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.

Stable carbon isotope ratios of soils, roots and litter along transects stretching from nearly monospecific stands of Ceratoides lanata , a species possessing c3 photosynthesis, to nearly monospecific stands of Atriplex confertifolia, a species possessing c4 photosynthesis, were analyzed to determine i f changes in the relative dominance of the shrubs have occurred in salt-desert communities. The a13c value , which reflects the proportion of 12c and 13c in a sample of plant tissue, can be used to distinguish between c3 and c4 species. Atriolex confertifolia and Ceratoides lanata have a13c values of -13.0 ofoo and - 25 ofoo, respectively. The a13c value of litter and roots was used as a measure of current community dominance. The a13c value of soil organic matter was employed as a measure of past community dominance . The differential between a13c values of roots and soils was consistently about 3.0 ofoo in Ceratoides- dominated stands. Root a13c values were always more negative than soil a13c values. The striking uniformity in the rootsoil differential l in Ceratuitles- duninateci stands is most likely the result of fractionation of carbon isotopes during decomposition. The differential between a13c values of roots and soils in Atriplexdominated stands was more variable. This most likely indicates a lack of long- term community stability in areas na The distribution of a13c values in relation to depth and among soil organic matter fractions was also studied. There was a trend for a13c values to become slightly less negative with depth . The a13c value of humic acid was most similar to the o13c value of the dominant vegetation. Fulvic acid was isotopically heavier than humic acid in all analyses. The implications of these trends are discussed.

Membrane processes are increasingly used in water treatment. Experiments were performed using stirred cell equipment, polymeric membranes and synthetic surface water containing natural organics, inorganic colloids and their aggregates, and cations. All processes could remove a significant amount of natural organics. Pretreatment with ferric chloride was required to achieve significant organic removal with MF and high MWCO UF. Additionally, fouling mechanisms for the three processes were investigated. Crucial parameters were aggregate characteristics (fractal structure, stability, organic-colloid interactions), solubility of organics and calcium, and hydrodynamics. In MF, fouling by pore plugging was most severe. Variations in solution chemistry changed the aggregation state of the colloids and/or natural organic matter and dramatically affected rejection and fouling behaviour. UF membrane fouling was mainly influenced by pore adsorption and could improve natural organics rejection significantly. Coagulant addition shifted fouling mechanism from pore adsorption to cake formation. Aggregate structure was most significant for flux decline. In NF, rejection of natural organics involved both size and charge exclusion. Fouling was caused by precipitation of a calcium-organic complex. Fouling could be avoided by pretreatment with metal salt coagulants. Thorough chemical characterisation of the organics used demonstrated that only size and aromaticity can be related to fouling. The study is concluded with a process comparison based on a water quality parameter and a cost comparison. Treatment cost of microfiltration with chemical pretreatment was similar to that of nanofiltration at a comparable natural organics rejection.

