Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2007. / Includes bibliographical references. / Present-day expeditionary oceanography is beginning to shift from a focus on short-term ship and submersible deployments to an ocean observatory mode where long-term temporally-focused studies are feasible. As a result, a critical need for in situ chemical sensors is evolving. New sensors take a significant amount of time to develop; thus, the evaluation of techniques in the laboratory for use in the ocean environment is becoming increasingly important. Laser-induced breakdown spectroscopy (LIBS) possesses many of the characteristics required for such in situ chemical sensing, and is a promising technique for field measurements in extreme environments. Although many LIBS researchers have focused their work on liquid jets or surfaces, little attention has been paid to bulk liquid analysis, and especially to the effect of oceanic pressures on LIBS signals. In this work, laboratory experiments validate the LIBS technique in a simulated deep ocean environment to pressures up to 2.76 x 10⁷ Pa. A key focus of this work is the validation that select elements important for understanding hydrothermal vent fluid chemistry (Na, Ca, Mn, Mg, K, and Li) are detectable using LIBS. A data processing scheme that accurately deals with the extreme nature of laser-induced plasma formation was developed that allows for statistically accurate comparisons of spectra. The use of both single and double pulse LIBS for high pressure bulk aqueous solutions is explored and the system parameters needed for the detection of the key analytes are optimized. Using both single and double pulse LIBS, the limits of detection were found to be higher than expected as a result of the spectrometer used in this experimentation. However, the results of this validation show that LIBS possesses the characteristics to be a viable chemical sensing method for in situ analyte detection in high pressure environments like the deep ocean. / by Anna Pauline Miranda Michel. / Ph.D.

No description available.

Wegen der zunehmenden Menge an LIBS-Daten von der Marsoberfläche sowie deren speziellen Herausforderungen bei der Analyse untersucht diese Arbeit, wie die Modellierung und Simulation von solchen LIBS-Spektren genutzt werden kann. Das Ziel ist es, Einblicke in die Eigenschaften von LIBS-Plasmen auf dem Mars zu erhalten und Modelle zu entwickeln, die bei der Analyse von realen Missionsdaten helfen können. Die Modellierung basiert sich auf einem stationären Plasma im lokalen thermischen Gleichgewicht (LTE). Das Plasma wird dabei in eine Reihe homogener Zonen unterteilt und Spektren werden mit dem Strahlungstransfer entlang einer eindimensionalen Sichtlinie durch diese Plasmazonen simuliert. Die Ergebnisse dieser Arbeit zeigen, dass auf LTE basierende Modelle gut auf LIBS-Spektren angewendet werden können, die unter Marsbedingungen gemessen wurden. Für zeitaufgelöste Daten kann die Anpassung eines Zwei-Zonen-Modells verwendet werden, um Einblicke in das Plasma zu erhalten und um die Elementkonzentrationen mit einer höheren Genauigkeit zu bestimmen, als es mit der Saha-Boltzmann-Methode möglich wäre. Allerdings sollten Nicht-Gleichgewichtseffekte in den frühesten und spätesten Phasen der Plasmalebensdauer berücksichtigt werden. Für zeitlich integrierte Spektren, wie sie bei aktuellen Marsmissionen gemessen werden, sind Anpassungen durch ein Zwei-Zonen-Modell aufgrund von zu langen Rechenzeiten nicht durchführbar. Stattdessen kann durch die Methode der spektralen Entmischung eine Überlagerung von Spektren unterschiedlicher Temperaturen und Dichten verwendet werden. Diese Methode ermöglicht keine direkten quantitativen Bestimmungen der Elementkonzentrationen, ist aber ein hervorragendes Werkzeug, um einen Überblick über die große Menge an Informationen zu erhalten, die in den Spektren enthalten sind. / Motivated by existing challenges in analysing LIBS spectra and the increasing quantity of Martian LIBS data, this thesis investigates the modelling and simulation of LIBS spectra for the application to LIBS data in Martian atmospheric conditions. This is done with the aim of providing insights into the characteristics of Martian LIBS plasmas as well as developing tools to assist the analysis of real mission data. The modelling of LIBS spectra is based on a stationary plasma in local thermal equilibrium (LTE). The plasma is then divided into a series of homogeneous zones and spectra are simulated using radiative transfer along a one-dimensional line-of-sight through the plasma zones. The results of this thesis show that spectral modelling based on LTE can be well applied to LIBS data in Martian atmospheric conditions. For time-resolved data, fits of a two-zone plasma model can be used to obtain insights into the plasma as well as improved concentration estimates compared to the Saha-Boltzmann plot method. However, attention to non-equilibrium effects should be given at the earliest and latest stages of the plasma lifetime. For time-integrated spectra, i.e. real mission data, fits of the two-zone model are not feasible due to too long computation times. Instead, a superposition of spectra of different temperatures and densities, i.e. the spectral unmixing method, can be used. Although not directly allowing for quantitative concentration estimates, the method is a great tool to overview the large amount of information contained in the spectra.

