Dissertations / Theses on the topic 'Environmental chemistry'

In many secondary education chemistry classrooms, teachers have a difficult time introducing chemistry topics in a way that will be interesting to the high school student. The development of a materials and environmental chemistry teacher's manual will help teachers introduce a variety of selected topics in an interesting fashion to the students. This manual focuses on the subjects covered for freshman and sophomore level students. The manual uses five separate experiments to introduce topics such as the electromagnetic spectrum and solubility. The five experiments include a test on tennis shoe stiffness and energy dissipation ability, pesticides in water, grease in vent hoods, concentration of salicin in willow, and a paint adhering test on a vehicle bumper. The manual introduces several chemistry concepts by relating the subject to projects that the students can understand because they are useful to society and the environment. By presenting the material in this manner, students should be able to focus on the specific concepts longer, thus understanding the concepts better. Some of the lessons cover a topic that is required by the American Chemical Society (ACS) for postsecondary education materials chemistry classes. The inclusion of these topics will increase the knowledge of future chemistry students in an area that will be required at multiple postsecondary education institutions. Each experiment topic includes background information, teacher information, lesson objectives, ACS topic and/or experimental subject covered, lesson, definitions, supplements, transparencies, and a worksheet.

Electroanalytical chemistry provides an elegant technique by which to explore, amongst others, various biological and environmental applications. To this end, four areas of electroanalytical chemistry are investigated in order to develop biologically- and environmentally-relevant sensors, together with exploring the electro-generation of a biologically important molecule and the diffusional factors that may affect this generation.The first study involves the dynamics of the bond cleavage involved in the electro-generation of nitric oxide from a range of N-nitrosoamines. Adsorption phenomena is found to be of pivotal significance in the release of nitric oxide from two of the compounds explored, namely cupferron and N-itrosodiphenylamine, whilst bis(nitroso)phenylenediamine released, as hoped, two moles of nitric oxide in a single step. The challenge is to isolate the product, and to determine which form of nitric oxide was generated, i.e. the cation, NO+ or nitric oxide, NO. Isolation remains a challenge, however analysis of the reaction mechanism does allow a prediction of the product, be it NO+ or NO. NO+ is a highly oxidising species and hence is difficult to isolate, therefore it is far more preferable to electro-generate NO, which cupferron was the only compound investigated that achieved this.The second study involved the investigation of axiosymmetric anisotropic diffusion to disc shaped microelectrodes, with theoretical expressions examined with experimental data in order to examine the factors. A ferrocene/PEG in acetonitrile system was examined in order to test this theory and to determine the effect of viscosity on the diffusion coefficients, and also if it was possible to investigate the anisotropy by effectively "blocking" either Dr or Dz. Excellent symmetry between theory and experiment was found, hence the focus turned to a ferricyanide in caesium pentadecafluorooctanoate/D2O system where once again the calculated value of root(Dr.Dz) affords a theoretical waveshape with reasonable agreement between theory and experiment. Potential step chronoamperometry then determined separate values for Dr and Dz, with the resulting values affording an anisotropic ratio of 1.7, suggesting radial diffusion dominance over planar diffusion.Third, the modification of electrodes is explored in order to develop biologically and environmentally relevant sensors. In a first strand, two liquid crystal ferrocene compounds are examined, immobilised on the surface of a glassy carbon electrode simply via solvent evaporation. Both compounds demonstrated typical ion transfer processes across the liquid | liquid interface, with both anion insertion and cation expulsion processes demonstrated. The differing voltammetry observed in the presence of different anions formed the basis of the anion sensor.In a second avenue in this modified electrode work a cation sensor is developed, working on the basis of a biofilm, i.e. developing a modification of the electrode surface to mimic the action of a biofilm in chelating with cations. With this in mind, a basal plane graphite electrode was modified with a diazonium salt and polyphenol, and through the introduction of alginic acid into the polyphenol layer a degree of selectivity between the Group 2 cations was demonstrated, although quantitative properties eluded the work.Last, an environmental sensor for cyanide was developed using an electrochemical probe, tetramethylphenylenediamine (TMPD). The reaction between the electro-generated TMPD.+ and cyanide is successfully followed colorimetrically, before product characterisation studies help to determine the reaction mechanism. Voltammetric studies form the basis of a sensor, with square wave voltammetry achieving a detection limit of 4.4 microM. The reaction between TMPD and cyanide allowed remediation studies to be undertaken, with river freshwater samples from North Yorkshire (54deg 15' 19.19" N, 1deg 46' 13.49" W) and the Rodalquilar mine, Spain, (36deg 50' 52.9" N, 2deg 02' 36.87" W) demonstrating the removal of cyanide by an impressive three orders of magnitude.

Lead emitted into the environment, primarily from the combustion of leaded petrol and industrial activities, such as metal smelting and coal burning, retains the isotopic signature of the ores from which it is derived. Accordingly, it is possible, at least in principle, to distinguish sources of lead pollution via isotope ratio measurements. In this study, inductively coupled plasma mass spectrometry (ICP-MS) was used to characterise and investigate the extent of variation of lead isotope ratios in contemporary and historical environmental materials in Scotland. Reliable analytical methods were established for atomic absorption spec trometric measurement of lead, ICP-MS determination of stable lead isotopes, 208Pb, 207Pb and 206Pb, and gamma spectrometric assay of radioactive 210Pb in lake sediments and peat cores. Leaded petrol, atmospheric particulates and street dust sampled in central Edinburgh between February 1989 and December 1991 had mean 206Pb/207Pb ratios of 1.082±0.024, 1.092±0.011 and 1.109±0.016, respectively. These isotope ratios were found to be depleted in 206Pb compared with a mean of 1.160±0.012 for tap water in contact with lead pipes and typical ratios of 1.17-1.19 for British lead ore deposits and coal. Paint, with an observed wide range of isotopic compositions (206Pb/207Pb ratio range of 1.083-1.183 and 208Pb/207Pb ratio range of 2.363-2.592), appears to have significantly influenced house dust and some street dust isotopic signatures. Such overlaps and influences may hinder the quantitative apportionment of sources and routes of exposure in general population studies, especially for children. The identification of sources and the quantification of inputs of lead to the Scottish environment during the last 100-200 years was investigated using 210Pb-dated sediments from oligotrophic, eutrophic and acidified lochs and ombrotrophic peat cores. Pollutant lead fluxes to 210Pb-dated sediments from Round Loch of Glenhead tripled in magnitude from approximately 3mg/m2/y in the early 1800s to reach a maximum of 32mg/m2/y in the early 1940s. A similar pattern of deposition was observed in sediments from Loch Lomond and 210Pb-dated peat cores, which reveal a 10-20 fold enhancement in the fluxes of lead deposited from the atmosphere since 1800 both at rural sites near the heavily populated and industrialised central belt and on a remote island off the north-west coast of Scotland. This has been accompanied, largely during the last 50 years, by a significant reduction in the 206Pb/207Pb ratios from the 19th century values of 1.17-1.18 to 1.14-1.15, attributed to increasing contributions from car-exhaust emissions of particulate lead derived from alkyllead petrol additives manufactured from ores comparatively depleted in 206Pb. Trends in 206Pb/207Pb ratios of pollutant lead in Loch Lomond and Round Loch of Glenhead sediments were found to be consistent with atmospheric deposition records observed in peat, decreasing from 19th century values of 1.17-1.19 to 1.12-1.14. The calculated relative contribution of petrol lead to post-1950 sediments from Loch Lomond of 50-75% is considerably higher than that determined for the same period in sediment from Round Loch of Glenhead (5-30%) and for a peat core from Flanders Moss, a rural location in Scotland (27-43%), and indicates the importance of localised inputs, especially near industrial centres.

