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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Theoretical Studies on Perfluorinated Acids of Environmental Significance

Hidalgo-Puertas, Abdel 04 September 2015 (has links)
A new approach for predicting octanol-water partition coefficients (Log P) of linear perfluorinated compounds, making use of the limited experimental data available, previous observations and the consistent similarities observed between the experimental and calculated (with electronic structure methods and using EPI suite) slopes of the linear plots of Log P values with the number of carbon atoms (N = 2 to 11) is described here. Eight families of linear organic compounds were investigated: carboxylic acids, perfluorinated carboxylic acids, sulfonic acids and perfluorinated sulfonic acids, together with their corresponding conjugate bases. To the best of our knowledge, this work reports the first application of density functional theory methods to the calculation of Log P values of perfluorinated compounds. A second part of the thesis, describes the study of the thermodynamic stability of the PFOA family of 39 structural isomers with the M06-2X, LC-ωPBE, B97D and B3LYP functionals and with the PM6 method. The PM6 results closely resemble the M06-2X results for neutral PFOAs, but greatly disagree regarding anions. The four functionals applied behave similarly from a qualitative point of view, but quantitatively speaking, the LC-ωPBE and B97D results are between the M06-2X and B3LYP stability results. M06-2X ranks highly substituted isomers as more stable than did B3LYP, and ranks less-branched isomers quite low in relative stability compared to B3LYP. Various similarities with a former PFOSs study applying the M06-2X and B3LYP functionals have been identified. The degree of branching within structural isomers cannot always be precisely determined, and is not the only aspect that determines thermodynamic stability; the pattern of substitution seems to also play a significant role. / Graduate
12

