Plant invasions can ensue when plants are introduced to regions without their specialist enemies (the Enemy Release Hypothesis). This assumes natural enemies limit survival and fecundity in an invader's native range. I tested this assumption for a native invasive species, Common Ragweed (Ambrosia artemisiifolia), by excluding natural enemies from seeds, seedlings and adults. At the adult stage, I added disturbance and conspecific density treatments. Protection from herbivores slightly improved performance at the seedling stage only, while disturbance greatly increased survival and fecundity. Increasing conspecific density reduced performance only in disturbed plots. I also tested herbivore tolerance using simulated damage. Heavy (75%) damage did not reduce fecundity; light damage even increased seed production. These results suggest enemies do not limit Ambrosia in its native range, especially compared to the effects of habitat disturbance. While enemy release may have occurred during Ambrosia’s invasions, it is not likely to be their principal cause.

Life cycle assessment is an important tool to evaluate the impact of 2nd generation lignocellulosic ethanol, and its potential greenhouse gas (GHG) emissions benefits relative to gasoline. The choice of feedstock, process technology, and co-products may affect GHG emissions and energy metrics. Co-products may improve both the financial and environmental performance of the biorefinery. 26 well-to-wheel models of future lignocellulose-to-ethanol pathways were constructed, considering corn stover, switchgrass, and poplar feedstocks, three pre-treatment technologies, four co-product options, and the use of ethanol in a light-duty vehicle. Model results showed that all pathways with lignin pellet co-production had significantly lower net GHG emissions relative to gasoline and corresponding pathways producing only electricity. Pathways co-producing xylitol had at least 66% greater GHG emission reductions relative to pathways co-producing only lignin pellets. All feedstock/pretreatment/co-product combinations led to GHG reductions of at least 60%, meeting the threshold stipulated under the Energy Independence and Security Act.

Life cycle assessment is an important tool to evaluate the impact of 2nd generation lignocellulosic ethanol, and its potential greenhouse gas (GHG) emissions benefits relative to gasoline. The choice of feedstock, process technology, and co-products may affect GHG emissions and energy metrics. Co-products may improve both the financial and environmental performance of the biorefinery. 26 well-to-wheel models of future lignocellulose-to-ethanol pathways were constructed, considering corn stover, switchgrass, and poplar feedstocks, three pre-treatment technologies, four co-product options, and the use of ethanol in a light-duty vehicle. Model results showed that all pathways with lignin pellet co-production had significantly lower net GHG emissions relative to gasoline and corresponding pathways producing only electricity. Pathways co-producing xylitol had at least 66% greater GHG emission reductions relative to pathways co-producing only lignin pellets. All feedstock/pretreatment/co-product combinations led to GHG reductions of at least 60%, meeting the threshold stipulated under the Energy Independence and Security Act.

Overheight vehicle impact to bridge decks is a major problem in the transportation networks in the United States. An important factor that causes this problem is inadequate vertical clearance of bridges. Using steel pedestals to elevate bridge decks is an efficient and cost-effective solution for this problem. So far, steel pedestals have been used in the low seismic regions of the United States and therefore, their design has been based on providing enough strength to carry vertical loads and the lateral behavior of bridges elevated with pedestals have not been a major concern. But even in low seismic zones the seismic hazard should not be completely ignored. Also there might be some bridges in medium or high seismic regions that need to be elevated because of the lack of enough vertical clearance and using steel pedestals can be considered as an option for elevating those bridges. To address the mentioned needs, this dissertation proposes a framework to determine the structural reliability of bridges elevated with steel pedestals by developing probabilistic capacity and demand models for the slab-on-girder bridges subjected to lateral loads. This study first compares the behavior of previously tested pedestals with the behavior of elastomeric bearings in low seismic regions using statistical tests. Then, to provide a general framework, which can be applied to all bridges that are elevated with steel pedestals, this dissertation develops probabilistic capacity and demand models for steel pedestals considering all the aleatory and epistemic uncertainties of the problem. Using the developed probabilistic models along with the available models for other components of bridges, seismic fragility curves for elevated bridges are obtained and used to determine the structural reliability. Finally, this study uses the developed framework in a decision analysis that helps the engineering community and decision makers to check if the installation of steel pedestals on a specific bridge has financial justification or not. Results show that for a typical two-span slab-on-girder bridge, the use of steel pedestals has financial justification only in low seismic regions and if the societal benefits of elevating the bridge can at least cover the installation cost of pedestals.