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No description available.

This study took place in Malawi, south eastern Africa. Metal contamination of water and soil is a threat to the environment and human health and is a serious concern in many countries including Malawi. Blantyre is the city of commerce where most of the industry is located along the banks of the main rivers. Some of the industries produce wastewater, which due to poor access to wastewater treatment plants, is discharged without treatment into the environment. A match factory in Blantyre uses chromium as a colouring agent for match heads and very high concentrations of chromium(VI) have been measured downstream the factory with concentrations up to 56 mg/l, which is much higher than the WHO guidelines of 0.05 mg/l.  Chromium(VI) mainly occurs as chromate CrO42- and dichromate Cr2O72- ions. They are both toxic and carcinogenic and can cause mutations and chromosomal aberrations.   The aim of the study was to evaluate the efficiency of Granular Ferric Hydroxide (GFH) in adsorbing and removing chromium from an aqueous phase. Wastewater was collected from the match factory and by optimizing relevant parameters the removal efficiency was maximized. The parameters optimized were pH, dosage and contact time and the effect of initial concentration. After respective experiment, all samples were analysed for chromium using microwave plasma atomic emission spectroscopy (MP-AES).   The optimum pH was chosen to 8.0, the dosage to 17.4 g GFH/l and the contact time to 2 hours for a 95% removal of total chromium in undiluted wastewater. The removal efficiency of the GFH was 2.84 mg Cr/g GFH. To implement wastewater purification with GFH a number of practical issues have to be taken into consideration. Above all, a sufficient stirring method has to be devised as the removal efficiency is much affected by improper stirring. / Denna studie genomfördes i Malawi, sydöstra Afrika. Metallföroreningar i vatten och mark är ett stort problem i många länder, inklusive Malawi. Landets centrum för industri och handel ligger i Blantyre där de flesta av industrierna ligger längs med floderna. En del industrier genererar utsläppsvatten och på grund av dålig tillgång till vattenreningsteknik och vattenreningsanläggningar släpps mycket av det förorenade vattnet obehandlat ut i naturen. En tändsticksfabrik i Blantyre använder kromsalter för att färga tändstickshuvudena röda och höga koncentrationer av sexvärt krom har uppmätts nedströms fabriken. De uppmätta koncentrationerna var upp till 56 mg/l vilket är betydligt högre än WHO:s riktvärde på 0,05 mg/l. Sexvärt krom förekommer som kromat CrO42- och dikromat Cr2O72- joner vilka båda är mycket toxiska och cancerframkallande och därmed ett hot mot miljö och människor. Syftet med studien var att undersöka om granulära järnoxider (GFH) kunde användas som en adsorbent för att rena utsläppsvatten från kromater. Utsläppsvatten hämtades från tändsticksfabriken och genom att optimera relevanta parametrar kunde GFHns adsorbtionseffektivitet maximeras. Parametrarna som optimerades var pH, dos, kontakttid och initialkoncentration. Efter respektive experiment mättes kromkoncentrationen med mikrovågsplasma atomemissionsspektroskopi (MP-AES) Det optimala pH-värdet valdes till 8.0, dosen till 17.4 g GFH/l med en kontakttid på 2 timmar för en 95.3% reningsgrad på outspätt utsläppsvatten. Adsorptionseffektiviteten på GFHn var 2.84 mg Cr/g GFH. För att implementera vattenrening med GFH behöver flera praktiska aspekter tas med i beaktning. Framförallt är det viktigt med en bra omrörning för att GFHn ska kunna adsorbera effektivt.

