In this dissertation, the intermolecular interactions between soil organic matter (SOM) and organofluorine compounds have been studied at the molecular-level using Nuclear Magnetic Resonance (NMR) spectroscopy. NMR probes the local magnetic environment surrounding atomic nuclei, and is uniquely capable as an analytical tool to probe molecular environments in complex disordered materials, such as soils. Several NMR techniques were employed in this work, including Pulse Field Gradient (PFG)-NMR based diffusion measurements, solid-state cross-polarization (CP), saturation transfer difference (STD) spectroscopy, and reverse-heteronuclear saturation transfer difference (RHSTD) spectroscopy. Using organofluorine compounds as molecular probes, xenobiotic interactions with SOM were studied. Using 1H{19F} RHSTD, the interaction sites in humic acid for organofluorine compounds were identified by direct molecular-level methods. Protein and lignin were identified as major binding sites, with different preferences exhibited for these sites by dissimilar organofluorine compounds: aromatic organofluorine compounds display varied preference for aromatic humic acid sites while perfluorooctanoic acid exhibits near total selectivity for protein-derived binding sites. The mechanisms underlying these preferences were probed in the solution state. Using crucial knowledge from the humic acid studies, a detailed molecular-level investigation of xenobiotic interactions in an intact and unmodified whole soil was made possible. A direct and in situ elucidation of the components in soil organic matter that interact with small organofluorine xenobiotic molecules has been presented, allowing, for the first time, resolution of multiple interactions occurring for xenobiotics simultaneously at different sites within a whole soil.

Quantification of natural organic matter (NOM) in water is limited by the complex and varied nature of compounds found in natural waters. Current characterization techniques, which identify and quantify fractions of NOM, are often expensive and time consuming suggesting the need for rapid and accurate characterization methods. In this work, principal component analysis of fluorescence excitation-emission matrices (FEEM-PCA) was investigated as a NOM characterization technique. Through the use of jar tests and disinfection by-product formation tests, FEEM-PCA was shown to be a good surrogate for disinfection by-product precursors. FEEM-PCA was also applied in order to characterize differences in humic-like, protein-like, and Rayleigh scattering between multiple source waters and due to differing treatment processes. A decrease in Rayleigh scattering influence was observed for a deep lake intake, and multiple processes were found to significantly affect humic-like substances, protein-like, and Rayleigh scattering fractions.

Dissolved organic matter (DOM) is comprised of a complex array of molecular constituents that are linked to many globally-relevant processes and yet this material is still largely molecularly uncharacterized. Research presented here attempted to probe the molecular complexity of this material from both Arctic and temperate climates via multifaceted and novel approaches. DOM collected from remote Arctic watersheds provided evidence to suggest that permafrost-disturbed systems contain more photochemically- and biologically-labile material than undisturbed systems. These results have large implications for predicted increasing temperatures where widespread permafrost melt would significantly impact stores of organic carbon in polar environments. In attempting to address the complexities and reactivity of DOM within global environments, more information at the molecular-level is necessary. Further research sought to unravel the molecularly uncharacterized fraction via use of nuclear magnetic resonance (NMR) spectroscopy in conjunction with hyphenated and varied analytical techniques. Directly hyphenated high performance size exclusion chromatography (HPSEC) with NMR was explored. This hyphenation was found to separate DOM into structurally distinct fractions but proved limited at reducing DOM heterogeneity. Of the many high performance liquid chromatography (HPLC) techniques tested, hydrophilic interaction chromatography (HILIC) was found the most effective at simplifying DOM. HILIC separations utilizing a sample from Florida resulted in fractions with highly resolved NMR signals and substantial reduction in heterogeneity. Further development with a 2D-HILIC/HILIC system to achieve additional fractionation was employed. This method produced fractions of DOM that were homogenous enough to produce excellent resolution and spectral dispersion, permitting 2D and 3D NMR experiments to be performed. Extensive NMR analyses of these fractions demonstrated strong evidence for the presence of highly oxidized sterols. All fractions, however, provided 2D NMR spectra consistent with oxidized polycyclic structures and support emerging data and hypotheses suggesting that cyclic structures, likely derived from terpenoids, are an abundant, refractory and major component of DOM. Research presented within this thesis demonstrates that HILIC and NMR are excellent co-techniques for the analysis of DOM as well as that oxidized sterols and other cyclic components with significant hydroxyl and carboxyl substituents are major constituents in DOM.