My Ph.D. activity developed along four lines of research dealing with non-thermal plasma (NTP) induced chemical processes for water remediation and biomedical applications. Specifically, I studied the effectiveness of atmospheric air plasma treatment in decomposing emerging organic contaminants (EOCs). The experimental setup used was a dielectric barrier discharge (DBD) reactor, a prototype developed in collaboration with the Department of Industrial Engineering of the University of Padova. Among EOCs, I chose six different contaminants, notably sulfamethoxazole, a veterinary antibiotic, triclosan, an antibacterial agent, perfluorooctanoic acid (PFOA), a perfluorinated organic contaminant, and the herbicides irgarol, metolachlor and mesotrione. Kinetics of their removal by plasma, intermediates of oxidation, possible degradation pathways and conversion to CO2 were evaluated. The achievement of more than 93% of conversion was observed for all the contaminants used at the initial concentration of 5 μM, except for PFOA (42%). An important advancement in my research involved the assessment of residual toxicity of plasma treated water samples. For this purpose, in collaboration with Prof. Giovanni Libralato (University of Naples), we tested the efficiency of plasma treatment in producing water free from ecotoxicological effects due to potentially toxic by-product residues. We tested one of the pollutants mentioned above, sulfamethoxazole (SMZ), an antibiotic listed among the most important emerging organic contaminants. A battery of acute and chronic toxicological test were employed: Daphnia magna, Raphidocaeilis Subcapitata and Vibrio Fischeri. It was found that toxicity of SMZ 5×10-4 M is minimized (V.fischeri) or reduced to zero (D. magna, R. Subcapitata) after 4 h of plasma treatment. To improve the efficiency of our DBD reactor, we tested the effect of addition of a photocatalyst, TiO2. We compared the kinetics of degradation of Irgarol in photocatalytic plasma process with those obtained when TiO2 was not included. The results obtained suggest that the effect of photoactivation by titanium dioxide in our reactor was negligible under the conditions employed. Possible reciprocal effects of different organic pollutants dissolved in water subjected to plasma induced advanced oxidation in our dielectric barrier discharge (DBD) reactor were then evaluated. As case study for this investigation, I chose the herbicides S-metolachlor and mesotrione, which are commonly applied in mixture. Results revealed that metolachlor does not affect mesotrione kinetics and viceversa when they are in solution, in 1:1 ratio. A new reactor was developed in our lab, in collaboration with Dr. Bosi from the Department of Industrial Engineering (University of Padova) with improved design and features with respect to the existing DBD reactor. The new reactor, operating in streamer discharge regime, was exhaustively characterized in collaboration with Dr. Gabriele Neretti (University of Bologna) and Dr. Barbara Zaniol (Consorzio RFX), and tested on phenol and metolachlor. Finally, during a four-month stage at the University of Bochum (Germany) I had the opportunity to work on a project dealing with plasma applications in the biomedical field under the supervision of Profs. Julia Bandow and Jan Benedikt. In particular, the effects of two plasma sources were tested in vitro on glyceraldehyde 3-phosphate dehydrogenase and E. coli. The results obtained for the enzyme suggest the importance of oxidation of the thiol group of the active site in plasma mode of action. The same approach was applied to assess the effect of ionic components of plasma by a new source developed by Prof. Benedikt (University of Bochum). The study of inactivation of the enzyme via plasma, with and without ions, showed a synergic effect between radicals and ions.
La Tesi riporta e discute i risultati ottenuti nell’applicazione di plasmi non termici per il trattamento ossidativo di inquinanti modello e ulteriori risultati relativi all’utilizzo del plasma in campo biomedico. L’apparato sperimentale impiegato è stato progettato e realizzato in collaborazione con il Dipartimento di Ingegneria Elettrica e produce una scarica a barriera di dielettrico (reattore DBD). Il sistema era già in uso nel periodo antecedente l’inizio della mia attività di dottorato. Le specie reattive che si generano a causa della scarica elettrica nell’aria umida sovrastante la fase liquida entrano in contatto con essa e possono reagire con l’inquinante organico in soluzione. Le specie reattive possono essere distinte in primarie, cioè generate direttamente dalla scarica per reazione del gas con gli elettroni energetici formando radicali, ioni e specie eccitate altamente reattive ed instabili, e secondarie prodotte per reazione delle stesse specie con le molecole del gas oppure con l’umidità presente. Il primo passo è stato quello di applicare tali scariche elettriche per il trattamento di diverse categorie di inquinanti emergenti allo scopo di valutare le potenziali applicazioni di questa tecnologia in relazione alle proprietà chimico fisiche degli inquinanti trattati. Sono stati selezionati i seguenti contaminanti organici persistenti: il sulfametossazolo, un antibiotico veterinario, il triclosan, un antibatterico, l’acido perfluoroacetico e tre erbicidi, l’irgarol, il metolachlor ed il mesotrione. Per tutti i composti in esame ho ottenuto profili esponenziali di degradazione in funzione del tempo di trattamento, da cui sono state ricavate le costanti cinetiche di pseudo-primo ordine. L’analisi HPLC-MS ha consentito l’identificazione degli intermedi e prodotti di degradazione, compatibili con possibili reazioni dovute all’azione dell’ozono e dei radicali ∙OH. Sono stati proposti inoltre i meccanismi di degradazione dei composti organici trattati. Lo scopo finale nell’uso di processi di degradazione avanzata è la completa conversione della componente organica a CO2. In seguito al trattamento al plasma, sono state riscontrate percentuali di mineralizzazione pari o maggiori al 93% per tutti gli inquinanti considerati, usati in concentrazione pari a 5 μM, fatta eccezione per l’acido perfluoroottanoico per cui la percentuale di mineralizzazione è stata considerevolmente più bassa (42%). Lo studio dei processi di degradazione al plasma è inoltre servito in alcuni casi da punto di partenza per ulteriori approfondimenti. È questo il caso dell’irgarol, in cui si è cercato di implementare l’effetto del plasma aggiungendo un fotocatalizzatore ampiamente utilizzato, TiO2. Non sono stati riscontrati tuttavia miglioramenti nell’effetto della scarica su tale inquinante indicando un trascurabile effetto fotocatalitico nelle condizioni sperimentali adottate. Un ulteriore avanzamento nelle ricerche in questo ambito è consistito nell’applicazione della scarica DBD su una miscela di inquinanti, il metolachlor e il mesotrione, solitamente utilizzati in combinazione in diverse formulazioni agricole. Gli studi cinetici effettuati hanno evidenziato che i due composti non si influenzano reciprocamente quando subiscono il trattamento al plasma in soluzioni miste in cui sono presenti in rapporto molare 1:1. Un importante parametro nella valutazione di una tecnica di depurazione consiste nell’analisi ecotossicologica del campione acquoso dopo il trattamento. A tale scopo, in collaborazione con il Prof. Giovanni Libralato del Dipartimento di Biologia dell’Università di Napoli, sono stati effettuati test tossicologici su campioni contenenti sulfametossazolo (SMZ), prima e dopo il trattamento nel reattore DBD. Allo scopo è stata utilizzata una batteria di test acuti e cronici per Vibrio Fischeri, Daphnia magna e Raphidocaelis subcapitata. I dati ottenuti a partire da una soluzione di SMZ 5·10-4 M hanno mostrato un elevato livello di tossicità della soluzione iniziale e la riduzione (V.fischeri) o l’azzeramento di tali effetti (D.magna e R.subcapitata) a seguito del trattamento nel reattore al plasma. Un nuovo reattore è stato inoltre ideato e realizzato in collaborazione con il Dr. Franco Bosi, del Dipartimento di Ingegneria Industriale dell’Università di Padova. La sorgente di plasma utilizza una scarica di tipo streamer ed è stata realizzata allo scopo di favorire un migliore trasporto delle specie reattive prodotte dalla scarica e ottimizzare la loro interazione con la soluzione da trattare. Il reattore è stato quindi caratterizzato in collaborazione con il Dr. Gabriele Neretti (Università di Bologna) e la Dr.ssa Barbara Zaniol (Consorzio RFX, Padova) e collaudato nel trattamento di due inquinanti organici, il fenolo ed il metolachlor. Infine nel corso di un periodo di quattro mesi di attività di ricerca presso il laboratorio della Prof.ssa Bandow dell’Università di Bochum (Germania) ho avuto modo di approfondire alcuni aspetti legati alle applicazioni del plasma atmosferico in campo biomedico. In particolare ho partecipato a studi sugli effetti di due diverse sorgenti al plasma su un enzima, gliceraldeide-3-fosfato deidrogenasi, in vitro e sul batterio E. coli. Il sito di attacco principale è risultato essere il sito attivo cisteina con conseguente ossidazione del gruppo -SH. Lo stesso approccio è stato applicato, in collaborazione con il Prof. Benedikt per lo studio degli effetti del plasma, in assenza e in presenza delle specie ioniche. I risultati ottenuti hanno evidenziato un effetto sinergico dovuto alla copresenza di specie neutre e ioniche.

