Dissertations / Theses on the topic 'Organic matter'

[Truncated abstract] Relationships between the persistence of organic matter added to soil, the dynamics of soil organic carbon (C) and phosphorus (P) were examined in four experiments on lateritic soils of Western Australia. The main objective was to quantify the release of P following organic matter application in soils which have high P adsorbing capacity. Another objective was to confirm that due to its recalcitrant materials, the effect of peat lasted longer in soil than other sources of organic matter in terms of increasing plant-available P fractions. Three experiments were conducted under glasshouse conditions for various lengths of time, with nine- to twelve-month incubations to investigate these hypotheses. As expected, organic matter with lower C:N ratios than peat (lucerne hay) decomposed more rapidly compared with peat, and the most active mineralisation took place within the first three months of incubation. Soil organic-C (extracted by 0.5 M K2SO4) had a significant positive correlation with P extracted with 0.5 M NaHCO pH 8.53. For a higher application rate (120 ton ha-1), peat was better than wheat straw and lucerne hay in increasing extractable bicarbonate-P concentrations in soil, especially at incubation times up to 12 months. Throughout the experiment, peat was associated with a steady increase in all parameters measured. In contrast to peat, nutrient release from lucerne hay and wheat straw was rapid and diminished over time. There was a tendency for organic-C (either in the form of total extractable organic-C or microbial biomass-C) to steadily increase in soil with added peat throughout the experiment. Unlike wheat straw and lucerne hay, extractable organic-C from peat remained in soil and there was less C loss in the form of respiration. Therefore, peat persisted and sequestered C to the soil system for a longer time than the other source of organic matter. Freshly added organic matter was expected to have a greater influence on P transformation from adsorbed forms in lateritic soils than existing soil organic matter. By removing the existing soil organic matter, the effect of freshly applied organic matter can be determine separately from that of the existing soil organic matter for a similar organic-C content. In order to do this, some soil samples were combusted up to 450° C to eliminate inherent soil organic matter. The release of P was greater when organic-C from fresh organic matter was applied to combusted soils than in uncombusted soils that contained the existing soil organic matter. The exception only applied for parameters related to soil micro-organisms such as biomass-C and phosphatase. For such parameters, new soil organic matter did not create conditions favourable for organisms to increase in activity despite the abundance of organic matter available. More non-extractable-P was formed in combusted soils compared to bicarbonate-P and it contributed to more than 50% of total-P. As for the first experiment, peat also showed a constant effect in increasing bicarbonate extractable-P in the soil

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.

Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2007.
Perdue, E. Michael, Committee Chair ; Ingall, Ellery, Committee Member ; Stack, Andrew, Committee Member ; Nenes, Athanasios, Committee Member ; Pfromm, Peter, Committee Member.

This study Is composed of three parts: (I) organic geochemical and organic petrological analysis of source rock samples from the Ghadames-El Borma basin are. described; (! I) organic geochemical characterisation of oils from a number of occurrences In Algeria has been carried out to give families or groups of different oil types; (iii) oiksource rock correlations In the Ghadames-El Borma basin between the oils In the Triassic reservoirs and, the putative source rock - sections are suggested. Sixty rock samples ranging from the-Triassic to Ordovician In age from the Ghadames-El Borma basin, have been Investigated using organic geochemical techniques In order to assess source rock potential. Rock-Eval pyrolysis data indicate that Devonian, constitute excellent - source rocks, Siludan and Ordovician are considered potentially ; noderate to good source beds, whereas Triassic sediments have little or no oil potential. Reflected and ultraviolet light I microscopy show that amorphous organic matter and Graptolite dominate the Ordovician strata, while Silurian and Devonlan'contain predominantly liptinitic materials such as acritarchs, algal bodies (Tasmanites) and spores; bitumen Is moderately abundant. Biological marker Investigation using capillary gas chromatography and the combined gas chromatography/mass spectrometry in energy Impact . -(GC/MS/El) and metastable ! on reaction monitoring (GC/MS/MRM) modes together with principal component analysis (PCA) have allowed a discrimination of samples Into three groups: (I) Ordovician, (ii) Silurian and Devonian and (iii) Triassic. Oil-oil correlation procedure has been carried out In areas with a number of different oil occurrences from southern and northern Algeria, namely from the Ghadames-El Borma, Sbaa, Illizi, Triassic province and Southeast Constantine basins. A range of approaches can be used which depend on the nature of the oils. In the present study, correlation parameters Include data derived from biological marker distributions as well as gasoline range hydrocarbons. Distributions of biological marker compounds together with principal component analysis (PCA) of sterane and terpane distributions reveal a discrimination of, the well numbers Into three groups: (1) Southeast Constantine (DK1, GKN1), Ghadames-El Borma, (ELB9), Sbaa (ODZI, DECI-11)A, in Amenas (TG22). (il) Ghadames-El Borma (KA2, ROM 1), Ain Amenas (ZR1 15) (iii)Gassi Touil (GT6, GT47), Rhourd-Nouss (RN48, RNSE6). Oils from Illizi basin (MRK16, STAI-18, STAH40 and MRK12) are poor In biological marker content and as yet cannot ba'assigned to any of the above groups. Maturity assessment has been based on paraffin index values (heptane and Isoheptane Indices) given by Thompson (1983) as well as steroid Isomerization and aromatization ratios. In this situation, oil mixing can be clearly seen using both gasoline derived I parameters and biological marker ratios (e. g. sterane Isomerization) if there Is no loss during migration. In the final part of this study,o il-sourcer ock correlationsh ave been considered for oils (Keskessa, El Borma and Rom field) and source rocks from the Ghadames-El Borma basin. However, such correlations were, In some cases, difficult to establish because molecular distributions may have changed during migration. Nevertheless, correlations procedures attempted using molecular parameters and PCA results of steranes and terpanes suggest that these particular oils may have been derived from Devonian or Silurian source rocks, as suggested by similarities In sterane and terpane compositions.

