Dissertations / Theses on the topic 'Environmental chemistry Statistical methods'
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Sofer, Tamar. "Statistical Methods for High Dimensional Data in Environmental Genomics." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10403.
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In this dissertation, we propose methodology to analyze high dimensional genomics data, in which the observations have large number of outcome variables, in addition to exposure variables. In the Chapter 1, we investigate methods for genetic pathway analysis, where we have a small number of exposure variables. We propose two Canonical Correlation Analysis based methods, that select outcomes either sequentially or by screening, and show that the performance of the proposed methods depend on the correlation between the genes in the pathway. We also propose and investigate criterion for fixing the number of outcomes, and a powerful test for the exposure effect on the pathway. The methodology is applied to show that air pollution exposure affects gene methylation of a few genes from the asthma pathway. In Chapter 2, we study penalized multivariate regression as an efficient and flexible method to study the relationship between large number of covariates and multiple outcomes. We use penalized likelihood to shrink model parameters to zero and to select only the important effects. We use the Bayesian Information Criterion (BIC) to select tuning parameters for the employed penalty and show that it chooses the right tuning parameter with high probability. These are combined in the “two-stage procedure”, and asymptotic results show that it yields consistent, sparse and asymptotically normal estimator of the regression parameters. The method is illustrated on gene expression data in normal and diabetic patients. In Chapter 3 we propose a method for estimation of covariates-dependent principal components analysis (PCA) and covariance matrices. Covariates, such as smoking habits, can affect the variation in a set of gene methylation values. We develop a penalized regression method that incorporates covariates in the estimation of principal components. We show that the parameter estimates are consistent and sparse, and show that using the BIC to select the tuning parameter for the penalty functions yields good models. We also propose the scree plot residual variance criterion for selecting the number of principal components. The proposed procedure is implemented to show that the first three principal components of genes methylation in the asthma pathway are different in people who did not smoke, and people who did.
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FREITAS, SONIA MARIA DE. "STATISTICAL METHODOLOGY FOR ANALYTICAL METHODS VALIDATION APPLICABLE CHEMISTRY METROLOGY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4058@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA metodologia estatística escolhida para validação de métodos analíticos aplicável à metrologia em química é fundamental para assegurar a qualidade, comprovar a eficiência e demonstrar a exatidão dos resultados das medições nas análises químicas. Essa metodologia, desenvolvida em conformidade com o rigor metrológico, resulta num sistema de medições validado, confiável e com incertezas quantificadas. Este trabalho propõe uma metodologia geral para validação de métodos analíticos. A metodologia desenvolvida resultou de uma síntese de métodos parciais descritos na literatura, e inclui uma escolha crítica de técnicas mais adequadas dentro das alternativas existentes. A abordagem proposta combina quatro diferentes aspectos da validação: a modelagem da curva de calibração; o controle da especificidade do método; a comparação da tendência e precisão (repetitividade e precisão intermediária) do método com um método de referência; e a estimação das componentes de incerteza inerentes a todos esses aspectos. Como resultado, além de uma proposta para validação de métodos para uso em análises químicas, obtêm- se a função de calibração inversa e as incertezas expandidas, que permitem obter os resultados analíticos associados aos valores da resposta, com suas respectivas incertezas associadas. Na modelagem geral para obtenção da curva de calibração, empregam-se técnicas estatísticas para avaliação da linearidade e para o cálculo do mínimo valor detectável e do mínimo valor quantificável. A especificidade do método analítico é avaliada pela adição de padrões a um conjunto de amostras representativas e posterior recuperação dos mesmos, com ajuste por mínimos quadrados e testes de hipóteses. Para estudar a tendência e a precisão do método quando comparado a um método de referência, utiliza-se um modelo hierárquico de quatro níveis e a aproximação de Satterthwaite para determinação do número de graus de liberdade associados aos componentes de variância. As técnicas estatísticas utilizadas são ilustradas passo a passo por exemplos numéricos.
The use of statistical methodology for analytical methods validation is vital to assure that measurements have the quality level required by the goal to be attained. This thesis describes a statistical modelling approach for combining four different aspects of validation: checking the linearity of the calibration curve and compute the detection and the quantification limits; controlling the specificity of the analytical method; estimating the accuracy (trueness and precision) of the alternative method, for comparison with a reference method. The general approach is a synthesis of several partial techniques found in the literature, according to a choice of the most appropriate techniques in each case. For determination of the response function, statistical techniques are used for assessing the fitness of the regression model and for determination of the detection limit and the quantification limit. Method specificity is evaluated by adjusting a straight line between added and recovered concentrations via least squares regression and hypotheses tests on the slope and intercept. To compare a method B with a reference method A, the precision and accuracy of method B are estimated. A 4-factor nested design is employed for this purpose. The calculation of different variance estimates from the experimental data is carried out by ANOVA. The Satterthwaite approximation is used to determine the number of degrees of freedom associated with the variance components. The application of the methodology is thoroughly illustrated with step-by-step examples.
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Yansane, Alfa Ibrahim Mouke. "Statistical Methods for Panel Studies with Applications in Environmental Epidemiology." Thesis, Harvard University, 2011. http://dissertations.umi.com/gsas.harvard:10049.
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Pollution studies have sought to understand the relationships between adverse health effects and harmful exposures. Many environmental health studies are predicated on the idea that each exposure has both acute and long term health effects that need to be accurately mapped. Considerable work has been done linking air pollution to deleterious health outcomes but the underlying biological pathways and contributing sources remain difficult to identify. There are many statistical issues that arise in the exploration of these longitudinal study designs such as understanding pathways of effects, addressing missing data, and assessing the health effects of multipollutant mixtures. To this end this dissertation aims to address the afore mentioned statistical issues. Our first contribution investigates the mechanistic pathways between air pollutants and measures of cardiac electrical instability. The methods from chapter 1 propose a path analysis that would allow for the estimation of health effects according to multiple paths using structural equation models. Our second contribution recognizes that panel studies suffer from attrition over time and the loss of data can affect the analysis. Methods from Chapter 2 extend current regression calibration approaches by imputing missing data through the use of moving averages and assumed correlation structures. Our last contribution explores the use of factor analysis and two-stage hierarchical regression which are two commonly used approaches in the analysis of multipollutant mixtures. The methods from Chapter 3 attempt to compare the performance of these two existing methodologies for estimating health effects from multipollutant sources.
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Farhat, Hikmat. "Studies in computational methods for statistical mechanics of fluids." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0026/NQ50157.pdf.
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Agrawala, Gautam Kumar. "Regional ground water interpretation using multivariate statistical methods." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2007. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Lafleur, Josiane. "Hybrid microscale analytical methods for environmental analysis." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86503.
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The contamination of natural resources by human activity can have severe socio-economical impacts. Environmental analytical chemistry plays an essential role in the solving of these environmental problems. However, conventional environmental analytical procedures are generally lengthy and necessitate several steps. Hybrid microscale analytical techniques have been developed with the objective of minimizing the number of sample preparation steps, avoiding the use of organic solvents and reducing the size of the samples required for an analysis as well as increasing the speed of analyses.An Inductively Heated - Electrothermal Vaporizer (IH-ETV) was coupled to an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) to vaporize mercury from single human hair strands without any prior sample preparation, such as the destruction of its matrix by digestion. The results were comparable to those obtained with a reference method.
For samples requiring chromatographic separation, sample handling was minimized by direct coupling of the chromatographic procedure to an ICP-MS through Laser Ablation (LA). Cr3+ and Cr6+ were separated on silica gel High Performance Thin Layer Chromatography plates (HPTLC) using aqueous mobile phases. LA was used to volatilize the chromium species directly from the chromatographic stationary phase material for ICP-MS detection. This procedure allows for a rapid separation and quantification, and requires only 0.5 μL of sample.
The same procedure was used to couple miniature Solid Phase Extraction (SPE) columns implemented on centrifugal microfluidic discs to an ICP-MS to determine pre-concentrated metal chelates from drinking water. The miniature SPE devices require only 1 - 600 μL samples, allowing a reduction of three to four orders of magnitude in sample size compared to the conventional procedure, and the device requires no more than a simple motor to actuate fluid flow. The centrifugal microfluidic SPE discs can be used to perform up to eight extractions simultaneously and allow the easy storage of samples before transport to the laboratory for LA-ICP-MS analysis.
Finally, the centrifugal microfluidic SPE discs were modified to allow their coupling to absorption and fluorescence spectrometers. As well as the advantages listed above, this hyphenated system allows the in-situ screening of aquatic organic pollutants trapped on the SPE column directly in the field using simple and small light sources and detectors.
La contamination des ressources naturelles par l'activité humaine peut avoir des impacts socio-économiques graves pour les communautés qui en dépendent et la chimie analytique environnementale constitue un élément essentiel dans la résolution de ces problèmes environnementaux. Cependant, les procédés conventionnels d'analyse sont généralement longs et nécessitent plusieurs étapes. Plusieurs techniques hybrides ont été développées afin de: minimiser le nombre d'étapes nécessaires à la préparation d'un échantillon, éviter l'utilisation de solvants organiques, réduire la taille des échantillons, en plus de réduire le temps nécessaire pour compléter une analyse.
Un vaporisateur électrothermique à chauffage induit (IH-ETV) fut couplé à un plasma à couplage inductif avec détection par spectrométrie de masse (ICP-MS). Cette procédure permet de quantifier le mercure contenu dans un brin de cheveu sans aucune préparation préalable de l'échantillon, telle que la destruction de sa matrice par digestion. Les résultats obtenus sont comparables à ceux obtenus avec la méthode de référence.