Metal oxide nanoparticles (MONPs) are increasingly being incorporated in domestic and industrial products. They are expected to pass into waste water treatment facilities, and may inadvertently be applied in biosolids to agricultural soils. Very few nanotoxicity studies have been conducted in soils and the risk that MONPs pose to soil organisms are poorly understood. The aim of this study was to investigate the behaviour and effects of two MONPs with different solubilities on terrestrial organisms in soils. Exposure of earthworms to soils amended with up to 10,000 mg/kg nano-sized TiO2, a virtually insoluble nanomaterial, resulted in no adverse effects on earthworm population parameters such as survival or reproduction. Earthworms avoided nano-TiO2 amended soils, but only at nanoparticle concentrations higher than those expected for agricultural soils. The mechanisms resulting in the avoidance response, and nano-TiO2 transformations in soils, could not be further investigated because techniques to track nanoparticles in complex media are lacking. Subsequent studies focused on a sparingly soluble nanomaterial, nano-CuO, which releases Cu2+ ions as it dissolves. To identify nanoparticle-specific effects on organisms, the effects of the Cu2+ ions must be determined but little is known about the effect of nano-CuO on Cu2+ activity in soils. Tests revealed that Cu2+ activity in nano-CuO amended soils increased over a 56 d period, but were not comparable to those in soils amended with similar concentrations of micrometer-sized CuO or Cu(NO3)2, which are commonly used as treatments to control for the effects non-nanosized Cu in nanotoxicity tests. These results have implications for the design of experiments that test effects of dissolving particulates. A subsequent barley growth test demonstrated that there was no significant difference in plant growth or shoot Cu concentrations between soils amended with nano-CuO, micrometer-sized CuO or Cu(NO3)2 once growth was normalised to Cu2+ activity. These results demonstrate that release of metal ions can play an important role in toxicity of soluble metal-based nanoparticles and highlight the importance of direct measurement of potentially toxic products of nanoparticle dissolution. There was no evidence of nanoparticle-specific toxicity under the conditions studied either for earthworms exposed to nano-TiO2 or barley exposed to nano-CuO. The study highlighted some of the challenges of understanding the fate and effects of nanomaterials in soils, including the lack of techniques to track nanomaterials in complex media and the difficulty in designing toxicity tests that control for temporal changes to both nanoparticles and soils.
Les nanoparticules des oxydes de métaux (MONP) sont davantage incorporés dans les produits domestiques et industriels. Une importante proportion de ces nanoparticules est susceptible de se retrouver dans les usines de traitement d'eaux usées et d'être épandue sur les terres agricoles sous forme de biosolides. Dû au fait que peu de recherches sur la nanotoxicité ont été faites dans les sols, le risque que pose ces MONP aux organismes du sols est peu connu. Le but de cette étude est donc d'observer la réaction et les effets de deux MONP de solubilité différente dans des sols agricoles et artificiels. L'exposition des vers de terre dans des sols amendés avec jusqu'à 10,000 mg par kg de sol de nano-TiO2, un nanomatériel pratiquement insoluble, n'a causé aucun effet sur leur survie ou leur reproduction. Les vers de terre n'ont évité les sols modifiés de nano-TiO2, qu'à des concentrations de nanoparticules beaucoup plus élevées que celles attendues dans les sols agricoles. Les mécanismes impliqués dans la réponse d'évitement et les transformations de nanoTiO2 dans les sols n'ont pu être étudiés plus à fond par manque de techniques développées pour suivre les nanoparticules dans les médias complexes. Dans les recherches subséquentes, un nanomatériel de très faible solubilité, le nano-CuO, qui relâche des ions Cu2+ au fur et à mesure qu'il se dissout, a été choisi comme matériel d'intérêt. Afin d'identifier les effets spécifiques des nanoparticules sur des organismes, les effets du Cu2+ doivent être déterminés. Cependant, peu est connu sur l'activité du Cu2+ dans les sols traités avec des nano-CuO. Les recherches ont démontré que l'activité de Cu2+ a augmenté durant une période de 56 jours pour les sols amendés de nanoparticules de CuO mais cette augmentation ne s'est pas produite, à des concentrations égales, pour des sols enrichis de CuO de diamètre micrométrique ou même de sels de Cu(NO3)2 ; ces deux derniers traitements sont souvent utilisés comme tests contrôles lors d'études de nanotoxicité. Ces résultats ont des implications pour la conception des expériences pour évaluer les effets sur la dissolution des particules. Une étude ultérieure sur la croissance d'orge a démontré qu'il n'y avait aucune différence significative dans la croissance des plantes ou des concentrations de Cu dans les feuilles entre les sols modifiés avec du nano-CuO, CuO de taille micrométrique ou le Cu(NO3)2 une fois que les données furent normalisées en activité de Cu2+. Ces résultats ont démontré que la dissolution d'ions de métaux peut jouer un rôle important sur la toxicité des nanoparticules. Ils soulignent aussi l'importance de mesurer directement la concentration de produits de la dissolution de nanoparticules. Il n'y avait aucune évidence de toxicité spécifique aux nanoparticules sous les conditions étudiées pour les vers de terre soumis au nano-TiO2 ou pour l'orge soumis au nano-CuO. Cette étude a révélé certaines lacunes de compréhension dans le comportement du nanomatériel ajouté aux sols, des difficultés de tenir compte des changements temporels des nanoparticules et des sols ainsi que le manque de techniques disponibles pour suivre les nanoparticules dans les médias complexes.

Although gas and liquid chromatography have emerged as dominant separation techniques in environmental analytical chemistry, these methods do not allow for the concurrent analysis of chemically diverse groups of persistent organic pollutants (POPs). There are also a small number of compounds which are not easily amenable to either of these traditional separation techniques. The main objective of this thesis was to address these issues by demonstrating the applicability of packed column supercritical fluid chromatography (pSFC) coupled to mass spectrometry (MS) in various aspects of environmental chemistry. First, pSFC/MS analytical methods were developed for legacy POPs (PCDDs, PCDFs, and PCBs) as well as the emerging environmental contaminant Dechlorane Plus (DP), and issues relating to the ionization of target analytes when pSFC was coupled to MS were explored. Novel APPI and APCI reagents (fluorobenzene and triethylamine) were optimized and real samples (water and soil) were analyzed to demonstrate environmental applicability. The possibility of chiral and preparative scale pSFC separations was then demonstrated through the isolation and characterization of thermally labile hexabromocyclododecane (HBCDD) stereoisomers. The analytical pSFC separation of the α-, β-, and γ-HBCDD enantiomers as well as the δ and ε meso forms was shown to be superior to results obtained using a published LC method. Finally, technical mixtures of phosphorus flame retardants (RBDPP, BPA-BDPP, and DOPO; a group of related compounds which are challenging to analyze concurrently) were examined using multiple analytical techniques and pSFC was found to be the only method which facilitated the accurate determination of the components of all 3 mixtures. This thesis confirms the potential of pSFC/MS as a fast, green, and cost effective means of separating and analyzing environmental contaminants.

This thesis focuses on the development of quantitative structure-activity relationship (QSPR) models for physicochemical properties, e.g., vapor pressure and partitioning coefficients. Such models can be used to estimate environmental distribution and transformation of the pollutants or to characterize solvents properties. Here, chemoinformatics was used as an efficient tool for modeling to produce safe chemicals based on green chemistry principles. Experimental determinations are only available for a limited number of the chemicals; however, theoretical molecular descriptors can be used for modeling of all organic compounds. In this thesis, we developed and validated a global and local QSPR model for vapor pressure of liquid and subcooled liquid organic compounds, in which perfluorinated compounds (PFCs) as outliers appeared in the model due to their molecular properties. Subsequently, after the update of the previous model, the vapor pressure of perfluorinated compounds (PFCs) for which no reliable experimental data are available was successfully predicted. At the same time, we used partitioning between n-octanol/water (Kow) and water solubility (Sw) to investigate the similarities and differences between linear solvation energy relationship (LSER) and partial least square projection to latent structures (PLS) models. Further, we developed QSPR model for prediction of melting points and boiling points of PFCs using multiple linear regression (MLR), PLS and associative neural networks (ASNN) approaches, meanwhile, the applicability domain of PFCs was also investigated. Experimental, semi-empirical and theoretical quantitative structure-retention relationship (QSRR) models were used to accurately predict retention factors (logk) in reversed-phase liquid chromatography (RPLC). These models are useful to characterize solvents for determination of the behavior and interactions of molecular structure and develop chromatographic methods. In both of QSPR and QSRR models using the PLS method, the first and second components captured main information which is related to van der Waals forces and polar interactions, and their results coincide with those from LSER. The results showed that the models of physicochemical properties and retention factors (logk) in chromatographic system can be successfully developed by the PLS method. PLS models were able to predict physicochemical properties of organic compounds directly from theoretical descriptors without prior synthesis, measurement or sampling. Further, the PLS method could overcome colinearity in data sets, and it is therefore a rapid, cheap and highly efficient approach

This thesis covers the use of chemistry in the automotive industry with emphasis on environmental compliance via chemical reporting by database and internal Energy Dispersive X-ray Fluorescence (XRF) screening, third party laboratory material testing, and the future of the chemist in the United States (U.S.) automotive industry. The third party testing was performed at Western Kentucky University (WKU) via the Materials Characterization Center (MCC), Institute for Combustion Science and Environmental Technology (ICSET) Thermodynamics Laboratory, and using the Scanning Electron Microscope/Energy Dispersive X-ray Spectrometer (SEM/EDX) managed by the WKU Biotechnology Center. Furthermore, the tests conducted were used to investigate material defects, provide solid third party quantitative results to support our XRF screenings to ensure environmental compliance, and determine cost effective material replacements. The company for which the testing was performed and information obtained is involved with the production of electronics for many of the major automotive companies throughout the world. The company specializes in the production of wiring harnesses, electrical control units (ECU), boxes (junction, fuse, relay, etc), and electrical components. These four areas control everything from the vehicle's lights, CD/DVD player, and heater to windows, locks, and navigation system. The automotive industry is extremely competitive; therefore, each company must continually change and improve in order to survive. New materials are constantly required to meet the reduced costs implemented by the customer, as well as, improve the function and quality of the components, while maintaining compliance with global environmental standards.

