils by BTEX / Doutorado / Quimica Analitica / Doutora em Ciências

Orientador: Ivo Milton Raimundo Júnior / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T23:35:46Z (GMT). No. of bitstreams: 1 Fontes_LaianedeMoura_D.pdf: 2914385 bytes, checksum: 3a68971b696f9f31967f1132ab348427 (MD5) Previous issue date: 2015 / Resumo: Este trabalho descreve o desenvolvimento de diferentes fases extratoras para a determinação de hidrocarbonetos aromáticos e de íons metálicos em água. Para o desenvolvimento das fases extratoras de polidimetilsiloxano e nanotubos de carbono (PDMS-NTC), os nanotubos foram tratados com ácido nítrico, octadecilamina e hipoclorito de sódio. Este último produziu grupos carboxílicos na superfície do nanomaterial, aumentando sua afinidade por hidrocarbonetos aromáticos. A fase extratora foi preparada pela dispersão dos NTC no PDMS e, depois de pronta, inserida num frasco preenchido com as soluções aquosas dos analitos. Após 60 minutos sob agitação, a fase extratora foi removida da solução, seca e inserida em um sistema de medidas, empregando-se um espectrofotômetro FT-NIR. A fase extratora com NTC oxidados com NaOCl possibilitou um aumento da capacidade de extração de 40% e 20% para tolueno e benzeno, respectivamente. No segundo momento, foram desenvolvidas membranas poliméricas plastificadas utilizando os reagentes complexantes Br-PADAP e TAN para a determinação de cobre e chumbo em água por espectroscopia de emissão óptica com plasma induzido por laser (LIBS). As membranas de PVC não forneceram resultados satisfatórios como fase extratora, pois a homogeneidade e estabilidade da superfície das membranas não puderam ser estabelecidas de maneira satisfatória. Papel de filtro analítico foi utilizado como fase extratora para a pré-concentração de íons cobre e chumbo em meio aquoso de forma eficiente, superando as desvantagens das medidas diretas de líquidos por LIBS. A capacidade de adsorção do papel de filtro foi favorecida pela utilização de soluções básicas, principalmente, entre pH 8,0 e 9,0. O tempo de extração foi de 30 minutos para cobre e 60 minutos para chumbo. Os limites de detecção encontrados foram de 0,22 e 0,53 mg L-1 para cobre e chumbo, respectivamente. Não foi observada interferência dos íons Ni (II), Zn (II), Cd (II) e Fe(III), tampouco influência da força iônica. O método proposto foi utilizado para a determinação de cobre e chumbo em amostra de água de torneira enriquecida em três níveis de concentrações. Recuperações na faixa de 98,8% - 114,3% foram obtidas indicando que a determinação direta de íons cobre e chumbo em amostras aquosas pela técnica LIBS utilizando papel de filtro como fase extratora apresenta potencial para a análise de amostras reais / Abstract: This work describes the development of extraction phases for determination of aromatic hydrocarbons and metal ions in water. For development of the phase based on polydimethilsiloxane and carbon nanotubes (PDMS-NTC), carbon nanotubes were previously functionalized with nitric acid, octadecylamine and sodium hypochlorite. The latter oxidizing agent produced carboxyl groups on the surface of the nanomaterial, increasing its affinity for aromatic hydrocarbons. The extraction phase was prepared by dispersing the functionalized NTC in PDMS, which was polymerized to form cylindrical monoliths. Extractions were performed by immersing the monolith in a flask filled with the aqueous solutions of analytes, containing 2.0 mol L-1 NaCl. After an extraction time of 60 min under constant stirring, the monolith was removed from the flask, dried and inserted in the measuring cell of the FT-NIR spectrophotometer. The extraction phase containing NTC oxidized by sodium hypochlorite allow an increase of the sensitivity of 40% and 20% for toluene and benzene, respectively. In the second part, plasticized polymeric membranes containing Br-PADAP or TAN as complexing reagents were developed for determination of lead and copper in