The biogeochemical cycling of carbon in Lochs Creran and Etive was investigated by using lignin as the biomarker for terrestrial organic matter. The oxygen uptake rate, percentage organic matter due to loss on ignition, Rp index, total carbon, total organic carbon (TOC), total nitrogen, C/N ratio, and phosphate content were used as the proxies to determine the biodegradability of the sediment organic matter. Total lignin in Lochs Creran and Etive ranged from 0.03 to 0.55mg/g, and Λ (mg/100mg OC) ranged from 0.37 to 0.98; the syringyl/vanillyl and cinnamyl/vanillyl ratios for both lochs ranged from 0.16-1.61 and 0-1.47, respectively. It was found that non-woody angiosperm tissues predominated in the lochs. The concentrations of lignin and the proxies were constant at individual locations, indicating continual but intermittent input of terrestrial materials into the lochs. However, total lignin and these proxies decreased significantly from the head to the mouth and outside the lochs, indicating the importance of the Rivers Creran and Etive in contributing terrestrial materials into the lochs and the importance of terrestrial organic matter in fuelling the biogeochemical cycling of organic matter in the lochs. Overall the effect of the hydrodynamic and hydrological regimes of the lochs, fish and shellfish farms, and bioturbation on the sediment organic matter was investigated. From the head to mouth of the lochs, in Creran, lignin contributed to 0.69% and 0.47% TOC at LC0 and LC6; in Etive, lignin contributed to 0.91% and 0.33% TOC at RE2 and Camas Nathais, respectively. The input of organic matter into Creran was 1.9 x 109 g/year. Of this, 1.2 x 109 g/year (63.16%) was labile fraction and 7.0 x 108 g/year (36.84%) consisted of refractory organic matter. There were overall 5.0 x 108 gC/year input of total carbon and 2.5 x 106 g/year input of lignin materials into Creran.

Flocculation is an important part of the carbon cycle. It is therefore crucial to understand how flocculation is regulated and how different environmental factors impact. A dilemma is that it has been found difficult to measure flocculation experimentally. In this thesis, flocculation of dissolved organic carbon in a Swedish lake was measured in a series of laboratory experiments. The method used was Dynamic Light Scattering (DLS). DLS is used to determine the size distribution profile of, for instance, small particles in suspension. DLS measures Brownian motion and relates it to the particle size by measuring the fluctuation in scattering intensity. It is not very effective to measure the frequency spectrum contained in the intensity fluctuations directly, so instead, a digital auto correlator is used. Since factors such as pH, salinity and calcium chloride content varies in lakes and is thought to have an impact on flocculation, this was investigated as well. As pH was changed in a range of 3 to 9, small changes in size distribution could be detected. Salinity and calcium chloride content have quite an impact on flocculation. Time also has a great impact, samples that were set to rest for a week showed a significant increase in particle size. For DLS to work, the samples need to be filtered of centrifuged to get rid of large particles. Different types of filters were tested to see which filter material was the best to use. When filtering the water we only want to filter out the large particles. Natural organic matter has a hydrophobic component which adsorbs to some filter types but not to others. It is crucial to know which filters this hydrophobic component adsorbs to, so that the loss of dissolved organic carbon during filtration can be minimalized.

