[pt] Muitos contaminantes orgânicos, incluindo derivados do petróleo, como por exemplo a gasolina, têm baixa solubilidade em água e migram na subsuperfície como uma fase separada da água sendo referidos como NAPLs (non aqueous liquid phases). Em seu processo de migração na subsuperficie os NAPLs deixam para trás segmentos de líquidos disconectados na forma de gânglios ou lentes que constituem a fase residual do contaminante. A presença do contaminante residual constitui-se numa das maiores dificuldades para a implementação de uma técnica adequada de limpeza ou recuperação de locais contaminados, uma vez que tais contaminantes representam uma fonte lenta e continua de contaminação de solos e água subterrânea, especialmente por sua dissolução na água. Nesta tese, estudou-se o efeito do etanol na dissolução de gasolina residual. Tal estudo foi motivado pela necessidade de se obter um melhor entendimento de um cenário de contaminação envolvendo gasolina e etanol uma vez que gasolina com 20 por cento de etanol em sua constituição e etanol puro estão sendo utilizados como combustível, no Brasil, nos últimos 20 anos. O uso de aditivos oxigenados à gasolina, tais como álcoois, objetiva aumentar o desempenho do motor dos automóveis bem como diminuir a emissão de CO2 destes para a atmosfera e este uso vem aumentando em muitos países. Experimentos tipo equilíbrio em lote e experimentos de coluna foram realizados para investigar efeitos do etanol na solubilidade de constituintes da gasolina e no coeficiente de transferência de massa da gasolina para fase aquosa. Colunas de solo arenoso com gasolina em saturação residual foram percoladas por soluções aquosas com diferentes teores de etanol. Os resultados das concentrações efluentes de contaminante ao longo do tempo, obtidas destes ensaios, foram interpretados segundo o modelo de dissolução proposto por Frind et al. (1997), modificado nesta tese para considerar os efeitos de cosolvência do etanol na solubilidade dos constituintes da gasolina. Os resultados experimentais obtidos indicam que um cenário de contaminação envolvendo etanol e gasolina deverá ser bastante diferente daquele de contaminação usual de gasolina.Em um cenário de contaminação envolvendo etanol e gasolina, concentrações mais altas de contaminantes na água serão esperadas bem como diferentes constituintes da gasolina, além do tradicional grupo BTEX (benzeno, tolueno, etilbenzeno e os isômeros xilenos) deverão estar presentes na água em concentrações nocivas ao meio ambiente. / [en] Many organic contaminants, including petroleum products, such as gasoline, have low aqueous solubilities and migrate through the subsurface as a separated phase called NAPLs (non aqueous liquid phases). In its flow path into the porous media the NAPLs let behind disconnected segments of organic liquids entrapped as ganglia or lenses that form the residual phase of the contaminant. The presence of the residual contaminant has been reported as one of the most difficulties in the development of an appropriate cleanup strategy as the residual phase represents a long and continuum source of contamination of soils and groundwater, specially by its dissolution into the water.In this thesis the effect of ethanol on dissolution of residual gasoline was studied, aiming at a better understanding of a scenario of groundwater contamination involving gasoline and ethanol, since 20 percent of ethanol has been added to the Brazilian gasoline in the last 20 years and also ethanol has been used as fuel in Brazil in these years. The use of oxygenated additives into the gasoline, such as alcohols, has the advantage of improving engine performance and reducing the air impact pollution by CO2 and its use has increasing in many countries.Equilibrium batch tests and column experiments were carried out to investigate the effect of ethanol on solubility of gasoline constituents and on the mass transfer coefficient from gasoline to aqueous phase. The results of the column experiments were interpreted with a dissolution numerical model proposed by Frind et al.(1997), modified in this thesis to include the cosolvent effects of the ethanol on the solubility of gasoline constituents.In terms of soil and groundwater contamination related to gasoline spills, chemicals like benzene, toluene, ethylbenzene and xylenes (BTEX group) have acute toxicity or carcinogenicity, are the most water- soluble and mobile gasoline components, receiving the greatest concern. In this work, an enormous enhancement of gasoline constituents solubility due to ethanol was observed, and it was also noticed that the mass transfer coefficient diminished due to ethanol. The highest increase in solubility were for the less water soluble components. Therefore, gasoline components, other than BTEX, are expected in significant concentrations, in a scenario of contamination involving ethanol and therefore more concern about this potential threat should be addressed.