water by laser induced breakdown spectroscopy (LIBS). The PVC membranes did not provide satisfactory results, as the homogeneity and the stability of the membrane could not be attained. Analytical filter paper was then employed as an extraction phase to efficiently pre-concentrate lead and copper ions from aqueous solution, circumventing the disadvantages of direct measurements of liquid phase by LIBS. The sorption capacity of the filter paper was enhanced in basic solutions, mainly within pH 8.0 and 9.0. The ideal extraction time for Cu(II) was 30 minutes and 60 minutes for Pb(II). The detection limits were estimated as 0.22 and 0.53 mg L-1 for Cu(II) and Pb(II), respectively. Interference of Ni (II), Zn (II), Cd (II) and Fe(II) ions were not observed, as well as the influence of the ionic strength. The proposed method was employed for determination of cooper and lead in tap water fortified at three concentrations levels. Recoveries in the range from 98.8% to 114.3% were obtained, indicating that direct determination of these ions in aqueous samples by the LIBS using filter paper as an extraction phase has a potential for analysis of aqueous samples / Doutorado / Quimica Analitica / Doutora em Ciências

[pt] Neste estudo foi avaliada a capacidade de adsorção do poluente orgânico tolueno em contato com a cepa Rhodococcus opacus. O tolueno foi selecionando por fazer parte do grupo de compostos BTEX (Benzeno, Tolueno, Etilbenzeno e Xileno), que possui elevada toxicidade, causando impacto ambiental em corpos hídricos, solo e ar, além de possuir características mutagênica e carcinogênica em humanos. A determinação e quantificação do tolueno na solução aquosa foram realizadas em um cromatógrafo a gás, acoplado ao espectrômetro de massas com amostrador automático headspace. A cepa Rhodococcus opacus foi caracterizada por análise de espectrometria no infravermelho e medição de potencial zeta, sendo a última realizada antes e após o contato com o tolueno. Os modelos de isotermas lineares de Langmuir, Freundlich e Temkin foram aplicados aos dados experimentais para descrever o processo de adsorção. Tendo o modelo de Langmuir se adaptado melhor ao processo em análise. As variáveis estudadas para otimizar as condições máximas de adsorção foram: tempo de contato, variação do pH, variação da biomassa. Este estudo mostrou que a cepa bacteriana R. opacus apresentou uma boa capacidade de biossorção, principalmente para concentrações baixas, onde removeu 95,99 porcento e 85,69 porcento das respectivas concentrações de 0,6 e 0,8 mg/L de tolueno, atendendo a resolução do CONAMA 357/2005 para águas salobras de Classe I. / [en] In this study was evaluated the adsorption capacity of the organic pollutant toluene by the Rhodococcus opacus strain. Toluene was chosen by being part of the group of BTEX compounds (benzene, toluene, ethylbenzene and xylene), which has high toxicity, causing environmental impact on water bodies, soil and air, and also are mutagenic and carcinogenic to humans. The determination and quantification of toluene in aqueous solution were performed on a gas chromatograph, coupled with a mass spectrometer with headspace autosampler. The strain Rhodococcus opacus was characterized by infrared spectrometry analysis and zeta potential measurement, the last done before and after the sorption. The isotherm linear models of Langmuir, Freundlich and Temkin were applied to the experimental data to describe the adsorption process. Having the Langmuir model better adapted to process analysed. The variables studied to optimize the maximum adsorption conditions were: contact time, pH variation, biomass variation. This study showed that the bacterial strain R. opacus has good biosorption capabilities, particularly at low concentrations, where it removed 95.99 percent and 85.69 percent of the respective concentrations of 0.6 and 0.8 mg/L of toluene, attending the CONAMA resolution 357/2005 for salt waters of Class I.