Natural organic matter (NOM) occurs ubiquitously in drinking water supplies and is problematic since it serves as a precursor to disinfection by-products (DBPs) formation. Stricter DBP regulations will drive utilities to consider advanced treatment processes for DBP control through NOM removal. Herein, the transformation of NOM in homogeneous (UVA/H2O2 and UVA/Fe/H2O2) and heterogeneous (UVA/TiO2) Advanced Oxidation Processes (AOPs) were studied. Organic matter from three different sources was investigated in this work, specifically a commercial humic acid, and two Australian surface water sources. The transformation of the organic matter as a result of oxidation was investigated through multiple analytical techniques, such as UV-Vis spectroscopy, DOC analysis, high performance size exclusion chromatography (HPSEC), resin fractionation, liquid chromatography with organic carbon detection (LC-OCD) and disinfection byproducts formation potential. The multi-analysis approach is required due to the complex and heterogeneous nature of NOM. Each analytical technique provides complementary information on different properties of NOM, leading to a comprehensive understanding on how AOPs transform the chemical and physical properties of NOM. Both homogeneous and heterogeneous AOPs were found to be effective for NOM removal. However, complete mineralisation was not achieved, even under prolonged irradiation. Large aromatic and hydrophobic organics were degraded into lower molecular weight hydrophilic compounds, which had weak UV absorbance at 254 nm. In the UVA/TiO2 treatment, multi-wavelength HPSEC analysis demonstrated the formation of low molecular weight compounds with strong absorbance at wavelength lower than 230 nm. These residual organic compounds, though recalcitrant, had a low reactivity to chlorine to form THMs, and were identified to be low molecular weight acids and neutral compounds from LC-OCD analysis. Finally, the current work reports the novel synthesis of magnetic photocatalyst for NOM oxidation from low cost precursors to solve the separation problem of nano-sized particles. Magnetite particles were coated with a layer of protective silica from sodium silicate precursor. Photoactive titanium dioxide was then deposited onto the silica coated particles using titanium tetrachloride precursor. The as-prepared magnetic photocatalyst exhibited excellent stability and durability. Although the photoactivity of the magnetic photocatalyst is lower than commercial TiO2 photocatalyst, it can be easily recovered by magnetic field.

In Belgium, the Boom Clay is currently studied as the reference host formation for the disposal of high-level and long-lived radioactive waste. In case of direct disposal of spent fuel, uranium isotopes are important contributors along with their daughters to the dose rate at very long term. Therefore, it is essential to study the migration of uranium in the host formation. The present work contributes to improve the knowledge of uranium speciation in the Boom Clay, U(IV) versus U(VI), and of the mechanisms controlling the uranium mobility such as solubility, sorption and complexation by organic matter. The information necessary to interpret the migration behaviour is derived from the study of naturally occurring uranium in the rock and from laboratory experiments conducted under conditions representative for the Boom Clay. Uranium naturally present in the Boom Clay is concentrated in detrital heavy minerals and in authigenic iron(II)-bearing minerals such as siderite and glauconite. Despite its reducing capacity, pyrite is surprisingly depleted in uranium relative to the mean content. Furthermore, uranium is also associated with the surfaces of clay minerals. The clayey fraction contains about 4 ppm uranium and is the main contributor to the total uranium content of the Boom Clay since it constitutes up to 60 wt. % of the rock. The correlation observed on the field between uranium and organic matter suggests that uranium is reduced, likely during the early diagenesis process of bacterially-mediated sulphate reduction. If hexavalent oxidation state of uranium predominates as predicted by geochemical calculations based on the most recent thermodynamic data of the Nuclear Energy Agency (NEA), less than 5% of uranium is complexed by humic acids in the Boom Clay pore water. The U(VI) speciation is dominated by the inorganic carbonate complexes, merely UO2(CO3)34-. The conditional constant determined for the complexation of U(VI) by humic acids under in situ Boom Clay conditions is log exp = 12.4. However, experimental studies show that UO2(CO3)34- is reduced by interaction with pyrite, the main reducing mineral present in the rock, and precipitates as a mixed oxide of U(IV)/U(VI), i.e. UO2+x. Moreover, electromigration experiments suggest that U(VI) is not stable in the Boom Clay: U(VI) is reduced and precipitates as U(IV) oxy-hydroxides. The experimentally measured solubility of U(IV) amorphous oxide, UO2(am), in Boom Clay pore water is about 10 8 mol•l 1. This solubility value is not increased by complexation of U(IV) with dissolved organic matter. The dominant effect of organic matter on the dissolution of UO2(am) is the stabilisation of U(IV) real colloids which increase the uranium concentration by three orders of magnitude. However, the mobility of these colloids is expected to be very limited because of the compaction level of the Boom Clay and its ultra-filtrating feature. The diffusive transport of dissolved uranium is furthermore retarded by significant sorption onto clay minerals. In conclusion, the presence of organic matter in the Boom Clay has no negative effect on the uranium retention which is dominated by the solubility and sorption of U(IV) species