The investigation of environmental impacts of 16 different contaminants originating from the E18 Highway (17 000 AADT) were carried out over the first six months of the highway‘s operational life. Investigative methods used include electrical resistivity surveying, water chemistry analyses, soil analyses, distribution modelling and transportation modelling. The investigation shows conclusively a year round infiltration due to melting of the snowpack from road salt, and a strong preferential anthropogenic pathway due to in-creased hydraulic conductivities of the road building materials relative to the natural soils. The resistivity surveys show values well below the expected values for the highway materials, indicating increased ionic content of the unsaturated zone. Time lapse resistivity modelling shows a clear downwards spreading of contamination from the roadway to subsurface distances greater than 5 m. Elevated concentrations of nearly every contaminant relative to baseline values were observed, with many concentrations of metals in the snow pack averaging values in excess of Swedish EPA groundwater limitations. Distribution modelling demonstrated a potential offset of peak values from the road surface due to ploughing and splash transport processes, but otherwise conformed to established distribution patterns. One dimensional transport modelling demonstrated the importance of adsorption and other retentive factors to the migration of contaminants to the water table, and provided an estimate for potential long term contaminant concentrations.

The unsaturated zone could provide an effective barrier against pathogenic microbes entering the groundwater. Knowledge relating to microbial fate in this zone is therefore important for increased understanding of groundwater vulnerability. This thesis examines the published literature that is related to the transport, retention and survival processes that apply to the fecal indicator bacterium Escherichia coli in unsaturated porous media. The main focus concerns the research findings under steady-state flow in homogeneous filter media, and under unfavorable attachment conditions, which are the most common in the natural environment. Experimental results in the literature for the pore-, column- and field-scale are examined and compared to commonly applied theories and modeling approaches. An analysis of the main factors that influence attenuation and biofilm formation is provided. Further, the findings are illustrated in a model of an unplanted, vertical flow constructed wetland. The results indicate that retention at the solid-air-water interface is a major attenuation process. In addition, they suggest that the flow velocity (as dependent on the grain size and the saturation) is a key influencing factor. However, it has not yet been established how the research findings relating to the main processes and influencing factors can be incorporated into predictive models; in the literature, a multitude of models have been proposed and alternative theories could describe the same observation. In this study, the transport and fate of Escherichia coli in different sand filters is, therefore, modeled using various literature models - derived under similar experimental conditions - in order to assess the possibility to compare and generalize the equations, evaluate their implications considering the different saturation settings and filter depths, and to define the spectra of the reduction efficiencies. It is discovered that the bacterial attenuation behaviors vary largely. This calls for clarification regarding the underlying processes. Future research is also recommended to include the ef-fects of structured filter media and sudden changes in the flow rate. / QC 20111208

The American Society of Testing and Materials (ASTM) has established a three tier risk-based corrective action (RBCA) program for cleaning up petroleum release sites, which is supported by the Environmental Protection Agency. RBCA programs make the cleanup of spill sites more efficient by requiring additional site information only when a more accurate risk assessment is needed. For spill sites that do not pass the first tier general assessment, a Tier 2 evaluation involving site specific information and screening level models to assess the potential risk must be conducted. Screening level models generally require site specific input parameters. To increase efficiency it would be helpful to know which parameters have large affects on model output and which parameters do not affect the model output significantly. There have been many studies focused on model sensitivity to input parameters. For an input parameter to vary there must be uncertainty about the value. This research proposes a method of including parameter uncertainty with model sensitivity to quantify the importance of a parameter, where the term importance is a combination of parameter uncertainty and sensitivity. Using the method developed in this thesis, an importance assessment was conducted on an analytical model for vadose zone transport. It was found that for sites posing high risk, with large spill volumes and shallow water table depths, the input parameters of water table depth and spill volume were the most important. The input parameters of precipitation and contaminant biodegradation half-life showed high importance in lower risk situations; when the water table was deep. A comparison of sensitivity analysis to importance showed differences in their results. The sensitivity analysis identified those parameters that the model was sensitive to, while the importance assessment identified the parameters that were sensitive and whose range of uncertainty was large enough to affect model output values. This information could be used for resource allocation decisions when acquiring additional site specific information.