Afin d'obtenir plus d'information sur la forme physico-chimiques de certains éléments, il est avantageux d'associer des techniques séparatives simples à l'ICP-MS. La chromatographie en couches minces (CCM) fut couplée directement à L'ICP-MS, à l'aide d'un système d'ablation laser (LA). Après leur spéciation sur du gel de silice à l'aide d'un éluant à base d'eau, Cr3+ et Cr6+ ont étés prélevés directement sur la phase stationnaire par LA. Cette procédure à permis la spéciation et quantification rapide du chrome à partir d'un échantillon de 0.5 µL.
La méthode LA-ICP-MS fut également utilisée pour déterminer des complexes métal-8-hydroxyquinoline préconcentrés par adsorption sur des microcolonnes d'extraction en phase solide (SPE) incorporées à des plateformes microfluidiques centrifuges. Ces dispositifs miniatures de SPE nécessitent des échantillons de 1 - 600 µL, une réduction de trois à quatre ordres de grandeur, comparativement à la méthode conventionnelle, en plus d'éliminer l'élution du complexe chélaté à l'aide d'un solvant organique. Ce dispositif permet l'extraction simultanée de huit échantillons et peut aussi servir à entreposer les échantillons durant leur transport au laboratoire pour l'analyse par LA-ICP-MS.
Finalement, ces plateformes microfluidiques ont été modifiées pour permettre le couplage avec un spectromètre d'absorption ou d'émission. En plus des avantages susmentionnés, ce dispositif permet le contrôle de polluants organiques aquatiques directement sur le site d'échantillonnage par absorbance et fluorimétrie mesurées directement sur la microcolonne SPE.
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Bell, Madison. "Developing Statistical and Analytical Methods for Untargeted Analysis of Complex Environmental Matrices." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41626.
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The main objective of this thesis was to develop statistical and analytical methods for untargeted analyses of complex environmental matrices like soil and sediment. Untargeted analyses are notoriously difficult to perform in matrices like soil and sediment because of the complexity of organic matter composition within these matrices. This thesis aimed to (1) Develop and compare extraction methods for untargeted analyses of soil and sediment while also developing data handling and quality control protocols; (2) Investigate novel applications of untargeted analyses for environmental classification and monitoring; and (3) Investigate the experimental factors that can influence the organic matter composition of untargeted extractions. CHAPTER TWO is a literature review of metabolomics protocols, and these protocols were incorporated into a proposed workflow for performing untargeted analysis in oil, soil, and sediment. This thesis contains the first application of untargeted analysis to freshwater lake sediment organic matter (i.e. sedimentomics) in CHAPTER THREE, and this has implications for discovering new biomarkers for paleolimnology (APPENDIX ONE). I demonstrated successful extraction methods for both sedimentomics and soil metabolomics studies in CHAPTER THREE and CHAPTER FIVE, respectively, using the proposed workflow from CHAPTER TWO. I also applied sedimentomics to the classification of lake sediments using machine learning and geostatistics based on sediment organic matter compositions in CHAPTER FOUR; this was a novel application of sedimentomics that could have implications for ecosystem classifications and advance our knowledge of organic matter cycling in lake sediments. Lastly, in CHAPTER FIVE I determined microbial activity, extraction method, and soil type can all influence the composition of soil organic matter extracts in soil metabolomics experiments. I also developed novel quality controls and quantitative methods that can help control these influences in CHAPTER FIVE and APPENDIX THREE. APPENDIX TWO was written in collaboration with multiple researchers and is a review of all “omics” types of analyses that can be performed on soil or sediment, and how methods like the untargeted analysis of soil and sediment organic matter can be linked with metagenomics, metatranscriptomics, and metaproteomics for a comprehensive metaphenomics analysis of soil and sediment ecosystems. In CHAPTER SIX the conclusions and implications for each chapter and overall for this thesis are detailed and I describe future directions for the field. In the end the overall conclusions of this thesis were: 1) Quality controls are necessary for sedimentomics and soil metabolomics studies, 2) Sedimentomics is a valid technique to highlight changes in sediment organic matter, 3) Soil metabolomics and sedimentomics yield more information about carbon cycling than traditional measurements, and 4) Soil metabolomics organic matter extractions are more variable and require more quality controls.
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Elayouty, Amira Sherif Mohamed. "Time and frequency domain statistical methods for high-frequency time series." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8061/.
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Advances in sensor technology enable environmental monitoring programmes to record and store measurements at high-temporal resolution over long time periods. These large volumes of high-frequency data promote an increasingly comprehensive picture of many environmental processes that would not have been accessible in the past with monthly, fortnightly or even daily sampling. However, benefiting from these increasing amounts of high-frequency data presents various challenges in terms of data processing and statistical modeling using standard methods and software tools. These challenges are attributed to the large volumes of data, the persistent and long memory serial correlation in the data, the signal to noise ratio, and the complex and time-varying dynamics and inter-relationships between the different drivers of the process at different timescales. This thesis aims at using and developing a variety of statistical methods in both the time and frequency domains to effectively explore and analyze high-frequency time series data as well as to reduce their dimensionality, with specific application to a 3 year hydrological time series. Firstly, the thesis investigates the statistical challenges of exploring, modeling and analyzing these large volumes of high-frequency time series. Thereafter, it uses and develops more advanced statistical techniques to: (i) better visualize and identify the different modes of variability and common patterns in such data, and (ii) provide a more adequate dimension reduction representation to the data, which takes into account the persistent serial dependence structure and non-stationarity in the series. Throughout the thesis, a 15-minute resolution time series of excess partial pressure of carbon dioxide (EpCO2) obtained for a small catchment in the River Dee in Scotland has been used as an illustrative data set. Understanding the bio-geochemical and hydrological drivers of EpCO 2 is very important to the assessment of the global carbon budget. Specifically, Chapters 1 and 2 present a range of advanced statistical approaches in both the time and frequency domains, including wavelet analysis and additive models, to visualize and explore temporal variations and relationships between variables for the River Dee data across the different timescales to investigate the statistical challenges posed by such data. In Chapter 3, a functional data analysis approach is employed to identify the common daily patterns of EpCO2 by means of functional principal component analysis and functional cluster analysis. The techniques used in this chapter assume independent functional data. However, in numerous applications, functional observations are serially correlated over time, e.g. where each curve represents a segment of the whole time interval. In this situation, ignoring the temporal dependence may result in an inappropriate dimension reduction of the data and inefficient inference procedures. Subsequently, the dynamic functional principal components, recently developed by Hor mann et al. (2014), are considered in Chapter 4 to account for the temporal correlation using a frequency domain approach. A specific contribution of this thesis is the extension of the methodology of dynamic functional principal components to temporally dependent functional data estimated using any type of basis functions, not only orthogonal basis functions. Based on the scores of the proposed general version of dynamic functional principal components, a novel clustering approach is proposed and used to cluster the daily curves of EpCO2 taking into account the dependence structure in the data. The dynamic functional principal components depend in their construction on the assumption of second-order stationarity, which is not a realistic assumption in most environmental applications. Therefore, in Chapter 5, a second specific contribution of this thesis is the development of a time-varying dynamic functional principal components which allows the components to vary smoothly over time. The performance of these smooth dynamic functional principal components is evaluated empirically using the EpCO2 data and using a simulation study. The simulation study compares the performance of smooth and original dynamic functional principal components under both stationary and non-stationary conditions. The smooth dynamic functional principal components have shown considerable improvement in representing non-stationary dependent functional data in smaller dimensions. Using a bootstrap inference procedure, the smooth dynamic functional principal components have been subsequently employed to investigate whether or not the spectral density and covariance structure of the functional time series under study change over time. To account for the possible changes in the covariance structure, a clustering approach based on the proposed smooth dynamic functional principal components is suggested and the results of application are discussed. Finally, Chapter 6 provides a summary of the work presented within this thesis, discusses the limitations and implications and proposes areas for future research.
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Gong, Mengyi. "Statistical methods for sparse image time series of remote-sensing lake environmental measurements." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8608/.
