This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3σblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses.

L'utilisation du biote dans le suivi de la contamination métallique des milieux aquatiques est aujourd'hui une approche pertinente, car elle permet (i) de répondre aux difficultés analytiques liées à la présence des métaux à faible dose dans l'eau, (ii) d'intégrer la contamination dans le temps et (iii) de renseigner sur la biodisponibilité des métaux et leur potentiel toxique. Toutefois, l'interprétation des niveaux de contamination des organismes en termes de contamination biodisponible des milieux est difficile car elle dépend de facteurs confondants (physicochimiques et biologiques). Dans ce contexte, l'objectif de ce travail de thèse est d'étudier la variabilité des capacités de bioaccumulation des métaux par voie dissoute chez le gammare, en s'appuyant sur un modèle cinétique. Des expérimentations en laboratoire ont permis d'étudier l'influence de facteurs physicochimiques (cations majeurs de l'eau) et biologiques (histoire de vie) sur les constantes d'accumulation et d'élimination du modèle pour le Cd, le Cu, le Ni et le Pb. Les résultats de ces travaux ont montré l'importance de prendre en compte l'influence des teneurs calciques du milieu et la pré-exposition des gammares à certains métaux dans l'interprétation de la bioaccumulation. Des suivis de la contamination dans des gammares transplantés in situ à l'échelle de la France ont montré les limites du modèle pour relier la contamination du milieu à celle des organismes. Ainsi, pour une meilleure caractérisation de la contamination biodisponible des milieux, il est nécessaire d'approfondir les connaissances sur l'influence d'autres facteurs physicochimiques et sur l'importance de la voie trophique comme source de contamination biodisponible pour les gammares / The use of biota in order to monitor metallic contamination in freshwaters is a relevant tool to (i) overcome difficulties of measuring low concentrations in water, (ii) integrate metal fluctuations over time and, (iii) quantify the bioavailable fraction of metals, considered as potentially toxic. However, the interpretation of metal contents in aquatic organisms in terms of bioavailable contamination in freshwaters remains complex because it depends on confounding factors (physicochemical and biotic factors). In this context, the aim of this work was to study the variability of waterborne metal bioaccumulation abilities in gammarids, using the kinetic model. In the laboratory, the influence of water chemistry (major ions) and biological factors (local acclimation) on the accumulation and elimination rate constants of the kinetic model was assessed. The results showed that the consideration of calcium concentrations in water and the pre-exposure of gammarids to some metals were crucial for a reliable interpretation of bioaccumulation. Meanwhile, metal contamination was followed in transplanted gammarids at the national-scale (France) and showed the limits of kinetic modelling to link metal contamination in water to bioaccumulation. Therefore, to better characterize the bioavailable contamination in freshwaters, it is necessary to further study the influence of other physicochemical factors, such as temperature, and the importance of food as a source of bioavailable metals for gammarids

