This thesis work aims to develop electrochemical sensors for sub-ppb level detection of inorganic and organic pollutants in drinking water with environmentally benign materials and processes. While traditional laboratory-based methods such as mass spectroscopy, and chromatography have been used to analyze the concentration of contaminants in drinking water, miniaturized electrochemical sensors offer a compelling alternative to those methods, enabling rapid on-site cost-effective detection of low concentrations of pollutants. In this research, a set of three-electrode sensors was designed and fabricated on a flexible substrate using a screen-printing technique. Additionally, an in-situ electrochlorination process was implemented to create the reference electrode. These sensors were utilized to precisely detect lead ions and perfluorooctane sulfonate (PFOS) in drinking water. The first set of sensors was fabricated to measure the concentration of lead ions, a toxic inorganic pollutant, in potable water. The novelty of the proposed research lies in using non-toxic, biodegradable sodium alginate grafted with 2- acrylamido-2-methyl propane sulfonic acid (AMPS) and conductive fillers for trace-level lead ion detection in water. The principle of square wave anodic square wave stripping voltammetry (SWASV) was used to determine the trace level lead ion concentration. Employing a similar approach with a different material, a PFOS sensor was developed. Utilizing chitosan, one of the sustainable and biodegradable biopolymers found in crustacean shells, rapid parts-per-trillion (ppt) level PFOS detection by electrochemical impedance spectroscopy (EIS) was demonstrated. The proposed sensors made low-cost electrochemical detection of contaminants such as lead ions and PFOS possible with eco-friendly materials and processes.

In an electrochemical sensor, the sensing performance is mainly dependent on the mass transport of the analyte towards the working electrode-electrolyte interface and working electrode properties. Carbon nanomaterials like carbon nanotubes are widely employed to modify the working electrode properties for sensitive detection. A simulation model is formulated to investigate the effects of modifying a planar bare electrode with carbon nanotubes on electrochemical detection of fenitrothion (FT, an organophosphate). The model revealed that porous electrodes caused the change in mass transport regime and influenced FT’s electrochemical response. The results aided in understanding the influence of the porous electrode on analyte detection and thus assisted in the fabrication of an ultrasensitive electrochemical sensor. Simulation supported synthesis of a highly sensitive ink to produce highly porous and electrocatalytic electrodes. Activated carbon (AC) possesses high porosity and surface area, but they suffer from lower electrical conductivity. To enhance their conductivity, AC was co-doped with nitrogen and sulfur. Multiwalled carbon nanotubes were incorporated to further improve their porosity and electrocatalytic properties. The synthesized nitrogen-sulfur co-doped activated carbon coated multiwalled carbon nanotube (NS-AC-MWCNT) ink produced highly porous electrocatalytic electrodes. The sensor revealed a 4.9 nM limit of detection (LOD) under optimized conditions. However, it failed to overcome the enzymatic sensors’ performances. The ultrasensitive performance was achieved by incorporating a detecting agent in the ink that instilled analyte capture ability. Metal oxides like ZrO2, MnO2, and MgO possessed affinity towards organophosphate (fenitrothion), heavy-metal ion (lead), and nutrient (nitrite). Metal oxides were modified with 3,4-dihydroxylbenzaldehyde (DHBA) – Chitosan (CHIT) to produce well dispersed and uniformly coated stable electrodes. The ZrO2-DHBA-CHIT/NS-AC-MWCNT sensor achieved a remarkable limit of detection of 1.69 nM for FT. The sensor's performance exceeded the enzymatic-based sensors. The commonly found chemical interferents had negligible interference. The sensor produced reliable and satisfactory performance in lake and tap water. The MnO2-DHBA-CHIT/NS-AC-MWCNT/GCE and MgO-DHBA-CHIT/NS-AC-MWCNT/GCE sensors produced an enormous improvement in the sensor performance compared to unmodified electrodes for lead and nitrite detection. The preliminary results on detecting other pollutants like lead and nitrite showed the importance of the methodology in providing a platform for a new class of metal oxide-based sensors. / Thesis / Doctor of Philosophy (PhD) / The growing population and rapid industrial development are affecting the water quality worldwide. The major water pollutants are organophosphates, heavy metal ions, and nutrients. These water pollutants are harmful, and their bioaccumulation poses a major health concern. In the USA alone, water quality issues are predicted to cost $210 billion annually. Therefore, sensors to detect water pollutants are developed to monitor their environmental footprints. Electrochemical sensors are popularly used to detect water pollutants owing to their low-cost and high sensitivity. The objective of this dissertation was to fabricate highly sensitive and specific electrochemical sensors to detect organophosphate (e.g., fenitrothion, FT), heavy metal ion (e.g., lead), and nutrient (e.g., nitrite). The sensors were fabricated with ink based on nanomaterials like carbon nanotubes and detecting agents like metal oxides. The fabricated sensors achieved very high sensitivity and specificity and can detect water pollutants in lake and tap water.