In analytical chemistry the main goal is normally to determine the identity and/or concentration of one or more species in a sample. The samples analyzed are often natural samples, containing numerous different species in a complex matrix and the choice of technique for multi-elemental detection is in general inductively coupled plasma spectrometry. The chemical forms of an element can affect many of its characteristics e.g. toxicity, which makes speciation analysis important. Therefore, determination of the identity and quantity of an element is still important, but for many applications measurements of total element concentration provides insufficient information. To be able to perform speciation analysis, separation, identification and/or characterization of the various forms of elements in the sample has to be accomplished. Speciation analysis has been employed in a wide range of disciplines, including for example environmental science, biology and clinical chemistry. This thesis describes work to improve and understand the elemental speciation analysis with liquid chromatography coupled to plasma spectrometry and also highlights the importance and potential of the synergy between atomic spectrometry and molecular mass spectrometry. The combination of the matrix tolerant, robust and very sensitive plasma spectrometry used together with molecular mass spectrometry, which provides structural information and the possibility to identify unknown species, is demonstrated to be a very powerful tool for speciation analysis. In this thesis methods are developed for on-line sample clean-up and pre-concentration coupled to liquid chromatography and plasma spectrometry, which makes handling of small sample volumes easier and also decreases the risk of contamination. The problems associated with organic modifiers in plasma spectrometry are also addressed. Applications of speciation analysis are exemplified by analysis of aluminium-chelated siderophores in field-soil solutions and organic phosphorous species in aquatic sediments. The possibility to analyze un-dissolved samples as slurries with minimal sample preparation is also discussed.

Le contexte de cette thèse est la production du vecteur énergétique hydrogène par thermolyse de la vapeur d’eau consistant en la dissociation de la molécule H2O en oxygène (O) et hydrogène (H). Le dispositif employé est une torche à plasma d’arc non transféré développée au LAEPT. Après l’exposition de la théorie sur la physique des plasmas et la spectrométrie d’émission atomique nécessaire à l’exploitation des mesures, cette thèse présente l’évolution de la torche à plasma ainsi que son environnement nécessitée par la présence de gaz instables et explosifs. Les mesures des différentes grandeurs électriques, hydrauliques et spéctrométriques ont permis la détermination des caractéristiques physique et chimique d’un plasma formé d’un mélange de vapeur d’eau – d’argon. La détermination de grandeurs telles que la température du jet plasma, la conductivité électrique, l’enthalpie massique et la densité électronique, est basée sur la comparaison entre expérimentation et théorie. / The context of this thesis is the production of hydrogen as an energy vector by steam thermolysis consisting in the dissociation of H2O molecule into oxygen (O) and hydrogen (H). The process used is a plasma torch device developed by the LAEPT. After presenting the theory of plasma physics and atomic emission spectroscopy which will help to make the most of the measured realized, this thesis will show the evolution of the plasma torch device and the experimental environment required to work with explosive and unstable gases. Some measurements like electrical, hydraulic and spectroscopy magnitudes made it possible to determine the chemical and physical characteristics of a water vapor – argon plasma. A comparison between experiments and theoretical knowledge will enable to determine the temperature of a flow of plasma, electrical conductivity, enthalpy and the electronic density.