Abiotic Reduction of Perfluoroalkyl Acids by NiFe<sup>0</sup>-Activated Carbon

Jenny E Zenobio Euribe (6638495) 14 May 2019 (has links)
<div> <p>In recent years, the presence of per- and polyfluoroalkyl substances (PFAS) in aquatic systems has led to research on their fate, effects and treatability. PFAS have been found in various environmental matrices including wastewater effluents, surface, ground, and drinking water. Perfluoroalkyl acids (PFAAs) are the class of PFAS most commonly tested due to their ability to migrate rapidly through groundwater and include perfluoroalkyl sulfonic acids (PFSAs) and perfluoroalkyl carboxylic acids (PFCAs). Of the globally distributed and persistent PFAAs, PFSAs are the most resistant to biological and oxidative chemical attack. This doctoral study focused on a reductive treatment approach with zero valent metals/bimetals nanoparticles (NPs) synthesized onto a carbon material to reduce NP aggregation. Initial work focused on exploring reactivity of different combinations of nano (n) Ni, nFe<sup>0</sup> and activated carbon (AC) at 22 <sup>o</sup>C to 60 <sup>o</sup>C for transforming perfluorooctanesulfonate (PFOS) from which nNiFe<sup>0</sup>-AC at 60 <sup>o</sup>C led to transformation of both linear (L-) and branched (Br-) PFOS isomers. The remaining research focused on work with nNiFe<sup>0</sup>-AC at 60 <sup>o</sup>C in batch reactors including optimizing nNiFe<sup>0</sup>-AC preparation, quantifying PFOS transformation kinetics and evaluating the effects of PFAA chain length (C4, C6 and C8) and polar head group (PFSA versus PFCA) as well a groundwater matrix on transformation magnitude. Optimization of analytical methods to provide multiple lines of evidence of transformation including fluoride, sulfite and organic product generation was an ongoing throughout the research.</p> <p>nNiFe<sup>0</sup>-AC prepared with a 3-h synthesis stirring time led to the highest PFOS transformation of 51.1 ± 2.1% with generation of ~ 1 mole of sulfite (measured as sulfate) and 12 moles of fluoride. Several poly/per-fluorinated intermediates with single and double bonds were identified using quadrupole time-of-flight mass spectrometry (QToF-MS) in negative electrospray ionization (ESI-) mode with MS/MS fragmentation confirmation as well as one and later two desulfonated products with QToF negative atmospheric pressure chemical ionization (APCI-). All organic transformation products were found in only particle extracts as well as most of the sulfite generated. PFOS transformation kinetics showed that generated fluoride concentrations increased for the first day whereas sulfate concentrations continued to increase during the 5-d reaction. The transformation products identified showed defluorination of single- and double-bond structures, formation of C8 to C4 PFCAs and paraffins from cleavage of the C-S bond.</p> <p>The length of the perfluoroalkyl chain affected the length of time to achieve peak removal, but overall magnitude of transformation when reactions appeared complete were similar for both PFSAs and PFCAs. Like PFOS, PFOA transformation maxed in 1 d whereas shorter chains required more time to reach their peak removal, which is hypothesized to be due to lower sorption of the shorter chain PFAAs to the reactive surfaces. Measured F mass balance was higher for PFOS and PFOA (>90% F) compared to shorter chain PFAAs (~50-70% F). The Perfluorohexanesulfonate (PFHxS) and perfluorobutanesulfonate (PFBS) degradation products include single bond polyfluoroalkyl sulfonates and shorter-chain perfluoroalkyl carboxylates. For example, PFHxS transformation resulted in perfluorohexane carboxylic acid (PFHxA) and perfluorobutane carboxylic acid (PFBA). PFCA transformation products included per- & polyfluoroalkyl carboxylates with single bonds and alcohols with single and double bonds. The effect of inorganic matrix on transformation with nNiFe<sup>0</sup>-AC at 60 <sup>o</sup>C was explored using a contaminated groundwater collected at a former fire-training area in Massachusetts. Transformation appeared ‘generally’ lower than in the single-solute clean water systems, which may have been due to the presence of PFAS precursors that degraded to PFAAs and competitive adsorption between anionic PFAAs and inorganic ions onto the NP surface.</p><p>The research presented here demonstrates that nNiFe<sup>0</sup>-AC at 60 <sup>o</sup>C can mineralize PFAAs even in a typical groundwater matrix. Additional lab and pilot scale studies are needed to clarify the mechanisms leading to transformation as well as why transformation reactions plateau prior to all the parent compounds being transformed. The latter may be due to a poisoning phenomenon that can occur in closed systems, which may not occur in a flowing system more characteristic of an environmental scenario, as well as surface area and reactive site constraints or particle passivation.</p></div>
13

Torr utan gifter?

JANSSON, ULRIKA, HALVARSSON, MARIA January 2013 (has links)
Arbetet har utförts i samarbete med Naturskyddsföreningen för att undersöka vilka vattenavvisande behandlingar som görs på ytterplagg för barn och hur tillverkarna förhåller sig till perfluorerade ämnen. I arbetet har vattenavvisande ytterplagg för barn i förskoleåldern studerats, med syfte att se i vilken mån perfluorerade ämnen används i plaggen. Barnen som har studerats är utomhus varje dag i alla väder. Vid kraftigt regn eller när det är mycket blött ute används vattentäta regnställ, vid lättare väta bär de ytterplagg med vattenavvisande funktion. En egen oljedropptestmetod har utvecklats. Testet har utförts på de plagg som hänger på förskolorna. Det finns flera typer av vattenavvisande behandlingar. De vanligaste är perfluorerade ämnen, silikoner, dendrimerer och vaxer. De har olika egenskaper och funktioner sinsemellan. De perfluorerade ämnena har den bästa vattenavvisande förmågan och de är också de enda som är oljeavvisande. Perfluorerade ämnen är persistenta, bioackumulerande, hormonstörande och toxiska. Hormonstörande ämnen kan bidra till fetma, cancer, neurologiska störningar, fortplantningsstörningar och missbildningar. Silikoner har goda vattenavvisande egenskaper. Råvaran till silikoner är persistent, bioackumulerande och toxisk. Även dendrimerer har goda vattenavvisande egenskaper. Lite är känt om miljö- och hälsopåverkan men partiklar i nanostorlek kan potentiellt ta sig in cellerna och orsaka cancer. Inga allvarligare miljö- och hälsokonsekvenser av vaxer/paraffiner har hittats. De har sämre vattenavvisande egenskaper, påverkar greppet och tål tvätt och nötning dåligt. De kläder som används på förskolorna håller generellt barnen torra, men en försämring kan märkas på gamla eller dåligt konstruerade plagg. Ytterplagg som behandlats med perfluorerade ämnen är vanliga. Företagen har fasat ut perfluorerade ämnen under de senaste åren, planerar att byta ut dem eller har vidtagit åtgärder enligt Reach. Dendrimerer är det vanligaste alternativet till perfluorerade ämnen. Inga krav förekommer från vare sig företag eller användare på att plaggen ska vara smuts- och oljeavvisande. / Program: Textilingenjörsutbildningen
14