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Remote-sensing technology is widely used in Earth observation, from everyday weather forecasting to long-term monitoring of the air, sea and land. The remarkable coverage and resolution of remote sensing data are extremely beneficial to the investigation of environmental problems, such as the state and function of lakes under climate change. However, the attractive features of remote-sensing data bring new challenges to statistical analysis. The wide coverage and high resolution means that data are usually of large volume. The orbit track of the satellite and the occasional obscuring of the instruments due to atmospheric factors could result in substantial missing observations. Applying conventional statistical methods to this type of data can be ineffective and computationally intensive due to its volume and dimensionality. Modifications to existing methods are often required in order to incorporate the missingness. There is a great need of novel statistical approaches to tackle these challenges. This thesis aims to investigate and develop statistical approaches that can be used in the analysis of the sparse remote-sensing image time series of environmental data. Specifically, three aspects of the data are considered, (a) the high dimensionality, which is associated with the volume and the dimension of data, (b) the sparsity, in the sense of high missing percentages and (c) the spatial/temporal structures, including the patterns and the correlations. Initially, methods for temporal and spatial modelling are explored and implemented with care, e.g. harmonic regression and bivariate spline regression with residual correlation structures. In recognizing the drawbacks of these methods, functional data analysis is employed as a general approach in this thesis. Specifically, functional principal component analysis (FPCA) is used to achieve the goal of dimension reduction. Bivariate basis functions are proposed to transform the satellite image data, which typically consists of thousands/millions of pixels, into functional data with low dimensional representations. This approach has the advantage of identifying spatial variation patterns through the principal component (PC) loadings, i.e. eigenfunctions. To overcome the high missing percentages that might invalidate the standard implementation of the FPCA, the mixed model FPCA (MM-FPCA) was investigated in Chapter 3. Through estimating the PCs using a mixed effect model, the influence of sparsity could be accounted for appropriately. Data imputation can be obtained from the fitted model using the (truncated) Karhunen-Loeve expansion. The method's applicability to sparse image series is examined through a simulation study. To incorporate the temporal dependence into the MM-FPCA, a novel spatio-temporal model consisting of a state space component and a FPCA component is proposed in Chapter 4. The model, referred to as SS-FPCA in the thesis, is developed based on the dynamic spatio-temporal model framework. The SS-FPCA exploits a flexible hierarchical design with (a) a data model consisting of a time varying mean function and random component for the common spatial variation patterns formulated as the FPCA, (b) a process model specifying the type of temporal dynamic of the mean function and (c) a parameter model ensuring the identifiability of the model components. A 2-cycle alternating expectation - conditional maximization (AECM) algorithm is proposed to estimate the SS-FPCA model. The AECM algorithm allows different data augmentations and parameter combinations in various cycles within an iteration, which in this case results in analytical solutions for all the MLEs of model parameters. The algorithm uses the Kalman filter/smoother to update the system states according to the data model and the process model. Model investigations are carried out in Chapter 5, including a simulation study on a 1-dimensional space to assess the performance of the model and the algorithm. This is accompanied by a brief summary of the asymptotic results of the EM-type algorithm, some of which can be used to approximate the standard errors of model estimates. Applications of the MM-FPCA and SS-FPCA to the remote-sensing lake surface water temperature and Chlorophyll data of Lake Victoria (obtained from the European Space Agency's Envisat mission) are presented at the end of Chapter 3 and 5. Remarks on the implications and limitations of these two methods are provided in Chapter 6, along with the potential future extensions of both methods. The Appendices provide some additional theorems, computation and derivation details of the methods investigated in the thesis.
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Zibdeh, Hazim S. "Environmental thermal stresses as a first passage problem." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/49971.
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Due to changes of the thermal environment, thermal stresses are produced in structures. Two approaches based on the stochastic process theory are used to describe this phenomenon.
The structure is idealized as a long hollow viscoelastic cylinder. Two sites are considered: Barrow (AK) and Yuma (AZ).
First passage concepts are applied to characterize the reliability of the system. Crossings are assumed to follow either the behavior of the Poisson process or Markov process. In both cases, the distribution of the time to first passage is taken to be the exponential distribution.
Because the material is viscoelastic, statistically and time varying barriers (strengths) with Normal, Log-Normal, or Neibull distributions are considered. Degradation of the barriers by aging and cumulative damage are incorporated in the analysis.Ph. D.
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Correia, Andrew William. "Estimating the Health Effects of Environmental Exposures: Statistical Methods for the Analysis of Spatio-temporal Data." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10828.
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In the field of environmental epidemiology, there is a great deal of care required in constructing models that accurately estimate the effects of environmental exposures on human health. This is because the nature of the data that is available to researchers to estimate these effects is almost always observational in nature, making it difficult to adequately control for all potential confounders - both measured and unmeasured. Here, we tackle three different problems in which the goal is to accurately estimate the effect of an environmental exposure on various health outcomes.
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Wu, Jian, and 武健. "Discriminative speaker adaptation and environmental robustness in automatic speech recognition." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31246138.
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Goodpaster, Aaron M. "Statistical Analysis Methods Development for Nuclear Magnetic Resonance and Liquid Chromatography/Mass Spectroscopy Based Metabonomics Research." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1312317652.
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Parsons, Robert Lee. "Assessment and optimization of site characterization and monitoring activities using geostatistical methods within a geographic information systems environment." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/32847.
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Wang, Yaoping. "Statistical Downscaling along the US Eastern Coast by Two Methods with Application on Intensity-Duration-Frequency curve Changes." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417824178.
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Woocay-Prieto, Arturo. "Groundwater hydrochemical facies, flowpaths and recharge determined by multivariate statistical, isotopic and chloride mass-balance methods." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Sutterlin, William R. "Using environmental chemistry technologies for the removal of arsenic from drinking water, and fat and oil based phase change materials for thermal energy storage /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p3137754.
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Zhang, Nianliu. "Understanding Environmental Reactions of Carbon Tetrachloride, Trichloroethylene, Perchloroethylene, and Arsenic Applying Computational Chemistry Methods." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195287.
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In recent years, as the progress of computational abilities has increased, computational chemistry has become an interesting tool for researchers for investigating mechanisms of environmental reactions when results of experimental explorations are not sufficiently clear. In this research, several environmental reactions have been investigated using ab initio and density functional theory (DFT) methods.This research investigated the effect of the reaction energy on the reaction pathway for C-Cl bond cleavage in carbon tetrachloride (CT). Ab initio and density functional theories were used to study adiabatic electron transfer to aqueous phase CT. The potential energies associated with fragmentation of the CT anion radical into a trichloromethyl radical and a chloride ion were explored as a function of the C-Cl bond distance during cleavage. The effect of aqueous solvation was simulated using a continuum conductor-like screening model. Solvation significantly lowered the energies of the reaction products, indicating that the dissociative electron transfer was enhanced by solvation. It was found that reductive dissociation electron transfer of CT undergoes a change from an inner-sphere to an outer-sphere mechanism as the reaction energy is increased. The results showed a liner relationship between the activation energy for the dissociation and the overall energy change, which is in good agreement with the results of the Marcus model.This research also investigated the thermodynamic favorability and resulting structures for chemisorption of trichloroethylene (TCE) and perchloroethylene (PCE) on iron surfaces using periodic DFT with the non-local Perdew-Burke-Enzerhof (PBE) functional. Chemisorption structures were obtained for four physically adsorbed initial configurations. An initial configuration with two carbons (C-bridge) physically adsorbed at bridge sites between adjacent iron atoms was shown to be the most stable configuration for TCE, while the mode with two carbons (C-hollow) physically adsorbed at hollow site was verified to be the most stable configuration for PCE. C-Fe bonds were formed via sigma or pi bonds in the complexes formed at C-bridge, top and hollow site. Upon binding with the iron surface, the interaction of the C=C bond still remained as sp2 hybridization. Moreover, the strong chemisorption induced dissociations of C-Cl bonds and formation of Cl-Fe bonds. For both TCE and PCE, modes with two Cl atoms (Cl-bridge) physically adsorbed at bridge sites were found to be the least favorable configuration, in which only two Cl atoms formed bonds with the Fe surface and no C-Fe bonds were formed. Negative net Mulliken charges on TCE and PCE indicated they are reduced upon adsorption to the iron surface.Finally, in this research, we evaluated the accuracies and costs of several DFT methods including Harris, PWC LDA, and BLYP GGA functionals for interaction of arsenite with ferric hydroxides by comparison to calculated and experimental properties of surface complexes. It was found that the approach of using low-level structures coupled with high level single-point energies was much less expensive than the approach of using high level functionals for both structures and energies and could obtain similar computed binding energies. Further work has been done to investigate the appropriate models for interaction of arsenite with ferric hydroxide between pH values of -4 through +4. The effect of solvation on single point energy was calculated using COSMO models. The bidentate corner-sharing complexes were more energetically favorable than monodentate corner-sharing complexes for the entire pH range. Lower binding energies at some pH values indicated monodentate binding may contribute to adsorption at low pH values and at high pH values. Adsorbed arsenite species were found to be fully protonated at low pH values and partly protonated at high pH values for the most favorable complex. Models for the interaction of arsenite with ferric hydroxide provided a relationship of adsorption and pH values that the adsorption of arsenite increased as pH value increased and there was a maximum point around pH 8.5-9.
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Gabrielsson, Jon. "Multivariate methods in tablet formulation." Doctoral thesis, Umeå : Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-268.
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Al-Masri, Mohammad Said. "Radiochemical methods for the determination of some naturally occurring alpha emitters in environmental aqueous samples." Thesis, University of Salford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386455.
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Campbell, Steven John. "Novel methods to characterise atmospherically relevant organic radicals and reactive oxygen species." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274099.
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A key reaction in the troposphere involves the oxidation of biogenic and anthropogenic alkenes with ozone, which contributes to local photochemical smog. It is generally accepted that this reaction proceeds via a reactive intermediate often called the Criegee intermediate (CI). This reaction is known to produce a plethora of oxidised organic compounds, which contribute to ozone formation and secondary organic aerosol production, two of the main characteristics of a polluted atmosphere. Furthermore, epidemiological studies have shown a close correlation between exposure to ambient organic aerosol and adverse human health effects. The toxicological mechanisms leading to this observation are still poorly characterised, although studies suggest that reactive oxygen species present in organic aerosol are a major contributor. Reactive oxygen species and reactive intermediates represent a large uncertainty in tropospheric chemistry, and pose an analytical challenge due to their high reactivity and typically low concentrations. This emphasises the need for the development of new methods to characterise the chemistry of these species. In this thesis, several novel laboratory based techniques have been developed in order to characterise and quantify reactive intermediates and reactive oxygen species. New methods to facilitate the detection of CIs in both the gas and particle phase are presented. Spin trap molecules are used to scavenge CIs to form stable 1:1 adducts which are subsequently detected and quantified using mass spectrometry. The chemistry of CIs with spin traps is extensively investigated. The unique capability of this technique to simultaneously characterise multiple CIs generated from a variety of atmospherically relevant organic precursors in the gas phase is demonstrated. This technique was further developed to facilitate the detection of CIs in secondary organic aerosol, representing the development of a method capable of characterising low volatility CIs and other reactive intermediates in the condensed phase. Furthermore, two new chemical fluorescence assays have been developed to quantify both organic radicals and reactive oxygen species in organic aerosol. A novel profluorescent spin trap assay was applied to quantify radical concentrations in organic aerosol. A series of experiments were then devised to investigate the lifetime of organic radicals in secondary organic aerosol. A second assay, based on physiologically relevant ascorbic acid chemistry, was also developed to measure the concentrations of toxicologically relevant reactive oxygen species in secondary organic aerosol. The quantitative capability of this assay was extensively characterised. The assay was incorporated into a prototype instrument capable of measuring particle-bound reactive oxygen species on-line, and the assays’ sensitivity to secondary organic aerosol was demonstrated.