The objectives of this study were to determine: (1) whether or not heterotrophic microorganisms exert an effect on the trihalomethane (THM) or total organic halogen (TOX) formation potentials of algal extracellular products (ECP), and (2) whether or not diurnal cycling of THM and TOX precursors occurs in vitro. These objectives were addressed through culture studies of heterotrophic microorganisms and pure algae from both the green and blue-green divisions. Culture conditions were varied to study different aspects of algal and bacterial interactions. Results from continuous light assays indicated that heterotrophs, grown in the same culture vessel with algae, affected an increase in the potential of chlorinated culture filtrate to form THMs. No significant changes in TOX-formation potential were observed. Heterotrophs grown in volumes of algal ECP (cell-free filtrates of algal cultures) used the algal-produced organic carbon as their sole carbon source. These microorganisms further reduced both the dissolved organic carbon (DOC) concentration and the concentration of the DOC fraction that reacted to form TOXs. The fraction which produced THMs was not reduced. Heterotrophic microorganism metabolic activity increased the rate at which THMs fanned from chlorinated algal ECP but did not alter the seven-day THM-formation potentials. Their activity also increased the initial rate of TOX formation, but decreased the seven-day formation potential of these compounds. Attempts to demonstrate diurnal cycling of the concentration of THM precursors and other halogenated organic precursors, a phenomenon previously demonstrated in a eutrophic reservoir, were unsuccessful. / M.S.