Perfluorooctane sulfonate (PFOS) and related chemicals in eggs from Sweden and China

Karimi, Yasmin January 2019 (has links)
Dietary intake is one of the major routes of human exposure to perfluoroalkyl and/or polyfluoroalkyl substances (PFAS). The objective of this study was to measure perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS) in organic and conventional egg from Sweden (n=8, consisted of 4 pooled eggs and 4 individuals) and China (n=9, consisted of 4 pooled eggs and 5 individuals) and compare the concentrations of PFAS between the two categories (organic and conventional). Also, to evaluate if there was any difference in concentrations of PFAS between both countries. In the end, evaluation of tolerable weekly intake of PFOS and PFOA due to consumption of egg recommended by the European Food Safety Authority (EFSA) was conducted if consuming these eggs would cause any human health risk. Liquid chromatography-mass spectrometry (LC-MS/MS) was used to analyze PFOS, PFOA and PFHxS in the egg samples. In egg samples from China, PFOA was the predominant PFAS; in an organic egg sample from Shenzhen with concentration up to 2000 pg/g, making up to 86% of the 3 PFAS. In contrast, PFOS had the greatest concentration of all PFAS in egg samples from Sweden and was detected in organic egg sample with concentration up to 184 pg/g, making up to 78% of the 3 PFAS. PFOA in samples from China was 18 times higher compared to egg samples to Sweden; results showed no significant differences in PFAS concentrations in egg samples between Sweden and China. In samples from China, concentrations of PFAS had total mean of 50 pg/g for PFOS, 373 pg/g for PFOA and 13 pg/g for PFHxS. In Sweden, mean concentrations of PFOS, PFOA, and PFHxS were found to be 5, 2, and 1,5 times (respectively) higher in organic eggs when compared to conventional. However, significant difference was only observed for PFOS in Swedish organic eggs (p&lt;0.05, t-7.96, df=6). The different concentrations of contamination between organic and conventional egg could be due to the fish powder in organic chicken feed and ingestion of soil through pecking. The result suggests that current concentrations of PFOS and PFOA in organic and conventional chicken eggs are unlikely to cause any immediate harm to Swedish populations. For Chinese population since the consumption of egg has a high risk of exceeding the TWI, the current concentration of PFOA in organic chicken eggs may cause harm to the population based on TWIs established by EFSA. Further investigation is needed with more samples to be analyzed to confirm this point.
15

Brominated flame retardants and perfluoroalkyl acids in Swedish indoor microenvironments : Implications for human exposure