Soil-bentonite cutoff walls are commonly used to contain contaminants in the subsurface. A key property in determining the effectiveness of a cutoff wall is its hydraulic conductivity. There are important difficulties and uncertainties regarding the accuracy of commonly used methods of measuring the hydraulic conductivity of cutoff walls. When predicting contaminant transport through cutoff walls, common practice is to use the average hydraulic conductivity of the wall. There are some cases, however, such as circumferential cutoff walls with inward hydraulic gradients, where it is also important to consider the variability in hydraulic conductivity from point to point in the wall in contaminant transport studies. A pilot-scale facility was envisioned where subsurface barrier issues such as those mentioned above could be studied. In 1998, the Subsurface Barrier Test Facility (SBTF) was constructed. In this facility, pilot-scale subsurface barriers can be installed using real construction equipment and tested in a controlled environment. The effectiveness of various methods of measuring the hydraulic conductivity of cutoff walls was studied by building and testing three pilot-scale soil-bentonite cutoff walls at the SBTF. The following currently used test methods were evaluated: API tests on grab samples, lab tests on undisturbed samples, piezometer tests (slug tests), and piezocone soundings. The use of slug tests in cutoff walls was improved in this research in the areas of avoiding hydraulic fracture and accounting for the close proximity of the trench walls. The SBTF allows for measurement of the global, average hydraulic conductivity of an installed pilot-scale cutoff wall, which is a useful value to compare to the results of the above-mentioned tests. The two main factors differentiating the results of the different test methods used for the pilot-scale walls were remolding and sample size. Remolding of the API samples significantly reduced the hydraulic conductivity of these samples compared to the hydraulic conductivity measured in lab tests on undisturbed samples, which were of similar size. For the other tests, the degree and extent of remolding were less significant compared to in the API tests. For these tests, the scale of the measurement is believed to be the main factor differentiating the results. Hydraulic conductivity was found to increase as the sample volume increased, with the global measurement of the average hydraulic conductivity producing the highest value. The influence of variability in hydraulic conductivity on contaminant transport through cutoff walls was studied from a theoretical standpoint using the one-dimensional advection-diffusion equation. Charts were developed that can be used to estimate the flux through a cutoff wall based on knowledge of the average hydraulic conductivity of the wall and an estimate of the variability in hydraulic conductivity. Data sets of hydraulic conductivity from lab tests on soil-bentonite samples from four cutoff wall case histories were used to estimate typical values of variability. The contaminant transport analyses showed that the effect of variability may be significant when the hydraulic gradient opposes the concentration gradient, which is the case for a circumferential cutoff wall with an inward hydraulic gradient. The goal of a circumferential cutoff wall with an inward hydraulic gradient is to reduce the outward diffusive flux of contaminant by inducing an inward advective flux. The effect of variability in hydraulic conductivity is to reduce the effectiveness of this scheme. / Ph. D.

Contaminant transport modeling is being used more often at petroleum hydrocarbon contaminated sites in an attempt to aid engineers in evaluating the feasibility of natural attenuation as a remediation alternative in groundwater systems. In this research, a three-dimensional sequential electron acceptor computer model, SEAM3D, developed by Waddill and Widdowson (1997) was used to simulate contaminant transport at a leaking underground storage tank site in Beaufort, South Carolina. Gasoline containing benzene, toluene, ethylbenzene, and xylene (BTEX) as well as methyl tertiary butyl ether (MTBE) leaked into the subsurface at the site late in 1990, and monitoring of the water table elevations and contaminant concentrations began in 1993. Using the field data, the groundwater flow model MODFLOW was used to develop and calibrate a flow model for the Laurel Bay site using GMS (Groundwater Modeling System) v2.1. MODFLOW was coupled with the SEAM3D contaminant transport model, and the available concentration levels were used to calibrate, verify, and validate the site model. The results indicated that SEAM3D simulated complex, interconnected processes including biodegradation, and the transport of multiple hydrocarbon compounds, electron acceptors, and end products over time and space at a specific petroleum hydrocarbon contaminated site. Once the model was calibrated and verified, the model output was used to study the changes in contaminant mass distribution, contaminant mass loss, and mass loss rates for each terminal electron accepting process (TEAP) over time. It was found that the natural attenuation capacity of the aquifer was insufficient to stabilize the plume and prevent it from reaching the defined point of contact (POC). Contamination was shown to have reached the POC by 1994, just four years into the simulation. Results indicated that despite oxygen limitation within the BTEX plume, aerobic biodegradation was responsible for the greatest amount of mass loss, close to 70 %, relative to the sum of the anaerobic processes after 20 years. / Master of Science