Recycling is an important part of the automotive industry and this thesis was made to examine the environmental impact from the production of a new produced rear subframe compared to a remanufactured subframe. A life cycle assessment has been done to investigate the inputs and outputs of the processes surrounding the new production and remanufacturing. The emissions from the processes have been categorized into four environmental categories. Based on the categories a comparison have been made to evaluate the environmental impact and conclude the differences between the two processes.

Plant invasions can ensue when plants are introduced to regions without their specialist enemies (the Enemy Release Hypothesis). This assumes natural enemies limit survival and fecundity in an invader's native range. I tested this assumption for a native invasive species, Common Ragweed (Ambrosia artemisiifolia), by excluding natural enemies from seeds, seedlings and adults. At the adult stage, I added disturbance and conspecific density treatments. Protection from herbivores slightly improved performance at the seedling stage only, while disturbance greatly increased survival and fecundity. Increasing conspecific density reduced performance only in disturbed plots. I also tested herbivore tolerance using simulated damage. Heavy (75%) damage did not reduce fecundity; light damage even increased seed production. These results suggest enemies do not limit Ambrosia in its native range, especially compared to the effects of habitat disturbance. While enemy release may have occurred during Ambrosia’s invasions, it is not likely to be their principal cause.

Since World War II, concern for the environmental impacts of human activities has grown. Agriculture plays a significant role in several impact categories including global warming. Governments, including the U.S., have recently begun or are considering the regulation of greenhouse gas (GHG) emission to mitigate the global warming effect. Because agriculture accounts for a large portion of anthropogenic greenhouse gas emissions, it is necessary to establish a baseline measure of the GHG emission of U.S. agriculture at the farm level. The objective of this research is to estimate the GHG emission levels for multicrop farms in the U.S. and identify the major sources of GHG emissions in their supply chains. To accomplish the objective, a partial life cycle assessment (LCA) methodology is used to establish a GHG baseline for the representative farms. LCA as defined by the International Organization for Standardization (ISO) includes four phases: goal and scope definition, inventory, impact assessment, and interpretation. It is a holistic approach that catalogues environmental impacts of all relevant processes at all stages of production, from raw material extraction to disposal. However, this study only catalogues impacts up to the farm gate. Partial LCAs are common in agriculture. Emissions of three GHGs, CO2, CH4, and N2O, are inventoried for 95 U.S. farms. The results are characterized using their 100-year global warming potentials into CO2 equivalents. The CO2 equivalents are then normalized over four functional units: enterprises, acres or head, harvest units, and pounds of production. The variation of GHG intensity between crops and farms is very large. However, it is clear that GHG intensity is affected by three characteristics: location, size, and irrigation practice. Crops grown in their associated regions tend to be more GHG efficient than those grown outside their associated regions. Also, crops grown on large farms tend to be more GHG efficient than the same crop grown on a small farm in the same area. Lastly, with the exceptions of cotton and soybeans, irrigated crops tend to be more GHG intensive than non-irrigated crops. These results combine to suggest that there may be a correlation between production efficiency and carbon efficiency.