Made available in DSpace on 2015-05-14T13:21:24Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1778944 bytes, checksum: c42dcebf9f7394f2955a83c25a92b1b5 (MD5) Previous issue date: 2009-07-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The present work shows an assessment of the environmental conditions of São Marcos Bay in the trace metal (Cu, Pb, Zn, Cd, Ni, Fe, Al and Mn) levels in water, sediment and fish. For this evaluation three points of collections were selected in the proximities of the Itaqui port, considering the drought and rain periods and the tide conditions. Physico-chemical parameters of the water were evaluated, such as: pH, temperature, salinity and conductivity. The results for these analyses showed that just the salinity (30 ) presented a value below the minimum indicated to characterize as saline water. The other parameters are in agreement with the expected for this type of water. The ecotoxicity test in the water of the Bay demonstrated poisonous effects in all sampling points, therefore confirmed the presence of substances that influence on the system in São Marcos Bay. The quantification of Cu, Pb, Zn, Cd, Ni, Fe, Al and Mn metals was carried out with Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) thecnique while Anodic Stripping Voltammetry with mercury film electrode was used to determine the other metals that were not quantified by ICP-OES in water samples. Fe and Al concentrations were the most abundant elements in water and sediment with 5,41 and 7,82 mg L-1 average in water for Fe and Al, respectively and 3427 and 4200 mg L-1 maximum for Fe and Al in sediments. For the fish samples only the Pb, Cd and Ni metals were not detected. The CONAMA 357/05 resolution was used for water results discussion and ANVISA 685/08 for the fish results discussion. / O presente trabalho apresenta uma avaliação das condições ambientais da Baía de São Marcos com relação aos níveis de metais-traço Cu, Pb, Zn, Cd, Ni, Fe, Al e Mn em água, sedimento e peixes. Para esta avaliação foram selecionados três pontos de coletas nas proximidades da região portuária do Itaqui, considerando os períodos de seca e chuva e as condições da maré (vazante e enchente). Parâmetros físico-químicos da água como: pH, temperatura, salinidade e condutividade foram avaliados. Os resultados para estas análises mostraram que apenas a salinidade apresentou-se abaixo de 30 que é o valor mínimo para caracterizar uma água como salina. Os demais parâmetros estão de acordo com o esperado para este tipo de água. O teste de ecotoxicidade realizado na água da Baía demonstrou efeitos tóxicos em todos os pontos de amostragem, confirmando-se que na Baía de São Marcos há a presença de substâncias que influenciam sobre o sistema de ensaio. A quantificação dos metais Cu, Pb, Zn, Cd, Ni, Fe, Al e Mn foi realizada por Espectroscopia de emissão ótica com plasma indutivamente acoplado (ICP-OES) e por voltametria de redissolução anódica com eletrodo de filme de mercúrio os metais que não foram quantificados por ICP-OES em amostras de água. Concentrações de Fe, Al foram as mais abundantes em água e sedimento de fundo com média de 5,41 e 7,82 mg L-1 em água para Fe e Al, respectivamente e máxima de 3427 e 4200 mg L-1 para Fe e Al em sedimentos. Para as amostras de peixes apenas os metais Pb, Cd e Ni não foram detectados. Os resultados foram discutidos com base na Resolução 357/05 CONAMA e Portaria 685/08 da ANVISA para água e peixe, respectivamente.

Philosophiae Doctor - PhD / The need for clean, non-toxic drinking water supplies, free of pollutants and metal contamination is vital in impoverished areas and the developing world alike. With this in mind, the development of accurate, inexpensive, portable and simple devices for remote sensing applications is therefore pivotal for early detection and the prevention of illnesses. Over the last two decades, adsorptive stripping voltammetry (AdSV) has emerged as a superior detection method over common analytical techniques due to its low-cost instrumentation, unskilled labour and ability to detect a wide range of analytes. / 2020-08-31

Rare earth elements (REEs) and their isotopes (such as Nd isotopes) can be potentially used to trace a wide range of oceanic processes in both modern and ancient oceans, but their successful application as tracers requires a comprehensive understanding of REE cycling in the modern ocean. Previous studies of REEs in seawater were largely constrained by analytical difficulties in generating accurate and precise REE data from seawater, which typically contain REE concentrations at a sub-ppt to ppt level. A new, and relatively simple, analytical method for precise and accurate determination of all dissolved REE concentrations in reasonably small (∼100 ml) seawater samples is presented in this thesis. With the application of the new method, this thesis reports the first full-depth, zonal ocean section of all dissolved REE concentrations, collected during the CoFeMUG cruise along ∼12°S in the South Atlantic. The section approach of this study places the distribution of dissolved REE concentrations in a well-constrained hydrographic context, allowing the first quantitative assessment (by an inverse model) of the relative importance of hydrographic controls resulting from advection/mixing of ocean circulation, together with non-conservative controls resulting from local particle scavenging and remineralization, in controlling the distribution of dissolved REEs in this region. A noteworthy decoupling of Ce and Mn with respect to their cycling in the water column was also observed in this study. The application of Nd isotopes as a tracer to reconstruct changes in ocean circulation in the NW European chalk shelf sea during rapid climatic events, including the mid-Cenomanian Event and oceanic anoxic event 2 (OAE 2), suggests a tight coupling between ocean circulation and transient climatic cooling during the general warm Late Cretaceous. An advected volcanic signal during OAE 2 was registered in the seawater Nd-isotope record from the English Chalk, probably suggesting a period of enhanced ocean ventilation/mixing at this time.

