Fluoride naturally occurs in some ground and surface waters at high concentrations all around the world. Due to increasing health concerns about over-exposure to fluoride in drinking water, the United States Environmental Protection Agency (USEPA) has begun to review fluoride as a drinking water contaminant. Should the USEPA decide to lower the fluoride maximum contaminant limit (MCL), many water systems in addition to those already struggling to meet the fluoride MCL will require defluoridation as part of their drinking water treatment process. Alum coagulation was investigated as a defluoridation treatment strategy in this research project. Surface and blended (ground/surface) drinking water sources with high fluoride concentrations pose a unique challenge to defluoridation by alum coagulation because of the presence of both natural organic matter (NOM) and fluoride. Defluoridation of synthetic and natural waters using jar tests elucidated interactions of fluoride, NOM, and aluminum during alum coagulation. Alum coagulation was able to remove 80% of fluoride from natural waters with a 500 mg/L alum dose; however, 50% fluoride removal was observed to be possible with an alum dose of 150-170 mg/L. The optimum pH for fluoride removal in synthetic and natural waters was observed to be approximately 6.5 and was found to be an important factor in determining the overall performance of alum coagulation. The presence of fluoride during alum coagulation was found to reduce the removal of three low molecular weight (LMW) organics, acting as surrogates for NOM, to different extents depending on their functionality. The presence of LMW organic acids in synthetic waters did not impact the removal of fluoride; however, increasing NOM concentrations in the natural waters likely accounted for decreasing fluoride removals observed in the natural waters. Additional jar tests with natural waters revealed that pH adjustment was unnecessary for defluoridation of high pH and high alkalinity waters and that an enhanced precipitation effect occurred at low alum doses when no pH adjustment was made during alum coagulation. The enhanced precipitation effect caused comparable or enhanced removals of fluoride and NOM to be observed despite system pH values being higher than the optimal defluoridation pH of 6.5. Lower aluminum residuals were also observed as part of the enhanced precipitation effect, suggesting that when precipitation begins under high pH conditions, fluoride interference does not occur and therefore promotes more precipitate formation with greater available surface area for adsorption. However, as precipitation occurs, pH drops, and fluoride increasingly interacts with the aluminum precipitate resulting in greater overall fluoride removals. / text

The structure and function of microbial communities are critical to the maintenance and sustainability of terrestrial ecosystem processes. Consequently, there is substantial interest in assessing how microbial communities respond to various land management practices, and if alterations to the characteristics of microbial communities has the potential to disrupt ecosystem processes. This thesis was conducted to identify the long term effects of fertilisation and different levels of post-harvest organic matter removal on the characteristics of the FH litter and soil microbial communities in six, second rotation Pinus radiata plantation forests located around New Zealand. The six sites, established between 1986 and 1994, were sampled in 2002 and 2003. Various physical and chemical properties of the sites were measured, and litterfall production was determined. The microbial biomass in the FH litter layer and soil was determined by chloroform fumigation-extraction, and Biolog plates were used to assess the relative differences in microbial community diversity, based on patterns of substrate utilisation. Fertilisation substantially altered the physical and chemical properties of the forest floor, including FH litter moisture content, mass, carbon content, nitrogen content and carbon: nitrogen ratio and soil pH, nitrogen content and carbon: nitrogen ratio. The same range of FH litter and soil properties were also significantly changed by different levels of organic matter removal. The biomass and diversity of the FH litter and soil microbial communities were significantly altered by fertilisation and organic matter removal, and the differences in the microbial community characteristics were significantly correlated to the effects of the fertilisation and organic matter removal treatments on the physical and chemical environment in the majority of cases. The physical and chemical properties of the sites were significantly correlated to estimates of wood production, and it was also found that the characteristics of the microbial community were strongly related to productivity at several sites. The results demonstrated that fertilisation and organic matter removal regimes have had long term effects on the microbial communities at the sites. The persistence of the effects of the organic matter removal treatments were particularly noteworthy, as these treatments were applied at site establishment, and despite no subsequent reinforcement over the life of the trials, were still substantially influencing the physical, chemical and microbiological properties of the FH litter and soil up to 17 years later. The results of this thesis also emphasised the value of long-term experiments in assessing the effects of disturbance on the physical, chemical and microbiological characteristics of forest ecosystems. Further research into the specific nature of the relationship between site productivity and microbial community characteristics was suggested as an important focus for future studies.