In this dissertation, the intermolecular interactions between soil organic matter (SOM) and organofluorine compounds have been studied at the molecular-level using Nuclear Magnetic Resonance (NMR) spectroscopy. NMR probes the local magnetic environment surrounding atomic nuclei, and is uniquely capable as an analytical tool to probe molecular environments in complex disordered materials, such as soils. Several NMR techniques were employed in this work, including Pulse Field Gradient (PFG)-NMR based diffusion measurements, solid-state cross-polarization (CP), saturation transfer difference (STD) spectroscopy, and reverse-heteronuclear saturation transfer difference (RHSTD) spectroscopy. Using organofluorine compounds as molecular probes, xenobiotic interactions with SOM were studied. Using 1H{19F} RHSTD, the interaction sites in humic acid for organofluorine compounds were identified by direct molecular-level methods. Protein and lignin were identified as major binding sites, with different preferences exhibited for these sites by dissimilar organofluorine compounds: aromatic organofluorine compounds display varied preference for aromatic humic acid sites while perfluorooctanoic acid exhibits near total selectivity for protein-derived binding sites. The mechanisms underlying these preferences were probed in the solution state. Using crucial knowledge from the humic acid studies, a detailed molecular-level investigation of xenobiotic interactions in an intact and unmodified whole soil was made possible. A direct and in situ elucidation of the components in soil organic matter that interact with small organofluorine xenobiotic molecules has been presented, allowing, for the first time, resolution of multiple interactions occurring for xenobiotics simultaneously at different sites within a whole soil.

Quantification of natural organic matter (NOM) in water is limited by the complex and varied nature of compounds found in natural waters. Current characterization techniques, which identify and quantify fractions of NOM, are often expensive and time consuming suggesting the need for rapid and accurate characterization methods. In this work, principal component analysis of fluorescence excitation-emission matrices (FEEM-PCA) was investigated as a NOM characterization technique. Through the use of jar tests and disinfection by-product formation tests, FEEM-PCA was shown to be a good surrogate for disinfection by-product precursors. FEEM-PCA was also applied in order to characterize differences in humic-like, protein-like, and Rayleigh scattering between multiple source waters and due to differing treatment processes. A decrease in Rayleigh scattering influence was observed for a deep lake intake, and multiple processes were found to significantly affect humic-like substances, protein-like, and Rayleigh scattering fractions.

The repercussions of climate change are felt worldwide, but Arctic and subarctic regions, where climate warming is expected to be amplified, are especially vulnerable. An episode of mass fish mortality in the Sutton River in the Hudson Bay Lowlands (HBL) of Northern Ontario has elicited the interest of the scientific community. Several lakes were sampled over three years in an effort to better understand and document the changes that may be occurring in these lakes. This study uses sediment cores to assess the history of mercury (Hg) deposition and to assess changes occurring in autochthonous productivity in these lakes. Sediments deposited after the onset of the industrial revolution contained significantly higher concentrations of Hg, with the highest concentrations found in the most recently deposited sediments. Hg concentrations in these pristine lakes rival those of lakes in heavily urbanized areas, indicating that they are in fact subjected to atmospheric deposition of Hg. There was a large variation in [Hg] of the surface sediments of 13 lakes; underscoring the importance of in situ processes in the fate of atmospherically deposited Hg. Methylmercury (MeHg) concentrations were not correlated with total mercury concentrations (THg), demonstrating how THg is a poor predictor of MeHg; the bioaccumulative neurotoxic form of mercury. The S2 fraction of Rock-Eval® Pyrolysis, C:N ratios and ∂13C signatures were used as proxies of autochthonous carbon and all indicated that the lakes have become increasingly productive, presumably due to warmer water temperatures and longer ice-free seasons. Additionally, I use molecular techniques to detect and quantify the merA gene in the sediment; a proxy of bacterial mercury resistance involved in redox transformations. In Aquatuk, Hawley and North Raft Lakes, I observed a subsurface increase in merA genes in the sediment core, independently of a control gene and the [THg]. While I have not been able to explain the driving variables of this subsurface increase, I believe that the role of merA within remote lake sediments deserves further work. Lastly, microcosms were used to measure the production of volatile elemental mercury (Hg(0)) from surface sediments of Aquatuk Lake. I used a combination of analytical and molecular techniques to show that the production of Hg(0) is biogenic and tested the effect of nutrients, pH and ionic strength on the Hg(0) production rates. Ionic strength alone had the greatest impact on Hg(0) production rates, with increased Hg(0) production as ionic strength increases.