El objetivo principal de esta tesis doctoral es el de contribuir al desarollo y evaluación en la aplicación y exposición de pesticidas en plantas y su impacto sobre la salud humana y los ecosistemas. Los modelos ambientales usados para la evaluación de impacto en el análisis de ciclo de vida y en analisis de riesgo ambiental relacionan las emisiones con su impacto, combinando el destino y la exposición estimada y relacionandolo con información toxicológica. Los pesticidas liberados en aire, agua y suelos llegan al cuerpo humano a través de los alimentos, principalmente por la ingestión de las partes comestibles de los vegetales. Por dicha razón, es de gran importacia el desarollo de métodos para el análisis de residuos tóxicos en productos agrícolas. De aquí emergen las siguientes preguntas:1. ¿Como puede ser modelada la cantidad residual y el lugar de destino de los pesticidas aplicados por aire en los invernaderos? ¿Cual es su compotamiento dinámico y como afecta la concentración residual en las partes comestibles de los vegetales?2. ¿Como puede medirse y modelarse la degradación de los pesticidas tanto en superficie como en el interior de vegetación?3. ¿Como puede hacerse una estimación de la vida media específica tanto en superficie como en el interior de vegetales partiendo de la información de degradación en el suelo?4. ¿Como puede desarollarse un indicador de riesgo con el cual se puedan analizar comparativamente pesticidas basado en el lugar de aplicación, tiempo de exposición y características toxicológicas?Después de una breve introdución al análisis medioambiental y los problemas específicamente relacionados con la aplicación de pesticidas y sus características en el capítulo uno, en el capítulo dos se propone un acercamiento a través del modelado de residuos de pesticidas en tomates cultivados en invernadero. Este modelo de destino y exposición tiene en consideración el tiempo transcurrido entre la aplicación, la cosecha y el consumo, la absorción del spray depositado en la superficie de las plantas, las propiedades de transporte a través de la cutícula, la degradación en el interior de la misma planta y perdidas debido al procesado del alimento. El modelo fue validado usando datos experimentales obtenidos a partir de ensayos de campo. También se presenta la fracción de pesticida ingerido por humanos debido al consumo de tomate mostrando un escenario realista de la exposición humana a estos productos.En el capítulo tercero se presentan dos algoritmos genéricos para la estimación de (i) la vida media específica de pesticidas en superficie y (ii) en el interior de las plantas, usados en el modelo de destino y exposición. También se propone una rutina de extrapolación para estimar la vida media de plaguicidas en superficie, basándose en un factor de conversión cuya base de cálculo parte de la vida media de estos en suelos. Más adelante se presenta un método de estimación tentativa para el cálculo de la vida media de pesticidas en el interior de las plantas, básandose en datos experimentales.El capítulo cuatro es una prolongación de los capítulos dos y tres. Los resultados antes obtenidos, se combinan aquí con un nuevo método de análisis experimental para medir absorción, transporte y persistencia de pesticidas en tomates tratados por (i) spray foliar estándar y (ii) aplicación en raíces por riego por goteo. Un modelo dinámico de absorción de pesticidas por raíz trata de estimar la dependencia temporal de la concentración del contaminante en los frutos. Finalmente, los resultados experimentales son comparados con el modelo en terminos de ingestión de fracción de pesticida por parte de la población humana. En esta investigación se intenta evaluar el comportamiento medioambiental de los pesticidas comparando los diferentes métodos de aplicación de un mismo ingrediente activo.El capítulo cinco ilustra el desarollo de un nuevo método llamado PestScreen, el cual calcula el nivel relativo de riesgo de pesticidas con el fin de clasificarlos ascendentemente dependiendo de su impacto. Esta aproximación es un método de estimación del nivel relativo de riesgo y permite comparar la peligrosidad tanto a nivel de salud humana como de impacto medioambiental, de diferentes tipos de pesticidas, a través de una categorización. Este método se desarolla como una herramienta para la evaluación e identificación de pesticidas con peligrosidad medioambiental usados en la agricultura. PestScreen incorpora tanto su efecto tóxico como su destino y exposición en varios compartimentos medioambientales. Esto se realiza combinando medidas de toxicidad química con la cantidad liberada, la persistencia medioambiental, el potencial de transporte en un radio amplio y la fracción ingerida por la población humana. En el capítulo seis los principales resultados son presentados y resumidos, finalmente se sugieren recomendaciones para investigaciones futuras. / The overall goal of this dissertation is to contribute to the development of best available practice in fate and the exposure assessment of pesticides for evaluating their impacts on human health and ecosystems. Environmental models used in Life Cycle Impact Assessment (LCIA) and Environmental Risk Assessment (ERA) relate emissions to impacts by combining fate and exposure estimates with toxicological assessment data. Pesticides released to air, water, soil and plants enter the human body through food commodities, particularly through the ingestion of arable parts of plants. Therefore, specific methods to assess the presence of residues in agricultural products are of importance for human exposure assessment. This raises the following questions:1. How can the fate (from air and soil) of pesticides in/on plants cultivated in greenhouses be measured and modelled? How does dynamic behaviour affect the final residues in arable parts of plants?2. How can the degradation of pesticides on plant surfaces and within plants be measured and modelled? 3. How can a substance specific half-life in/on plants be estimated from soil degradation data using extrapolation routines?4. How can a risk indicator for comparative assessment of pesticides be developed using fate, exposure, and toxicity characteristics?After a short introduction to environmental assessment approaches and the specific problems related to the application of pesticides and their characteristics in Chapter 1, Chapter 2 proposes an approach for modelling pesticide residues in greenhouse tomato plants. This fate and exposure model considers the time between pesticide application and harvest, the time between harvest and consumption, the absorption of spray deposit on plant surfaces, transfer properties through the cuticle, degradation inside the plant and loss due to food processing. The model is validated with experimental data which was obtained from field trials conducted in the Catalan Institute for Food and Agricultural Research and Technology (Institut de Recerca i Tecnologia Agroalimentàries; IRTA) in Cabrils (Barcelona). Human intake fractions of pesticides due to ingestion of tomatoes representing a realistic scenario of human exposure to pesticide residues in foods are presented.In Chapter 3, two generic estimation routines for substance specific half-lives of pesticides (i) on plant surfaces and (ii) within plants to be used in fate and exposure models are presented. First, an extrapolation routine for the estimation of pesticide half-lives on plant surfaces based on a conversion factor from half-lives of pesticides in soil is proposed. Furthermore, a tentative estimation method for the calculation of metabolism half-lives of pesticides in inner parts of plants based on experimental data is presented.Chapter 4 presents a follow-up of Chapter 2 and Chapter 3. Previous results are combined with new experimental assessment to measure the uptake, translocation and persistence behaviour of pesticides in tomato fruits treated by (i) standard foliar spray application and (ii) soil application using direct localised drip irrigation into root zone. A dynamic root uptake model for pesticides aiming at the estimation of time dependent contaminant concentrations in fruits is proposed. Finally, experimental results are compared with model estimates in terms of human population intake fractions of pesticides. These investigations aim to evaluate the environmental performance of pesticides when the same active ingredient is applied to crops by different application techniques. Chapter 5 illustrates the development of a new method entitled PestScreen, to calculate the relative risk level of pesticides with the aim of ranking them from lowest to highest degree of concern. The approach is an estimation method of relative risk levels and allows comparing environmental and human health risks of specific pesticide types through their ranking. The method is developed to serve as an analytical tool in screening and identification of pesticides of environmental concern used in agriculture. PestScreen incorporates both the toxic effects of pesticides and their fate and exposure characteristics in different compartments of the environment. This is done by combining measures of chemical toxicity pertaining to both human health and the environment with chemical release amounts and information on overall environmental persistence, long-range transport potential and human population intake fractions. In Chapter 6 the most important results are summarized and recommendations for further research are discussed.