Verunreinigtes Grundwasser stellt eine ernsthafte Bedrohung für die Trinkwasser-Ressourcen auf der ganzen Welt dar. Verunreinigte Grundwasser können zwar in Brunnen detektiert werden, eine ordnungsgemäße Sanierung ist jedoch häufig nur erfolgreich, wenn die Quelle der Verunreinigung erfasst und entfernt wird. Wenn von Anbeginn eines Sanierungsprojektes ein Schwerpunkt auf die Erkennung und Eingrenzung des Verunreinigungsherdes gelegt wird, kann die Sanierung direkt an dieser Stelle ansetzen und zudem hohe Grundwasser-Sanierungskosten verringert werden. ModBack ist eine Software, die mehrere bestehende Modellierungs-Werkzeuge in einer, ein-fach zu verwendenden, ESRI ArcGIS 10-basierten Schnittstelle vereinigt und hilft mögliche Schadstoffquelle Zonen im Untergrund abzugrenzen. Diese Software ist in Visual Basic 3.5 geschrieben und verwendet ArcObjects Bibliotheken, um die erforderlichen GIS-Anwendungen zu implementieren. Es kann ohne Änderung auf allen Microsoft Windows-basierten PC‘s mit ausreichend RAM und mindestens Microsoft. NET Framework 3.5 verwendet werden. Die Nutzung von ModBack erfordert zusätzliche Installation der folgenden Software: Processing Modflow Pro 7.0 (PMWin), MODPATH, CSTREAM (Bayer-Raich et al., 2003a, Bayer-Raich et al., 2003b, Bayer-Raich et al., 2004), Golden Software Surfer, Microsoft Excel und NAS (eine Software zur Berechnung des natürlichen Schadstoffabbaus). Die grafische Benutzeroberfläche (GUI) von ModBack ist in vier Verfahrensschritte Dateneingabe, Grundwassermodellierung, Partikel Backtracking und Analysen getrennt. Geographischen Eingangsdaten werden für eine geografische Übersicht des Testfeldes benötigt. Sie bestehen meist aus georeferenzierten Informationen des Testfeldes und Informationen zur unterirdischen Grundwasserverunreinigungen. Grundwasseranalysen werden entweder durch konventionelle Probennahme aus Grundwassermessstellen oder durch die Durchführung integraler Pumpversuche an Kontrolleben mit eine bestimmten Konzentration/Zeit- Serie (CT-series) gesammelt. Aus den Pumpversuchen resultierende hydraulische Daten werden zusammen mit allen anderen verfügbaren Informationen zur Erstellung eines grundlegenden Grundwasserströmungsmodells des Testfeldes verwendet. Nachfolgende Backtracking Verfahren, als auch die Berechnung von advektivem Schadstofftransport beziehen sich auf die-ses Strömungsfeld und werden entlang einer zuvor definierten Kontrollebene berechnet. Eine Analyse der Backtracking-Ergebnisse erfolgt innerhalb ModBack. Die potenzielle Quelle von Kontaminationen oder deren Abwesenheit werden basierend auf dem Verfahren nach Jarsjö et al. (2005) bestimmt. Die Länge einer Schadstofffahne kann anhand von Fahnenlängen Statistiken und /oder dem Abbau erster Ordnung Abbau Gleichungen oder Berechnungen auf ortsspezifische hydraulischen und chemischen Parametern beruhen. Ferner ist ein analytisches Instrument enthalten, um die Verteilung der Verunreinigungen über eine Steuerebene zu identifizieren. Alle relevanten Ergebnisse können als Vektordaten in ModBack graphisch dargestellt und gespeichert werden und sind somit kompatibel mit weiteren GIS-Software Produkten. ModBack wurde bereits an Testgebieten in Slowenien und Süddeutschland angewendet, um die möglichen Zonen der Verunreinigungsquelle oder deren Abwesenheit zu begrenzen. Auf dem Testgelände in Süddeutschland sind diese Abgrenzungen vergleichbar mit früheren Untersuchungen vor Ort und unterstützt somit die Funktionalität der Software ModBack. Mit ModBack, steht ein Werkzeug zur Verfügung, die bereits jetzt Um-welt-Beratern, Ingenieuren und Umwelt-Agenturen ermöglicht denkbare Quellen der Verunreinigung bei der Planung der Untersuchungen vor Ort und Sanierungsmaßnahmen abzugrenzen, und hilft Kosten deutlich zu senken.

"Brownfields" are real estate property with subsurface or surface contamination. The redevelopment of Brownfields is required to clean, improve and protect the environment. Piles foundations are often used in Brownfields to support structures. Regulators are concerned about the environmental safety of pile foundations in Brownfields sites. Piling in Brownfields may lead to transport of contaminants from the contaminated region to the underground aquifers. The purpose of this investigation is to determine the potential for contaminant transport due to pile foundation in Brownfields. This investigation is an extension of previous research conducted at the University of New Orleans and ascertains the potential for contaminant transport from concrete piles of different shape, depth of penetration and method of installation. The results of large scale model tests and Finite Element studies are presented. The investigation indicates the possibility of contamination only in selected cases of piles.