Dissolved organic matter (DOM) is the prevalent form of organic carbon in most aquatic environments. It is an ultra-complex mixture that plays a crucial role in global carbon cycling. Despite its importance it is still poorly understood due to its extreme heterogeneity and intricacy. Major advances in chemical characterization of DOM were possible with the introduction of high-resolution mass spectrometry (HRMS). This technique, in combination with direct infusion (DI) as sample introduction, is the most powerful tool for the DOM analysis to date. A compelling alternative to DI is represented by upfront separation with liquid chromatography (LC); however, current techniques involve only offline LC-HRMS approaches, which exhibit important logistical drawbacks, making DOM analysis more challenging. The aim of the presented studies was to develop new methods able to enhance the analysis of the dissolved organic matter and enable a wider range of researchers to participate in the advancement of this field. In the first study, the application of the Orbitrap mass spectrometer for resolving complex DOM mixtures was investigated and the results were compared to the more established state-of-the-art technique, Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The Orbitrap was capable of excellent reproducibility and detection of the majority of ionizable organic molecules in typical aquatic mixtures. The main disadvantage of the technique is that fewer molecular formulas can be resolved and detected because of lower resolution and sensitivity. This means that many sulfur peaks and all phosphorous containing peaks are not determined. Despite this drawback, our results suggest that the Orbitrap is an appropriate technique for the investigation of very subtle biogeochemical processing of bulk DOM. The lower costs (purchase and maintenance) and wider availability of Orbitrap mass spectrometers allow a greater number of laboratories to participate in the characterization of DOM. In the second study, the first online method involving reverse phase chromatography and ultrahigh resolution mass spectrometry for the analysis of DOM was developed. This method overcomes the disadvantages of typical offline approaches. It enhances enormously the amount of information achievable in a single run, maintaining high resolution data, reducing analysis time and potential contamination. The introduction of in silico fractionation makes the method extremely flexible, allowing an easy, fast, and detailed comparison of DOM samples from a variety of sources.

Dissolved organic matter (DOM) is the most dynamic and least understood part of the global oceanic carbon cycle. Furthermore the molecular composition of DOM is largely unknown. This study focused on the distribution pattern, removal processes and molecular characterisation of DOM in a range of estuaries and coastal zones in New Zealand. Doubtful Sound, the longest fjord in Fiordland National Park, South Island, New Zealand was of particular interest, because of the combination of extreme rainfall, enhanced production of DOM within the temperate rainforest which largely appears in the relatively deep ([greater than or equal to] 5 m) low salinity layer (LSL) at the fjord surface. A typical river estuary (Freshwater River) located in Stewart Island, New Zealand was also investigated. Optical water properties such as the UV/Vis absorption coefficient at 355 nm (a[CDOM](355)) and excitation-emission matrix fluorescence (EEM) were determined for samples from freshwater, across the LSL into open ocean water. These optical properties showed a marked decrease with salinity and highest levels of EEM fluorescence and a[CDOM] (355) in the brackish surface water. In addition to the observed changes in the optical properties, ultrahigh resolution Electrospray Ionisation Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR-MS) determination of molecular formulae revealed that in the fjord about 20 % of these formulae changed along a vertical salinity gradient across the LSL between the brackish surface water and the saline water at 5 m depth. This trend was even more pronounced along the salinity gradient of the Fresh Water River Estuary in Stewart Island, where 60 % of all assigned molecular masses changed from freshwater over the mixing zone to ocean water. Associated with these changes was a marked increase in aromaticity with increasing salinity. Comparable behaviour with increasing salinity was also observed in estuarine samples from the Cape Fear River system, North Carolina, USA. In contrast, only minor changes were determined in molecular formulae for surface water samples collected along a transect off the Otago Coast and across the Subtropical Convergence (STC) into Subantarctic Water (SAW). However, a comparison of the molecular formulae assigned to the DOM pool for the STC water and a freshwater stream in Doubtful Sound, revealed that 75 % of all the assigned formulae for the open ocean sample were common to these two markedly different types of natural waters. This seemingly refractory DOM contained nearly 600 assigned molecular formulae, which were all very similar (only spaced by two hydrogen and CH₂ groups) and could be explained with only 9 general molecular formulae. However, the comparison of all assigned formulae for the freshwater sample suggested that about 90 % of the assigned molecular formulae for the terrestrially-derived DOM changed as it moved from rivers to the open ocean and that only 10 % remained the same. Singlet oxygen showed a very close relationship with the optical properties such as the absorption coefficients (a[CDOM](355)) and the EEM fluorescence intensities and these results suggested that singlet oxygen steady state concentrations are linked to CDOM. Photodegradation processes were confirmed to be responsible for a significant destruction of CDOM. Samples collected from different salinity waters showed major differences in wavelength-dependent photo-decay of CDOM suggesting that the rate of photodegradation in the UV range decreased with increase in salinity whereas it was enhanced for longer wavelength radiation ([greater than or equal to]400 nm). Additionally, the predominantly unsaturated compounds produced during estuarine mixing were found to be highly photolabile and were either destroyed or new unsaturated compounds were produced within 21 h of solar irradiation.

Characterizing dissolved organic matter (DOM) composition remains a major unresolved problem in aquatic ecology. "Tryptophan-like" dissolved organic matter fluorescence (FDOM) was found to be a much better predictor of heterotrophic bacterial metabolism in 28 Quebec lakes than dissolved organic carbon (DOC), describing 52, 44, 51 and 55% of the variability in bacterial production (BP), bacterioplankton respiration (BR), total bacterial carbon consumption (TBCC), and total plankton community respiration (CR), respectively. In addition, the study provides indirect support for the view that FDOM represents a product of bacterial activity, rather than a bioavailable substrate. This is the first field study to show that fluorescence spectroscopy can be used to characterize an aspect of DOM composition that is related to bacterial metabolism, and provides results that encourage further exploration of the potential uses of DOM fluorescence spectroscopy as a predictive tool.