The objective of these studies was to develop near-infrared reflectance spectroscopy calibration equations from diet-fecal pair datasets to predict the diet quality and intake of donkeys. One hundred-forty diet-fecal pair samples were generated from two independent in vivo feeding trials conducted in the United States (N = 100) and Africa (N = 40). At each site, ten female donkeys were fed mixed diets blended from 25 forage and crop residues. The modified partial least square model (MPLS) was used to develop calibration equations for crude protein (CP), digestible organic matter (DOM), dry matter digestibility (DDM) and organic matter digestibility (OMD), for the US, Africa and US/Africa combined datasets, and dry matter (DM) and organic matter (OM) intake calibrations from the US datasets. Crude protein (CP) equations were developed with standard error of calibration (SEC) < 1.0 and coefficient of determination (R2) > 0.90, (SEL = 0.5). The US, US/Africa and Africa CP equations had SEC value of 0.77, 0.97 and 0.88 with corresponding R2 of 0.97, 0.95 and 0.88, respectively. Validation of the US CP equation resulted in a standard error of prediction (SEP) of 1.79 with corresponding coefficient of correlation (r2) of 0.82 and slope of 0.84 indicating high accuracy of prediction. In vivo derived DOM equations were also developed for the US, Africa and US/Africa datasets with SEC values of 2.58, 4.91 and 3.52, and R2 of 0.60, 0.81 and 0.84, respectively. In addition, the SEC and R2 values were 3.25 and 0.72 for US OMD, 3.28 and 0.79 for US DDM, and 4.2 and 0.85 for US/Africa OMD, and 4.3 and 0.87 for US/Africa DDM equation, respectively. Calibration equations for predicting DMI and OMI have resulted in SEC values of 3.45 and 3.21 (g/kgw0.75) and R2 values of 0.89 and 0.84, respectively. The present study explored the relationship between DMI and diet quality attributes. Crude protein and digestible organic matter to crude protein ration (DOM/CP) with r2 values of 0.60 and 0.39, respectively, have shown good correlations with intake. The present studies have confirmed the potential for the fecal NIRS profiling for predicting CP, DOM, DDM, OMD, DMI and OMI of donkeys. Both calibration and validation results have indicated that the present donkey equations were comparable to previously developed equations for ruminants; they have the capability for accurate prediction of diet quality and intake, and can be a useful tool for monitoring the nutritional well-being of donkeys with acceptable accuracy. Research works to further expand the present calibration equations with additional diet-fecal samples particularly from Africa that did not meet the required accuracy level is recommended.