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Hartley, William. "A study of novel methods for the in situ remediation of arsenic contaminated soils." Thesis, Liverpool John Moores University, 2002. http://researchonline.ljmu.ac.uk/4998/.
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Wang, Bo. "Novel statistical methods for evaluation of metabolic biomarkers applied to human cancer cell lines." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1399046331.
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Ganti, Satyakala. "DEVELOPMENT OF HPLC METHODS FOR PHARMACEUTICALLY RELEVANT MOLECULES; METHOD TRANSFER TO UPLC: COMPARING METHODS STATISTICALLY FOR EQUIVALENCE." Diss., Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/118587.
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ChemistryPh.D.
High Pressure Liquid Chromatography (HPLC) is a well-known and widely used analytical technique which is prevalent throughout the pharmaceutical industry as a research tool. Despite its prominence HPLC possesses some disadvantages, most notably slow analysis time and large consumption of organic solvents. Ultra Pressure Liquid Chromatography (UPLC) is a relatively new technique which offers the same separation capabilities of HPLC with the added benefits of reduced run time and lower solvent consumption. One of the key developments which facilitate the new UPLC technology is sub 2-µm particles used as column packing material. These particles allow for higher operating pressures and increased flow rates while still providing strong separation. Although UPLC technology has been available since early 2000, few laboratories have embraced the new technology as an alternative to HPLC. Besides the resistance to investing in new capital, another major roadblock is converting existing HPLC methodology to UPLC without disruption. This research provides a framework for converting existing HPLC methods to UPLC. An existing HPLC method for analysis of Galantamine hydrobromide was converted to UPLC and validated according to ICH guidelines. A series of statistical evaluations on the validation data were performed to prove the equivalency between the original HPLC and the new UPLC method. This research presents this novel statistical strategy which can be applied to any two methodologies to determine parity.
Temple University--Theses
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Larsen, Joshua. "Pore Scale Computational Fluid Dynamic Modeling| Approaches for Permeability Modeling and Particle Tracking Using Lattice Boltzmann Methods." Thesis, The University of Arizona, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10978423.
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Knowledge of colloid mobility is important for understanding nutrient cycling, the transport of some contaminants, and for developing environmental remediation systems such as geologic filters. The interaction forces between colloids and soil materials are central to colloid transport and immobilization. These forces act at the microscale (nanometers to microns) and include: fluid drag (friction), Brownian motion, gravity and buoyancy, and fluid chemical forces (including DLVO and van der Waals mechanisms). Most vadose zone studies, however, consider colloids at the continuum scale in terms of solute transport mechanisms using parametrized forms of the advection-dispersion equation and absorption isotherms. A comprehensive, generally applicable, well-documented and publicly available framework for simulating colloids at the microscale is still lacking.
Colloid transport and mobility are mechanisms that fundamentally occur at the microscale. As such, representation of the pore-structure needs to be obtained that is meaningful for the pore-scale fluid flow field and colloid mobility (pore-scale colloidal force balances cause the colloidal transport field to be different from the fluid flow field). At the same time, the pore-structure needs to be relevant for continuum-scale experiments or simulations. There are two ways by which a pore-structure can be obtained: by direct three-dimensional imaging (typically with x-ray tomographic techniques) or by reconstruction techniques that yield a synthetic, but presumably representative, pore-structure. Both techniques are examined in this dissertation, but the synthetic route must be used if little micro-scale information is available.
This dissertation addresses three main objectives. In chapter 2 it addresses the relation between image quality obtained with two different x-ray tomography techniques (a synchrotron and an industrial scanner) and the obtained flow field. Chapter 3 discusses the development of the LB-Colloids software package, while chapter 4 applies the code to data obtained from a breakthrough experiment of nanoparticulate TiO2.
In chapter 2, pore-scale flow fields for Berea sand stone and a macropore soil sample were obtained with lattice Boltzmann simulations which were volume-averaged to a sample-scale permeability and verified with an observed sample-scale permeability. In addition, the lattice Boltzmann simulations were verified with a Kozeny-Carman equation. Results indicate that the simulated flow field strongly depends on the quality of the x-ray tomographic imagery and the segmentation algorithm used to convert gray-scale tomography data into binary pore-structures. More complex or advanced segmentation algorithms do not necessarily produce better segmentations when dealing with ambiguous imagery. It was found that the KC equation provided a reliable initial assessment of error when predicting permeability and can be used as a quick evaluation of whether simulations of the micro-scale flow field should be pursued. In the context of this study, this chapter indicated that LB is able to generate relevant pore-scale flow fields that represent sample-scale permeabilities. However, because the remainder of the study was focused on the development of a pore-scale colloid mobility framework we decided to focus primarily on synthetically-generated pore-structures. This also allowed us to focus on actual mechanisms that were free of imaging and segmentation artifacts.
Chapter 3 discusses the development of the LB-Colloids package. This simulation framework is able to simulate large collections of individual colloids through pore representations and porous media. The general workflow for users is as follows: 1) Obtain a pore structure by tomographic imaging or by synthetic means. The latter can be accomplished though the included PSPHERE module which is able to generate a random porous medium using user-supplied porosity and particle size. 2) The pore-scale fluid flow field in the porous medium is generated with a lattice Boltzmann method and a user-specified body force that controls the volume averaged Darcy velocity. 3) Mobility and attachment/detachment of colloids is simulated by accounting of the force balance (fluid drag, Brownian motion, gravity and buoyancy forces, and fluid-chemical forces including DLVO and van der Waals mechanisms). Colloid mobility is carried out at a submicron to nanometer scale and requires grid refinement of the LB flow field. To speed up computations the fluid-chemical forces are precomputed for every grid cell.
Because of computational considerations, the LB-Colloids package is presently only able to deal with 2D representations of the porous medium. Code-development and testing (chapter 4) would have taken too long for a full 3D approach. The main draw-back of the 2D approach is that these cannot accurately represent 3D pore-structures. However, no fundamental “new” mechanisms are needed for a 3D approach and we expect that this can be easily built into the clean and well-documented LB-colloids code. The LB-Colloids framework is applied on data obtained from a break-through experiment of TiO2 nanoparticles. (Abstract shortened by ProQuest.)
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Abu, Hmeidan Hani Yousef. "Characterizing Current and Geologic Phosphorus in Utah Lake Sediment Using Field Samples, Laboratory Methods, and Statistical Analysis: Implications for Water Quality Issues." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6696.
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Phosphorus is an essential nutrient for aquatic life forms and plays a major role in the algae blooms that occur in lakes and reservoirs. It is considered a primary limiting nutrient of phytoplankton growth in streams, lakes, and reservoirs. Excess amounts of phosphorous may cause excess growth and biomass of algae. If phosphorus is available in excess, often from sewage and industrial discharges, the high levels in a lake or reservoir can lead to eutrophication. Utah Lake is a shallow, basin-bottom lake in a semi-arid climate with sediments that are thousands of feet thick. Starting 165 years ago, humans have been discharging wastewater into Utah Lake, which in our day has raised serious questions on how the state can mitigate the negative effects of the external nutrient loading. Even though Utah Lake receives a significant amount of anthropogenic phosphorous, there are high levels of phosphorous in geologic deposits in the area, providing a long-term natural source. This study intends to provide data on the current distribution of phosphorous in lake sediments, potential for that phosphorous to be released into the water column affecting phytoplankton growth, and how historic lake sediment phosphorous levels compare to the levels in current sediments. Sediments play an important role in the overall metabolism of shallow lakes. They supply the water column with phosphorus and must be considered as they serve as a sink and source. More than 50 branches of surface flow discharge into Utah Lake, 15 of which are major. Based on previous data, a positive retention of phosphorus from these branches occurs in the lake, of which the sediment plays a role. Phosphorus release from sediment occurs under very complicated processes under many different conditions. Some main influential factors include the iron and calcium content, redox potential, microbial processes, turbidity, sediment resuspension, temperature, and pH. In this study, I analyzed 85 sediment samples sampled across Utah Lake for total phosphorus. I created Geospatial maps to show the phosphorous distribution. The data showed an average phosphorus level of 666 ppm and varied in distribution throughout the lake, though the majority of the lake had levels in the 600 to 800 ppm range. There were a few samples, which had lower total phosphorus levels, in the 200 to 300 ppm range. Based on the map, I found that these lower values were in locations representing potential springs. I hypothesize that this underground water source leached some of the phosphorous from the sediments in these areas. I found that total phosphorus concentrations in current lake sediment are quite similar to phosphorus levels in historic lake sediments levels. I also performed laboratory experiments to characterize sediment-water interactions and estimate the amount of phosphorus that could be released from lake sediments to the water column.
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Palagama, Dilrukshika S. W. "Development of Liquid Chromatography-Mass Spectrometry Methods for Identification and Quantification of Microcystins in Water and Biological Fluids, and their Removal from Water." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1544703858711738.