The goal of this study was to investigate some of the fundamental chemistry of the reactions between the hydroxyl radical and apply this knowledge to the treatment of chemical contaminants in real world waters. To accomplish this goal, the techniques of electron pulse radiolysis were used to quantify second-order rate constants for the reaction between the HO^· radical and well characterized OM samples. Studies of HO^· radical reactivity with model polyethylene glycol polymers were performed to help understand OM-HO^· reactivity. Experiments using steady state radiolysis were performed in order to assess the effect of long-term, seasonal variability in OM composition on the degradation of probe compounds used as model chemical contaminants. In addition, the photochemical production of HO^· from OM sensitization was also investigated.

Organic matter (OM) is ubiquitous to all aquatic environments and plays an essential role in global biogeochemical cycles and transportation of organic carbon throughout the hydrological continuum. Excitation-emission matrix (EEM) fluorescence spectroscopy has been used to characterise naturally occurring aquatic fluorescent OM (AFOM), classifying this AFOM as either humic-like, derived from terrestrial sources, or protein-like, of microbial origin. The research here explores in situ bacterial-OM interactions and AFOM evolution over time by employing fluorescence techniques. Protein-like AFOM, with a particular focus on Peak T, has been linked to bacterial activity. Previous research has related this AFOM to other water quality parameters, in addition to attempting to use it as a bacterial enumeration proxy. The work in this study provides extensive evidence for the bacterial production of Peak T, confirming the suggestions within the literature. However, the universal presence of Peak T within the bacterial cultures studied here, permits the conclusion that Peak T fluorescence cannot be used for bacterial enumeration but can provide information regarding microbial community presence and activity. In addition to this, the application of in situ Peak T fluorescence sensing for monitoring microbial activity in freshwater systems is explored. The development of a new generation multichannel fluorimeter is detailed, informed by the research undertaken within this thesis. This research has challenged the current understanding of the role of bacteria in AFOM production and processing, highlighting the ability of bacteria to engineer both protein- and humic-like AFOM in situ. Using microbiological methods alongside fluorescence measurements, over a variety of temporal scales, has exposed the fast-acting dynamics of this AFOM production by metabolically active bacteria. The variation in AFOM production by different bacterial species has also been demonstrated here, determining fluorescence as a potential measurement for monitoring the presence of specific species using fluorescence peaks as biomarkers. This thesis has highlighted the potential application of in situ fluorimeters to provide essential biological information regarding water quality, although further work is required to validate this novel water quality parameter within the field.

The organic matter in five oil shales (three from the Kimmeridge Clay sequence, one from the Oxford Clay sequence and one from the Julia Creek deposits in Australia) has been isolated by acid demineralisation, separated into kerogens and bitumens by solvent extraction and then characterised in some detail by chromatographic, spectroscopic and degradative techniques. Kerogens cannot be characterised as easily as bitumens because of their insolubility, and hence before any detailed molecular information can be obtained from them they must be degraded into lower molecular weight, more soluble components. Unfortunately, the determination of kerogen structures has all too often involved degradations that were far too harsh and which lead to destruction of much of the structural information. For this reason a number of milder more selective degradative procedures have been tested and used to probe the structure of kerogens. These are: 1. Lithium aluminium hydride reduction. - This procedure is commonly used to remove pyrite from kerogens and it may also increase their solubility by reduction of labile functional groups. Although reduction of the kerogens was confirmed, increases in solubility were correlated with pyrite content and not kerogen reduction. 2. O-methylation in the presence of a phase transfer catalyst. - By the removal of hydrogen bond interactions via O-methylation, it was possiblo to determine the contribution of such secondary interactions to the insolubility of the kerogens. Problems were encountered with the use of the phase transfer catalyst. 3. Stepwise alkaline potassium permanganate oxidation. - Significant kerogen dissolution was achieved using this procedure but uncontrolled oxidation of initial oxidation products proved to be a problem. A comparison with the peroxytrifluoroacetic acid oxidation of these kerogens was made. 4. Peroxytrifluoroacetic acid oxidation. - This was used because it preferentially degrades aromatic rings whilst leaving any benzylic positions intact. Considerable conversion of the kerogens into soluble products was achieved with this procedure. At all stages of degradation the products were fully characterised where possible using a variety of techniques including elemental analysis, solution state 1 Hand 13C nuclear magnetic resonance, solid state 13C nuclear magnetic resonance, gelpermeation chromatography, gas chromatography-mass spElctroscopy, fourier transform infra-red spectroscopy and some ultra violet-visible spectroscopy.