Björklund, Justina January 2011 (has links)
Humans are exposed to persistent organic pollutants (POPs) such as brominated flame retardants (BFRs, specifically polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD)) and perfluoroalkyl acids (PFAAs, specifically perfluoroalkane sulfonate (PFOS) and perfluorooctanoic acid (PFOA)). They are used in consumer products found in cars, offices, homes and day care centers. Diet was earlier thought to be a major human exposure route for legacy POPs, but does not account for body burdens found for many new POPs and indoor exposure from air and dust has been hypothesized as also important. In this thesis, BFRs in air and dust, and PFAAs in dust from different indoor microenvironments in Sweden were analysed, and the results used to estimate human exposure. BFRs and PFAAs were detected in dust from all microenvironments and PBDEs in all air samples. BFR and PFAA exposure occurs mostly in peoples’ homes with toddlers having higher intakes from dust ingestion than adults. Inhalation and dust ingestion play minor roles compared to diet for humans with median exposures, but in worst case scenarios, dust ingestion may be significant for a small part of the Swedish population. Sampling using home vacuum cleaner bag dust and researcher-collected above floor dust was compared. Correlations were seen for ∑OctaBDE and ∑DecaBDE but not for ∑PentaBDE and HBCD. Higher PBDE concentrations were found in above floor dust but higher HBCD concentrations were found in vacuum cleaner bag dust. BDE-47 concentrations were correlated between vacuum cleaner bag dust and breast milk, indicating exposure through dust ingestion. Similar concentrations of PBDEs were measured in indoor and outgoing air from day care centers, apartment and office buildings. Indoor air explained 54-92% of ∑PentaBDE and 24-86% of BDE-209 total emissions to outdoor air in Sweden, supporting the hypothesis that the indoor environment is polluting ambient air via ventilation systems. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 3: Accepted. Paper 4: Manuscript.</p>
16

Advanced Oxidation Techniques For The Removal Of Refractory Organics From Textile Wastewaters

Erol, Funda 01 September 2008 (has links) (PDF)
Ozonation is an efficient method to degrade refractory organics in textile wastewaters. In recent years, catalytic ozonation is applied to reduce ozone consumption and to increase chemical oxygen demand and total organic carbon (TOC) removal efficiencies. The ozonation of two industrial dyes, namely Acid Red-151 (AR-151) and Remazol Brilliant Blue R (RBBR) was examined separately both in a semi-batch reactor and also in a fluidized bed reactor (FBR) by conventional and catalytic ozonation with alumina and perfluorooctyl alumina (PFOA) catalysts. The conventional and catalytic ozonation reactions followed a pseudo-first order kinetics with respect to the dye concentration. The highest COD reductions were obtained in the presence of the catalysts at pH=13, with alumina for AR-151 and with PFOA for RBBR. Residence time distribution experiments were performed to understand the degree of liquid mixing in the reactor. The behaviour of the FBR was almost equivalent to the behaviour of one or two completely stirred tank reactors in series in the presence of the solid catalyst particles. The volumetric ozone-water mass transfer coefficients (kLa) were found at various gas and liquid flow rates and catalyst dosages in the FBR. A model was developed to find kLa in the reactor by comparing the dissolved O3 concentrations in the experiments with the model results. kLa increased significantly by the increase of gas flow rate. Higher catalysts dosages at the fluidization conditions yielded higher kLa values indicating higher rates of mass transfer. Dye ozonation experiments without catalyst and with alumina or PFOA catalyst were conducted at different conditions of the inlet dye concentration, gas and liquid flow rates, inlet ozone concentration in the gas, catalyst dosage, particle size and pH. The dye and TOC removal percentages were increased with the increase of gas flow rate and with the decrease of both the liquid flow rate and inlet dye concentration. The addition of the catalyst was beneficial to enhance the TOC degradation. The ozone consumed per liter of wastewater was much lower when the catalyst was present in the reactor. In terms of TOC removal and O3 consumption, the most efficienct catalyst was PFOA. According to the organic analysis, the intermediate by-products were oxalic, acetic, formic and glyoxalic acids in RBBR and AR-151 ozonation. The dye and dissolved ozone concentration profiles were predicted from a developed model and the model results were compared with the experimental results to obtain the enhanced kLa values. The presence of the chemical reaction and the catalysts in the FBR, enhanced the kLa values significantly. The enhancement factor (E) was found as between 0.97 and 1.93 for the non-catalytic ozonation and 0.96 and 1.53 for the catalytic ozonation at pH = 2.5. The dimensionless number of Hatta values were calculated between 0.04-0.103 for the sole ozonation of RBBR and AR-151 solutions. According to the calculated Ha values, the reaction occurred in the bulk liquid and in the film being called as the intermediate regime in the literature.
17