The objective of drinking water treatment is to provide water which is free of pathogens, is chemically and biologically stable, and is of good aesthetic quality. Natural organic matter (NOM) is present in all natural waters and can make meeting these goals more challenging. Not only does it undergo adverse reactions with disinfectants such as chlorine, it also impacts the biological stability of water within the distribution system and contributes to undesirable aesthetic qualities such as taste and odour. NOM has also been implicated in membrane fouling, which continues to be a significant operational problem preventing wider implementation of this process. Due to its highly variable heterogeneous nature, NOM can be difficult to characterize in terms of its specific composition, however recent analytical advancements are allowing for a better understanding of its behaviour in water treatment. Two promising tools for NOM characterization include Liquid Chromatography Organic Carbon Detection (LC-OCD) and Fluorescence Excitation Emission Matrix (FEEM) analyses. In this research both techniques were applied to samples taken from five full scale facilities in Ontario, Canada over all four seasons. The source waters for these treatment locations consisted of both river (Grand River, Ottawa River) and Great Lake waters (Lake Huron, Lake Erie, Lake Ontario), and an additional raw source (Saugeen River) was also monitored. The plants all employed granular media filtration, but had differences including enhanced coagulation, ozonation, biofiltration and sand ballasted flocculation. Other relevant water quality parameters were also monitored (TOC, DOC, UV254, pH, conductivity etc.) as well as plant operating conditions (dosages, flows, filter run times etc.) to investigate their impact on removal of specific NOM fractions. Four of the waters (Grand River, Ottawa River, Lake Erie and Lake Ontario) were selected based on the initial survey due to their NOM composition, for bench scale ultrafiltration (UF) membrane fouling experiments. The experiments were run at constant flux for a period of five days, with an automated permeation cycle and backwash. The impact of biopolymers on hydraulically reversible and irreversible fouling was of specific interest. Important seasonal trends were identified for all waters, with biopolymer content increasing at higher temperatures. Useful comparisons could also be made between different treatment processes including conventional and enhanced coagulation. The enhanced process while significantly improving the removal of humic substances, was not beneficial in terms of biopolymer removal, suggesting a different removal mechanism for these two fractions. The removal of low molecular weight ozonation by-products during full scale biofiltration was well demonstrated, and other fractions (building blocks, biopolymers) had varying degrees of removal, which was more dependent on temperature. Principle component analysis (PCA), an advanced multivariate statistical method, was successfully applied to a FEEM data set containing five different waters at varying degrees of treatment. Three principle components related to humic-like, protein-like and particulate/colloidal material were identified, and served as useful complementary information to the LC-OCD results. The humic-like component was found to have relatively good correlation to the humic fraction from LC-OCD analysis, with some deviation in the post-ozonation samples (which underwent greater structural changes not captured by LC-OCD). The biopolymer fraction was shown to have good correlation to hydraulically reversible membrane fouling across all four waters. The same could not be said for hydraulically irreversible fouling for which a combined fouling layer (with particulate and colloidal material) is hypothesized. This research provides those working in the water treatment sector with greater insight into NOM behaviour during various levels of treatment. As biopolymers were demonstrated to impact hydraulically reversible fouling (relatively independent of water quality), their removal prior to membrane filtration could significantly extend operational cycles by extending time between backwashes, thereby reducing energy requirements. As biopolymers are also suspected in forming a combined fouling layer, their removal can potentially minimize chemical cleaning requirements (and extend the life cycle of the membranes). The removal of biopolymers through coagulation was well demonstrated. Biofiltration is also expected to perform well as a membrane pre-treatment due its ability to remove biopolymers and particulate/colloidal matter. The ability of biofiltration to control biological re-growth in the distribution system (by removing low molecular weight biodegradable products) was also shown using LC-OCD and FEEM analysis.

Copper-induced toxicity in aqueous systems depends on its speciation and bioavailability. Dissolved organic matter (DOM) and reduced sulfur species can complex copper, influencing speciation and decreasing bioavailability. DOM composition in estuaries can vary, depending on allochthonous, autochthonous, or wastewater source. At a molecular level, variability in DOM quality potentially results in different copper binding affinities. The aim of this study was to characterize and quantify DOM and reduced sulfur in estuaries and investigate possible correlations between these parameters and the capacity to complex copper, reducing its toxicity. This study will have implications on the development of marine-specific toxicity prediction models. DOM was characterized in seventy-one estuarine samples through DOC concentration and fluorescence measurements, combined with spectral resolution techniques, to quantify humic-, fulvic-, tryptophan-, and tyrosine-like fractions. Reduced sulfur was measured by the chromium-reducible sulfide (CRS) technique. Acute copper toxicity tests were done on a subset of samples expressing extreme DOC, fluorescent allochthonous, autochthonous, and CRS concentrations. The results showed significant differences in DOM quality, independent of DOC concentration. In terms of total fluorescent material, humic-like material ranged from 9.48% to 66.1%, followed by fulvic-like with a range of 14.5% to 63.2%, and 0.00% to 36.5% for tryptophan-like and 0.64% to 25.2% for tyrosine-like material. CRS was widely variable among the samples; concentrations ranging from 0.5 nM to 7800 nM. The toxicity results suggested DOC was a very good predictive measure of copper EC50 in estuaries (r2 = 0.84) independent of DOM quality. Furthermore, CRS was saturated at low copper concentrations indicating strong binding sites for copper, suggesting that while CRS is protective, it does not bind copper at toxicologically relevant concentrations and therefore is not a good predictive measure of copper toxicity.