Researchers have looked at the possibility of using single molecules as functional building blocks in electronics circuits since the 1970s. The field of molecular electronics, despite its experimental and theoretical challenges, has continued to grow incessantly from a simple scientific curiosity to an emerging field with hundreds of publications per year. Thanks to the development of scanning probe microscopy a variety of techniques currently used to characterise the electrical properties of single molecules has been developed, and molecular systems mimicking the behaviour of traditional electronic components, such as transistors or rectifiers, have been prepared. Despite the obvious fact that supramolecular interactions must play a role in the charge transfer process, only a small number of reports on the subject have been published. In this thesis a set of molecular wires with an oligothiophene central unit, sandwiched between two insulating chains, has been used to probe the effect of such interactions on molecular conductance using several scanning tunnelling microscopy techniques. It has been found that the side-chain length has little effect on molecular conductance, but the presence of water in the surrounding environment triggers an increase in conductance and a switch in the behaviour from activationless to thermally-activated. Furthermore, upon exposure to electron-withdrawing small molecules, these oligothiophene molecular wires form charge transfer complexes, with conductance enhanced by a factor up to 100. Measurements performed in UHV confirmed the observed behaviour, and theoretical calculations were performed to explain it in the coherent tunnelling regime. A gateway state arising from coupling of the molecular backbone to the sulfur contacts accounts for the observed shallow decay of conductance with length, while shifting of transport resonances upon interaction with water and the appearance of interference features upon charge transfer complexation explained the temperature dependence and the conductance enhancement, with experimental observation closely matched by DFT calculations.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
O objetivo da dissertação é avaliar o potencial do Departamento de Química da PUC-Rio de desenvolver e adotar métodos de Química Analítica Verde, tendo em vista a inserção de um conjunto de ações no escopo da Agenda Ambiental PUC-Rio. No contexto institucional no qual a pesquisa se insere, considera-se que os resultados desta pesquisa terão um grande potencial de aplicação em diversos departamentos da PUC-Rio, em particular no Departamento de Química. Poderá servir de embrião ou estímulo para a proposição de um conjunto de ações que contribuirão para o enriquecimento e materialização da Agenda Ambiental PUC – Rio. Quanto aos fins, a pesquisa pode ser considerada aplicada e descritiva. Quanto aos meios de investigação, a metodologia compreende pesquisa bibliográfica e documental, pesquisa de campo, com entrevistas semi-estruturadas e estudo de caso. Destacam-se como resultados: (i) mapeamento das metodologias analíticas que estão sendo desenvolvidas e empregadas em nível mundial e que vêm contribuindo para o avanço da Química Analítica Verde; (ii) perfis verdes das práticas ministradas pelo Laboratório de Química Geral, do Departamento de Química da PUC-Rio, adotando-se ferramentas de avaliação usadas no campo da Química Analítica Verde, em nível mundial; (iii) indicação de práticas que poderão ser modificadas ou substituídas para atender aos princípios da Química Verde’aplicáveis, aos critérios definidos pelo Green Chemistry Institute e critérios complementares; (iv) conjunto de ações de Química Analítica Verde que poderão ser inseridas na Agenda Ambiental PUC-Rio.
The objective of this dissertation is to assess the potential of the Chemistry Department at PUC-Rio to develop and adopt Green Analytical Chemistry’s methods, within the perspective of contributing for the success of PUC-Rio’s Environmental Agenda. Within the institutional context in which this research is situated, it is assumed that its results will have a great potential for application in various departments of PUC-Rio, in particular in the Department of Chemistry. This research can be considered descriptive and applied and the methodology encompasses bibliographical and documental research, field research by mean of semi-structured interviews and case study. The main results can be summarized as follows: (i) survey of analytical methods that have been developed and used worldwide and have contributed to the advancement of Green Analytical Chemistry, (ii) green profiles of the laboratorial practices taught by General Chemistry Laboratory within the Chemistry Department at PUC-Rio; (iii) indication of laboratorial practices that can be improved or replaced by greener ones; (iv) a set of Green Analytical Chemistry’s actions to be considered in future revisions of PUC-Rio’s Environmental Agenda.

Engineered nanoparticles are defined as having a dimension that is between one and one hundred nanometres. With toxicology studies reporting various degrees of toxicity the need to investigate nanoparticle fate and behaviour is vital. Monodispersed engineered nanoparticles were synthesised in-house to produce suitable materials to examine such processes. Iron oxide nanoparticles (5 nm) and citrate coated silver nanoparticles (20 nm) were subjected to different conditions of pH, ionic strength and different types of commercially available natural organic matter. Changes in particle size and aggregation were examined using a multi-method approach. Results showed that the natural organic matter was able to absorb onto nanoparticle surfaces and improve their stability when subjected to changes in pH and ionic strength, where they would normally aggregate. The presence of higher concentrations of NOM in some cases promoted aggregation due to bridging. This work also concluded that silver nanoparticles could be produced in the presence of NOM without additional stabilisers and that they themselves were stable. This work has demonstrated that engineered nanoparticles could remain stable within a range of environmental conditions, and thus raise future pollution concerns.

Chemistry
Ph.D.
The focus of the thesis research was to investigate the surface reactivity of three different minerals, pyrite (FeS2), an ordered form of ferrihydrite (an iron oxyhydroxide phase), and birnessite (MnO2), toward environmentally relevant aqueous reactants. In particular, research was carried out with the goals of 1) understanding the redox chemistry of nitrite (NO2-) and nitrate (NO3-) on pyrite and 2) understanding the redox (photo) chemistry of arsenite (AsO2-, As(III)) on ordered ferrihydrite and birnessite. A motivation for all these studies stemmed in part from the recognition that NO2-, NO3-, and As(III) are all environmental pollutants when they are present at sufficiently high concentration in the environment. The removal of these species or conversion of each of them on mineral surfaces to more benign chemical species is of importance in the realm of environmental chemistry. In the case of NO2- and NO3- on pyrite, an additional and primary motivation for the research was that it has been hypothesized in the "origin-of-life" community that the reaction of NO2- and NO3- with iron sulfide (e.g., pyrite) may have played a role in the production of ammonia (NH3) on early Earth. Such prebiotic chemistry had been hypothesized to an essential step in the production of biomolecules that included proteins. With regard to the NO2- reaction with pyrite, results detailed in this thesis showed that ammonia in µmol/kg quantities could be produced by reacting NO2- in the presence of pyrite under anaerobic conditions. The concentration of NH3 (detected as ammonium, NH4+, in solution) was a strong function of the reaction temperature. At the lower temperatures studied (22oC and 70oC), a small amount of NH4+ was formed, but µmol.kg-1 amounts of NH4+ were formed at a reaction temperature of 120oC. Only about 5% of the initial NO2- concentration was converted to NH4+. In the NO3-/pyrite system, the NO3- reactant concentration remained unchanged at all the three reaction temperatures studied, consistent with the low amounts of NH4+ formed in these experiments. Finally, it was shown using in situ infrared spectroscopy that surface-bound NO formed on pyrite during the conversion of the nitrogen oxides to ammonia. Overall, it was shown that the kinetics of NH4+ formation was slower for NO3- than that observed for NO2-. Studies presented in this thesis that focused on the surface reactivity of As(III) on ordered ferrihydrite and birnessite nano particles showed that As(III) could be oxidized to arsenate (referred to as As(V)) in the presence of simulated solar radiation. In the ordered ferrihydrite circumstance the adsorption of As(III) and photo-induced oxidation to As(V) was compared to the same reaction on the more disordered and smaller ferrihydrite particles (known as "2-line" ferrihydrite). A comparison of the adsorption rate of As(III) on the two surfaces in the presence of light after normalizing for differences in surface area showed that the ordered ferrihydrite exhibited a higher arsenic adsorption rate. Also, the oxidation rate of As(III) to As(V) in the presence of light on the ordered ferrihydrite showed a strong dependence on the amount of dissolved oxygen in solution while the oxidation rate on the more disordered form showed no such dependence. It was proposed that differences in the rates of the heterogeneous oxidation rate of ferrous iron with dissolved oxygen on the two surfaces were the reason for this behavior. Finally, the photo-induced oxidation of As(III) to As(V) on Na- and K-birnessite at solution pHs of 5.0 and 7.4 was investigated. It was shown that the oxidation rate of As(III) to As(V) occurred at a faster rate on birnessite in the presence of light when compared to the same system in the dark. Mn(II) formed during the reductive dissolution of birnessite during the oxidation of As(III) was experimentally observed at pH 5.0, but not at pH 7.4. Experiments were also conducted that investigated the reductive dissolution of Na- and K-birnessite (having different sizes and average oxidation states) by As(III) under more alkaline conditions. These experiments were conducted at pH 8.5 and the post-reaction samples were analyzed with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was shown under these alkaline conditions using X-ray diffraction that structural changes occurred in/on both the Na- and K-birnessite during the As(III) oxidation reaction.
Temple University--Theses

A former industrial site now used for recreational activities was investigated for total PTE content, uptake of the PTEs by foraged fruits and mobility of the PTEs using single extraction such as HOAc and EDTA. In order to evaluate the health risks arising from ingestion of the PTE contaminated soil, the oral bioaccessibility using in vitro physiologically based extraction test (PBET) and tolerable daily intake (TDI) or mean daily intake (MDI) was used. The PBET simulates the transition of the PTE pollutants in the soil into human gastrointestinal system while the TDI or MDI is the mass of soil that a child would require to take without posing any health risk. In addition to the former industrial site, an investigation of the urban road dust from Newcastle city centre and its environs was undertaken with the view to looking into the PTE content, oral bioaccessibility and the platinum group elements (PGEs). Optimized microwave procedure was applied to 19 samples obtained from a former industrial site (St Anthony's lead works) in Newcastle upon Tyne. Of the range of PTEs potentially present at the site as a consequence of former industrial activity (As, Cd, Cr, Cu, Ni, Pb and Zn), the majority of top soil samples indicated elevated concentrations of one or more of these PTEs. In particular, data obtained using either inductively coupled plasma mass spectrometry (ICP-MS) or flame atomic absorption spectroscopy (FAAS) indicates the high and wide concentration of Pb on the site (174 to 33,306 mg/kg). Comparing the resulting PTEs data with UK Soil Guidelines Values (SGVs) suggests at least parts of the site represent areas of potential human health risk. It was found that Pb soil values exceeded the SGV on 17 out of the 19 sampling sites; similarly for As 7 out of 19 sampling sites exceeded the SGV. While for Cd and Ni the soil levels were below the stated SGVs. Samples of foraged fruits collected from the same site were also analysed for the same PTEs. The foraged fruit was gathered over two seasons along with samples of soil from the same sampling areas, acid digested using a microwave oven, and then analysed by ICP-MS. The foraged fruits samples included blackberries, rosehips and sloes which were readily available on the site. The concentration levels of the selected elements in foraged samples varied between not detectable limits and 24.6 mg/kg (Zn). Finally, the soil-to plant transfer factor was assessed for the 7 elements. In all cases, the transfer values obtained were below 1.00,except Cd in 2007 which is 1.00, indicating that the majority of the PTE remains in the soil and that the uptake of PTE from soil to plant at this site is not significant. The determination of total or pseudo total PTE content of soil is often insufficient to assess the risk to humans. A range of extraction protocols were applied to the 19 samples urban topsoils, and report on the correlations between pseudo total PTE content and results obtained following a physiologically-based extraction procedure (oral bioaccessibility), EDTA and HOAc extraction protocols (reagent-specific available fraction), for a broad range of PTEs (As, Cd, Cu, Cr, Ni, Pb, Zn). Results of the single-reagent extraction procedures did not, in general, provide a good indication of oral bioaccessibility but shows positive correlation with the pseudo total PTE content. The bioaccessibility data shows that considerable variation exists both spatially across the site, and between the different PTEs, but correlates well with the pseudo-total concentrations for all elements (r2 exceeding 0.8). One of the main objectives of this work is to show the role of bioaccessibility in generic risk assessment. Comparison of the pseudo-total PTE concentrations with SGV or generic assessment criteria (GAC) indicated that all of the PTEs investigated need further action, such as receptor exposure modelling.