The aim of this study is to attain a better understanding of the fate of carbon and the degree of preservation of organic matter in impacts craters. This topic is relevant to prebiotic chemistry, planetary exploration and panspermia. Three natural impact craters were investigated: The Eocene Haughton impact structure on Devon Island in the Canadian High Arctic, where the target is composed of a thick sedimentary sequence with pre-impact hydrocarbons, the Ordovician Lockne impact structure in central Sweden, where organic- and uranium-rich Alum Shale is present in the target, and the Pre-Caledonian Gardnos impact structure in south-central Norway, also with carbon-rich shales in the target. An analogue example of rapid heating of organic matter by igneous intrusion in carbon-rich rock, and an experimental hypervelocity impact in a carbon-rich rock were also studied. In the Haughton impact crater, fossil biological markers are preserved within lithic clasts in the impact melt breccia. Fossil biological markers are also preserved in the experimental impact crater, and in the material excavated during the experimental impact. Instantaneous melting and quenching in the Gardnos suevite (impact melt rock) has caused the incorporation of disordered carbon in the suevite melt. In the Haughton impact melt breccias, around 20% total organic carbon is preserved after impact, and in the Gardnos impact crater, at least 38% of the original carbon is preserved in a disordered form. In the Lockne impact crater, carbon is particularly preserved by polymerisation around radioactive minerals. This study shows that organic matter does not necessarily oxidise or change in to highly crystalline forms during an impact event, but that substantial amounts can be preserved in a disordered form.

Soil organic carbon (SOC) protection processes have received much interest recently due to the possibility to enhance the carbon sink in agricultural soils with atmospheric CO2 reduction purposes. Further knowledge of these mechanisms is thus fundamental to promote effective C sequestration practices in terrestrial sinks, as recognized by Article 3.4 of the Kyoto Protocol. In a long-term experiment established in the early 1960s in north-eastern Italy, we used a combination of physical fractionation and chemical extraction techniques aiming to isolate homogeneous pools of SOC. In particular we wet-sieved large macroaggregates into three aggregate-size classes (2000-250 μm, 250-53 μm and <53 μm) in contrasting soils (clay, sandy and peaty) fertilized with manure or mineral fertilizers. We analyzed the organic (OC) and humic (HC) carbon of each aggregate fraction, the molecular weight of the humic substances (HS) extracted, the HS functional groups by NMR and DRIFT spectroscopy and the porosity of the different aggregate fraction by MIP (Mercury Intrusion Porosimetry). The aims were to evaluate the protection processes in the different SOC pools isolated analyzing the effect of the different fertilization types on the aggregates, the organic matter distribution and to investigate the composition and role of HC as binding agent. The thesis is structured in four chapters. The first chapter is a review on the SOC topic, its protection processes and the analytical methods for its study. The second chapter focuses on aggregate distribution, OC, HC, HS gel filtration and the rule of HC as persisting binding agent. The third chapter had a qualitative description of C functional groups (NMR-DRIFT) in HS extracts from the different aggregate fractions. The final chapter had the correlation between the porosity of the different aggregate fractions and the different parameters measured in chapter II and III.
I meccanismi di protezione del carbonio organico del suolo rappresentano un argomento di grande attualità poiché, attraverso di essi, si esplica l'azione di carbon sink indicata nelle politiche volte alla mitigazione dell'effetto serra. Una maggior conoscenza di questi processi è quindi fondamentale per promuovere strategie di sequestro efficaci, così come previsto dall'articolo 3.4 del protocollo di Kyoto. Per realizzare lo studio è stato effettuato,a partire da macroaggregati prelevati da una prova di lungo periodo, un frazionamento degli aggregati stabili all'acqua con l'obiettivo di isolare dei pool di carbonio omogenei e riconducibili a specifici meccanismi di stabilizzazione. Sono stati frazionati in questo modo differenti suoli (argilloso, torboso e sabbioso) trattati con letame e con fertilizzanti minerali, ottenendo tre classi di aggregati (2000-250 μm, 250-53 μm and <53 μm). È stato quindi determinato, per i diversi aggregati, il carbonio organico (OC) e umico (HC), le frazioni umiche a diverso peso molecolare (HS), i gruppi funzionali presenti nelle sostanze umiche (spettroscopia NMR e DRIFT) e la porosità degli aggregati (porosimetria a intrusione di mercurio MIP). L'obiettivo è stato quello di valutare l'effetto delle differenti tesi sull'aggregazione e sulla distribuzione del carbonio organico, nonché valutare il ruolo delle sostanze umiche quali agenti leganti persistenti. Più in generale si è cercato di studiare quali meccanismi di protezione governano le diverse frazioni di aggregati. La tesi è stata strutturata in quattro capitoli; il primo capitolo è una review sul carbonio organico del suolo, i suoi meccanismi di protezione e le relative tecniche di analisi. Il secondo capitolo è dedicato alla distribuzione del carbonio organico e umico negli aggregati, delle frazioni umiche a diverso peso molecolare nonché del ruolo del carbonio umico come agente legante persistente. Il terzo capito è incentrato sull'analisi qualitativa degli estratti umici dei diversi aggregati sulla base dei gruppi funzionali rilevati dall'analisi NMR e DRIFT. Il quarto capitolo analizza le correlazioni fra la porosità dei diversi aggregati e le caratteristiche quali-quantitative del carbonio umico.