Copper-induced toxicity in aqueous systems depends on its speciation and bioavailability. Dissolved organic matter (DOM) and reduced sulfur species can complex copper, influencing speciation and decreasing bioavailability. DOM composition in estuaries can vary, depending on allochthonous, autochthonous, or wastewater source. At a molecular level, variability in DOM quality potentially results in different copper binding affinities. The aim of this study was to characterize and quantify DOM and reduced sulfur in estuaries and investigate possible correlations between these parameters and the capacity to complex copper, reducing its toxicity. This study will have implications on the development of marine-specific toxicity prediction models. DOM was characterized in seventy-one estuarine samples through DOC concentration and fluorescence measurements, combined with spectral resolution techniques, to quantify humic-, fulvic-, tryptophan-, and tyrosine-like fractions. Reduced sulfur was measured by the chromium-reducible sulfide (CRS) technique. Acute copper toxicity tests were done on a subset of samples expressing extreme DOC, fluorescent allochthonous, autochthonous, and CRS concentrations. The results showed significant differences in DOM quality, independent of DOC concentration. In terms of total fluorescent material, humic-like material ranged from 9.48% to 66.1%, followed by fulvic-like with a range of 14.5% to 63.2%, and 0.00% to 36.5% for tryptophan-like and 0.64% to 25.2% for tyrosine-like material. CRS was widely variable among the samples; concentrations ranging from 0.5 nM to 7800 nM. The toxicity results suggested DOC was a very good predictive measure of copper EC50 in estuaries (r2 = 0.84) independent of DOM quality. Furthermore, CRS was saturated at low copper concentrations indicating strong binding sites for copper, suggesting that while CRS is protective, it does not bind copper at toxicologically relevant concentrations and therefore is not a good predictive measure of copper toxicity.

Electrodialysis (ED) experiments were conducted on reverse osmosis (RO)-concentrated solutions of NOM from six rivers. The ED processes successfully recovered 88 11% of TOC, and removed 83% 19% of SO42- and 67% 18% of H4SiO4. More importantly, the molar ratios of SO42- /TOC and H4SiO4 /TOC were reduced to a mean value of 0.0046 and 0.032, respectively, surpassing the goal for removal of SO42- (0.008) and almost achieving the goal for removal of H4SiO4 (0.021). The ED process can lower the SO42- /TOC ratio in samples whose initial SO42- /TOC ratios are already far below the limit of 0.008 used in this study. The coupled RO/ED process that has been described here offers a fast, simple, chemically mild (relative to other methods), and reproducible method of isolation of large quantities of relatively unfractionated, low-ash NOM from freshwaters. RO/ED was also successfully used for isolating and concentrating marine dissolved organic matter (DOM). The effort successfully recovered a median of 72% of the TOC from 200 L samples within six to nine hours of processing through a combination of ED and RO, greatly exceeding the current norm of 30%. The relatively high recovery of DOM implies that classes of DOM previously missing are included in these samples and should yield new insight into the chemistry of marine DOM. Freshwater samples processed by electrodialysis were analyzed for elemental composition and by capillary zone electrophoresis (CZE), 1H and 13C nuclear magnetic resonance spectroscopy (NMR), and electro-spray ionization mass spectrometry (ESI-MS). Bulk elemental composition, 1H- and 13C-NMR, and ESI-MS data provide evidence linking bioavailabilty to the bulk chemistry of NOM: the H/C and N/C molar ratios are positively and strongly correlated with bioavailability, as hypothesized. Using an independent dataset (STORET) of water quality parameters, calculated BOD/TOC ratios were found to be moderately correlated with measured bioavailabilities and can be used as a surrogate for bioavailability of geochemically diverse riverine DOM.