Hydrotalcite-like compounds with Mg\(^2\)\(^+\)/Al\(^3\)\(^+\) and Zn\(^2\)\(^+\)/Al\(^3\)\(^+\) cations in the layer at different mole ratios with different anions in the galleries were synthesised in this study. The materials have been characterised by a range of techniques. The influence of layer cations, and interlayer anions, which in turn influences the crystallinity, can affect the properties of the hydrotalcites. Dodecylsulfate (DS) and dodecylbenzenesulfonate (DBS) anions were intercalated successfully into the galleries and characterisation studies by the same technique that were used for the parent hydrotalcites show that the hydrotalcites structure was maintained and the interlayer space expanded, suggesting that intercalation of other organic compounds may be possible. The intercalated dodecylsulfate and dodecylbenzenesulfonate anions arranged themselves in monolayer and bilayer configuration in the interlayer. These modified hydrotalcites have well-ordered layered structures, divalent/trivalent mole ratios that are close to those of the host precursors, and hydrophobic properties. SEM images show that the modification led to many of the particles being broken down into smaller pieces due to thermal pre-treatment and regeneration with organic anions, but overall morphology was maintained as the host. They show thermal transitions that are comparable to the host, exhibiting three decomposition steps but with increase in the temperature at which weight losses are completed. They show capacity to uptake phenol and 2-chlorophenol (2-CP) from aqueous solution with the compounds containing DBS anions showing higher sorption capacities for 2-CP than the corresponding DS-containing compounds. A pseudo second order reaction best described the sorption process.

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.

A new model for the simulation of street canyon atmospheric chemical processing has been developed, by integrating an existing Large-Eddy Simulation (LES) dynamical model of canyon atmospheric motion with a detailed chemical reaction mechanism, the Reduced Chemical Scheme (RCS), comprising 51 chemical species and 136 reactions, based upon a subset of the Master Chemical Mechanism (MCM). The combined LES-RCS model is used to investigate both the effects of mixing and chemical processing upon air quality within an idealised street canyon. The effect of the combination of dynamical (segregation) and chemical effects is determined by comparing the outputs of the full LES-RCS canyon model with those obtained when representing the canyon as a zero-dimensional box model (i.e. assuming mixing is complete and instantaneous). The LES-RCS approach predicts lower (canyon-averaged) levels of NOX, OH and HO2, but higher levels of O3, compared with the box model run under identical chemical and emission conditions. Chemical processing of emissions within the canyon leads to a significant increase in the Ox flux from the canyon into the overlying boundary layer, relative to primary emissions, for the idealised case and a number of pollution scenarios considered. These results demonstrate that within-canyon atmospheric chemical processing can substantially alter the concentrations of pollutants injected into the urban canopy layer, compared with the raw emission rates within the street canyon and that such variations have a considerable effect on average within canyon concentrations and the flux of pollutants out of the canyon into the urban background environment.

The aim of this project was to determine whether otolith trace dement chemistry can be used [Q track migrations in fully marine fish. This question was addressed through a semi-controlled experiment where Irish Sea and North Sea plaice (Pleurononectes platessa) were maintained in a monitored environment. The relationships between water, blood and otolith chemistry were assessed and with reference to environmental and physiological variables and through comparisons of otolith trace clement chemistry in wild plaice tagged by data storage tags (DST).

To evaluate the precision of a three dimensional cloud chemistry model, the ion concentrations of simulated clouds are compared with the chemical analysis of cloud water samples collected in the Muskoka, Ontario area. Five summer case studies are presented.
In general, the simulated concentrations of NO$ sbsp{3}{-},$ NH$ sbsp{4}{+},$H$ sp+$, H$ sb2O sb2$ and the concentrations of SO$ sbsp{4}{2-}$ calculated with the perfect nucleation condition concur with the observed concentrations. For the four polluted cases, more than 80% of the cloud water SO$ sbsp{4}{2-}$ comes from nucleation, whereas for the clean case, it is mostly created by SO$ sb2$ oxidation. The relative importance of $ rm H sb2O sb2$ and O$ sb3$ in SO$ sb2$ oxidation, as well as the relative importance of nucleation and NH$ sb3$ absorption on the cloud water NH$ sbsp{4}{+}$ budget vary according to the chemical state of the atmosphere.

Part I describes the preparation of a number of useful intermediates from the sultone F5SCHCF2OSO2 (1). These intermediates include the following: the ketene F5SC(SO2)=C=O (21), the unique sultone F4S=CCF2OSO2 (23), and various ionic intermediates of the form Y+ [F5SC(SO2F) COX]-. These intermediates play an important role in providing new pathways for preparing fluorosulfonic acid precursors. Fluorosulfonic acids are excellent candidates to improve the efficiency of environmentally safe fuel cells. It was possible to obtain new derivatives of 1 by various reactions of 21, 23 and the ionic intermediates, but it was not possible to introduce an alkyl substituent with either of the intermediates. Part II is concerned with the synthesis of SF5 containing epoxides as possible monomers. When polymerized, materials of high dielectric strength and high chemical resistance should be obtained. The reaction chemistry of one of the epoxides was investigated and it was found that all reactions studied were accompanied by the loss of the SF5 group. Thus, it was not possible to obtain any polymeric materials. Part III deals with the synthetic accessibility of SF$\sb5$ malonic esters and thence of SF$\sb5$ acrylic esters. These compounds should serve as building blocks in the synthesis of SF$\sb5$ containing pyrimidines. The CF3 analogue, 5-trifluoromethyl uracil, is used as an antiviral drug. In order to synthesize either SF5 malonic ester or 2-SF5 acrylic ester an SF5 group has to be introduced at a secondary carbon. A secondary SF$\sb5$ compound could be synthesized (F5SCH (COOC2H5) (CHBrOAc)) but could not be converted to the respective malonic ester F5SCH (COOC2H5) compound. Part IV describes the reactions and preparations of Parts I-III.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 35-37).
An investigation into the nitrogen chemistry of the anoxic layer of an urban constructed wetland in Singapore was conducted. This pilot-scale wetland treats stormwater runoff from the Balam Estate housing development for several water quality parameters of concern, including nitrate. Earlier sampling in the wetland had indicated that the concentration of nitrate was lower in the outflow from the rain garden than in its inflow, but no research had been done on other nitrogen species or transformation pathways. Preliminary analyses suggest that, although the saturated layer is sufficiently anoxic and denitrification is occurring as per performance objectives, organic nitrogen is being added to the infiltrating water throughout this layer, causing a net export of total nitrogen from the anoxic zone. This organic nitrogen could be either re-released from reserves adsorbed onto organic material during previous storm events, or leached directly from the anoxic layer material which includes wood chips and sand. Readings at outflow pipes indicate that a percentage of this nitrogen is likely re-mineralizing to ammonia upon exposure to more oxygen-rich conditions in the outflow pipes. Further study in the Balam Rain Garden using isotope labeling to more clearly delineate nitrogen fate and transport is suggested.
by Halle Ritter.
M.Eng.

The purpose of this study was to develop the on-line method of analysis which leads to the study of polycyclic aromatic hydrocarbons (PAHs) during combustion in an atmospheric fluidized bed combustor (AFBC) system. The study of PAHs is important because they may be produced upon the combustion of coal. The US EPA prioritizes PAHs as major pollutants due to their mutagenic and carcinogenic effects. Standards of PAHs were analyzed by injection into the gas chromatograph-mass spectrometer (GC-MS). These standards were then analyzed using the on-line method. Two coals were burned in the AFBC system and effluent samples were collected. These were analyzed with the GC-MS to see if there were any PAHs or chlorobenzenes present.

Total mercury (Hg) concentration provides insufficient information to understand Hg behavior in Hg-contaminated soil systems and to seek potential remediation technologies, because the distribution, mobility, bioavailability, and toxicity of Hg are dependent on Hg forms present in soils. The phase association of Hg in soil is investigated to evaluate potential environmental risk through combination of total Hg determination, soil fractionation, and speciation analysis of Hg in a Hg-contaminated DOE site. Besides total Hg concentration analysis, sequential extraction procedures and thermal desorption techniques were employed to study Hg binding forms in soils in this study. Total mercury concentrations ranging from less than 100 ng/g to more than 30,000 ng/g were detected. The highest form of mercury present in the soil is organically-bound mercury, followed by elemental mercury, and mercury sulfide. Bioavailable and mobile mercury is minimal.