The aim of this work was to assay the effects of previous history of organic amendment to soils in the field on the ability of those soils to mineralise mustard, a non-legume green manure. Soil and 15N labelled mustard mineralisation was followed in laboratory microcosms. Volatilised N was assayed by direct acid trapping of N in glass fibre disks, followed by direct combustion isotope ratio mass spectrometry. Animal manures, green manures and straw added to the soil in the field in the previous season, same season and for 7 years continuously did not significantly affect these soils' ability to mineralise mustard in microcosms. Nitrification and mineralisation were the dominant processes during the first 12 days of incubation. Volatilisation rates were 1000-fold lower than mineralisation or nitrification rates. Mustard N accounted for between 1-3% of the soil mineral N, whereas only a maximum of 0.01% of mustard N was volatilised over 24 days. Soils sampled at different times in the season decomposed mustard at similar rates at stimulated low spring temperatures. Nitrification rate was reduced 5-fold more than the mineralisation rate at 8oC. Straw incorporation for seven years did not affect the subsequent recovery of 15N enriched fertiliser or of 15N from labelled straw, by oil seed rape. 15N labelled fertiliser contributed up to 63% of the winter barley N. The labelled barley straw subsequently contributed 16% of the oil seed rape N in the absence of any applied fertiliser. Ploughing in straw in the autumn, in the absence of applied fertiliser had no yield penalty or effect on crop uptake, and may retain more mineral N in the upper soil layers, lessening the risk of leaching over the winter period. The results obtained here emphasise the importance of additions of organic materials to soil in supplying plant nutrients and minimising nutrient losses.

Thesis (Ph. D)--Ohio State University, 2003.
Title from first page of PDF file. Document formatted into pages; contains xvi, 134 p. : ill. (some col.). Includes abstract and vita. Advisor: Arthur J. Epstein, Dept. of Physics. Includes bibliographical references (p. 128-134).

This research examines the composition, sedimentary history and chemical properties of sedimentary organic matter [SOM] and its application in determining the content and source of heavy metals and hydrophobic organic contaminants [HOCs] and their fate in waste disposal sites. Previous research has utilised Oxford Clay (OxC) from across the outcrop. In this study a continuous shallow core of OxC and adjoining Kellaways Sand (KS) from Brogborough, UK was used. This avoided the influence of different sedimentary conditions, thereby reducing the problem of sample variability. Relationships have been made between sedimentary and organic petrology and SOM abundance and metals concentration (V, Cr, Co, Ni, Cu, Zn and As). The co-association/binding of different metals to different types of SOM components from the OxC was shown to be dictated by the depositional environment. The organic rich parts (Total Organic Carbon (TOC) > 5 %) of the OxC displayed positive correlations between the elements V, Co, As and total pyrite % (p<1.1E-3, ? >0.7); however, there was an apparent negative correlation with TOC % (p<4.3E-5, ?<-0.4). This may be because of: 1) the rapid accumulation of the OM reduced the time for development of the pyrite (Ave. dia. =5.3?m, SD=2.4); and/or 2) the insufficient concentration of Fe to allow pyrite formation. This could be due to the high sedimentation rate that accelerates the accumulation of OM, which prevents its decomposition in the water column, as well as reducing the time for pyrite that is entrapped in the marine snow to capture metals from seawater during its settlement. Cu has a significant positive correlation with TOC (p=1.9E-2, ?=1.3), which could be the consequence of Cu being an essential element in OM. The OxC with a lower OM content (TOC < 5 %) showed a different distribution of metals. V, Cr and Cu found in OM was found to have a significant positive correlation with TOC (p<2.9E-2, ?>0.05). The Kellaways Sand core showed that the V, Co, Ni, Cu, Zn and As had a strong connection both with TOC (p<1.6E-3, ?=0.03~37.3) and pyrite (p<4.9E-3, ?=0.23~5.5), suggesting that both OM and pyrite were major metal sinks in Kellaways Sand. The more significant positive correlation between V, Cr and pyrite compared to V, Cr and TOC implies that pyrite contains more V and Cr than did TOC. Other studies used the OxC from Bletchley, the Kimmeridge Clay (KC) from Kimmeridge Bay, Dorset, and Tertiary mud (Wittering Formation-WF) from Whitecliff, Isle of Wight due to their distinctive OM characteristics (AOM rich and/or phytoclast rich). Organic material was isolated for identification and analysis using a novel extraction method (heavy liquid extraction) and traditional methods involving HF digestion. These organic materials were then used to determine influences of extraction on HOCs (toluene and naphthalene) sorption and desorption. Organic petrology classification was applied to identify the various types of isolated OM. AOM from KC displayed a higher sorption capacity (Kd=6,481, 59,670; for toluene and naphthalene, respectively) compared to literature values. AOM rich sorbent extracts demonstrated a higher absorption capacity than the phytoclasts rich sorbents (e.g. WF, Kd=219, 20,661; for toluene and naphthalene, respectively). However, the phytoclast rich sorbent showed a higher sorption/desorption hysteresis capacity for toluene than AOM. Implications of results in landfill design/risk assessment and modelling are discussed.