[EN] The contamination of water resources with many industrial, agricultural and other chemicals is one of the key environmental problems that humanity is facing nowadays. Despite the fact that they are usually present at very low concentration, they possess a significant risk to aquatic and human life. To address this issue many national and international institutions set different regulations to monitor and control the water quality. Currently, the monitoring of compounds included in official watch lists is conducted by chromatographic and mass spectroscopic methods. These techniques are approved as "gold standards" for analytical quantitation of organic residues in water. Although they are sensitive and reproducible, cannot be used on-site. The need of sampling and centralized laboratory measurements makes not only the overall cost high but lowering the efficiency of the analysis. Therefore, there is an urgent need to develop suitable field methods to facilitate the in situ measurements at a low cost. Biosensors are therefore an alternative technology that can provide sensitive results in a fast and affordable way. This thesis has focused on the development of a biosensor based on immunoassays and compact disk technology, for the multiplex detection of priority water contaminants. As the methods based on the immunorecognition events are challenging in terms of the selectivity and sensitivity, the major part of the thesis was the selection of the immunoreagents, assay form and procedure. For the detection part, gold nanostructures were selected as sensitive tags for signal enhancement. Therefore, different nanoparticles were studied in order to select the optimal size in terms of the signal enhancement, sensitivity and antibody amount used. Also, the assays performances with signal enhancement and without any amplification were evaluated. The best immunoassay was selected for developing the multiplexed assay. Furthermore, an approach to improve the readout sensitivity of microimmunoassays based on used of gold nanoparticles as both capture and detection species was demonstrated. The method is based on the performance of the immunorecognition event in a homogeneous mode and detection part in the heterogeneous format. Finally, representative water samples were analysed to confirm the applicability of the multi-residue assay. The analytical properties have been established for each methodology and the obtained results have been validated by comparison with reference techniques. The investigations carried out in this work, have resulted in new insights in immunoassay technique that could be useful for screening applications. / [ES] La contaminación de aguas superficiales causada por plaguicidas y productos industriales es actualmente, uno de los grandes problemas medioambientales. Aunque estas sustancias están presentes a niveles muy bajos, tienen efectos perjudiciales en el medio en general y especialmente en humanos. Por este motivo, diferentes instituciones han regulado los niveles de contaminantes en áreas de controlar de la calidad de las aguas, creando listas prioritarias de sustancias peligrosas y tóxicas para el medio ambiente. Actualmente, la monitorización de los contaminantes incluidos en las listas oficiales se realiza mediante técnicas cromatográficas y espectrometría. Estos métodos analíticos están aprobados como técnicas de referencia para la determinación de residuos orgánicos presentes en aguas naturales. A pesar de ser técnicas fiables, reproducibles y sensibles, los métodos cromatográficos no están exentos de inconvenientes. Este tipo de metodologías requiere una instrumentación costosa y una laboriosa preparación de muestra, que hacen que el análisis sea en general complejo. Por ello, el desarrollo de métodos analíticos alternativos que faciliten hacer medidas in-situ a bajo coste y con gran capacidad de trabajo es de gran utilidad. En este sentido, las técnicas inmunoquímicas tienen un gran potencial analítico ya que son en general sensibles y selectivas, se pueden utilizar en el lugar de la toma de muestra y tienen capacidad multianalito. Esta tesis se ha centrado en el desarrollo de un sistema biosensor, basado en la tecnología de disco compacto, para la detección multianalito de diversos contaminantes prioritarios en aguas naturales. Las limitaciones más críticas para el desarrollo de un biosensor multianalito mediante métodos inmunoquímicos son los relacionados con su sensibilidad y selectividad. Por lo tanto, una parte importante de la tesis se ha centrado en la selección de inmunoreactivos, formato y optimización de diferentes parámetros claves del ensayo. Una estrategia utilizada para aumentar la sensibilidad de los ensayos ha consistido en marcar la inmunoreacción con nanopartículas de oro. Para ello, se ha estudiado diferentes tipos (esféricas y cilíndricas) de distinto tamaño y se han comparado sus prestaciones analíticas (relación señal ruido, sensibilidad etc.) También, se han desarrollado inmunoensayos cuantitativos sin necesidad de amplificación de la señal. Por otro lado, se ha desarrollado una aproximación que hemos denominado "inmunocaptura" basada en el uso de nanopartículas de oro como especie de captura de analitos en disolución y que actúa como marcador de la inmunointeracción que tiene lugar en la fase sólida. Finalmente, se han analizado muestras de agua naturales dopadas con distintos niveles de los analitos objeto de estudio para evaluar la utilidad de las metodologías desarrolladas como herramienta de screening masivo en el área medioambiental. Los resultados obtenidos han sido comparados con los obtenidos mediante las técnicas de referencia. Las investigaciones realizadas han permitido desarrollar nuevos formatos de ensayo y conocimientos inmunoquímicos aplicados a la tecnología de disco compacto, aportando nuevas herramientas de screening que permiten la determinación simultánea de contaminantes en aguas naturales por debajo de las concentraciones establecidas en la normativa europea de calidad de agua. / [CA] La contaminació d'aigües superficials causada principalment per plaguicides i altres productes industrials és un dels grans problemes mediambientals actuals. Malgrat que aquestes substàncies estan presents en nivells molt baixos, tenen efectes perjudicials en humans i animals. Per aquest motiu, diferents institucions estatals han regulat els nivells de contaminants en àrees de control de la qualitat de l'aigua, creant llistes prioritàries de substàncies perilloses i tòxiques per al medi ambient. Actualment, la monitorització dels contaminants inclosos en les llistes oficials es realitza mitjançant tècniques cromatogràfiques i d'espectroscòpia de masses. Aquests mètodes analítics estan aprovats com a tècniques de referència per a la determinació de residus orgànics presents en aigües naturals. Malgrat ser tècniques fiables, reproduïbles i sensibles, els mètodes cromatogràfics no estan exempts d'inconvenients. Aquest tipus de metodologies requereix una instrumentació costosa i una laboriosa preparació de mostres que fan que l'anàlisi sigui, en general, complex. Per això, el desenvolupament de mètodes analítics alternatius que facilitin la possibilitat de fer mesures in-situ a baix cost i amb gran capacitat analítica és de gran utilitat. En aquest sentit, les tècniques inmunoquímiques tenen un gran potencial analític ja que són, en general, sensibles i selectives, es poden utilitzar en el lloc de presa de la mostra i tenen capacitat multianalit. Aquesta tesi s'ha centrat en el desenvolupament d'un sistema biosensor, basat en la tecnologia de disc compacte, per a la detecció multianalit de diversos contaminants prioritaris en aigües naturals. Les limitacions més crítiques per al desenvolupament d'un biosensor multianalit mitjançant mètodes inmunoquímics són sensibilitat i selectivitat. Per tant, una part important de la tesi es va centrar en la selecció de inmunoreactius, format i optimització de diferents paràmetres clau de l'assaig. La detecció es va dur a terme mitjançant l'ús de nanopartícules d'or com a marcadors de la inmunointeracció i amplificació de la senyal analítica. S'han estudiat diferents estructures d'or (esferes i cilindres) de diferents tamanys, i s'han comparat les seves prestacions analítiques (relació senyal-soroll, sensibilitat, etc.). També s'han desenvolupat immunoassaigs quantitatius sense necessitat d'amplificació del senyal. Per altra banda, s'ha desenvolupat una aproximació que hem denominat "inmunocaptura", basada en l'ús de nanopartícules d'or com a espècie de captura d'analits en dissolució i que actua com a marcador de la inmunointeracció que té lloc en la fase sòlida. Finalment, s'han analitzat mostres d'aigües naturals dopades amb diferents nivells dels analits objecte d'estudi per avaluar la utilitat de les metodologies desenvolupades com a eina de "screening" massiu en l'àrea mediambiental. Els resultats obtinguts han sigut avaluats per comparació amb els obtinguts mitjançant tècniques de referència. Les investigacions realitzades han permès desenvolupar nous formats d'assaig i coneixements inmunoquímics aplicats a la tecnologia de disc compacte, aportant noves eines de "screening" que permetin la determinació de contaminants en aigües naturals per sota dels límits de concentració establerts per les normes internacionals de la qualitat de l'aigua. / Dobosz, PD. (2017). Screening methodologies for the determination of water contaminant residues by compact disk technology [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/79548