Catalytic Ozonation Of Industial Textile Wastewaters In A Three Phase Fluidized Bed Reactor

Polat, Didem 01 December 2010 (has links) (PDF)
Textile wastewaters are highly colored and non-biodegradable having variable compositions of colored dyes, surfactants and toxic chemicals. Recently, ozonation is considered as an effective method that can be used in the treatment of industrial wastewaters / catalytic ozonation being one of the advanced oxidation processes (AOPs), is applied in order to reduce the ozone consumption and to increase the chemical oxygen demand (COD) and total organic carbon (TOC) removals. In this study, catalytic ozonation of industrial textile wastewater (ITWW) obtained from AKSA A.S. (Yalova, Istanbul) textile plant has been examined in a three phase fluidized bed reactor at different conditions. The effects of inlet chemical oxygen demand concentration (CODin), pH, different catalyst types [perflorooctyl alumina (PFOA) and alumina] and catalyst dosage on ozonation process were determined. Moreover, the changes in the organic removal efficiencies with gas to liquid flow rate ratio were investigated. The dispersion coefficients (DL) and volumetric ozone-water mass transfer coefficients (kLa) were estimated at various gas and liquid flow rates in order to observe the effect of liquid mixing in the reactor on ozonation process. It was observed that increasing both gas and liquid flow rates by keeping their ratio constant provided higher organic removal efficiencies due to the higher mixing in the liquid phase. The dyes present in ITWW sample were known to be Basic Blue 41 (BB 41), Basic Red 18.1 (BR 18.1) and Basic Yellow 28 (BY 28). The &ldquo / absorbance vs. concentration&rdquo / calibration correlations were developed to estimate the amounts of these colored dyes in the ITWW sample. This provided the opportunity to examine the degradation of each dye in this wastewater separately. While PFOA catalyst was found to increase the removal efficiency of BY 28 at an acidic pH of 4, alumina yielded highest color removals for BB 41 and BR 18.1 at a pH of 12. The highest TOC and COD reductions being 24.4% and 29.5%, respectively, were achieved in the catalytic ozonation of the ITWW using alumina as the catalyst at a pH of 12 and at a gas to liquid flow rate ratio of 1.36 (QG = 340 L/h, QL = 250 L/h). At the same conditions, also the highest overall color removal in terms of Pt-Co color unit, namely 86.49%, were obtained due to the lower BY 28 concentration in the WW sample than those of the BB 41 and BR 18.1. In addition, the oxidation of BB 41, BR 18.1 and BY 28 dyes were investigated in a semi-batch reactor by sole and catalytic ozonations with alumina and PFOA catalyst particles. The sole and catalytic ozonation reactions followed a pseudo-first order kinetics with respect to dye concentration. The highest TOC and COD removals being 58.3% and 62.9%, respectively, were obtained at pH of 10 for BB 41 and 55.2% and 58.8%, respectively, for BR 18.1 with alumina catalyst. On the other hand, for BY 28 PFOA catalyst yielded highest TOC and COD reductions being 61.3% and 66.9%, respectively, at pH of 4.
18

Catalytic Ozonation Of Synthetic Wastewaters Containing Three Different Dyes In A Fluidized Bed Reactor