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No. of bitstreams: 1 angelamariaferreiradeoliveiralourdes.pdf: 1193191 bytes, checksum: 66a561f0014fed2c1b249bc429df57de (MD5) Previous issue date: 2014-07-28 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Uma das fontes de elementos essenciais utilizados em fertilizantes são os resíduos industriais, tais como o pó de aciaria. Essas substâncias constituem uma alternativa viável ao fornecimento de nutrientes para as plantas. Mas, por outro lado, esses resíduos podem conter elementos altamente tóxicos. Neste trabalho, amostras de fertilizantes, pó de aciaria e amostras de fertilizantes fortificadas com pó de aciaria foram caracterizadas utilizando espectrometria de absorção atômica com chama (F AAS), espectrometria de emissão com chama (F AES), espectroscopia no infravermelho (IV), espectroscopia Raman e difração de raios X (DRX). Para a determinação de Cr, K, Na, Pb e Zn nas amostras investigadas por F AAS e F AES, otimizou-se um procedimento de extração usando banho de ultrassom, cujas condições ótimas para a extração foram: 50 mg de fertilizantes, 5,00 mL de água régia diluida (50% v/v) e seis etapas de 20 minutos de sonicação, sendo intercaladas com 1 minuto de agitação. Os resultados obtidos foram concordantes a 95% de confiança para todos os analitos em relação ao método de referência adotado (por adição de padrão), apresentando adequadas precisão (RSD < 10%) e exatidão (recuperações entre 90 a 103% para os fertilizantes e de 85,0 a 105,4% para o pó de aciaria). As espectroscopias do Infravermelho e Raman mostraram-se eficientes para a análise mineralógica, cujos resultados foram confirmados utilizando-se a técnica de DRX. Assim, com as técnicas utilizadas (IV, Raman e DRX) foi possível conhecer a composição orgânica e inorgânica das amostras analisadas. A análise exploratória dos dados obtidos usando as técnicas de PCA (análise de componentes principais) e HCA (análise hierárquica de clusters) permitiu a diferenciação de amostras fortificadas a partir de 5% de pó de aciaria (F AAS e F AES) das amostras não fortificadas, a associação quimiométrica desses com os dados dos espectros de IV, permitiram que a classificação ocorre-se mesmo na presença de pó de aciaria puro. Os dados obtidos através dos espectros de IV e Raman, juntos permitiram a classificação de amostras fortificadas a partir de 1% de pó de aciaria. / Industrial residues, such as flue dust, has being used as a source of essential trace elements in fertilizers . These residues have different essential elements and can supply the plant necessity for mineral nutrients. On the other hand, these residues may also contain highly toxic elements. In this work, samples of fertilizers, flue dust and fertilizer samples spiked with different concentrations of flue dust were characterized using different analytical techniques such as: flame atomic absorption spectrometry (F AAS), flame atomic emission spectrometry (F AES), infrared spectroscopy (IR), Raman spectroscopy and X-ray diffraction (XRD). For the determination of Cr, K, Na, Pb and Zn in the investigated samples by F AAS and F AES an extraction procedure using ultrasound bath was optimized. The optimum conditions for the analytes extraction were: 50 mg of fertilizers, 5.00 mL of diluted aqua regia solution (50 v/v %). The developed method was conducted in six steps of sonication per 20 minutes with intervals of 1 minute (on stirring). The results were in agreement at 95% confidence level for all analytes investigated in relation to the reference method adopted (standard addition). Appropriated precision (RSD <10%) and accuracy were obtained with recoveries between 90-103% for fertilizers and 85-105% for flue dust sample. The IR and Raman spectroscopy proved mineralogical (organic and inorganic) information, which were attested by DRX. Exploratory data analysis using PCA (principal component analysis) and HCA (hierarchical cluster analysis) techniques allowed differentiating spiked samples (from 5% of flue dust) and non-spiked samples by using data from F AAS and F AES analysis. The association of elemental data with IR and Raman data allowed differentiating spiked samples from 1% of industrial flue dust.

Dependence of glutathione concentration on the amount of thallium in the plant was studied. Observed plant was maize (Zea mays) which was divided to two parts – root and overground. Two culture procedures were elaborated where seeds and young seedlings were cultivated in a solution of thallium of concentration 0, 1, 3, 5, 8, a 10 µmol/l. Extraction agents used during extraction were phosphate buffer and solution of ascorbic acid. Determination of glutathione was realized by capillary electrophoresis (CE) and high performance liquid chromatography (HPLC). Diode array detector (DAD) was used in both methods. Quantification of the thallium amount in the plant was done by method of inductively coupled plasma-atomic emission spectrometry (ICP-AES).