El objetivo es desarrollar una herramienta de apoyo a la toma de decisiones para la planificación estratégica de cadenas de suministro (CS). La tarea consiste en determinar el número, ubicación y capacidad de todos los nodos de la CS, su política de expansión, el transporte y la producción entre todos los nodos de la red. El problema se formula como un modelo de programación lineal entera mixta (MILP) que se resuelve utilizando diferentes herramientas. En primer lugar se desarrolló una estrategia de descomposición para acelerar el proceso de resolución En segundo, se utilizó el algoritmo de aproximación para resolver el problema MILP estocástico. Por último, el modelo multi-objetivo incorpora las soluciones de compromiso entre los aspectos económicos y ambientales. Todas las formulaciones se aplicaron al caso real de la industria de caña de azúcar en Argentina. El objetivo de las herramientas es ayudar a los responsables de planificación estratégica de las infraestructuras para la producción de productos químicos. / The aim of this thesis is to provide a decision-support tool for the strategic planning of supply chains (SCs). The task consists of determining the number, location and capacities of all SC facilities, their expansion policy, the transportation links that need to be established, and the production rates and flows of all materials involved in the network. The problem is formulated as a mixed-integer linear programming (MILP) model, which is solved using several mathematical programming tools. First, a decomposition strategy was developed to expedite the solving procedure. Second, the approximation algorithm was utilized to solve the stochastic version of the MILP. Finally, the multi-objective model was developed to incorporate the trade-off between economical and ecological issues. All formulations were applied to a real case based on the Argentinean sugarcane industry. The tools presented are intended to help policy-makers in the strategic planning of infrastructures for chemicals production.

Steam generators in nuclear power plants experienced varying degrees of under-deposit pitting corrosion. A probabilistic model to accurately predict pitting corrosion is necessary for effective life-cycle management of steam generators. This thesis presents an advanced probabilistic model of pitting corrosion characterizing the inherent randomness of the pitting process and measurement uncertainties of the in-service inspection (ISI) data obtained from eddy current (EC) inspections. A Bayesian method is developed for estimating the model parameters. The proposed model is able to estimate the number of actual pits, the actual pit depth as well as the maximum pit depth, which is the main interest of the pitting corrosion model. A MATLAB program of the Markov chain Monte Carlo technique is developed to perform the Bayesian estimations. Simulation experiments are performed to check the behavior of the Bayesian method. Results show that the MCMC algorithm is an effective way to estimate the model parameters. Also, the effectiveness and efficiency of Bayesian modeling are validated. A comprehensive case study is also presented on the in-service inspection data of pitting corrosion in a steam generator unit. The Weibull distribution is found to be an appropriate probability distribution for modeling the actual pit depth in steam generators.