This study examined the interaction of model cationic, neutral and anionic endocrine disrupting compounds, pharmaceuticals and personal care products (EDC/PPCPs) with bulk and fractionated freshwater and waste water dissolved organic matter (DOM). The chemical composition of the freshwater DOM (Suwannee River, GA, SROM) proved to be rich in plant-derived hydrophobic aromatics, while the wastewater DOM (WWOM) contained a greater proportion of microbial biomolecular products, presumably resulting mainly from human waste. Studies focused on the fluorescence quenching of excitation-emission matrices (EEMs) of WWOM indicated that interaction with bis-phenol A (BPA), carbamazepine (CBZ), and ibuprofen (IBU) occurred preferentially with soluble protein-like and fulvic acid-like constituents. However, upon introduction to bulk SROM, BPA and CBZ were observed to quench humic acid-like regions of the EEMs, while negatively charged ibuprofen preferentially quenched the protein-like and fulvic acid components irrespective of DOM source and/or fraction. Despite this evidence of EDC/PPCP interactions with both DOM types, the strength of bonds formed was generally not sufficient to preclude full recovery and quantification of all three contaminants by liquid chromatography tandem mass spectrometry (LC-MSMS). An important exception, however, was for the hydrophilic acid fraction (HiA) of both DOM types, whose apparent bonding to cationic CBZ and anionic IBU significantly diminished LC-MSMS recovery. Thus, water sources rich in HiA character might produce a concentration underestimation of ionized EDC/PPCPs even with the use of sophisticated instruments such as LC-MSMS.The results of this research are consistent with the evolving ""supramolecular"" theory of natural organic matter, which postulates that organic matter itself is comprised of fragments of partially degraded biomolecules that are aggregated into ""supramolecular"" structures of apparent higher molar mass via relatively weak electrostatic, hydrophobic, and van der Waals interaction. Our findings suggest that EDC/PPCP contaminants, which comprise many of the same functional groups as waste water and freshwater DOM, may be incorporated into such DOM supramolecular structures, likely via the same types of intermolecular bonding, when they are present in natural waters under environmentally-relevant conditions.

No description available.

During the Fukushima Daiichi power plant incident sea water was used in an attempt to cool reactor Unit 3. Since sea water contains an excessive amount of chloride, 36Cl has likely been formed and spread in the environment. Because of the long residence time and the presumed high mobility in water there is an increased interest to learn more about the biogeochemical cycle of chlorine from a radiation risk assessment perspective. Chlorine occurs in inorganic form as chloride (Clin) or bound to organic matter as organic chlorine (Clorg) and is commonly found in the environment due to both anthropogenic and natural processes. Though there are still uncertainties regarding all of the components of the chlorine cycle in soil, the chlorination of organic matter has been exemplified by research. The reverse process, Clorg mineralizing into Clin, has however not been thoroughly investigated. For this study the objective was to observe at what rate Clorg mineralizes into Clin, this by using 36Cl as a tracer in forest soil. 36Cl was added to the soil and 36Clorg was formed over a period of approximately 100 days. After chlorination the samples were incubated in different conditions and the amount of 36Clorg was observed over a period of time (180 days). The result showed no evident dechlorination during the experiment period which indicates that Clorg can be stable in the organic horizon in forest soil.

No description available.