A contaminação de solos e águas subterrâneas por compostos orgânicos constitui-se em sérios e preocupantes problemas à saúde do homem e ao meio ambiente. A presença de gasolina como agente poluidor em solos e águas, se deve, na maioria das vezes, a defeitos na estrutura dos tanques de estocagem em postos de abastecimento, vazamentos em tubulações de refinarias, acidentes com caminhões de transporte etc. Das substâncias que compõe a gasolina, mais de 200 são reconhecidamente tóxicas, dentre elas encontram-se o benzeno, tolueno, etilbenzeno e xilenos (BTEX). O combustível derramado, inicialmente estará presente na Zona Não-Saturada sob a forma adsorvida ou de vapor. Em contato com a fase aquosa, devido o fenômeno de cossolvência, os compostos BTEX se dissolverão parcialmente, sendo os prim eiros contaminantes a atingir a água subterrânea deteriorando sua qualidade. A contaminação depende principalmente da extensão do vazamento, das características do solo e, em geral, só são percebidas quando descobertos seus efeitos deletérios. Atualmente, dentre os métodos de descontaminação in situ, destacam-se os Processos Oxidativos e os Processos Oxidativos Avançados (POAs). Nos oxidativos utilizam-se reagentes como peróxido de hidrogênio, permanganato e persulfato; os POAs se baseiam na produção de radicais hidroxil (OH° ) que podem ser obtidos a partir do Reagente Fenton e Foto - Fenton. Os agentes oxidantes promovem total degradação de grande variedade de substâncias perigosas resultando em compostos inócuos como gás carbônico e água. O uso dessas técnicas de descontaminação, entretanto, na maioria das vezes, leva a efeitos secundários indesejáveis ao meio ambiente. Visando estudar as alterações no solo e na água, foram realizados experimentos laboratoriais utilizando um Latossolo artificialmente impactado por gasolina e tratado com os reagentes Fenton, peróxido de hidrogênio, persulfato de sódio e permanganato de potássio. Os estudos permitem afirmar que os tratamentos oxidativos resultam em diminuição do pH, redução dos teores de bases trocáveis e, por se tratar de processos pouco seletivos, ocasionam a degradação da matéria orgânica natural do solo. Essas alterações favorecem a dessorção de íons metálicos que são liberados para fase aquosa em concentrações que excedem até centenas de vezes o limite estabelecido pela legislação. Os resultados obtidos comprovam que os efeitos secundários consequentes das técnicas de degradação oxidativa, aplicadas às áreas impactadas por c ompostos benzênicos, afetam o meio ambiente e alteram a qualidade das águas tornando -as inadequadas para o consumo humano. / The contamination of soils and groundwater by organic compounds is a serious and worrying problem for the health of the human being and the environment. The presence of petrol as a polluting agent in soil and water occurs, in most cases, due to defects in the structure of the storage tanks at petrol, stations, leaks in tubing of the oil refineries, accidents envolving tanker lorries etc. Among the substances that are in the chemical composition of gasoline, more than 200 are known to be toxic, including benze ne, toluene, ethylbenzene and xylene (BTEX). The spilt petrol shall be present, in the early stages, in the Non -Saturated Zone in the adsorbed or vapour forms. In contact with the aqueous phase, due to the phenomenon of cosolvence, the BTEX compounds shall partially dissolve, and the first contaminants to reach the water causing a deterioration in its quality. Contamination depends mainly on the extention of the leak, the characteristics of the soil and, in general, are only perceived when their harmful effects are discovered. Currently, among the in situ methods of decontamination we could mention the Oxidative Processes and the Advanced Oxidative Processes (AOPs). In the oxidative process, reagents such as hydrogen peroxide, permanganate and persulphate a re used; in contrast, the AOPs are based on the production of hydroxyl radicals (OH°) which can be obtained based on the Fenton reagent and photo-Fenton. Oxidising agents bring about the total degradation of many harmful substances which are turned into harmless compounds such as carbon dioxide and water. The use of these decontamination techniques, however, often leads to undesirable secondary effects on the environment. Aiming to study the changes to soil and water, laboratory experiments were conducted using a Latosoil which was artificially impacted by petrol, and then treated with Fenton, hydrogen peroxide, sodium persulphate and potassium permanganate reagents. The studies conducted as part of this project allow us to say that oxidising treatment results in a decline of pH, reduction of the content of exchangeable bases and, as these processes are of low selectivity, they also lead to the degradation of the natural organic matter of the soil. These changes favour the dessorption of metallic ions, which are released into the aqueous phase at concentrations which are often hundreds of times more than the limit established by legislation. The results obtained also proved that the secondary effects resulting from degradation techniques based on oxidation as applied to areas that have had the impact of benzene compounds affect the environment and also change the quality of the waters, that are unsuitable for human consumption.