Balci, Ayse Irem 01 October 2011 (has links) (PDF)
Environmental regulations have imposed limitations on a wide variety of organic and inorganic pollutants in industrial textile wastewaters. There are several degradation methods used in literature studies. Among these methods ozonation is one of the most considered way to degrade refractory chemicals in textile wastewaters. In recent years, catalytic ozonation as being one of the advanced oxidation processes (AOPs), is applied to reduce the ozone consumption and to increase the Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removals. Ozonation and catalytic ozonation of single and mixed dye solutions have been examined both in a semi-batch reactor and also in a three phase fluidized bed reactor. The dyes that are used in this study are Basic Blue 41 (BB-41), Basic Yellow 28 (BY-28) and Basic Red 18.1 (BR-18.1), these dyes are obtained from AKSA A.S. (Yalova, Istanbul) textile plant. In order to measure the concentration of each dye in the mixed dye solution, &ldquo / absorbance vs. concentration&rdquo / calibration correlations were developed. The effect of inlet dye concentration, inlet gas and liquid flow rates, pH, catalyst type [perflorooctyl alumina (PFOA) and alumina] and catalyst dosage were determined experimentally. Catalyst characterization analyses were done in order to determine the maximum number of times that the catalyst can be used and it was found to be 3 times. Gas washing bottle experiments are conducted to find the v amount of ozone required to oxidize one mole of each dye used in the study. Oxidation of BB-41, BR-18.1 and BY-28 dyes were investigated in a semi-batch reactor as single dye solutions by sole and catalytic ozonation with alumina and PFOA catalyst particles. The highest TOC and COD removals being 58.3% and 62.9%, respectively, were obtained at pH of 10 for BB-41 and 55.2% and 58.8%, respectively, for BR-18.1 with alumina catalyst. On the other hand, for BY-28 PFOA catalyst yielded highest TOC and COD reductions being 61.3% and 66.9%, respectively, at pH of 4. Minimum fluidization velocity (uL,min), the hold-up values of gas, liquid and solid phases, the dispersion coefficients (DL), and volumetric ozone-water mass transfer coefficients (kLa) were estimated at various gas and liquid flow rates in order to observe the effect of liquid mixing in the reactor on ozonation process. While PFOA catalyst was found to be effective in oxidizing BY-28 in acidic conditions (pH=4), BR-18.1 and BB-41 are degraded in alkaline medium (pH=10) with alumina catalyst better compared to acidic conditions. For catalytic ozonation reactions in fluidized bed reactor, the highest dye removals in mixed dye solution were observed for BY- 28 being 99.29% for gas flow rate (QG) of 340 L/h, liquid flow rate (QL) of 150 L/h and pH=4, initial dye concentration being 30 mg/L of each dye with PFOA catalyst, while for BR-18.1 and BB-41 being 95.39% and 97.95% respectively for QG = 340 L/h, QL = 150 L/h and pH=10, initial dye concentration being 30 mg/L of each dye with alumina catalyst. The highest TOC and COD reductions, 25.2% and 32.4%, respectively, were achieved in the catalytic ozonation of the mixed dye using PFOA as the catalyst at a pH of 4 and at a gas to liquid flow rate ratio of 2.26 (QG = 340 L/h, QL = 150 L/h). Highest dye removals were obtained at the same gas and liquid flow rates as those of the highest TOC and COD reductions in the experiments. Empirical TOC removal equations were obtained as a function of inlet TOC concentration, solution pH, gas and liquid flow rates.
19

1H NMR-based Metabolomics for Elucidating the Mode of Action of Ccontaminants in the Earthworm Eisenia Fetida after Sub-lethal Exposure