Water managers must balance the need for clean and safe drinking water with ever-increasing amounts of waste-water. A technique for treating and storing surface water called “managed aquifer recharge” (MAR) is frequently used to help maintain this balance. When MAR is used to produce drinking water, water managers must ensure that disease-causing microbial contaminants are removed from the water prior to its distribution. This thesis examined the processes responsible for removing a specific class of microbial contaminants called “enteric viruses” during MAR. Viruses are naturally removed in groundwater through adsorption and inactivation mechanisms. This thesis investigated how these virus removal mechanisms were affected by ionic strength (IS), dissolved organic carbon (DOC), and the age of the sand used in a MAR infiltration basin. This was done using batch and flow-through column experiments designed to mimic conditions characteristic of a basin infiltration MAR scheme in Uppsala, Sweden. Bacteriophage MS2 was used as a proxy for enteric viruses. All of the experiments were conducted at 4°C. Experimental data were modeled to describe the fate and transport of viruses in the infiltrated groundwater. Conventional least-squares optimization and generalized likelihood uncertainty estimation (GLUE) were compared as model fitting-approaches in order to determine how data uncertainty affects parameter estimates and model predictions. Results showed that the sand used in the infiltration basins accumulates adsorbed organic matter as it is exposed to infiltrating surface waters. This reduced the amount of MS2 that was removed due to adsorption and inactivation. Results from GLUE indicated that MS2 is more likely to inactivate in a time-dependent manner when in the presence of sand with high concentrations of organic matter. Both model fitting techniques indicated that virus attachment rates were significantly lower for sand with high organic carbon content. Neither methodology was capable of adequately capturing the kinetics of virus adsorption. Uncertainties in the experimental data had a large effect on the conclusions that could be drawn from fitted models. This study showed that the presence of natural organic matter reduces the value of the infiltration basin as a microbial barrier.

Initialement émis lors des essais nucléaires atmosphériques, le tritium (3H) est l’un des principaux radionucléides rejetés par les installations nucléaires. Il est présent dans toutes les composantes environnementales sous différentes formes, libres (HT, HTO, CH3T) ou liée à la matière organique (TOL). Le tritium suit les mêmes dynamiques d’incorporation et de dégradation dans les organismes que l’hydrogène et se met rapidement à l’équilibre avec le milieu ambiant. Des études ont montré un déséquilibre TOL/HTO dans différents compartiments et matrices environnementales. Ce travail vise à expliquer la variabilité des concentrations en 3H et l’origine des déséquilibres observés en se basant sur l’hypothèse de la rémanence. Une approche multi-échelles axée sur le rôle du transfert différé de la matière organique entre les compartiments environnementaux a été menée. Les résultats acquis ont permis d’établir des gammes de concentrations en HTO dans des cours d’eau non influencés par des rejets tritiés et d’identifier les principaux paramètres liés à la variabilité observée. Les résultats ont aussi permis de comprendre l’origine du TOL à partir d’analyses statistiques, qui tendent à confirmer que des zones de rémanence en TOL issus des essais nucléaires, peuvent conduire à des déséquilibres significatifs entre formes libre et liée. De plus, l’étude d’une archive sédimentaire a montré l’existence d’un pic de concentrations en TOL en profondeur, provenant vraisemblablement des retombées de ces essais. Enfin, l’instrumentation d’un site atelier, à proximité d’installations nucléaires, a permis de confirmer l’existence d’un marquage de la matière organique et la rémanence du TOL. / Initially emitted in the environment by atmospheric nuclear weapons tests, tritium (3H) is one of the main radionuclide released by nuclear facilities. It is present in all environmental media in several different forms, bound to organic matter (OBT) or in free forms (HT, HTO, CH3T). Furthermore, 3H follows the same dynamics of incorporation and degradation in living organisms as the hydrogen and is quickly balanced with the surrounding environment. Numerous studies have shown disequilibrium of OBT/HTO in different environmental compartments and matrices. This research work aims to explain the variability of 3H concentrations and the origin of disequilibrium of OBT/HTO based on the persistence hypothesis. In this study, a multi-scale approach was used, focusing on the role of delayed transfer of organic matter between natural compartments. The main results have established the ranges of HTO concentrations in several rivers that are not influenced by atmospheric releases from nuclear facilities, and also identified key environmental parameters linked to the observed variability. The results also made it possible to understand the origin of OBT using statistical analyses. The results tend to confirm that atmospheric nuclear tests led to areas of persistence of OBT, and can lead to significant disequilibrium between bound and free forms. Moreover, the study of a sediment core has shown a peak of OBT at depth, in all likelihood from the global fallout associated with atmospheric nuclear weapons tests. Also, a study site impacted by industrial releases of tritium for the last fifty years has confirmed the persistence of OBT in organic matter, especially in abiotic matrices.