A contaminação de solos e águas subterrâneas por compostos orgânicos constitui-se em sérios e preocupantes problemas à saúde do homem e ao meio ambiente. A presença de gasolina como agente poluidor em solos e águas, se deve, na maioria das vezes, a defeitos na estrutura dos tanques de estocagem em postos de abastecimento, vazamentos em tubulações de refinarias, acidentes com caminhões de transporte etc. Das substâncias que compõe a gasolina, mais de 200 são reconhecidamente tóxicas, dentre elas encontram-se o benzeno, tolueno, etilbenzeno e xilenos (BTEX). O combustível derramado, inicialmente estará presente na Zona Não-Saturada sob a forma adsorvida ou de vapor. Em contato com a fase aquosa, devido o fenômeno de cossolvência, os compostos BTEX se dissolverão parcialmente, sendo os prim eiros contaminantes a atingir a água subterrânea deteriorando sua qualidade. A contaminação depende principalmente da extensão do vazamento, das características do solo e, em geral, só são percebidas quando descobertos seus efeitos deletérios. Atualmente, dentre os métodos de descontaminação in situ, destacam-se os Processos Oxidativos e os Processos Oxidativos Avançados (POAs). Nos oxidativos utilizam-se reagentes como peróxido de hidrogênio, permanganato e persulfato; os POAs se baseiam na produção de radicais hidroxil (OH° ) que podem ser obtidos a partir do Reagente Fenton e Foto - Fenton. Os agentes oxidantes promovem total degradação de grande variedade de substâncias perigosas resultando em compostos inócuos como gás carbônico e água. O uso dessas técnicas de descontaminação, entretanto, na maioria das vezes, leva a efeitos secundários indesejáveis ao meio ambiente. Visando estudar as alterações no solo e na água, foram realizados experimentos laboratoriais utilizando um Latossolo artificialmente impactado por gasolina e tratado com os reagentes Fenton, peróxido de hidrogênio, persulfato de sódio e permanganato de potássio. Os estudos permitem afirmar que os tratamentos oxidativos resultam em diminuição do pH, redução dos teores de bases trocáveis e, por se tratar de processos pouco seletivos, ocasionam a degradação da matéria orgânica natural do solo. Essas alterações favorecem a dessorção de íons metálicos que são liberados para fase aquosa em concentrações que excedem até centenas de vezes o limite estabelecido pela legislação. Os resultados obtidos comprovam que os efeitos secundários consequentes das técnicas de degradação oxidativa, aplicadas às áreas impactadas por c ompostos benzênicos, afetam o meio ambiente e alteram a qualidade das águas tornando -as inadequadas para o consumo humano. / The contamination of soils and groundwater by organic compounds is a serious and worrying problem for the health of the human being and the environment. The presence of petrol as a polluting agent in soil and water occurs, in most cases, due to defects in the structure of the storage tanks at petrol, stations, leaks in tubing of the oil refineries, accidents envolving tanker lorries etc. Among the substances that are in the chemical composition of gasoline, more than 200 are known to be toxic, including benze ne, toluene, ethylbenzene and xylene (BTEX). The spilt petrol shall be present, in the early stages, in the Non -Saturated Zone in the adsorbed or vapour forms. In contact with the aqueous phase, due to the phenomenon of cosolvence, the BTEX compounds shall partially dissolve, and the first contaminants to reach the water causing a deterioration in its quality. Contamination depends mainly on the extention of the leak, the characteristics of the soil and, in general, are only perceived when their harmful effects are discovered. Currently, among the in situ methods of decontamination we could mention the Oxidative Processes and the Advanced Oxidative Processes (AOPs). In the oxidative process, reagents such as hydrogen peroxide, permanganate and persulphate a re used; in contrast, the AOPs are based on the production of hydroxyl radicals (OH°) which can be obtained based on the Fenton reagent and photo-Fenton. Oxidising agents bring about the total degradation of many harmful substances which are turned into harmless compounds such as carbon dioxide and water. The use of these decontamination techniques, however, often leads to undesirable secondary effects on the environment. Aiming to study the changes to soil and water, laboratory experiments were conducted using a Latosoil which was artificially impacted by petrol, and then treated with Fenton, hydrogen peroxide, sodium persulphate and potassium permanganate reagents. The studies conducted as part of this project allow us to say that oxidising treatment results in a decline of pH, reduction of the content of exchangeable bases and, as these processes are of low selectivity, they also lead to the degradation of the natural organic matter of the soil. These changes favour the dessorption of metallic ions, which are released into the aqueous phase at concentrations which are often hundreds of times more than the limit established by legislation. The results obtained also proved that the secondary effects resulting from degradation techniques based on oxidation as applied to areas that have had the impact of benzene compounds affect the environment and also change the quality of the waters, that are unsuitable for human consumption.