Lankadurai, Brian 08 August 2013 (has links)
There is a growing need to develop rapid and cost-effective ecotoxicological tools for risk assessment because traditional methods examine endpoints such as mortality, which do not provide any insight into the mode of action (MOA) of the chemical. Research presented within this thesis illustrates the potential of 1H NMR-based metabolomics as a rapid and routine ecotoxicological tool that can elucidate a chemical’s MOA and also aid in the identification of metabolites of exposure. Metabolomics involves measuring the fluctuations in the endogenous metabolites of an organism within a cell, tissue, bio-fluid or whole organism in response to an external stressor. We focused on the model polycyclic aromatic hydrocarbon (PAH) phenanthrene, and the perfluoroalkyl acids (PFAAs) perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), due to their recalcitrant nature and widespread prevalence in soil environments. 1H NMR-based metabolomics analysis of the exposure of Eisenia fetida earthworms to sub-lethal phenanthrene exposure via filter paper contact tests revealed a concentration-dependent two-phased MOA: a linear correlation between the metabolic response and exposure concentration at low concentrations followed by a plateau in the responses at high concentrations. Alanine, glutamate, maltose, cholesterol and phosphatidylcholine emerged as potential indicators of phenanthrene exposure. An increased energy demand and an interruption in the conversion of succinate to fumarate in the Krebs cycle were observed due to phenanthrene exposure. Sub-lethal PFOA and PFOS exposure to E. fetida via contact tests for two days revealed heightened responses with higher PFOA and PFOS concentrations. Leucine, arginine, glutamate, maltose, and ATP were identified as potential indicators of PFOA or PFOS exposure. E. fetida responses were then investigated after exposure for two, seven and fourteen days to an artificial soil that was spiked with sub-lethal PFOS concentrations. An exposure time-dependent operation of two separate MOAs were identified. Both the contact tests and artificial soil exposure studies identified an elevation in fatty acid oxidation, a disruption in energy metabolism and biological membrane structure, and also an interruption of ATP synthesis following PFOA and PFOS exposure. This thesis illustrates the promise of NMR-based metabolomics as a routine tool for ecotoxicological assessment of contaminated sites.
20

1H NMR-based Metabolomics for Elucidating the Mode of Action of Ccontaminants in the Earthworm Eisenia Fetida after Sub-lethal Exposure

Lankadurai, Brian 08 August 2013 (has links)
There is a growing need to develop rapid and cost-effective ecotoxicological tools for risk assessment because traditional methods examine endpoints such as mortality, which do not provide any insight into the mode of action (MOA) of the chemical. Research presented within this thesis illustrates the potential of 1H NMR-based metabolomics as a rapid and routine ecotoxicological tool that can elucidate a chemical’s MOA and also aid in the identification of metabolites of exposure. Metabolomics involves measuring the fluctuations in the endogenous metabolites of an organism within a cell, tissue, bio-fluid or whole organism in response to an external stressor. We focused on the model polycyclic aromatic hydrocarbon (PAH) phenanthrene, and the perfluoroalkyl acids (PFAAs) perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), due to their recalcitrant nature and widespread prevalence in soil environments. 1H NMR-based metabolomics analysis of the exposure of Eisenia fetida earthworms to sub-lethal phenanthrene exposure via filter paper contact tests revealed a concentration-dependent two-phased MOA: a linear correlation between the metabolic response and exposure concentration at low concentrations followed by a plateau in the responses at high concentrations. Alanine, glutamate, maltose, cholesterol and phosphatidylcholine emerged as potential indicators of phenanthrene exposure. An increased energy demand and an interruption in the conversion of succinate to fumarate in the Krebs cycle were observed due to phenanthrene exposure. Sub-lethal PFOA and PFOS exposure to E. fetida via contact tests for two days revealed heightened responses with higher PFOA and PFOS concentrations. Leucine, arginine, glutamate, maltose, and ATP were identified as potential indicators of PFOA or PFOS exposure. E. fetida responses were then investigated after exposure for two, seven and fourteen days to an artificial soil that was spiked with sub-lethal PFOS concentrations. An exposure time-dependent operation of two separate MOAs were identified. Both the contact tests and artificial soil exposure studies identified an elevation in fatty acid oxidation, a disruption in energy metabolism and biological membrane structure, and also an interruption of ATP synthesis following PFOA and PFOS exposure. This thesis illustrates the promise of NMR-based metabolomics as a routine tool for ecotoxicological assessment of contaminated sites.

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