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Thesis (Ph.D.) -- Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Michael D. Bryant. Vita. Includes bibliographical references.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2006. / Includes bibliographical references. / To provide a new perspective on the fate of both natural organic matter and hydrophobic organic contaminants (HOCs) in marine sediments, we have investigated the relationship between radiocarbon (14C) age and the different modes of association in aquatic sediments and soils. Radiocarbon is a sensitive tracer of OM provenance, with variations in its natural abundance reflecting the age and origin of material. The main objective has been to determine the significance of these associations, and to assess how they affect the transport, bioavailability, preservation and residence times of organic compounds in the environment. Our results indicate that the majority of HOCs that persist in marine sediments are solvent-extractable and incorporation into insoluble sediment residues is not quantitatively significant. For pristine sediments, systematic variations in 14C content are observed between different chemically defined sedimentary organic fractions. These variations are dependent on organic matter inputs and/or the affects of diagenesis. Our observations also provide evidence for the protection of labile marine carbon by chemical binding. / (cont.) Finally, the persistence of n-alkanes from biogenic sources compared to those derived from petroleum indicates that protective matrix association can play a crucial role in determining the long-term fate of a compound. Overall, it is clear that both natural organic compounds and HOCs can undergo very different fates depending on their mode of introduction to, and physical disposition in environmental matrices. / by Helen K. White. / Ph.D.

Soil microorganisms are primarily limited by carbon (C) availability. The majority of C entering belowground food webs comes directly from local flora. Plant derived labile C compounds affect microbial community structure and function, which in turn drive ecosystem function. Research has focused on dissolved organic C (DOC) from litter leachates and root exudates. These compounds are often readily assimilable by soil microorganisms and are precursors for stable soil organic matter formation. Due to diffusion limitation DOC rarely travels far beyond its origin, meaning most soil microorganisms are unable to access these compounds unless they are located near the C source. However, recent studies have illuminated the importance of volatile organic compounds (VOCs) in soil ecosystems. VOCs are produced in abundance and, as vapors, they are able to travel through soil more rapidly than DOC. This dissertation aims to investigate the importance of VOCs commonly produced during the decomposition of leaf litter. We used three separate microcosm experiments to answer the following questions. 1) How do abundant VOCs affect microbial activity in soil? 2) How do VOCs affect nitrogen (N) transformations and the microbes associated with N transformations? 3) How do VOCs affect microbial community composition? 4) Are VOCs from decomposing litter incorporated into soil C pools? In chapter 2, we show that methanol and acetone – common litter derived VOCs – increase microbial activity and labile soil C, while also decreasing available nitrate, and ammonia oxidizing archaea. Interestingly, this decrease in nitrifiers did not affect nitrification rate after VOC addition was ceased. In chapter 3, we demonstrate that soil microbial taxa respond differently to DOC and VOCs at different soil moisture levels. Specifically, DOC primarily affected taxa abundance in wetter soils, while the insoluble VOC α-pinene had the largest impact at lower moisture levels, and methanol affected abundance at all moisture levels. Finally, in chapter 4, we demonstrate that VOCs from decomposing leaf litter altered soil bacterial and fungal communities, and VOC derived C entered all measured soil organic matter pools without direct contact between decomposing litters and the soil. This work demonstrates the importance of VOCs on soil microbial communities and ecosystem function. The VOC induced increase in microbial activity, and the effects of VOCs at low moisture levels suggest that VOCs may function in the bulk soil in a manner similar to DOC in rhizosphere soil. Additionally, the incorporation of VOC-C into soil organic matter pools identifies a hitherto unrecognized mechanism for soil organic matter formation. / Doctor of Philosophy / Soil microorganisms live in an environment where their access to carbon containing compounds limits their growth. In these belowground environments most of the carbon flows from aboveground plant matter through soil microbes into the organisms that consume those microbes. The carbon from plants not only feeds the soil microbes but also changes the type of microbes and how those microbes process important chemicals in the environment – e.g., carbon and nitrogen. Previously, research has focused on carbon compounds that are able to dissolve in water. Often, these compounds originate from liquids that plants release from their roots, or dissolve like tea when leaves are soaked in water. Soil microorganisms can often use these dissolved carbon compounds and directly incorporate them into their biomass. Additionally, these compounds can be stored in soil - sequestering that carbon in the soil, potentially long term. However, dissolved compounds are unable to move very quickly through soil, and the soil microorganisms that live far from the source of these compounds do not have access to them. However, recent studies have found that another form of carbon, volatile organic compounds, are also produced in abundance in the soil environment. These compounds can travel through the air in the soil, as well as in the soil water. When in the air, VOCs travel very quickly and can also travel farther than dissolved compounds. This dissertation aims to investigate the importance of volatile organic compounds that are produced during the decomposition of leaves. We carried out three experiments using small volumes of soil under controlled conditions in the laboratory. We aimed to answer the following questions. 1) How do abundant volatile organic compounds affect microbial activity in soil? 2) How do volatile organic compounds affect microbial processing of nitrogen containing compounds, and the populations of microorganisms that process those compounds? 3) How do volatile organic compounds affect the composition of microorganism in the soil? 4) Are volatile organic compounds from decomposing leaves able to be stabilized in the soil. In chapter 1, we show that methanol and acetone – common volatile compounds produced during the decomposition of leaves– increase microbial activity, and microbial available carbon in soil. Methanol and acetone also decreased available nitrate (an important N containing compound) and a group of organisms that produce nitrate called ammonia oxidizing archaea. Interestingly, once we stopped adding methanol and acetone to the soil the production of nitrate did not differ, meaning that the nitrate producing community was able to recover from the reduction in ammonia oxidizing archaea. In chapter 2, we demonstrated that soil microbial taxa respond differently to dissolved carbon and volatile organic compounds across a gradient of soil moisture. Specifically, dissolved carbon primarily affected taxa abundance in wetter soils, while the insoluble volatile α-pinene had the largest impact at lower moisture levels, and the volatile compound methanol affected abundance of microbial taxa at all moisture levels. Finally, in chapter 3, we demonstrate that volatile organic compounds produced during the decomposition of leaves altered the composition of both bacterial and fungal communities in the soil. Also, and possibly most interestingly, carbon from those volatile organic compounds was stored in all of the pools of carbon that we measured. Together these chapters demonstrate the importance of volatile organic compounds on soil microbial communities and ecosystem function. Since volatile organic compounds induced an increase in microbial activity we are able to infer that soil microorganisms are using these compounds; paired with our observation that volatile organic compounds affected microbial taxa at lower moisture levels than the dissolved compounds did, we can infer that volatile compounds may function as a carbon source in parts of the soil that do not have access to dissolved carbon. Additionally, the incorporation of carbon from volatile organic compounds into soil identified a hitherto unrecognized mechanism for soil carbon sequestration.