With the advent of increased usage of coal as an energy source, environmental considerations must be examined. The purpose of this study is to understand the emission behavior of chlorine and sulfur during combustion in an atmospheric fluidized bed combustion (AFBC) system. A two-phase investigation was carried out in order to evaluate combustion performance, the extent of hydrochloric acid formation during combustion, and the effect of combustion conditions (limestone addition) on chlorine and sulfur emission. Two 1,000-hour burns were conducted with the 12-inch (0.3 m) laboratory AFBC system at Western Kentucky University. Operating conditions similar to those used at the 160-MWe AFBC system at the Shawnee Steam Plant near Paducah, Kentucky were used. The first 1000-hour burn was done with a low-chlorine (0.012% CI and 3.0% S) Western Kentucky University # 9 coal. The second 1000-hour burn was done with a high-chlorine (0.28% CI and 2.4% S) Illinois # 6 coal. The behavior of chlorine and sulfur was studied by collection of samples of chloride and sulfate emissions from the combustion flue gases in a buffer solution and analyzed by ion chromatography (IC). The results indicated that the greater the increase in bed temperature, the higher the concentration of hydrogen chloride and sulfur dioxide emitted from the AFBC system. The higher contents of chlorine and sulfur in the coals also contribute to higher emissions. The limestone is effective in capturing the hydrogen chloride and sulfur dioxide emissions, especially at lower temperatures (optimal temperature at 1120 K). Sulfur dioxide emissions are more easily retained by limestone than by hydrogen chloride in our experimental conditions. There is no significant change in the emission of HC1 when the Ca/S ratio is varied. When the sulfur or chlorine content in coal reaches a certain point, the Ca/S ratio in the combustion mixture will be an important factor in the absorption of S02 and HC1.

This thesis is concerned with measurements of persistent organic pollutants (POPs) in environmental samples. The POPs consist of several groups of compound with many isomers, hence analysing POPs in a complex environment is a This thesis is concerned with measurements of persistent organic pollutants (POPs) in environmental samples. The POPs consist of several groups of compound with many isomers, hence analysing POPs in a complex environment is a challenging task. Studies of the abundance or dynamics of such substances in the environment require careful consideration of several key steps. The environmental and analytical problems must be correctly defined, suitable analytes, sampling strategies and techniques must be selected, the chemical analyses must be reproducible and accurate, and the data evaluation protocols must be rigorous and appropriate. The aim of this thesis was to evaluate the use of pollutant profiles in order to assess complex patterns of environmental exposure. When combined with multivariate data analysis (MVDA) a maximum of information may be extracted from analytical data. Nevertheless, good quality data is essential for correct evaluation of the environmental phenomena under investigation. The precision and accuracy of a solid phase assisted liquid extraction method was therefore assessed by comparison to a reference method. The validated method was used in two human exposure studies. The concentrations of PCBs and dioxins were determined in human tissues from general populations in Sweden and Spain. Although it was concluded that the populations were exposed to similar degree to PCBs and dioxins, principal component analysis (PCA) showed that the compound profiles differed between the populations. PCA was also used to differentiate between occupationally exposed workers and matched controls and between exposed workers with recent and earlier exposure. In addition, the analysis indicated that the differences in PCB patterns in workers with recent and earlier exposure were related to differences in the metabolic degradation rates of individual PCBs. The PCA model was further used to select PCB congeners that were representative of each group. Finally, the emission of polycyclic aromatic hydrocarbons (PAHs) in a traffic tunnel was estimated by measuring 29 individual PAHs. The sampling periods were chosen to reflect a maximum variation in the traffic composition. An excellent prediction of the percentage of heavy-duty vehicles was obtained using partial least squares (PLS) regression. It was shown by PCA that it might be possible to predict source compositions at other locations with the aid of multivariate statistical tools. Thus, properly gathered pollutant profiles and MVDA may be combined to extract a large amount of significant information from environmental source and exposure data.

14 MeV neutron activation analysis, based on the 82Se(n,2n) Se81m nuclear reaction, has been investigated for the measurement of selenium in environmental waters. The levels of the selenium present in environmental waters and the relatively high limit of detection achievable with fast neutron activation analysis resulted in the need to develop a concentration procedure for the extraction of selenium from large volumes of environmental water before neutron activation.

Steel slag wastes are large volume residues generated in increasing quantities globally during steel production. While there are many afteruses for slag, roughly a quarter produced globally is stockpiled or landfilled where it may pose environmental risks. Furthermore as resource pressures increase there is a growing interest in recovering valuable metals from industrial by-products. Given the uncertainties in environmental risks and opportunities for further valorisation of wastes, an improved understanding of leaching processes from steel slag would help inform long term management of these industrial by-products. This thesis aims to investigate a series of alkaline disposal sites (both steel slag and limespoil) to improve our understanding of the geochemical nature and fate of notable contaminants, as well as valuable metals of interest, in highly alkaline settings. The results of the field investigations show that leachates are characterised by high pH ( > 11) and negative redox potential, excess deposition of secondary precipitates, and increased mobility of lithium ( > 800 ppb), strontium ( > 2500 ppb) and vanadium ( > 50 ppb), present in concentrations greater than those typically encountered in natural surface waters. Furthermore, these slag deposits were enriched with less mobile elements such as molybdenum (60 ppb) and nickel (61 ppb) with associated low environmental concern, but high resource value. Laboratory batch tests showed that acid leaching promotes the leaching of the elements of interest particularly vanadium. However, such approach may not be viable at legacy sites due to cost. On the other hand, compost amendment of slag enhanced the leaching of molybdenum and vanadium by a factor of 3.6 and 2.5 respectively above water leaching alone. Column experiments reinforced these patterns in showing enhanced leaching of vanadium, molybdenum, and lithium when organic amendment is in contact with hyperalkaline leachate under aerobic conditions. This is most likely due to alkaline hydrolysis of organics within the system and subsequent metal complexation. Analysis of secondary precipitates (notably calcium and magnesium carbonates) forming around the slag suggest these are key in controlling solubility of contaminants and metals of potential resource value (e.g. Ni).

This thesis details the use of microfluidic devices and chemiluminescence detection in order to develop a portable method of analysis for measuring chemical species in the environment. Chapter 1 outlines microfluidic technology, including fabrication techniques, fluid manipulation and mixing within the devices. Their advantages for analytical environmental purposes are demonstrated along with a review of their uses in environmental applications. Chemiluminescence detection provides a sensitive method of analysis for measuring chemical species in the environment and chemiluminescence theory and reagents are addressed. Chapter 2 details the development of a portable battery operated chemiluminescence detection system, which can be used in conjunction with microfluidic devices. The fabrication of the micro fluidic devices used in this work is documented. Different micro fluidic channel manifolds were investigated for chemiluminescence reactions and a serpentine design (200 μm width, 65 μm depth) with a channel length of 206 mm was selected as the most suitable design. Methods of fabrication for incorporating immobilised reagents on solid supports within a microfluidic device were also designed. Chapter 3 documents the investigation of the luminol-cobalt(II) chemiluminescence reaction within a microfluidic device using the portable chemiluminescence detection system to produce a miniaturised analytical system for the determination of hydrogen peroxide in rainwater. Enhancement of the chemiluminescence signal by 132 %was achieved by means of using the mirror reaction to apply a reflective surface directly VI to the top of the micro fluidic device. Immobilisation techniques for immobilising luminol using adsorption and covalent attachment onto a solid support were investigated as a means of producing a reagentless system, however poor sensitivity was observed and this was not progressed for the analytical system. Using the luminol-cobalt(II) chemiluminescence reaction within a microfluidic device a method of measuring hydrogen peroxide in the low micromolar concentrations was achieved, producing a limit of detection of 4.7 nmol L⁻¹ with a small sample volume (10 μL min⁻¹). A small reagent consumption size (1.2 mL per hour) and a low waste production size (2.4 mL per hour) were also achieved. This system was then used for the determination of hydrogen peroxide in rainwater samples during rainfall events showing the hydrogen peroxide concentration varied from 0.1 to 3.2 μmol L⁻¹. The method was also applied to the analysis of hydrogen peroxide in snow demonstrating the hydrogen peroxide concentration varied from 0.2 to 0.5 μmol L⁻¹ in samples taken at ground level. Chapter 4 details the development of a heterogeneous (two site) sandwich immunoassay within a microfluidic device to produce a miniaturised analytical system for the determination of E. coli bacteria in seawater. There is a need for rapid sensitive methods of analysis to measure E. coli in seawater as an indicator of faecal contamination. A review of traditional methods and current research on the area is presented. Immunological techniques based on using antibodies to specifically bind to their respective antigens were found to be the most amenable method of analysis for E. coli and an outline of how they work is shown. HRP was selected as the sensitive enzyme label for the antibody in the sandwich immunoassay. The chemiluminescence detection of HRP using the luminol-hydrogen peroxide VB chemiluminescence reaction was investigated within a microfluidic device, the detection was optimised and p-iodophenol was selected as an enhancer for the reaction. The investigation into the immobilisation of E. coli specific antibodies using covalent attachment onto controlled pore glass is presented, an optimal loading of 1.5 μg g⁻¹ was achieved. The development of an ELISA method for the purpose of screening the antibody for their specificity towards different isolates of E. coli and their non-specificity towards other bacteria is detailed. Finally, a microfluidic immunoassay was developed. Regeneration of the immobilised antibodies was achieved using 0.5 mol L⁻¹ sodium hydroxide, allowing the immobilised antibodies to be reused. The microfluidic immunoassay provided a rapid method for the determination of E. coli with an analysis time of 13 min for each sample. The assay also used a low reagent consumption and waste production. This would enable the rapid testing of a number of small samples to provide high temporal and spatial resolution data. Sensitivity provided a problem with the immunoassay and ways to overcome this were addressed.