Magister Scientiae - MSc (Dept. of Chemistry) / This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3σblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses. / South Africa

En conditions hivernales rigoureuses, l'application des fondants routiers (principalement du chlorure de sodium - NaCl) permet d'assurer la sécurité des usagers de réseaux. Toutefois, son utilisation généralisée entraîne des risques de contamination des écosystèmes aquatiques et terrestres. En milieu routier, le Na+ et Cl- sont transportés par les eaux de ruissellement vers des ouvrages de traitement tels que les bassins de rétention-décantation. Or, ces bassins n'ont pas la capacité de traiter efficacement cet apport de fondants sous forme dissoute. L'objectif de cette thèse est d'étudier le transfert de ces fondants au sein du système routier et de déterminer leur rôle dans la libération des polluants en période hivernale. Les caractéristiques du bassin situé à Azerailles (Lorraine, France) sur une route nationale moyennement fréquentée ont été étudiées, ainsi que les conditions météorologiques, les salages, la composition des matières en suspension (MES) et la concentration en éléments traces métalliques (ETM). Les résultats ont permis de montrer que entre 50 et 90 % du Cl- ont été collectés par le bassin. Il joue un rôle de tampon qui permet une libération du Cl- dilué durant la période de ruissellement suivant la période de salage. La présence de NaCl dans les eaux a joué un rôle sur la diminution de la qualité des matières en suspension, en mettant en évidence la présence de polluants organiques en période de salage. Elle entraîne également une modification de la chimie des eaux et une augmentation des polluants métalliques (zinc). / In severe winter conditions, the application of deicer salts (mainly sodium chloride -NaCl) ensures the safety of network users. However, its spreading carries contamination risks of aquatic and terrestrial ecosystems. On the road, Na+ and Cl- are transported by runoff water to retention-decantation ponds. These ponds do not have the capacity to efficiently treat this flux of deicer salts in dissolved form. In addition, they allow the modification of water and soil chemistry, generating the mobility of metallic pollutants. The objective of this thesis is to study the deicer salt transfer and to determine its role in the release of pollutants during winter. The characteristics of the pond located in Azerailles (Lorraine, France) on a medium-frequented national road were studied, as well as the weather and salting conditions, the composition of the suspended matters and the concentration of traces metals. The results highlighted that between 50 and 90 % of Cl- was collected by the pond. The pond acts as a buffer which allows a release of the collected Cl- diluted during the runoff period following the salting period. The presence of NaCl in runoff water reduced the quality of suspended solids with the presence of organic markers of road pollution and the increase of zinc. It also influenced the increase of zinc in water, the chemical composition and the speciation of elements.

No description available.

The purpose of this research was to characterize the residual solids produced from hydraulic fracturing operations in the Marcellus Shale region. Four field samples were evaluated: drilling mud, treated sludge from the chemical treatment of process water, solids from the gravity settling of produced water, and sludge solidified prior to disposal in a municipal landfill. Cement kiln dust (CKD), used for solidification, was also considered in this study. All samples were subjected to a variety of laboratory techniques to determine their elemental composition and the potential for the elements to leach from the landfill. Strong acid digestion using a 3:1 combination of nitric acid to hydrochloric acid in a microwave with closed vessels was used to determine overall elemental composition. Leaching experiments were performed with de-ionized water and acetic acid (0.57%, pH 2.88) in an attempt to respectively evaluate the effects of weak and strong fluids that might be encountered by the residuals in landfill environments. Elements were analyzed by means of ICP-MS revealing the increased tendency for alkali metals, alkaline earth metals and halogens to leach. Leachablility was further increased for metals when exposed to acidic conditions. / Master of Science

The process of natural gas extraction through hydraulic fracturing produces large quantities of fluid containing naturally-occurring salt, radionuclides, and heavy metals which form residual solids during storage and treatment. The purpose of this research was to characterize the residual solids from hydraulic fracturing operations in the Marcellus Shale to predict the leaching behavior of select elements in disposal environments. Samples collected for this research were: (1) drilling mud, (2) treated sludge from the chemical treatment of process waters, (3) solids from the gravity settling of produced water, and (4) sludge solidified prior to disposal in a municipal landfill. These samples were subjected to various digestion techniques to determine the composition and leaching potential for elements of concern. Strong acid digestions were performed to determine the total environmentally available composition, whereas weak acid digestions were used to predict the leaching potential of these solids under various environmental conditions. The extraction fluids for the leaching experiments included weak acetic acid, acid rain, reagent water, and synthetic landfill leachate. Solids were agitated in a standard tumbling apparatus to simulate worst-case conditions based on ASTM and EPA recommendations. Results from EPA's Toxicity Characteristic Leaching Procedure (TCLP) were used to determine if solids were considered hazardous based on the metal leaching potential. The results from strong and weak acid digestions were compared to better understand the types and quantity of materials that have the potential to leach from the samples. This research may be used to develop best management practices for hydraulic fracturing residual solids. / Master of Science