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Salley, Devon Mr. "Advancing Methods to Measure the Atmospheric CO2 Sink from Carbonate Rock Weathering." TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1603.
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With rising atmospheric CO2 concentrations, a detailed understanding of processes that impact atmospheric CO2 fluxes is required. While a sink of atmospheric carbon from the continents to the ocean from carbonate mineral weathering is, to some degree, offset by carbonate mineral precipitation in the oceans, efforts are underway to make direct measurements of these fluxes. Measurement of the continental sink has two parts: 1) measurement of the dissolved inorganic carbon (DIC) flux leaving a river basin, and 2) partitioning the inorganic carbon flux between the amount removed from the atmosphere and the portion from the bedrock. This study attempted to improve methods to measure the DIC flux using existing data to estimate the DIC flux from carbonate weathering within the limestone karst region of south central Kentucky. The DIC flux from the Barren River drainage basin upstream from Bowling Green in southern Kentucky and northern Tennessee, and the upper Green River drainage basin, upstream from Greensburg, Kentucky, was measured, each for a year, using U.S.G.S. discharge data and water-chemistry data from municipal water plants. A value of the (DIC) flux, normalized by time and area of carbonate rock, of 4.29 g km-3 day-1 was obtained for the Barren River, and 4.95 kg km-3 for the Green. These compared favorably with data obtained by Osterhoudt (2014) from two nested basins in the upper Green River with values of 5.66 kg km-3 day-1 and 5.82 kg km-3 day-1 upstream from Greensburg and Munfordville, respectively. Additional normalization of the values obtained in this study
by average precipitation minus evapotranspiration over the area of carbonate rock, or water available for carbonate dissolution, resulted in values of 5.61x107 g C (km3 H20)- 1 day-1 (grams of carbon per cubic kilometer of water, per day) for the Barren, and 7.43x107g C (km3 H20)-1 day-1 for the Green River. Furthermore, a statistical relationship between the total DIC flux and time-volume of water available for dissolution has been observed, yielding an r2 value of 0.9478. This relationship indicates that the primary variables affecting DIC flux for these drainage basins are time and the volume of water available for dissolution.
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Scott, Andersson Åsa. "Development of an Environment-Accident Index : A planning tool to protect the environment in case of a chemical spill." Doctoral thesis, Umeå universitet, Kemi, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-178.
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The increasing mass and complexity of chemicals being produced and transported has resulted in more rigorous demands on both authorities as well as chemical-handling industries to assess the risks involved. The Environment-Accident Index (EAI), has been proposed as a planning tool created as an equation in which chemical properties (variables describing the chemical involved) are combined with site-specific properties (variables describing the accident site). The EAI is intended to facilitate assessment of the environmental effects related to chemical accident scenarios and hence assist the organisation of preventative programs. The main objective of the work described in this thesis was to evaluate, develop and improve the proposed EAI. The steps involved in the development process included I) evaluation of the feasibility of the EAI approach, II) selection of a representative and diverse set of chemical accidents to be used in the development III) the use of questionnaires and expert judgements to develop response values for environmental effects of a chemical accident, and IV) to create a new EAI model using multivariate modelling (PLS). The EAI approach proved to be useful in the work to protect the environment in case of a chemical accident. A representative set of accidents was selected by means of statistical multivariate design (PCA) based on assembled data related to a set of 55 chemical accidents. The selection generated a set of accidents representing a diverse spectrum of chemical accident scenarios. To develop a measure of environmental effects of the chemical accidents i.e. responses, an expert panel was asked to judge their environmental effects (such as effects on animal life in the aquatic or terrestrial environment). The results showed that the judgements give a rough estimate of environmental effects that could be used as responses in the development of the EAI. The developed responses were then related to the chemical and site-specific properties to create a new EAI model. This resulted in a PLS-based EAI connected to a new classification scale. The advantages of the new EAI are that it can be calculated without the use of tables; it can estimate the effects for all included responses, and make a rough classification of chemical accidents according to the new classification scale. Finally, the new EAI is a more stable model than the previously proposed EAI, and it is founded on a valid base of accident scenarios, making its use for a variety of chemicals and situations more reliable since it covers a broader spectrum of accident scenarios. The new EAI can be expressed as a regression model to facilitate calculation of the index for people that do not have access to PLS. The highest priorities for further refining the new EAI in the future are: external validation of the EAI; further refinement of the formula’s structure; adjustment of the new classification scale; and real-life evaluation of the EAI.
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Salih, Isam M. Musa. "Radon in natural waters : Analytical Methods; Correlation to Environmental Parameters; Radiation Dose Estimation; and GIS Applications." Doctoral thesis, Linköpings universitet, Medicinsk radiofysik, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5221.
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Investigations of radon in natural water and its relation to physical and chemical parameters are outlined in this thesis. In particular, a method for measuring 222Rn in water at low concentrations (~20 mBq.l-1) is described, followed by discussions concerning the design and its application to study both radon and parameters influencing radon levels in natural waters. A topic considered is the impact of fluoride and other aquatic parameters on radon in water. Moreover, variables such as uranium series radionuclides and stable elements in water, bedrock and sediment radioactivity and geology are investigated in two case studies. This was performed by employing radiometric-, chemical-, statistical- and GIS & geostatistical- analyses. The general water chemistry and presence of some elements such as fluoride was observed to influence radon levels in water. Health aspects of radon in drinking water are discussed based on radiation dose assessments. The radiation doses are compared with and added to doses incurred from ingestion of uranium, radium and polonium isotopes in drinking water and inhalation of radon in air in order to estimate total exposures for different age categories. The results may have a potential for future epidemiological studies.
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Steinberg, Rebecca M. "Predicting Post-Mining Hydrologic Effects of Underground Coal Mines in Ohio throughMultivariate Statistical Analyses and GIS Tool Building." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1555429886192267.
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Miller, Benjamin Verlinden. "The Hydrology of the Carroll Cave-Toronto Springs System: Identifying and Examining Source Mixing through Dye Tracing, Geochemical Monitoring, Seepage Runs, and Statistical Methods." TopSCHOLAR®, 2010. http://digitalcommons.wku.edu/theses/216.
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In karst areas relationships between activities occurring on the surface and the overall health of the subsurface environment are often highly interconnected. However, the complex nature of karst flow systems can often make identification of these connections difficult. Carroll Cave, a large stream cave system located in the central Missouri Ozarks, is known for its biological and speleological significance. A dye tracing project to delineate a Carroll Cave recharge area through dye tracing has identified an area of 18.5 km2 which contributes water to the cave. The water from Thunder River within Carroll Cave was positively traced to eight springs of the thirteen springs at a distributary spring system known as Toronto Springs. Through examination of the geochemistry of the individual springs, differences in water chemistry between the various outlets has become evident. Additional work with YSI Sonde dataloggers and consideration of carbonate chemistry relationships has sought to further define the variations in hydrochemical behavior, thus aiding in the discrimination potential spring sources. Primary sources thought to contribute water to the spring system include Carroll Cave and Wet Glaize Creek, with some minor influence from other losing streams in the vicinity. Seepage runs along Wet Glaize Creek have also identified major losing reaches, in close proximity to structural features, which may contribute water to Toronto Springs. Examination of the measured parameters and derived have identified that Carroll Cave and Wet Glaize Creek are the primary end members for Ca2+, Mg2+, HCO3-, specific conductance, and temperature. Using these parameters a two end member mixing model has been developed which describes the mixing zone setting at Toronto Springs and calculates the average proportions of flow contributions by the end members. By using a multi-proxy approach of dye tracing, seepage runs, and geochemistry for the individual springs, the source waters and pathways for the springs at Toronto Springs have been identified.
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Farthing, Brendan J. "Statistical aspects in the design and analysis of long term ecological monitoring efforts." Thesis, Queensland University of Technology, 2002. https://eprints.qut.edu.au/37118/1/37118_Farthing_2002.pdf.
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There is increasing public concern about the health of our environment and the burden placed on it by the way the world uses its natural resources. This requires
decisions be made about the best manner to care for these resources. To make these decisions, long term ecological monitoring efforts are necessary as they provide
decision makers with accurate information concerning the status of measures in time. The planning of such efforts is a study of decision making in itself. This thesis has considered ways in which those responsible for the planning of long term ecological monitoring surveys can go about this process. To start, the concept of a
Decision Support System (DSS) is explored. This provides a framework under which a number of alternative decisions may be considered and the best one chosen to solve
a problem. We then move on to model based methods for survey design, using the DSS concept to varying degrees. This involves specifying a model for data analysis
and then designing a sampling scheme to best estimate parameters of interest under
this model. One such method is to consider the power of a linear regression to detect changes in a variable over time (Gerrodette 1987). This is explored and extended
upon, but it was found that some assumptions underlying the procedure may be violated in practice. In an attempt to rectify such violations a Bayesian spatiotemporal
model was developed and applied to a real data set from the Queensland Department of Natural Resources (QDNR). Three approaches that use the output of this model to help design future schemes are then discussed. The first being a
survey sampling approach similar to the power analysis approach already explored.
The second is a simulation method, in which a hypothetical data set is sampled and modelled in an effort to select the best procedure for the decision to be made. The final approach is Bayesian survey design which closely follows the ideas of Bayesian
experimental design (Chaloner & Verdinelli 1995). The aim of this approach is to select a plan that maximises a utility function which assigns a value of worth to
various decisions outcomes. In this way, the decision-theoretic principles of a DSS are satisfied. This may be the best manner to proceed with the planning of a future
survey design, however it is a mathematically and numerically challenging exercise.