Selenium has aroused much interest in the last decade. It is an essential trace element for man and animals and has been found to be the cofactor in two enzyme systems. The first, glutathionine peroxidase, acts as an anti-oxidant by destroying peroxides which attack cellular membranes. The second, iodothyronine 5'-deiodinase, converts thyroxine to triiodothyronine with the release of iodine. Selenium is obtained in the diet from plant and animal products and the amount present is dependent largely on the Se content and the chemical species present in local soils. Soils low in Se can lead to deficiency problems to the grazing ruminants, and have necessitated the use of Se fertilisers or direct Se injection into the livestock. The disposal of sewage sludge onto agricultural land will increase as new EC legislation comes into force in 1998. This may alleviate Se deficiency in soils or result in toxicity problems. The aims of this project were firstly to develop and validate a method to accurately measure Se in plants, soils and sewage sludges, examine which soil fractions Se was associated with and finally to study the uptake of Se by plants grown on sewage sludge amended soils. The Se concentration in samples was determined using isotope dilution - mass spectrometry by gas chromatography - mass spectrometry (GC-MS). This was the first application of the determination of Se in environmental samples and the use of a benchtop GC-MS for those analyses. Samples were spiked with 76-Se isotope solution. Plants were digested using nitric acid and hydrogen peroxide initially on a heating block and latterly by microwave oven digestion techniques. Soils and sewage sludges were digested using nitric acid and hydrofluoric acid. Selenium in the digests was reduced to Se(IV) and derivatised to 5'-nitropiazselenol. Validation of the methodology was achieved by the use of certified reference materials which gave results within the certified range with a low standard deviation. The Se content of four different freely drained acid Scottish soils under grasslands was in the range 0.5-0.8 mg-1 air dried soil and three sewage sludge samples contained between 1.1 and 3.5 mg g-1 dry matter. The ability of the digestion techniques to release organically bound Se as selenomethionine and selenocysteine was found to be around 100% efficient and the use of a microwave oven increased the number of samples which could be processed. A sequential extraction procedure was used to determine the soil fractions with which Se was associated. The four soils and the sewage sludge examined were all found to have less than 5% of the total Se available for plant uptake. The uptake of Se by plants grown in soils to which Se had been added as sodium selenate or sodium selenate was studied using both stable and radio isotopes of Se. Results obtained showed that the uptake of Se by plants grown in soils treated with selenite could be related to the soil characteristics, with ferric oxide levels, clay levels and organic matter content being the important factors. The uptake of Se by plants in the soils treated with selenate were less obviously related to soil properties but pH and P levels both appear to be important factors. Good reproducibility was obtained in all cases. Plants grown on sewage sludge amended soils were not found to contain measurable amounts of Se.

The work presented in this thesis focuses on acquisition of data such as environmental and experimental conditions and the control of experimental apparatus. A suite of software applications will be described which captures data from a standard data acquisition card, processes this and archives it in an appropriate repository. The software revolves around a central message broker, controlling the flow of messages between intercommunicating components. The automation section will focus on the control of many components of an experiment studying the air/liquid interface using the technique of second harmonic generation (SHG). Software will be described that can be used to controls actuators, laser sources and other hardware within the laboratory. This software will use the same message broker to send and receive messages relating to the devices they are controlling. These tools were used to run a number of SHG experiments studying the air/liquid interface of para-nitrophenol (PNP), benzo-15-crown-5 (B15C5) and 4'-nitrobenzo-15- crown-5 (NB15C5). The complete experimental process was automated and results made available through a web interface, allowing real-time monitoring and decision making of each experiment.

Reactive halogen radicals (e.g. Br, Cl and their oxide forms) dominate tropospheric oxidation mechanisms during Arctic springtime (Feb. – Apr.) by depleting ozone and changing the fate of pollutants. During ozone depletion events, reactive bromine radicals rapidly oxidize mercury which gets subsequently deposited, becoming more bioavailable. During Arctic springtime, a heterogeneous surface reaction (referred to as BrO recycling) between hypobromous acid (HOBr) and bromide (Br-) rapidly increases the abundance of reactive bromine episodically up to 40 pptv peaks. However, as spring transitions to summer (May - June), elevated reactive bromine levels suddenly decrease. There are two key requirements to maintain BrO recycling including surface area and sea salt (i.e. bromide) abundance. This study investigated environmental factors that impact BrO recycling during late spring (May-June) in the Arctic, including temperature, snowpack depth and rain/snow precipitation events. Near horizon BrO was measured using Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) at Barrow, AK and above frozen Arctic sea ice. The late spring “end” to elevated reactive bromine (referred as the Seasonal End Date, SED) was objectively determined at all sites (N=12). Air temperature-derived melt onset dates were determined for all sites (N=12) and occurred within two days of the SED (RMS = 1.8 days, R² = 0.989). Through these studies, we determined BrO recycling is hindered by melt onset of snowpack, ending the reactive bromine season.

The body of work in this dissertation focuses on the properties of an environmental thin film system, including the roughness and composition of the surface. The deposition of particles, such as airborne soil and plant pollen, from the atmosphere creates a thin film known as “environmental film” or “urban film” that covers virtually all of Earth’s solid surfaces. Environmental films have been shown to accumulate a variety of chemicals, including toxic pollutants. To investigate the means by which environmental films uptake chemicals, model films are made in the lab and real films are collected outside. Model films serve to mimic the properties of native films and allow for a simple analysis of a complex system. Native films serve to provide real field samples to analyze. The properties of model and native films are characterized using reflected light to determine what the film is made of and microscopes capable of imaging small particles. The results of the model film study indicate a model capable of reproducing the surface roughness and other properties of native films. This study serves as a platform with the goal of making model films that better mimic native films. The results of the native film study indicate successful imaging using microscopes capable of revealing the structure and chemical composition of the films. This imaging adds an important contribution to the field that has not previously been performed.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, February, 2021
Cataloged from the official PDF of thesis.
Includes bibliographical references.
The heterogenization of molecular catalysts to polarized interfaces provides an appealing approach to the design of more efficient and selective electrochemical devices. The well-defined nature of molecular catalysts renders them amenable to synthetic tuning to unravel structure-function relationships. From these studies, key insight to optimization of their activity is obtained. However, recent work has established that outer-sphere effects such as the surface structure and ligation method can impact reactivity as much as catalyst structure. This thesis explores these environmental contributions to reactivity with a particular focus on exploring the impact of electronic coupling between a molecular site and the band structure of graphitic carbon electrodes or using this coupling as a tool to understand the reactivity of molecules confined to solid-liquid interfaces. Chapters two through four explore environmental contributions to porphyrin electrocatalysis.
We report on how the magnitude of electronic coupling conferred by the linkage tunes the rate of oxygen reduction catalysis. We further demonstrate solvent-dependent concerted proton electron transfer for a cobalt porphyrin attached to graphitic carbon by an alkyl-tether. Building on these results, we present a mechanistic basis for the stark differences in the selectivity and activity of heterogenized and soluble cobalt porphyrins for the CO₂ reduction reaction. Chapters five and six address charge effects at solid-liquid interfaces. In chapter five, we analyze the rate of dissociative ligand exchange for identical heterogeneous and soluble binding sites and find a modest rate enhancement that we attribute to the enhanced charge stabilization by the solid support.
Chapter six details our attempt to use ambient pressure X-ray photoelectron spectroscopy to experimentally test our previously established model for catalysts strongly electronically coupled to the band states of graphitic carbon by direct measurement of the interfacial electrostatic potential drop.
by Corey J. Kaminsky.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemistry

The present Thesis studies three alternative solvent groups as sustainable replacement of traditional organic solvents. Some aspects of fluorinated solvents, supercritical fluids and ionic liquids, have been analysed with a critical approach and their effective “greenness” has been evaluated from the points of view of the synthesis, the properties and the applications. In particular, the attention has been put on the environmental and human health issues, evaluating the eco-toxicity, the toxicity and the persistence, to underline that applicability and sustainability are subjects with equal importance. The “green” features of fluorous solvents and supercritical fluids are almost well-established; in particular supercritical carbon dioxide (scCO2) is probably the “greenest” solvent among the alternative solvent systems developed in the last years, enabling to combine numerous advantages both from the point of view of industrial/technological applications and eco-compatibility. In the Thesis the analysis of these two classes of alternative solvents has been mainly focused on their applicability, rather than the evaluation of their environmental impact. Specifically they have been evaluated as alternative media for non-aqueous biocatalysis. For this purpose, the hydrophobic ion pairing (HIP), which allows solubilising enzymes in apolar solvents by an ion pairing between the protein and a surfactant, has been investigated as effective enzymatic derivatisation technique to improve the catalytic activity under homogeneous conditions in non conventional media. The results showed that the complex enzyme-surfactant was much more active both in fluorous solvents and in supercritical carbon dioxide than the native form of the enzyme. Ionic liquids, especially imidazolium salts, have been proposed some years ago as “fully green” alternative solvents; however this epithet does not take into account several “brown” aspects such as their synthesis from petro-chemical starting materials, their considerable eco-toxicity, toxicity and resistance to biodegradation, and the difficulty of clearly outline applications in which ionic liquids are really more advantageous than traditional solvents. For all of these reasons in this Thesis a critical analysis of ionic liquids has been focused on three main topics: i) alternative synthesis by introducing structural moieties which could reduce the toxicity of the most known liquid salts, and by using starting materials from renewable resources; ii) on the evaluation of their environmental impact through eco-toxicological tests (Daphnia magna and Vibrio fischeri acute toxicity tests, and algal growth inhibition), toxicity tests (MTT test, AChE inhibition and LDH release tests) and fate and rate of aerobic biodegradation in soil and water; iii) and on the demonstration of their effectiveness as reaction media in organo-catalysis and as extractive solvents in the recovery of vegetable oil from terrestrial and aquatic biomass. The results about eco-toxicity tests with Daphnia magna, Vibrio fischeri and algae, and toxicity assay using cultured cell lines, clearly indicate that the difference in toxicity between alkyl and oxygenated cations relies in differences of polarity, according to the general trend of decreasing toxicity by decreasing the lipophilicity. Independently by the biological approach in fact, all the results are in agreement, showing a lower toxicity for compounds with oxygenated lateral chains than for those having purely alkyl lateral chains. These findings indicate that an appropriate choice of cation and anion structures is important not only to design the IL with improved and suitable chemico-physical properties but also to obtain safer and eco-friendly ILs. Moreover there is a clear indication that the composition of the abiotic environment has to be taken into account when the toxicity of ILs in various biological test systems is analysed, because, for example, the data reported in the Thesis indicate a significant influence of salinity variations on algal toxicity. Aerobic biodegradation of four imidazolium ionic liquids, two alkylated and two oxygenated, in soil was evaluated for the first time. Alkyl ionic liquids were shown to be biodegradable over the 6 months test period, and in contrast no significant mineralisation was observed with oxygenated derivatives. A different result was observed in the aerobic biodegradation of alkylated and oxygenated pyridinium ionic liquids in water because all the ionic liquids were almost completely degraded after 10 days, independently by the number of oxygen in the lateral chain of the cation. The synthesis of new ionic liquids by using renewable feedstock as starting materials, has been developed through the synthesis of furan-based ion pairs from furfural. The new ammonium salts were synthesised in very good yields, good purity of the products and wide versatility, combining low melting points with high decomposition temperatures and reduced viscosities. Regarding the possible applications as surfactants and biocides, furan-based salts could be a valuable alternative to benzyltributylammonium salts and benzalkonium chloride that are produced from non-renewable resources. A new procedure for the allylation of ketones and aldehydes with tetraallyltin in ionic liquids was developed. The reaction afforded high yields both in sulfonate-containing ILs and in ILs without sulfonate upon addition of a small amount of sulfonic acid. The checked reaction resulted in peculiar chemoselectivity favouring aliphatic substrates towards aromatic ketones and good stereoselectivity in the allylation of levoglucosenone. Finally ILs-based systems could be easily and successfully recycled, making the described procedure environmentally benign. The potential role of switchable polarity solvents as a green technology for the extraction of vegetable oil from terrestrial and aquatic biomass has been investigated. The extraction efficiency of terrestrial biomass rich in triacylglycerols, as soy bean flakes and sunflower seeds, was comparable to those of traditional organic solvents, being the yield of vegetable oils recovery very similar. Switchable polarity solvents as been also exploited for the first time in the extraction of hydrocarbons from the microalga Botryococcus braunii, demonstrating the efficiency of the process for the extraction of both dried microalgal biomass and directly of the aqueous growth medium. The switchable polarity solvents exhibited better extraction efficiency than conventional solvents, both with dried and liquid samples. This is an important issue considering that the harvest and the dewatering of algal biomass have a large impact on overall costs and energy balance.

The present Thesis studies three alternative solvent groups as sustainable replacement of traditional organic solvents. Some aspects of fluorinated solvents, supercritical fluids and ionic liquids, have been analysed with a critical approach and their effective “greenness” has been evaluated from the points of view of the synthesis, the properties and the applications. In particular, the attention has been put on the environmental and human health issues, evaluating the eco-toxicity, the toxicity and the persistence, to underline that applicability and sustainability are subjects with equal importance. The “green” features of fluorous solvents and supercritical fluids are almost well-established; in particular supercritical carbon dioxide (scCO2) is probably the “greenest” solvent among the alternative solvent systems developed in the last years, enabling to combine numerous advantages both from the point of view of industrial/technological applications and eco-compatibility. In the Thesis the analysis of these two classes of alternative solvents has been mainly focused on their applicability, rather than the evaluation of their environmental impact. Specifically they have been evaluated as alternative media for non-aqueous biocatalysis. For this purpose, the hydrophobic ion pairing (HIP), which allows solubilising enzymes in apolar solvents by an ion pairing between the protein and a surfactant, has been investigated as effective enzymatic derivatisation technique to improve the catalytic activity under homogeneous conditions in non conventional media. The results showed that the complex enzyme-surfactant was much more active both in fluorous solvents and in supercritical carbon dioxide than the native form of the enzyme. Ionic liquids, especially imidazolium salts, have been proposed some years ago as “fully green” alternative solvents; however this epithet does not take into account several “brown” aspects such as their synthesis from petro-chemical starting materials, their considerable eco-toxicity, toxicity and resistance to biodegradation, and the difficulty of clearly outline applications in which ionic liquids are really more advantageous than traditional solvents. For all of these reasons in this Thesis a critical analysis of ionic liquids has been focused on three main topics: i) alternative synthesis by introducing structural moieties which could reduce the toxicity of the most known liquid salts, and by using starting materials from renewable resources; ii) on the evaluation of their environmental impact through eco-toxicological tests (Daphnia magna and Vibrio fischeri acute toxicity tests, and algal growth inhibition), toxicity tests (MTT test, AChE inhibition and LDH release tests) and fate and rate of aerobic biodegradation in soil and water; iii) and on the demonstration of their effectiveness as reaction media in organo-catalysis and as extractive solvents in the recovery of vegetable oil from terrestrial and aquatic biomass. The results about eco-toxicity tests with Daphnia magna, Vibrio fischeri and algae, and toxicity assay using cultured cell lines, clearly indicate that the difference in toxicity between alkyl and oxygenated cations relies in differences of polarity, according to the general trend of decreasing toxicity by decreasing the lipophilicity. Independently by the biological approach in fact, all the results are in agreement, showing a lower toxicity for compounds with oxygenated lateral chains than for those having purely alkyl lateral chains. These findings indicate that an appropriate choice of cation and anion structures is important not only to design the IL with improved and suitable chemico-physical properties but also to obtain safer and eco-friendly ILs. Moreover there is a clear indication that the composition of the abiotic environment has to be taken into account when the toxicity of ILs in various biological test systems is analysed, because, for example, the data reported in the Thesis indicate a significant influence of salinity variations on algal toxicity. Aerobic biodegradation of four imidazolium ionic liquids, two alkylated and two oxygenated, in soil was evaluated for the first time. Alkyl ionic liquids were shown to be biodegradable over the 6 months test period, and in contrast no significant mineralisation was observed with oxygenated derivatives. A different result was observed in the aerobic biodegradation of alkylated and oxygenated pyridinium ionic liquids in water because all the ionic liquids were almost completely degraded after 10 days, independently by the number of oxygen in the lateral chain of the cation. The synthesis of new ionic liquids by using renewable feedstock as starting materials, has been developed through the synthesis of furan-based ion pairs from furfural. The new ammonium salts were synthesised in very good yields, good purity of the products and wide versatility, combining low melting points with high decomposition temperatures and reduced viscosities. Regarding the possible applications as surfactants and biocides, furan-based salts could be a valuable alternative to benzyltributylammonium salts and benzalkonium chloride that are produced from non-renewable resources. A new procedure for the allylation of ketones and aldehydes with tetraallyltin in ionic liquids was developed. The reaction afforded high yields both in sulfonate-containing ILs and in ILs without sulfonate upon addition of a small amount of sulfonic acid. The checked reaction resulted in peculiar chemoselectivity favouring aliphatic substrates towards aromatic ketones and good stereoselectivity in the allylation of levoglucosenone. Finally ILs-based systems could be easily and successfully recycled, making the described procedure environmentally benign. The potential role of switchable polarity solvents as a green technology for the extraction of vegetable oil from terrestrial and aquatic biomass has been investigated. The extraction efficiency of terrestrial biomass rich in triacylglycerols, as soy bean flakes and sunflower seeds, was comparable to those of traditional organic solvents, being the yield of vegetable oils recovery very similar. Switchable polarity solvents as been also exploited for the first time in the extraction of hydrocarbons from the microalga Botryococcus braunii, demonstrating the efficiency of the process for the extraction of both dried microalgal biomass and directly of the aqueous growth medium. The switchable polarity solvents exhibited better extraction efficiency than conventional solvents, both with dried and liquid samples. This is an important issue considering that the harvest and the dewatering of algal biomass have a large impact on overall costs and energy balance.

2016 - 2017
In the last year, the stable isotope ratio analysis has become a useful tool with many applications in different scientific area. In particular the characteristic isotope signature of materials has permitted to identify authenticity and traceability of food sample and isotope composition has become a valuable marker in environmental studies. This work shows the applicability of analytical methods for isotopic carbon determination in food and environmental samples and the innovative use of δ13C in cultural heritage as valuable tool to trace pollutant fate. The first part is dedicated to the improvement of spectroscopic methods as Fourier Transform Infrared (FT-IR) and Non-Dispersive Infrared spectroscopy (NDIRS) and their application to identify geographical origin in sample like pasta, cocoa, olive oil. The results conducted in order to assess the robustness of the two alternative methods respecting IRMS showed a strong correlation like a demonstration of the positive relationship between the tested analytical methods. A new method was developed 13C NMR spectroscopy to determine the bulk 13C/12C carbon isotope ratio of inorganic carbonates and bicarbonates at natural abundance. In literature the use of 13C NMR spectroscopy was focused on 13C position-specific isotope analysis of organic molecules; in this work it was reported the improvement of NMR methodology able to obtain stable carbon isotope ratio in bulk material using an internal standard...[edited by Author]
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