En els darrers anys, el desenvolupament de reaccions de carboxilació reductiva de (pseudo) halogenurs orgànics amb diòxid de carboni (CO") catalitzada per metalls per a la preparació d'àcids carboxílics s'ha convertit en una poderosa alternativa a l'ús d'èspecies organometàl·liques, en la majoria dels casos sensibles a l'aire. Tanmateix, l'ús d'alcohols simples no protegits o d'hidrocarburs insaturats en combinació amb CO" per obtenir àcids carboxílics mitjançant una reacció de formació d'un enllaç C-C han rebut molta menys atenció. Aquests representen una alternativa atractiva als halurs orgànics, ja que són abundants i fàcilment disponibles. En aquesta tesi doctoral es descriu la carboxilació selectiva d'alcohols al·lílics amb CO2, una metodologia capaç d'obtenir àcids carboxílics insaturats amb un control excel·lent de la selectivitat obtinguda.

Soluble organic matter represent less than 1% of total soil organic matter (SOM) - but it contributes to many terrestrial ecosystem processes, due to its high mobility and reactivity in soil. Although it has been suggested that soluble organic matter (OM) may serve as an early indicator of soil quality changes as a result of shifts in land-use and management practices, only a few studies have addressed the dynamics of soluble OM in relation to land-use and specifically soil depth. This study focuses on two aspects of soluble OM. In the first part, I hypothesized that extractable OM obtained by aqueous solutions is a continuum of substances that depending on the extraction method can be separated into two operationally different fractions. The size and properties of these fractions may consistently differ among different land uses and at different soil depths. The objective of this part of the study was then to assess dynamics (size and properties, biodegradability and seasonality) of water extractable organic matter (WEOM) and salt extractable organic matter (SEOM) in a sequence of human dominated land-uses at topsoil and subsoil. At the second part of the study, I tested the regulatory gate hypothesis –abiotic solubilization of OM- as a primary controlling factor in soluble OM production. The objective of this study was to evaluate the impact of the microbial activity on the net production of dissolved organic matter (DOM) from the native SOM in the presence of added DOM and plant residue. For the first part of the experiment, the soil samples were collected from four land-uses under bog pine (Halocarpus bidwillii) woodland, tussock grassland (Festuca novae-zelandiae and Heiracium pilosella), cropland (Medicago sativa) and plantation forest (Pinus nigra). The selected land uses were located in the Mackenzie Basin, Canterbury, New Zealand and occurring on the same soils, topography and experienced similar climates. Soil samples were obtained from topsoil (0-20 cm) and subsoil (60-80 cm) at the end of each season (November, February, May and August) during 2007-2008. The sampled soils were adjusted to the same water status prior to extraction. While WEOM was obtained during a mild extraction procedure and using 0.01M CaCl2, SEOM was extracted with 0.5M K2SO4 at high temperature (75οC for 90 min). Both extracts were filtered through a 0.45 μm filter size. In the first part of the study, I assessed the biodegradation dynamics of WEOM and SEOM (spring samples), using a double-exponential decay model. The WEOM and SEOM were inoculated and incubated at 22°C for 90d under aerobic conditions. Subsamples were removed on days 1, 3, 7, 12, 16, 30, 42, 60, 75, and 90, filtered (0.22 μm), and analyzed for organic C and N content, UV absorption, and 13C natural abundance (δ13C). The results of the biodegradation experiment indicated a similar pattern for both C and N of SEOM and WEOM as that of previously shown for soil DOM. However, C and N mineralization rate were considerably larger in the WEOM than SEOM. The parameters of the double-exponential model suggested that regardless of the land-use and soil depth, both the WEOM and SEOM can be modeled in two biological pools, with a largely similar “fast decomposable” but different “slowly decomposable” pools. However, since the extraction was not sequentially followed, a very small portion of the SEOM was comprised of the WEOM and given the greater observed biodegradability of the WEOM, the overall biodegradable portion of the SEOM would be lower than the observed. Despite a greater biodegradability of the organic N than C of both WEOM and SEOM; mainly due to a longer HL of the slowly biodegradable pool of C; the C/N ratio of the samples did not change very much during the biodegradation. This led us to conclude that the biodegradation of soluble OM may occur as a function of N availability. Parallel to C and N loss, a considerable increase in SUVA254 of SEOM, and particularly WEOM occurred during the incubation period. The greater increase in the proportion of aromatic compounds (assessed by SUVA) in the WEOM than SEOM, implied consumption of simple compounds (vs. very humified) during decomposition and further supported the observed faster biodegradation rate of the WEOM. The data indicated a relatively strong correlation (R2=0.66 and 0.74 for the WEOM and SEOM, respectively) between the amount of biodegraded C and the increase in SUVA254. This suggested that SUVA254 can be used as a simple, low-cost but reliable approach for describing the biodegradability of soluble OM, as previously suggested by others. At the end of the bioassay, the 13C natural abundance of the WEOM was significantly depleted, and showed a clear relationship with the proportion of the biodegraded C. This confirmed the previously suggested preferential biodegradation of simple organic constituents (13C enriched), resulting in the accumulation of more depleted 13C compounds (often recalcitrant compounds). Moreover, the results of the δ13C technique revealed that the relatively greater 13C enrichment of the WEOM obtained from subsoil, seems to be due to the presence of root exudates (often highly 13C enriched). In contrast, a proportionally greater 13C depletion observed in the SEOM particularly at subsoil samples, suggests that there is a close relationship between the SEOM and the typically 13C depleted humified SOM. The results of the biodegradation model (half-life of both C and N), in addition to dynamics of SUVA254 and δ13C of the WEOM and SEOM were very comparable between top and subsoil samples. This implied that the potential biodegradability of soluble OM under laboratory conditions does not necessary reflect the reported lower in situ biodegradability at soil depth, in agreement with recent evidence suggested by others. Instead, this may be largely due to the lack of optimum conditions (oxygen, nutrients, and moisture) for the decomposer community at soil depth. Although there was a tendency for a generally greater biodegradability of the samples from the soils under the crop land (both WEOC and SEOC), along with relatively greater increase in SUVA, there was not a consistent trend of the effect of land use on the biodegradation of either WEOM or SEOM. The lower C/N ratio of the soils under the crop land seemed to be related with the observed proportionally greater biodegradability of these soils. During the second part of the study, I assessed seasonal variations of the size and properties of the previously defined WEOM and SEOM, collected from top-and subsoil from the land-uses. I observed that 10-year after conversion of the degraded tussock grassland to cropland or plantation, the total C stock of topsoil (0-20 cm) when above- and below-ground plant biomass is excluded; has remained unchanged. This was attributed to the limited biomass production of the region, more likely as a result of low productivity of the soil, but also harsh climatic conditions. Not only soil depth, but land-use affected both C concentration and C/N ratio of soil organic matter (SOM), with the greatest C concentration of soils under grassland and plantation in topsoil and subsoil, respectively. Despite the WEOM, the size of SEOM was largely unaffected by land-use and soil depth; instead, the properties of SEOM was more consistent with the effect of soil depth. Given the observed large temporal and spatial variability of the WEOM, the study suggests that the SEOM more consistently reflects the influence of land use and soil depth. No consistent effect of seasonality was observed in terms of size or properties of the SOM and the WEOM and SEOM. Overall comparison of the size and properties of the WEOM and SEOM indicated that OM extraction efficiency may vary largely, depending on extraction conditions. Using more concentrated salt solutions consistently yielded greater amount of OM (N, and especially C) release from soil with properties resembling more those of total soil OM (more humified) compared to the WEOM. The SEOM was also less variable by time and space. The last part of the study was aimed to assess biotic vs. non-biotic solubilization of OM in the presence of added plant residue. Given the need to recognize the source of the solubilized OM during the experiment, I used enriched (13C) plant residue as the source of fresh OM. The above-ground part of ryegrass was added to soil either as plant residue or residue extract (extracted with CaCl2 followed by 0.45μm filtration) -termed DOM. These two forms of added OM (residue/DOM) were conceived to represent two levels of bioavailability for the decomposer community for further assessing possible biotic solubilization of OM. Two soils similar in their OM content and other properties, but different in mineralogy were selected for the experiment. Soils were incubated for 90d under sterilized vs. non-sterile conditions and leached regularly with a dilute aqueous solution (0.05M CaCl2). Plant residue was added to soil (1:100, residue: soil, w/w) prior to the start of the incubation, but DOM was frequently applied to the soils along with each leaching experiment. The greater C and N concentration in the leachates of both sterilized residue-amended and DOM-amended soils compared to that of living soils, indicated a high microbial activity, as determined by CO2 loss, in the living soils. However, the proportion of the solubilized C (determined by 13C) from sterilized soils was largely comparable to that of living soils. This supports the recently suggested “regulatory gate” hypothesis, stating that solubilisation of OM largely occurs independent of the size or community structure of microorganisms. In addition, I observed that even with the presence of adequate amount of added fresh OM (ryegrass residue), about 70% of the solubilized C consistently originated from the humified soil OM, highlighting the role of native soil OM as the source of soluble OM in soil. In addition, in the DOM-amended soils, there was strong evidence, indicating that in the sterilized soils, the added DOM was exchanged with the humified soil OM as observed by an increase in SUVA, and humification index (HI) of the leached OM. Although the results of the study did not show a considerable difference in the solubilisation rate of added OM as a function of biological activity (either in the residue- or DOM-amended soils), there was clear evidence that the presence of microbial activity has resulted in further decomposition of the solubilised OM through biological transformations. Together, the results suggested that the proposed fractionation method can be used to separate two operationally defined pools of soluble OM with consistent differences in their size (C and N), properties (δ13C, SUVA254, and C/N ratio) and biodegradability across the land-uses and soil depth. The second part of the study supported the primary role of abiotic factors on the production of soluble OM from native soil OM. Although the abiotic mechanisms involved in the solubilization remain to be addressed by future studies. Cons and pros of the methods with some suggestions for further works have been mentioned in the last chapter.