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Pham, Minh H. "Signal Detection of Adverse Drug Reaction using the Adverse Event Reporting System: Literature Review and Novel Methods." Scholar Commons, 2018. http://scholarcommons.usf.edu/etd/7218.
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One of the objectives of the U.S. Food and Drug Administration is to protect the public health through post-marketing drug safety surveillance, also known as Pharmacovigilance. An inexpensive and efficient method to inspect post-marketing drug safety is to use data mining algorithms on electronic health records to discover associations between drugs and adverse events.
The purpose of this study is two-fold. First, we review the methods and algorithms proposed in the literature for identifying association drug interactions to an adverse event and discuss their advantages and drawbacks. Second, we attempt to adapt some novel methods that have been used in comparable problems such as the genome-wide association studies and the market-basket problems. Most of the common methods in the drug-adverse event problem have univariate structure and thus are vulnerable to give false positive when certain drugs are usually co-prescribed. Therefore, we will study applicability of multivariate methods in the literature such as Logistic Regression and Regression-adjusted Gamma-Poisson Shrinkage Model for the association studies. We also adopted Random Forest and Monte Carlo Logic Regression from the genome-wide association study to our problem because of their ability to detect inherent interactions. We have built a computer program for the Regression-adjusted Gamma Poisson Shrinkage model, which was proposed by DuMouchel in 2013 but has not been made available in any public software package. A comparison study between popular methods and the proposed new methods is presented in this study.
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Olsen, Jacob Milton. "Measuring and Calculating Current Atmospheric Phosphorous and Nitrogen Loadings on Utah Lake Using Field Samples, Laboratory Methods, and Statistical Analysis: Implication for Water Quality Issues." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6765.
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Atmospheric nutrient loading and transport though precipitation and dry deposition is one of the least understood yet one of the most important pathways of nutrient transport into many lakes. These nutrients, phosphorus and nitrogen, are essential for aquatic life and often play major roles in algae blooms that occur in lakes and reservoirs. Often heavy algal growth intensifies a variety of water quality problems. Utah Lake may be even more susceptible to atmospheric deposition due to its large surface area to volume ratio and proximity to Great Basin dust sources. In this study, eight months of atmospheric deposition data were collected and analyzed from five locations near Utah Lake. Geospatial maps were created to show the temporal distribution of phosphorus and nitrogen. Evaluation of the atmospheric deposition results indicate that between 8 to 350 tons of total phosphorus and 46 to 460 tons of dissolved inorganic nitrogen were deposited onto the surface of Utah Lake over an eight-month period. Both estimates were based on assuming that the deposition decreased exponentially from the sampling station to the middle of the lake. The large difference results from using only samples with no visible particles or insects present to give the low estimate and all samples to give the high estimate. These nutrient loading values are very significant in that it has been estimated that only about 17 tons year-1 of phosphorus and about 200 tons year-1 of nitrogen are needed to support a eutrophic level of algal growth in Utah Lake. Atmospheric deposition was found to be a major contributor in providing a eutrophic nutrient load to Utah Lake. Further, it is likely that the actual deposition loading is much higher than 8 tons per 8 months thus indicating that deposition alone adds a eutrophic phosphorus loading to the lake. Since conditions are similar in much of the Great Basin and other areas of Western United States, this seems to be a very significant finding relative to nutrient evaluation and feasible management scenarios. The results also indicate that one might expect to see more cyanobacteria blooms (Harmful Algal Blooms) in shallow ponds in this area if atmospheric deposition is the main source of nutrients, since N to P ratios are low and thus more situations arise where a shortage of ionic nitrogen favors these nitrogen-fixing cyanobacteria.
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Geng, Dawei. "Gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry methods for the determination of environmental contaminants." Doctoral thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-51727.
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The recent developments and improvements of instrumental methods for the analyses of the environmental contaminants, especially the persistent organic pollutants (POPs), have made it possible to detect and quantify these at very low concentrations in environmental and biotic matrices. The main objective of this thesis is to demonstrate the capability of the atmospheric pressure chemical ionization technique (APCI), using gas chromatography coupled to tandem mass spectrometry for the determination of a wide range of environmental contaminants, including the POPs regulated by Stockholm Convention, such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), but also the derivates of PBDEs and novel brominated flame retardants (NBFRs). The APCI was operated in charge transfer condition, preferably producing molecular ions. Multiple reaction monitoring (MRM) experiments were optimized by adjusting cone voltage, collision energy and dwell time. Optimization of source parameters, such as gas flows and temperatures was also performed. Low concentration standards were analyzed, achieving a visible chromatographic peak for 2 fg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) demonstrating the excellent sensitivity of the system. Adequate linearity and repeatability were observed for all the studied compounds. The performance of APCI methods was validated against the conventional methods using gas chromatography coupled to high resolution mass spectrometry for chlorinated compounds in a wide range of matrices including environmental, air, human and food matrices. The GC-APCI-MS/MS method was successfully applied to a set of 75 human serum samples to study the circulating levels of POPs in epidemiologic studies. Moreover the method was utilized to establish temporal trends of POPs in osprey eggs samples collected during the past five decades.
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Rocha, Flavio Roberto. "Desenvolvimento e aplicação de métodos eletroanalíticos em fluxo para determinação de traços de H2O2, HSO3- e hidroximetanosulfonato na fase líquida da atmosfera." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-27112015-130934/.
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Visando a determinação de baixas concentrações de H2O2, HSO3- e Hidroximetanosulfonato (HMS) em água de chuva, desenvolveu-se novos métodos amperométricos em fluxo com detecção em eletrodo de gota pendente de mercúrio. A determinação analítica de H2O2 baseou-se na sua oxidação (reversível) em meio alcalino (NaOH 11mM), no potencial de -0,07V vs Ag/AgCI, em célula de fluxo adaptada a polarógrafo comercial. O limite de detecção foi 0,1 µM. Para obter melhor seletividade, utilizou-se medidas diferenciais com e sem adição da enzima catalase. Para o HSO3- mostrou-se mais favorável sua redução a -0,8V, em meio ácido (tampão de HAc/Ac· 12/12mM). A interferência do oxigênio dissolvido foi eliminada por desgaseificação contínua com nova versão de dispositivo anteriormente desenvolvido. A corrente residual foi determinada mascarando o sinal do HSO3- por adição de HCHO. O HM:S foi determinado indiretamente. Após sua decomposição em HSO3- e HCHO, em pH em tomo de 12, reverteu-se o pH do fluxo para meio ácido e procedeu-se a determinação do HSO3- liberado. Aplicou-se as metodologias desenvolvidas às amostras de água de chuva, durante período de 12 meses. Foram observadas variações das concentrações das referidas espécies químicas em diversos eventos de precipitações, acompanhando-se o ciclo das estações climáticas e a intensidade da radiação solar. As concentrações de H2O2 variaram entre 0,3 a 34µM, HSO3- não foi encontrado no período, enquanto HMS apresentou concentrações entre 0,1 e 1,5µM.Aiming the detennination of traces of H2O2, HSO3- an hydroximethanesulfonate (HMS) in rain water, a new flow method was developed, with amperometric detection at the hanging mercury drop electrode. The analytical detennination of H2O2 was based on its (reversible) oxidation in alkaline mediwn (NaOH 11 mM), by fitting a new flow adapter to a commercial multimode stand with the electrode operated as HMDE at -0.07V versus Ag/AgCl. Detection limit was 0.1µM. To increase selectivity, differential measurements were done by subtracting the residual current after destruction of the analyte with the enzyme catalase. For the determination of HSO3-, results were more favorable for its reduction at -0.8V in acidic medium (HAc/Ac-) buffer, 12mM/12mM). The residual current was determined by masking the HSO3- signal with HCHO. HMS was determined indirectly. After its decomposition in alkaline medium (pH around 12) into SO3-2 and HCHO, the pH is lowered to 1.5 before detection of the HSO3-. Interference of oxygen was overcome by in-line degassing with a new two channel version of a previously described vacuum operated permeation device. The new methods were applied to rain samples collected during a one year period. Concentration of H2O2 ranged from 0.3 to 34µM. HSO3- was not detected during the period and HMS appeared at concentrations between 0.1 to 1.5µM. Although difficult to interpret, the results show correlation with intensity of solar radiation and, less clearly, with the seasons of the year.
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Hoi, Ka In. "Enhancement of efficiency and robustness of Kalman filter based statistical air quality models by using Bayesian approach." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2488003.
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Lewtas, Paul. "Investigation of interferences and development of pre-treatment methods for arsenic analysis by Anodic Stripping Voltammetry." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2015. https://ro.ecu.edu.au/theses/1590.
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Contamination of drinking water is a serious health issue in many developing countries and there is a recognised need for low cost portable systems that are capable of analysing drinking water down to low ppb levels. Anodic Stripping Voltammetry (ASV) instruments meet these requirements but suffer interferences from other species which may also be present in the sample, particularly organics, other metals and sulfides. The last of these has received surprisingly little attention in the literature, despite being a proven interferent.
This study investigates the impact of each of these interference types, as well as a number of traditional and novel techniques in resolving them in a three phase process. First, each interferent was evaluated individually to determine the concentration at which it would significantly and reliably cause significant errors in the determination of arsenic by ASV. Secondly, each individual interferent was subjected to a number of pretreatments to determine the most suitable pretreatment method to remove that interference. Thirdly, a combined pretreatment method, capable of pretreating a single sample contaminated with significant levels of all three interferent types was developed and tested.