[pt] Neste trabalho são avaliados os parâmetros de transporte da bactéria Escherichia coli ATCC11229, microrganismo indicador de contaminação fecal, através de colunas de areia de quartzo saturadas. Com este propósito foi desenvolvido o equipamento para a execução dos ensaios Advecção-Dispersão-Sorção (ADS), com injeção contínua de uma suspensão bacteriana em água destilada em uma concentração inicial de 10 (8) bactérias/mL, por até doze horas em temperatura ambiente e sob condições que permitiram desprezar os efeitos do crescimento e decaimento dos microrganismos. Para a determinação dos parâmetros de transporte foram executados ensaios microbiológicos, ensaios de batelada e oito ensaios ADS para diferentes valores de gradiente hidráulico. Os ensaios de batelada mostraram uma baixa adsorção bactéria-solo nas condições avaliadas. As curvas de chegada obtidas nos ensaios ADS, mostraram elevados valores para o fator de retardamento entre três e nove, variando proporcionalmente com o incremento de gradiente hidráulico. Os valores de dispersão hidrodinâmica variaram entre 1,44x10(-2) cm(2)/min e 5,47x10(-2) cm(2)/min. Os resultados dos ensaios sugerem que os processos físico-químicos têm pouca influência no transporte deste microrganismo em areia de quartzo, enquanto que o processo de filtração mecânica, forças hidrodinâmicas, a forma e distribuição de tamanho dos grãos parecem explicar mais adequadamente o comportamento das curvas de chegada. / [en] This study deals with the assessment of the transport parameters of the Escherichia coli ATCC11229 bacteria, a fecal contamination indicator, through saturated quartz sand columns. With this purpose, it was developed an equipment to carrying out Advection-Dispersion-Sorption (ADS) experiments, with continuous input of bacterial distilled water suspension at an influent concentration of 10(8) cell/mL for about twelve hours, at environmental temperature and under conditions that allow disregard the effect of the growth and decay of the microorganisms. Microbiological experiments, batch tests, and eight ADS experiments at several hydraulic gradient values, were executed for determine the transport parameters. The batch tests indicated a low bacterium-soil adsorption under evaluated conditions. The breakthrough curves, obtained by ADS experiments, showed high values for the retardation factor, ranged from three to nine with increasing the hydraulic gradient. The hydrodynamic dispersion values ranged between 1,44x10(-2)cm(2)/min and 5,47x10(-2) cm(2)/min. The results of the experiments suggested that the physical-chemical processes have a little influence on the transport of this microorganism in quartz sand, whereas the straining process, hydrodynamic forces, the shape and grain distribution, would can explain more appropriately the behavior of the breakthrough curves.

This manuscript based thesis examines and advances methods for constraining sources of atmospheric trace constituents with a Lagrangian particle dispersion model. The method of Bayesian inversion is demonstrated, and a new method is introduced to a class of similar problems where established methods are not applicable. First, A new regression based methodology was developed and applied to observations of atmospheric methanesulfonic acid mass concentrations at Alert, Nunavut. The methodology was used to compare the importance of phytoplankton blooms vs. the ice-free ocean as sources of the dimethylsulfide precursor, and to compare the importance of bromine monoxide vs. hydroxyl as agents oxidizing dimethylsul de to methanesulfonic acid. These issues are relevant to the application of methanesulfonic acid concentrations in ice cores to determine historic sea ice properties. The analysis indicated that source regions to Alert during the spring are primarily ice-free ocean with a significant contribution from ice edge blooms, and during the summer to be dominated by the ice-free ocean. The model also indicated that oxidation of DMS by BrO was the dominant source of MSA in the spring, while DMS oxidation by OH was the dominant source in the summer. Secondly, Bayesian inversion was applied to observations of atmospheric elemental carbon mass concentrations at Tsinghua University in Beijing, China. The analysis provided evidence that current bottom-up elemental carbon emissions estimates in northern China are likely underpredicted. Global chemical transport models show ubiquitous underestimates of the atmospheric burden of elemental carbon, especially near large sources of emissions. Northern China is among the regions with the most intensive elemental carbon emissions in the world, and an underestimate of emissions in this region may be partially responsible for the global chemical transport model underestimates.