Of the organic matter in soils typically < 1% by weight is dissolved in the soil solution (dissolved organic matter; DOM). DOM is a continuum of molecules of various sizes and chemical structures which has largely been operationally defined as the fraction of total organic carbon in an aqueous solution that passes through a 0.45 µm filter. Although only representing a relatively small proportion, it represents the most mobile part of soil organic carbon and is probably enriched with highly labile compounds. DOM acts as a source of nutrients for both soil and aquatic micro-organisms, influences the fate and transport of organic and inorganic contaminants, presents a potential water treatment problem and may indicate the mobilisation rate of key terrestrial carbon stores. The objective of this research was to ascertain some of the biologically relevant characteristics of soil DOM and specifically to determine: (1) the influence of method and time of extraction of DOM from the soil on its biochemical composition and concentration; (2) the dynamics of DOM biodegradation; and, (3) the effects of repeated applications of trace amounts of DOM on the rate of soil carbon mineralization. To examine the influence of method and time of extraction on the composition and concentration of DOM, soil solution was collected from a raised peat bog in Central Scotland using water extraction, field suction lysimetry, and centrifugation techniques on a bimonthly basis over the period of a year (Aug 2003 – Jun 2004). Samples were analysed for dissolved organic carbon (DOC), dissolved organic nitrogen (DON), protein, carbohydrate and amino acid content. For all of the sampled months except June the biochemical composition of DOC varied with extraction method, suggesting the biological, chemical and/or physical influences on DOC production and loss are different within the differently sized soil pores. Water-extractable DOC generally contained the greatest proportion of carbohydrate, protein and/or amino acid of the three extraction methods. Time of extraction had a significant effect on the composition of water- and suction-extracted DOC: the total % carbohydrate + protein + amino acid C was significantly higher in Oct than Dec, Feb and Jun for water-extracted DOC and significantly greater in Dec than Aug, Apr and Jun for suction-extracted DOC. There was no significant change in the total % carbohydrate + protein + amino acid C of centrifuge-extracted DOC during the sampled year. Time of extraction also had a significant effect on the % protein + amino acid N in water- and centrifuge-extracted DON: Oct levels were significantly higher than Feb for water-extracted DON and significantly higher in Aug and Apr for centrifuge-extracted DON. Concentrations of total DOC and total DON were also found to be dependent on time of extraction. DOC concentrations showed a similar pattern of variation over the year for all methods of extraction, with concentrations relatively constant for most of the year, rising in April to reach a peak in Jun. DON concentrations in water- and centrifuge-extracted DON peaked later, in Aug. There were no significant seasonal changes in the concentration of suction-extracted DON. A lack of correlation between DOC and DON concentrations suggested that DOC and DON production and/or loss are under different controls. Laboratory-based incubation experiments were carried out to examine the dynamics of DOC biodegradation. Over a 70 day incubation period at 20oC, the DOM from two types of peat (raised and blanket) and four samples of a mineral soil (calcaric gleysol), each previously exposed to a different management strategy, were found to be comprised of a rapidly degradable pools (half-life: 3 – 8 days) and a more stable pool (half-life: 0.4 to 6 years). For all soil types/treatments, excepting raised peat, the total net loss of DOC from the culture medium was greater than could be accounted for by the process of mineralization alone. A comparison between net loss of DOC and loss of DOC to CO2 and microbial biomass determined by direct microscopy suggested that at least some of the differences between DOC mineralised and net DOC loss were due to microbial assimilation and release. Changes in the microbial biomass during the decomposition process showed proliferation followed by decline over 15 days. The protein and carbohydrate fractions showed a complex pattern of both degradation and production throughout the incubation. The effects of repeated applications of trace amounts of litter-derived DOC on the rate of carbon mineralization over a 35 day period were investigated in a laboratory based incubation experiment. The addition of trace amounts of litter-derived DOC every 7 and 10.5 days appeared to ‘trigger’ microbial activity causing an increase in CO2 mineralisation such that extra C mineralised exceeded DOC additions by more than 2 fold. Acceleration in the rate of extra C mineralised 7 days after the second addition suggested that either the microbial production of enzymes responsible for biodegradation and/or an increase in microbial biomass, are only initiated once a critical concentration of a specific substrate or substrates has been achieved. The addition of ‘DOC + nutrients’ every 3.5 days had no effect on the total rate of mineralization. To date DOC has tended to be operationally defined according to its chemical and physical properties. An understanding of the composition, production and loss of DOC from a biological perspective is essential if we are to be able to predict the effects of environmental change on the rate of mineralization of soil organic matter. This research has shown that the pools of DOC extracted, using three different methods commonly used in current research, are biochemically distinct and respond differently to the seasons. This suggests some degree of compartmentalisation of biological processes within the soil matrix. The observed similarities between the characteristics of the decomposition dynamics of both peatland and agricultural DOC suggests that either there is little difference in substrate quality between the two systems or that the microbial community have adapted in each case to maximise their utilisation of the available substrate. The dependency of the concentration and biochemical composition of DOC on the seasons requires further work to ascertain which biotic and/or abiotic factors are exerting control. Published research has focussed on factors such as temperature, wet/dry cycles, and freeze/thawing. The effect of the frequency of doses of trace amounts of DOC on increasing the rate of soil organic C mineralization, evident from this research, suggests that the interval between periods of rainfall may be relevant. It also emphasises how it can be useful to use knowledge of a biological process as the starting point in determining which factors may be exerting control on DOC production and loss.