The molecular size, charge, and solubility, distributions of natural DOC in raw and treated surface waters were investigated to determine the types of organic compounds removed by coagulation and settling. The distribution of organic precursors that react with chlorine to form organic halide compounds was also determined, along with the reaction rates. DOC removal by coagulation was size dependent. Compounds over 5,000 d were readily removed while compounds under 1,000 d were largely unaffected. Acidic and basic molecules were precipitated much more effectively than neutral ones. Both hydrophilic and hydrophobic molecules were selectively removed compared to compounds of intermediate solubility. Two groups of organic halide precursors were identified. Fulvic acids had high specific organic halide yields, and fast reaction rates with chlorine, but could be effectively removed by coagulation. Nonpolar neutral compounds were lower in molecular weight, slower to react with chlorine, and produced less organic halide, but could not be precipitated by coagulation. / Ph. D. / incomplete_metadata

The Arctic has long been considered to be a pristine environment, far from population centers and pollution sources. The detection of synthetic organochlorine compounds in various elements of the Arctic food web has confirmed the global dispersion of pollutants, particularly of persistent compounds such as organochlorines and heavy metals. Levels of heavy metals, although elevated, appear to be naturally so throughout much of the Arctic. Arctic pollution is both a humanitarian and ecological concern. Many arctic coastal communities depend heavily on marine mammal fat for sustenance, and are therefore potentially exposed to high levels of organochlorines and some metals. From an ecological perspective, the structure of arctic food webs, the importance of lipid mobilization for winter survival, and the adaptive physiologies of arctic organisms may result in an enhanced response to contaminant exposure. This thesis assesses the exposure and effect of organochlorine and heavy metal exposure in inland freshwater ecosystems of Arctic Alaska, and evaluates the physiological response of arctic grayling to experimental polychlorinated biphenyl (PCB) exposure. / Graduation date: 1995

Mémoire (M.P.Aquat.)--Université du Québec à Chicoutimi, 1990. / Document électronique également accessible en format PDF. CaQCU

Thesis (M.S.)--Oregon State University, 2011. / Printout. Includes bibliographical references (leaves 69-74). Also available on the World Wide Web.

M.Sc. / The contamination of water by toxic compounds is one of the most serious environmental problems today. These toxic compounds mostly originate from industrial effluents, agriculture runoff, natural sources (e.g. heavy metals in water from rocks and soil erosion) and human waste. The contamination, which is both “organic” and “inorganic” has an impact on the environment and human health. The demand for water and the pressure to re-use this valuable resource has increased the need for improved techniques and materials to remove pollutants from water. The Nanomaterials Science research group at the University of Johannesburg has focused on developing synthetic polymers that can be employed in water treatment and pollutant monitoring. Recently, cyclodextrins (CD) and carbon nanotubes (CNTs) have been included in polymers for this application. For example, CD-co-hexamethylene-/toluene-diisocyanate polyurethanes and CNT-modified equivalents have been developed and have been successfully applied in removing organic contaminants from water to very low levels.1 Calixarenes are synthetic analogues of cyclodextrins that can be exploited via chemical modification to express a range of properties. In the present study, calixarenes, thiacalixarenes and carbon nanotube-based polymeric materials incorporating these molecules have been synthesised, characterised and tested for removing both organic pollutants (such as p-nitrophenol) and inorganic pollutants (Cd2+, Pb2+) from water. Lead(II) and Cadmium(II) are a threat in South Africa because of their toxicity, and while p-nitrophenol is much less of a problem it represents a useful model organic pollutant. The absorption capacity of the polymers towards heavy metals and organic contaminants was tested by mixing the polymer with synthetic water containing known concentration of the contaminants at about 10 mg/L. Atomic absorption spectrometry (AAS) and ultraviolet-visible spectrometry (UV-vis) were used to determine the levels of heavy metals and organic contaminants, respectively. The target pollutants (Cd2+, 1 see KL Salipira MTech dissertation, University of Johannesburg 2008 Pb2+ and p-nitrophenol) were all successfully removed from water by the various polymers, however the degree of removal and loading capacities of the polymers differed. This information gives some insight into what functional components are needed for making successful adsorbents. It was observed, for example, that ptert- butylcalix[8]arene/hexamethylene diisocyanate (C8A/HMDI) had a higher adsorption capacity towards p-nitrophenol and Pb2+ than towards Cd2+, and also a higher capacity than the corresponding calix[4]arene polymers with smaller calixarene cavities.

No description available.