Supported lipid bilayers (SLBs) are one of the most common model membranes used in the field of cell membrane biology as they provide a well-defined model membrane platform for determination of molecular-level interactions between different biomolecules (e.g. proteins, peptides) and lipid membrane. Compared to model organisms, the use of SLB is preferable since it mimics cell plasma membrane in a very simple and well-controlled way. Therefore, molecular structure of membrane and experimental conditions (e.g. solution chemistry, temperature, and pH) can be easily adjusted to the required conditions of any systematic research. In addition, SLBs are typically easy to form, cheap and very reproducible and they are compatible with different surface characterization techniques, such as quartz crystal microbalance with dissipation (QCM-D), ellipsometry and atomic force microscopy (AFM). This study demonstrates that QCM-D analysis of SLBs serve as powerful tool to investigate and characterize the mechanisms of interactions between lipid membrane and gold nanoparticles (NPs), environmentally relevant polymers, and disease-inducing peptides. Due to many critical applications of gold NPs in drug delivery and diagnostics, understanding of membrane-NP interactions is crucial especially for determination of NPs cytotoxicity. In this study we focus on membrane disruption as one of the different mechanisms by which metal NPs induce cytotoxicity. The use of SLB is beneficial for this goal as it elucidates the unique mechanism of membrane disruption without interference of other mechanisms taking place simultaneously in biological cells. For NP-membrane interaction studies, a SLB composed of L-α-phosphatidylcholine (egg PC) was formed on a SiO2-coated crystal and QCM-D analysis was performed to obtain information about mass and viscoelastic changes of SLB resulting from interactions with gold NPs. For better understanding of the mechanisms of NP-membrane interactions, we systematically changed the NPs properties and the experimental conditions. In order to understand the effect of NP size, gold NPs with diameters of 2,5,10, and 40 nm were tested and compared to each other. NPs were tested in their citric acid-stabilized state as well as in the presence of poly (methacrylic acid) (PMAA), representing an organic coating that could become associated with NPs in the environment. The results indicated that when dissolved in water, gold NPs with the dimeters of 2, 5, 10, and 40 nm did not perturb the membrane, but in the presence of environmentally relevant polymer, the larger nanoparticles were found to disrupt the membrane. In order to elucidate the effect of surface chemistry, 10 nm - gold NPs with various functionalizations (i.e. anionic, cationic and non-ionic ligands) were tested. Control experiments were designed to test the effect of NPs in the absence of humic substances which means the NPs were dissolved in water. In these cases, regardless of the type of NP functionalization, no substantial bilayer mass changes were observed. This suggests that the charge and chemistry of the ligands had a minor effect on NP-membrane interactions. Furthermore, in both the control and humic acid experiments, there were small dissipation changes (less than 1 unit) indicating that the overall membrane structure was not perturbed. In order to mimic environmentally-relevant conditions, mass and viscoelasticity of SLB was characterized in the presence of four different natural polymers, also known as natural organic materials (NOMs): Fulvic and humic acids extracted from Suwannee River (SRFA and SRHA), which had relatively lower molecular weights and a commercial humic acid (HA) and the humic acid extracted from Elliott soil (ESHA) with higher molecular weight. The results showed that NOMs with lower molecular weights, adsorbed to the bilayer, while higher molecular weight components, did not induce any changes to the bilayers. In addition, the NPs in SRFA and SRHA increased the mass of the bilayer by 20-30 ng, while the NPs in HA and ESHA changed the mass of the bilayer by < 10 ng. It was concluded that the presence of humic substances as well as their physical and chemical properties exert a direct impact on the interactions between cell membrane and the nanoparticles. In addition to the field of NP toxicity, SLBs play a pivotal role in the field of neurodegenerative diseases, such as Alzheimer’s disease (AD), in which the pathological cascade of events starts from interactions of a misfolded peptide with cell membrane. In this thesis, we confirm the validity of QCM-D analysis of SLB as an important platform for investigation of amyloid β (the peptide associated with AD) interactions with lipid membrane. Adsorption of Aβ peptide to cell membrane is known to take place on the so-called “lipid raftâ€� which are membrane microdomains enriched with cholesterol, sphingomyelin and ganglioside. The formation of SLBs containing lipid rafts is not only important for the field of AD research, but also it is important for other in vitro studies of cell biology as the lipid rafts are responsible for a variety of biological functions such as association of some membrane proteins and cellular signaling. However, the presence of lipid raft components such as sphingomyelin and cholesterol makes the formation of the bilayer more challenging which leads to adsorption of intact vesicles on the substrate without formation of the bilayer. In this study, the formation of lipid bilayer composed of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dioleoyl- sn-glycero-3-phospho-L-serine (DOPS), cholesterol (Chol), sphingomyelin (SM), and ganglioside (GM) was investigated using QCM-D. A challenge was that the raft-containing vesicles remained intact on the SiO2 crystal. Therefore, different experimental conditions were tested to induce vesicle fusion, such as pH, temperature, osmotic pressure, and vesicle size. The key parameter in forming the bilayer was found to be applying osmotic pressure to the vesicles by having the vesicles exterior concentration of NaCl higher than interior concentration. When this concentration gradient was applied to the vesicles before flowing them on the substrate, vesicle rupture was favored and formation of a complete bilayer could occur. Here, we report the effects of each tested variable on the adsorption and fusion of the raft-containing vesicles, and the results are discussed based on the mechanisms of vesicle-vesicle and vesicle-substrate interactions.After developing the robust method for formation of SLB with lipid rafts, we used that as a template to characterize the mechanism of interactions between Aβ peptide and cell membrane which leads to onset of AD. The mechanism of Aβ toxicity leading to AD has not fully discovered yet, due to the complexity of the process including several steps of Aβ peptide adsorption on membrane, conformational change from disordered in solution to a membrane-bound α-helix structure and then formation of β-sheet aggregates that serve as fibrillation seeds. In this study, we showed that QCM-D technique as a promising tool to conduct systematic studies on the mechanism of interactions between Aβ peptide with lipid membrane. To our knowledge, this was the first time QCM-D was utilized for characterization of Aβ fibrillation starting from monomer states until formation of mature fibrils. The data indicated that peptide-membrane interactions follow a two-step kinetic pathway starting with the adsorption of small (low-n) oligomers until covering all the adsorption sites on the surface. In the second step, the membrane structure is destabilized as the result of interaction with oligomers which leads to lipid loss from the surface. Consistency of the results with the data obtained via other techniques substantiates QCM-D technique as a robust approach to answer the remaining unanswered questions in the field of Alzheimer’s disease.