<p>The most widely used gasoline additive methyl tert-butyl ether (MTBE) has been questioned recently, since frequent detection of this compound in groundwater indicates that it could be a risk to our environment. Consequently, legislative efforts have been made by some local governments to phase out the use of MTBE. Among a number of alternative substitutes, ethyl tert-butyl (ETBE) seems to be the more promised one due to its lower water solubility, suggesting that it could pose less impact to our water supply. However, a thorough understanding of its environmental fate is needed before ETBE is widely accepted as a more environmentally friendly gasoline additive. As a part of this effort, the degradation of MTBE and ETBE as well as their effects on the fate of aromatic gasoline components, i.e. BTEX (benzene, toluene, ethyl-benzene and xylenes) were studied on two soils contaminated with MTBE-blended or ETBE-blended gasoline. During a period of 5 months, the general aerobic degradation of the gasoline and its different additives were monitored by gas chromatography – thermal conductivity detection (GC-TCD) and concentration changes of MTBE and ETBE were monitored with the help of gas chromatography - mass spectrometry (GC-MS). The results of this study showed that the degradation of MTBE, ETBE and BTEX occurred in all the systems, nevertheless MTBE and ETBE degraded far more slowly in contrast with the degradation of BTEX, indicating that MTBE and ETBE are more persistent. When the degradation of MTBE and ETBE were compared, ETBE decreased a little faster than MTBE, implying that ETBE advantages slightly in degradation over MTBE. Concerning the effects of MTBE and ETBE on the fate of BTEX, the results showed that MTBE might enhance whereas ETBE might inhibit the degradation of BTEX though at a lower level. In addition, less degradation of MTBE and ETBE was observed in organic-rich soil in all the cases, probably because that there are more other substrates available for the microorganisms in organic-rich soil.</p>

The most widely used gasoline additive methyl tert-butyl ether (MTBE) has been questioned recently, since frequent detection of this compound in groundwater indicates that it could be a risk to our environment. Consequently, legislative efforts have been made by some local governments to phase out the use of MTBE. Among a number of alternative substitutes, ethyl tert-butyl (ETBE) seems to be the more promised one due to its lower water solubility, suggesting that it could pose less impact to our water supply. However, a thorough understanding of its environmental fate is needed before ETBE is widely accepted as a more environmentally friendly gasoline additive. As a part of this effort, the degradation of MTBE and ETBE as well as their effects on the fate of aromatic gasoline components, i.e. BTEX (benzene, toluene, ethyl-benzene and xylenes) were studied on two soils contaminated with MTBE-blended or ETBE-blended gasoline. During a period of 5 months, the general aerobic degradation of the gasoline and its different additives were monitored by gas chromatography – thermal conductivity detection (GC-TCD) and concentration changes of MTBE and ETBE were monitored with the help of gas chromatography - mass spectrometry (GC-MS). The results of this study showed that the degradation of MTBE, ETBE and BTEX occurred in all the systems, nevertheless MTBE and ETBE degraded far more slowly in contrast with the degradation of BTEX, indicating that MTBE and ETBE are more persistent. When the degradation of MTBE and ETBE were compared, ETBE decreased a little faster than MTBE, implying that ETBE advantages slightly in degradation over MTBE. Concerning the effects of MTBE and ETBE on the fate of BTEX, the results showed that MTBE might enhance whereas ETBE might inhibit the degradation of BTEX though at a lower level. In addition, less degradation of MTBE and ETBE was observed in organic-rich soil in all the cases, probably because that there are more other substrates available for the microorganisms in organic-rich soil.