Chlorine is still the most commonly used disinfectant in many water treatment plants all over the World. However, studies conducted demonstrated that the chlorine reacts with the natural organic matter (NOM) in source waters, and leads to the formation of a variety of chlorinated organic compounds, disinfection by-products (DBPs). Among these, the most common are the trihalomethanes (THMs). In this study, kinetics of the THM formation was investigated. Kinetic experiments were carried out with the raw waters from Devege&ccedil / idi and Atat&uuml / rk Reservoirs as well as with water containing a model compound, humic acid. THM and Chlorine concentrations were measured for 6 weeks on a seasonal basis. The simulation model developed by USEPA was used for predicting THM concentrations. The results of this study have shown that THM formation increases with increasing time and higher chlorine doses result in higher THM formation. Also, higher organic matter concentrations resulted in higher chlorine demands and both these parameters increased the TTHM concentrations. But, on the contrary to the standard THMFP testing, THM formation did not complete in seven days. In addition, THM formation and chlorine consumption were very rapid during the first 24 hr followed by a more gradual formation and decay after 24 hr. THM formation rates ranged between 35-66 &micro / g/L.day for Atat&uuml / rk Reservoir, between 80-167 &micro / g/L.day for Devege&ccedil / idi Reservoir and between 85-248 &micro / g/L.day for humic acid during the first 24 hr, and ranged between 2-6 &micro / g/L.day for Atat&uuml / rk Reservoir, between 7-16 &micro / g/L.day for Devege&ccedil / idi Reservoir and between 3-14 &micro / g/L.day for humic acid after 24 hr.