Modifications to the basic analysis methodology provided by the instrument manufacturer had to be made, particularly in the elimination of residual interferents affecting clean test solutions analysed after a contaminated test solution. A number of pretreatment methods were successful for sulfide contamination, however only the ion exchange resin was reliably successful for copper interference and only UV digestion was totally successful for organic contamination at the levels investigated. Although other pretreatment methods did partially improve the response of test solutions contaminated with the organic interferent,their performance was not sufficient to consider them for the final combined pretreatment method. The final combined pretreatment method for all three interferences was successfully tested on artificial sample solutions.
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Dahl, Joakim. "Detection of human-induced stress in streams : comparison of bioassessment approaches using macroinvertebrates /." Uppsala : Dept. of Environmental Assessment, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/s332.pdf.
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Eriksson, Sune. "Acrylamide in food products : Identification, formation and analytical methodology." Doctoral thesis, Stockholm : Dept of environmental chemistry, Stockholm university, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-700.
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Dai, Chengxin. "Exploring Data Quality of Weigh-In-Motion Systems." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1018.
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This research focuses on the data quality control methods for evaluating the performance of Weigh-In-Motion (WIM) systems on Oregon highways. This research identifies and develops a new methodology and algorithm to explore the accuracy of each station's weight and spacing data at a corridor level, and further implements the Statistical Process Control (SPC) method, finite mixture model, axle spacing error rating method, and data flag method in published research to examine the soundness of WIM systems. This research employs the historical WIM data to analyze sensor health and compares the evaluation results of the methods. The results suggest the new triangulation method identified most possible WIM malfunctions that other methods sensed, and this method unprecedentedly monitors the process behavior with controls of time and meteorological variables. The SPC method appeared superior in differentiating between sensor noises and sensor errors or drifts, but it drew wrong conclusions when accurate WIM data reference was absent. The axle spacing error rating method cannot check the essential weight data in special cases, but reliable loop sensor evaluation results were arrived at by employing this multiple linear regression model. The results of the data flag method and the finite mixed model results were not accurate, thus they could be used as additional tools to complement the data quality evaluation results. Overall, these data quality analysis results are the valuable sources for examining the early detection of system malfunctions, sensor drift, etc., and allow the WIM operators to correct the situation on time before large amounts of measurement are lost.
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Spinnel, Erik. "PLE with integrated clean up followed by alternative detection steps for cost-effective analysis of dixons and dioxin-like compounds." Doctoral thesis, Umeå universitet, Kemi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1665.
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Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are two structurally related groups of chemicals, generally referred to as `dioxins´. These are of great concern due to their high toxicity and global spread. Other groups of compounds with similar chemical structure and toxicity mechanisms are the brominated analogues polybrominated dibenzo-p-dioxins (PBDDs) and polybrominated dibenzofurans (PBDFs), and the dioxin-like polychlorinated biphenyls (PCBs). Numerous studies have been undertaken to investigate sources and transport routes of dioxins. However, much remains to be done, including analytical, inventories of dioxin-like compounds, such as PBDD/Fs, and the development of more convenient analytical methods. The currently standard procedure for analyzing dioxins (and dioxin-like compounds) is to use Soxhlet extraction followed by multi-step clean-up and gas chromatography - high resolution mass spectrometry (GC- HRMS) for detection. Unfortunately, this method is very solvent, labor and time-consuming, making it very expensive. The main aim of the studies this thesis was to develop pressurized liquid extraction (PLE) with integrated clean up techniques for fast, convenient preparation of dioxin samples. PLE with integrated clean-up has previously been used for extracting dioxins from biological samples, but in these studies the possibility of extending its use to abiotic samples was explored. The results show that PLE with an integrated carbon trap is suitable for analyzing dioxins in various types of soil samples, sediment and flue gas samples. The results also showed that it has potential for analyzing dioxins in fly ash. The thesis focuses on developments of the methodology for dioxin analysis, but also includes results obtained from PBDDs and dioxin-like PCB analyses. In addition, the possibility of using various other kinds of detection techniques rather than GC-HRMS, such as enzyme-linked immunosorbent assays (ELISAs) or two-dimensional gas chromatography with micro electron capture detection (GCxGC-µECD) was explored. The results indicate that ELISA and GCxGC-µECD could serve as complementary detection systems in some cases. However, it is not yet possible to fully replace GC-HRMS. A further refinement of the PLE with in-cell clean-up technique is the modular approach developed in these studies. With this technique it is possible to include various steps for both clean-up and fractionation. For example, sulphuric acid impregnated silica could be combined with active carbon for the simultaneous removal of lipids (along with other interferences) and fractionation of PCBs and PCDD/Fs. It was shown that the method could provide data that agreed reasonably well with both reference values and values obtained using traditional methods. In general PLE proved to have high extraction efficiency and to yield very similar congener profiles to the reference method. In addition, it was shown that it allowed one-step extraction and clean-up of a salmon sample. Such single-step procedures are the ultimate goals for any extraction technique, and it would be highly desirable to develop one-step methods that could be extended to other types of samples. For the rest of the matrices tested (soil, sediment, mussel and crab tissue and flue gas) the method was successful, however a final polishing step is currently required, involving either dilution or clean-up using miniaturized multilayer silica columns, to obtain extracts that are pure enough for GC-HRMS analysis. Using the developed modular-PLE system substantial costs could be saved. It was estimated that the method could reduce the cost of preparing samples by up to 90%, which would greatly facilitate large-scale inventories.
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Brittle, Seth William. "Bioavailability and Transformation of Silver Nanoparticles in the Freshwater Environment." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1484594585990252.
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Souza, Erica Rodrigues de. "Avaliação do praguicida aldicarbe e seus produtos de transformação em matriz ambiental -- desenvolvimento e comparação de técnicas analíticas." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/9/9141/tde-26012017-172922/.
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Os praguicidas carbamatos surgiram na década de 70. Este grupo de substâncias possui atividade anticolinesterásica, com variado grau de toxicidade. São solúveis em água e termicamente instáveis. O praguicida aldicarbe faz parte do grupo dos carbamatos, sendo um metil carbamato de oxima. Contaminações de águas subterrâneas e superficiais pelo aldicarbe já foram demonstradas, devido a alta solubilidade deste composto em água e sua alta capacidade de lixiviação em solo. Este trabalho visa o desenvolvimento de métodos analíticos para separação e quantificação de aldicarbe, aldicarbe sulfóxido e aldicarbe sulfona, por cromatografia líquida de alta eficiência, cromatografia líquida acoplada à espectrometria de massas e eletroforese capilar. O trabalho objetiva ainda avaliar a toxicidade aguda das três substâncias utilizando a bactéria marinha luminescente Vibrio fischeri. Amostras de água ultrapura, superficial e subterrânea foram submetidas a etapas de extração em diferentes cartuchos de fase sólida para avaliação da recuperação dos analitos e a realização da pré concentração dos mesmos. No método proposto por cromatografia líquida acoplada a espectrometria de massas, obteve-se limite de quantificação de 10 µg.L-1, sendo que o alcançado no método proposto por cromatografia líquida com detecção por arranjo de diodos foi de 2 µg.L-1. Já o método desenvolvido por eletroforese capilar com detecção por arranjo de diodos teve um limite de quantificação de 10 mg.L-1. Os resultados de CE50 obtida para o aldicarbe, aldicarbe sulfona e aldicarbe sulfóxido, no teste de toxicidade com a bactéria luminescente Vibrio fischeri foram respectivamente: 56,0 mg.L-1, 47,0 mg.L-1 e 7,8 mg.L-1. O método desenvolvido por cromatografia líquida se mostrou com sensibilidade satisfatória para análise de aldicarbe e seus produtos de transformação em água com níveis de quantificação dos compostos abaixo do limite determinado pela OMS (10 µg.L-1. O método por eletroforese capilar não se mostrou com sensibilidade ideal para detecção dos analitos em níveis de traços. No teste de toxicidade aguda, observou-se que o aldicarbe sulfóxido é cerca de 7 vezes mais tóxico para a bactéria que o próprio aldicarbe, o que já é descrito na literatura para outras espécies.Carbamates pesticides first appeared in the 1970s. This group of substances possesses anticholinesterasic activity, with varied toxicity degree. They are soluble in water and thermally unstable. The aldicarb pesticide belongs to the carbamates group, being an oxime methyl carbamate. Contaminations of underground and superficial waters by aldicarb have been demonstrated, due to the high solubility of this compound in water and its high capacity of lixiviation in soil. This dissertation aims to develop analytical methods for separation and quantification of aldicarb, aldicarb sulfoxide, and aldicarb sulfona, by high efficiency liquid chromatography, liquid chromatography-tandem mass spectrometry and capillary electrophoresis. The dissertation also focuses on evaluating the acute toxicity of the three substances using the luminescent marine bacterium Vibrio fischeri. Samples of ultrapure water, superficial and underground, were submitted to extraction stages in different cartridges of solid phase for evaluating the recovery of analytes and conducting their pre-concentration. In the method proposed by liquid chromatography-tandem mass spectrometry, a quantification limit of 10 µg.L-1 was obtained, in comparison with the 2 µg.L-1 achieved in the method proposed by liquid chromatography with diode-array detection. The method developed by capillary electrophoresis with diode-array detection had a quantification limit of 10 mg L-1. The results of CE50 obtained for the aldicarb, aldicarb sulfone and aldicarb sulfoxide, in the toxicity test with the luminescent bacterium Vibrio fischeri were respectively: 56.0 mg.L-1, 47.0 mg.L-1 e 7.8 mg.L-1 The method developed by liquid chromatography showed satisfactory sensitivity for analysis of aldicarb and its transformation products in water with quantification levels of the compounds below the limit determined by OMS (10 µg.L-1
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Moller, Jurgen Johann. "The implementation of noise addition partial least squares." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/3362.