Dissolved organic matter (DOM) plays a vital role in biogeochemical processes and can flux CO2 to the atmosphere when labile fractions are degraded, hence DOM degradation is increasingly studied. Some studies have suggested that fluorescence-derived substrate characteristics are useful metrics for estimating bioavailability (as prerequisite condition for biodegradability), however, recent findings on soil organic matter emphasize the importance of ecosystem scale factors such as physical separation of substrate from soil microbial communities and soil physiochemical cycles driving organic matter stability. I extend this principle to soil derived DOM and hypothesize that such environmental conditions, covariant with season, land use and landscape position, impact the composition of soil DOM and activity and abundance of the microbial community, which together govern DOM biodegradability. As a result, DOM bioavailability may not reliably be predicted using substrate characteristics alone. To test these hypotheses, I assessed aqueous soil extracts for water extractable organic carbon (WEOC) content, biodegradability, microbial biomass and fluorescence spectroscopy on water extractable organic matter (WEOM) across a range of environmental conditions in northern Vermont, USA. My results indicate that changes in environmental conditions affect composition, quantity, and biodegradability of DOM. WEOC concentrations were highest in the fall and lowest in the summer, while no significant differences were found between land covers or landscape position, however, DOM biodegradability was significantly higher in the agricultural (AG) site across seasons. Despite a shift in utilized substrate from less aromatic DOM in summer to more aromatic DOM in winter, biodegradability was similar for all seasons. The only exception were cold temperature incubations where microbial activity was depressed, and processing was halted. These results indicate that bioavailability cannot be reliably predicted based on fluorescence-based metric alone, rather, my core findings illustrate a complex picture of how environmental conditions, landscape characteristics, and substrate composition interact to drive the biodegradability of labile carbon pools in the soil environment. This thesis includes i) a background and comprehensive review of literature to inform the reader of any relevant topics, ii) a paper submitted for publication to Biogeochemistry (Chapter 2), and iii) supplemental information containing figures and tables pertinent to the paper.