Ethanol is used as fuel in neat form in some countries (Brazil and India) or blended with gasoline (Europe, Canada and the United States). The benefits of ethanol use include octane enhancement, a cleaner environment and a secure renewable energy supply. BTEX compounds (benzene, toluene, ethylbenzene, m-xylene, p-xylene and o-xylene) are aromatic hydrocarbons present in gasoline. The fate of these compounds in the environment is of great health concern due to their carcinogenic (benzene) and toxic properties, and due to their high solubility in water compared to the other gasoline hydrocarbons. Ethanol present in gasoline may affect BTEX degradation, in an event of a spill into the subsurface environment. To address the effects of ethanol on subsurface microorganisms, microbial activity and growth in the presence of ethanol (concentrations ranging 0 to 70% v/v) were assessed. Microcosms studies showed that ethanol at concentration ranging 0. 5 to3% (v/v) enhanced microbial activity and did not interfere inmicrobial growth at 10oC temperature, when another source of carbon was present (glucose). Ethanol at 0. 5% concentration enhanced microbial activity over water soluble gasoline components and R2A medium combined. Both microbialactivity and growth were not detected at ethanol concentrations equal and above 5%. Biodegradation study was conducted, in which subsurface material and ground water were exposed to BTEX and ethanol at 0. 5 and 1. 5% (v/v) concentration. The controls had BTEX alone and ethanol alone, sterile and nutrient-free. Total BTEX degradation was observed whenever ethanol was absent. Ethanol and BTEX were simultaneously degraded, however in microcosms containing 0. 5% ethanol, BTEX degradation was slowed, compared to microcosms without ethanol. Competition for inorganic nutrients was the major problem in slowed BTEX degradation in the presence of ethanol. In microcosms where 1. 5% ethanol was present, BTEX compounds and ethanol degradation were not observed.

Ethanol can affect the biodegradation of gasoline hydrocarbons in groundwater. High concentrations of ethanol can be toxic to subsurface microorganisms that are otherwise capable of degrading hydrocarbons, such as benzene, toluene, ethylbenzene and xylenes (BTEX). At lower concentrations, ethanol may hinder BTEX degradation through substrate competition and the depletion of inorganic nutrients (e.g., nitrogen and phosphorus), oxygen and other electron acceptors needed for BTEX degradation. A series of laboratory experiments were designed to study the effect of ethanol on aquifer microorganisms and on aerobic BTEX biodegradation. A microcosm experiment was conducted to investigate the effect of ethanol on the biodegradation of BTEX. Microcosms were set up with Borden aquifer material and groundwater in which oxygen and nutrients were not limited. These microcosms contained BTEX in combination with a range of ethanol concentrations. Under these favourable conditions, the presence of ethanol up to concentrations of 1.9% (v/v) (equivalent to 15000 mg/L) caused little inhibition of BTEX degradation. Further experiments were conducted to study the antimicrobial effects of higher concentrations of ethanol. Following exposure to ethanol concentrations of 25% (v/v) or higher, microbial activity and survival was significantly diminished. Results suggest that a high concentration ethanol slug will have a major impact on the microbial community but that there would likely be potential for recovery. The recovery potential was examined further in laboratory column experiments designed to simulate a dynamic field situation where a high ethanol pulse is followed by a BTEX plume. These column experiments were conducted with Borden aquifer material and groundwater under aerobic conditions. The concentration of the ethanol pulse was 25% (v/v), which was expected to significantly alter the microbial population without destroying it. Following the ethanol exposure, groundwater and BTEX were allowed to flow through one column to simulate the reinoculation of microorganisms from upgradient groundwater advecting into the contaminated zone. The other column was fed with sterile groundwater and BTEX to evaluate the regeneration of within-column microorganisms that survived the ethanol exposure. Recovery in both columns was rapid. Unfortunately, during the recovery phase, sterility of the influent groundwater could not be maintained. As a result, recovery by regeneration could not be evaluated. Nonetheless, it is evident that recovery in terms of aerobic BTEX biodegradation was significant under the conditions of the column experiment. Ethanol did not appear to pose a long-term impact on BTEX biodegradation when oxygen and nutrients were in excess. In field situations, nutrients and electron acceptors may be limited; however, ethanol toxicity is not likely to cause a prolonged inhibition of BTEX biodegradation.