Plant residues added to soil are a source of nutrients for plants and soil organisms and increase soil organic matter which has an important role in improving soil structure and fertility, hence maintaining soil quality for sustainable agriculture. In order to utilize plant residues for increasing soil organic matter more effectively, it is necessary to understand the mechanisms of plant residue decomposition. Soil organic matter decomposition is influenced by several factors such as plant residue quality, temperature, water availability, soil structure and soil texture, particularly clay content. The interaction of clay and decomposition of organic matter has been studied in the past. Nevertheless, many studies investigated this interaction in natural soil or under field conditions over long periods of time. Variation in environmental factors may influence the interaction of clay and decomposition of organic matter, thus in most previous studies their effect cannot be separated from the direct effect of clay on decomposition. To study the direct effect of clay on organic matter decomposition, four experiments with different objectives were carried out using isolated natural clay, under controlled conditions (e.g. temperature and organic matter input) and a short incubation period (approximately one month). All experiments were carried out using a sand matrix to which different clay types, clay fractions (natural or with iron oxide partially removed) or clay concentrations were added together with mature wheat straw (C/N 122 in most experiments, except Experiment 2 where the wheat straw had a C/N of 18) and a microbial inoculum. To investigate the effect of clay type, two clay types were added. They were isolated from Wiesenboden (W) and Red Brown Earth (RBE) soil. Clay types from both soils contained kaolinite and illite, but smectite only occurred in W clay. Iron oxide is thought to be important for the binding of organic matter to clay, therefore two clay fractions were used, the clay with native iron oxide (natural clay) and clay from which iron oxide was partially removed by citrate-dithionite-bicarbonate treatment (citrate-dithionite clay, CD clay). The following parameters were measured: pH, water loss, respiration rate, microbial community structure using phospholipid fatty acid analysis and, in some experiments, particulate organic matter. In all experiments, the water content of the substrate mixes was adjusted only at the start; water loss was greatest in the control and decreased with increasing clay content. The aim of the first experiment was to study the effect of the concentration of W clay on decomposition of wheat residues. Respiration (i.e. decomposition of the wheat straw) was affected by clay in two ways (i) decreased decomposition, thus protection of organic matter, in the initial phase at all concentrations (5, 10, 20 and 40%) and throughout the incubation period at ≤ 20% clay, and (ii) greater water retention at higher clay concentration particularly 40% clay that allowed maintenance of higher respiration rates towards the end of incubation. Generally, clay concentration had an effect on microbial community structure but not on microbial biomass. The effect of clay concentration was also investigated in the second experiment, but using RBE clay and a narrower range of concentrations (0, 2.5, 5, 10 and 20% clay) than in the first experiment with W clay. The wheat residue used in this experiment had a lower C/N ratio compared to the other three experiments (C/N 18 compared to 122). In contrast to the first experiment, cumulative respiration of the clay treatments was greater than that of control throughout the incubation, thus clay increased rather than decreased decomposition. This may be due to the properties of the wheat residue used in this experiment which contained more water-soluble compounds, the diffusion of which would be enhanced in treatments with clay compared to the control due to their higher water availability. However, considering only the treatments with added clay, cumulative respiration followed the same pattern as in the first experiment, with highest cumulative respiration at 20% clay. In general, microbial community structure, microbial biomass and microbial groups (i.e. bacterial and fungal fatty acids) were affected by the presence of clay and sampling time, but there was no clear relationship between these factors and the richness and diversity of the microbial community. The aim of the third experiment was to determine the effect of clay concentration (5 and 40% of W clay) and fraction (natural or citrate-dithionite clay) on decomposition of wheat straw and microbial community structure. Clay fraction and concentration strongly affected the respiration rate and microbial community structure as well as microbial biomass but not the concentration of particulate organic matter (POM). Compared to the control, partial removal of iron oxide strongly increased decomposition at both concentrations whereas clay with iron oxides reduced the decomposition. Microbial community structure was affected by clay fractions, particularly at 40% clay. The aim of the fourth experiment was to determine the effect of clay fraction (natural and citrate-dithionite clay) and clay type (W clay or RBE clay) at 5% clay on decomposition of wheat straw and microbial community structure. Clay type and the partial removal of iron oxide had a significant effect on the decomposition rate but did not affect POM concentration. As in the third experiment, partial removal of iron oxide increased respiration rate, the effect was less pronounced in RBE clay than in W clay. Clay type and fraction strongly affected microbial community structure. In conclusion, the experiments showed that native clay generally reduces organic matter decomposition by binding and occlusion. The importance of iron oxide for the protective effect of clay on organic matter decomposition was shown by the fact that partial removal of iron oxide strongly increased decomposition rate compared to the native clay. The two clay types differed in their effect. The W clay containing smectite protects organic matter to a greater extent than RBE clay with predominantly illite and kaolinite due to its higher surface area and CEC that lead to binding and or occlusion. The results also showed that although clay reduces organic matter decomposition under optimal water availability, this effect can be reversed as the substrates dry out because the greater water retention of substrates with clay concentrations > 10% compared to the pure sand matrix allows maintenance of a greater microbial activity. Clay type, fraction and concentration affected microbial community structure via their effect on organic matter and water availability. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1521949 / Thesis (M.Ag.Sc.) -- University of Adelaide, School of Earth and Environment Science, 2010

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 3 uppsatser.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 3 uppsatser.