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Thesis (MComm (Statistics and Actuarial Science))--University of Stellenbosch, 2009.When determining the chemical composition of a specimen, traditional laboratory techniques are often both expensive and time consuming. It is therefore preferable to employ more cost effective spectroscopic techniques such as near infrared (NIR). Traditionally, the calibration problem has been solved by means of multiple linear regression to specify the model between X and Y. Traditional regression techniques, however, quickly fail when using spectroscopic data, as the number of wavelengths can easily be several hundred, often exceeding the number of chemical samples. This scenario, together with the high level of collinearity between wavelengths, will necessarily lead to singularity problems when calculating the regression coefficients. Ways of dealing with the collinearity problem include principal component regression (PCR), ridge regression (RR) and PLS regression. Both PCR and RR require a significant amount of computation when the number of variables is large. PLS overcomes the collinearity problem in a similar way as PCR, by modelling both the chemical and spectral data as functions of common latent variables. The quality of the employed reference method greatly impacts the coefficients of the regression model and therefore, the quality of its predictions. With both X and Y subject to random error, the quality the predictions of Y will be reduced with an increase in the level of noise. Previously conducted research focussed mainly on the effects of noise in X. This paper focuses on a method proposed by Dardenne and Fernández Pierna, called Noise Addition Partial Least Squares (NAPLS) that attempts to deal with the problem of poor reference values. Some aspects of the theory behind PCR, PLS and model selection is discussed. This is then followed by a discussion of the NAPLS algorithm. Both PLS and NAPLS are implemented on various datasets that arise in practice, in order to determine cases where NAPLS will be beneficial over conventional PLS. For each dataset, specific attention is given to the analysis of outliers, influential values and the linearity between X and Y, using graphical techniques. Lastly, the performance of the NAPLS algorithm is evaluated for various
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Breitenstein, Johann. "Application de la chromatographie d'exclusion stérique multi-détection à l'étude de la spéciation de la matière organique dissoute en milieu estuarien et côtier Measuring dissolved organic matter in estuarine and marine waters: size-exclusion chromatography with various detection methods, in Environmental Chemistry 15(7), October 2018." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0074.
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La matière organique dissoute (MOD) est un des principaux vecteurs de carbone à l’océan.Cependant, elle est profondément altérée lors de son transit dans les eaux estuariennes et son séjour en milieu côtier. L’objectif de cette thèse est d’apporter de nouveaux éléments sur la composition, le rôle dans les cycles biogéochimiques le long du transfert terre-mer et le devenir dans l’océan côtier de la MOD.L’analyse de la MOD a été réalisée à l’aide d’une technique d’analyse globale et semi-spécifique : la chromatographie d’exclusion stérique multi-détection (SEC-mDEC), qui permet de séparer la MOD en six fractions de tailles aux propriétés diverses. La dynamique de ces composés a été étudiée de manière saisonnière dans l’estuaire de l’Aulne et la rade de Brest. Dans l’estuaire, le couplage de la SECmDEC avec la fluorescence 3D a aussi été étudié.Initialement conçue pour l’analyse des eaux douces, la SEC-mDEC adaptée à l’analyse des milieux à salinité variable a permis de démontrer que la MOD est impliquée dans de nombreux processus biogéochimiques. Dans l’estuaire de l’Aulne, elle permet de tracer les apports terrigènes et marins.Des modifications substantielles sont apportées à la MOD par le développement des microorganismes et les processus de flocculation en amont du gradient halin. Dans la rade de Brest, l’ensemble des fractions de taille permet de dessiner un continuum de réactivité autour de la dégradation bactérienne du bloom phytoplanctonique. Ces résultats démontrent que l’utilisation du seul carbone organique dissous global des échantillons n’est pas suffisante pour contraindre la dynamique de la MOD dans le continuum terre-merDissolved organic matter (DOM) is one of the most important vector of carbon to the ocean.However, DOM is deeply altered during its transit through estuarine waters and its residence time in Coastal waters. The purpose of this thesis is to bring new insights on the DOM composition, role in biogeochemical cycles during land-sea transfer and fate in Coastal areas. DOM analysis was performed with a global and semi-specific tool: size-exclusion chromatography multi-detection (SEC-mDEC), which allow the separation of DOM into six size fractions of different nature. Dynamics of these compounds are studied seasonally in the Aulne estuary and the bay of Brest. The coupling between SEC-mDEC and 3D fluorescence was studied in the estuary.Initially design for freshwater analysis, the adapted SEC-mDEC for estuarine and marine water analyses permitted the demonstration that DOM is involved in several biogeochemical processes. In the Aulne estuary, DOM tracks the contribution of both riverine and marine sources. Substantial changes are made to the DOM by microorganisms and flocculation processes upstream. In the Bay of Brest, ail fractions enable to design a reactivity continuum from the bacterial degradation of the phytoplanktonic bloom.Results demonstrate that the single use of the global dissolved organic carbon is not enough to constrain DOM dynamic in the land-sea continuum
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Bergknut, Magnus. "Characterization of PAH-contaminated soils focusing on availability, chemical composition and biological effects." Doctoral thesis, Umeå : Umeå University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-789.
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Semones, Molly C. "Regulation and Testing for Marine Biotoxins." Ohio University Honors Tutorial College / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1283867789.
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Carvalho, Jose Joao. "Immunochemical and chromatographic methods for two anthropogenic markers of contamination in surface waters." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16420.
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Koffein (1,3,7-Trimethylxanthin) und Coprostanol (5beta-cholestan-3beta-ol) wurden im Berliner Oberflächenwasser nachgewiesen. Ihre Konzentrationen korrelierten mit dem Verunreinigungsgrad der Proben, was nahelegt, dass sie sich als Marker für menschliche Aktivität eignen. Bemerkenswerterweise wurde Koffein in jeder einzelnen Oberflächenwasserprobe oberhalb der Bestimmungsgrenze von 0,025 µg/L gefunden. Um Oberflächenwasserproben in größeren Serien zu untersuchen, war die Entwicklung zweier neuer Methoden erforderlich: ein Immunoassay, basierend auf einem monoklonalen Antikörper für Koffein und eine dispersive flüssig-flüssig Mikroextraktionsmethode (DLLME), gefolgt von Flüssigkeitschromatographie gekoppelt mit Tandem-Massenspektrometrie (LC-MS/MS) für Coprostanol. Der entwickelte Koffein-Immunoassay zeigt die beste je erhaltene Nachweisgrenze für Koffein (0,001 µg/L), erlaubt Hochdurchsatz-Analysen und erfordert keine Probenvorbereitung. Der Assay wurde auch erfolgreich für die Messung von Koffein in Getränken, Haarwaschmitteln, Koffeintabletten und menschlichem Speichel angewendet. Antikörper gegen Coprostanol sind nicht kommerziell erhältlich. Eine neue Strategie Anti-Coprostanol-Antikörper zu generieren wurde erarbeitet, die eine analoge Verbindung – Isolithocholsäure (ILA) – als Hapten verwendet, mit der eine Gruppe von Mäusen immunisiert wurde. Ein polyklonales Anti-ILA-Serum wurde produziert, welches Coprostanol bindet, aber die niedrige Affinität erlaubte nicht den Aufbau eines Immunoassays, der die Messung von Umweltkonzentrationen des Anayten (im Bereich ng/L) zulässt. Spezifische Anti-ILA-Immunglobuline G wurden auch in den Faeces der Mäuse gefunden. Coprostanol wurde in den Wasserproben durch die Verwendung einer neuentwickelten LC-MS/MS-Methode unter APCI-Ionisation (atmospheric pressure chemical ionisation) gemessen. Konzentrationen oberhalb von 0,1 µg/L wurden nach Voranreicherung der Probe mittels DLLME bestimmt.Caffeine (1,3,7-trimethylxanthine) and coprostanol (5beta-cholestan-3beta-ol) were detected in samples of Berlin’s surface water. Their concentrations correlated with the contamination status of the samples, suggesting their usefulness as markers of human activity. Remarkably, caffeine concentrations were always well above the limit of quantitation of 0.025 µg/L. In order to screen surface water samples in larger series, the development of two novel methods was required: a monoclonal antibody-based immunoassay for caffeine and a dispersive liquid-liquid microextraction (DLLME) method, followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) for coprostanol. The caffeine immunoassay developed shows the best analytical limit of detection (LOD) obtained so far for caffeine (0.001 µg/L), allows high-throughput analysis, and does not require sample pre-treatment. The assay was also successfully employed to measure caffeine in beverages, shampoos, caffeine tab-lets, and human saliva. Antibodies to coprostanol are not commercially available. A new strategy to generate anti-coprostanol antibodies was elaborated using an analogous com-pound as hapten – isolithocholic acid (ILA) – and immunizing a group of mice. A polyclonal anti-ILA serum was produced, which binds coprostanol but the low affinity did not permit setting up an immunoassay to measure environmental concentrations of the analyte (in the range of ng/L). Specific anti-ILA immunoglobulin G were also found in the faeces of the immunized mice. Coprostanol was quantified in the water samples using a newly developed LC-MS/MS method using atmospheric pressure chemical ionisation (APCI). Concentrations above 0.1 µg/L were determined after sample preconcentration using DLLME. This extraction method also proved to be successful for enrichment of coprostanol-related compounds such as cholesterol, cholestanol, cholestanone, ergosterol, and stigmasterol.