Thesis (M.S.)--University of Tennessee, Knoxville, 2009. / Title from title page screen (viewed on Mar. 19, 2010). Thesis advisor: Qiang He. Vita. Includes bibliographical references.

Thesis (M.S.)--Rutgers University, 2007. / "Graduate Program in Civil and Environmental Engineering." Includes bibliographical references (p. 71-76).

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-04-08T12:32:34Z No. of bitstreams: 0 / Made available in DSpace on 2016-04-08T12:32:34Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-04-08T12:32:34Z No. of bitstreams: 0 / Made available in DSpace on 2016-04-08T12:32:34Z (GMT). No. of bitstreams: 0 / A casca da castanha de caju (CCC), um resíduo agrícola da produção de castanha, proveniente da região nordeste do Brasil foi caracterizada e submetida ao processo de pirólise lenta. As propriedades do bio-carrvão, do bio-óleo e dos gases produzidos foram investigados e potenciais aplicações foram propostas. A CCC foi caracterizada pela seguintes técnicas: análise elementar CHNS, umidade total, conteúdo de cinzas, matérias voláteis, poder calorífico superior e por análise termogravimétrica. A análise termogravimétrica sob fluxo de nitrogênio mostrou que a decomposição é dominada pela degradação da hemicelulose e celulose na faixa de 250 a 350oC e pela decomposição da lignina na faixa de 400 a 500oC. Na presença de ar, o perfil de degradação é semelhante, porém observa-se uma maior degradação da lignina. A pirólise lenta da casca da castanha de caju foi realizada em um reator tipo batelada aquecido por chama ar-GLP sob diferentes fluxos (mL min-1) de nitrogênio ou ar. O sólido obtido (bio-carvão), líquido (fase aquosa + bio-óleo) e a fase gás foram quantificados e caracterizados por diferentes técnicas. Os experimentos realizados sob fluxo de nitrogênio apresentaram um rendimento de cerca de 30, 40 e 30% em massa paras as fases sólido, líquida e gás, respectivamente. Sob fluxo de ar ocorreu uma diminuição no rendimento da fase líquida, principalmente na produção de bio-óleo, e um aumento da fase gás. Os bio-carvões produzidos apresentaram elevados teores de carbono, na faixa de 70-75% em massa, poder calorífico na faixa de 25 a 28 MJ kg-1, características de carbono amorfo, sem morfologias definidas e ausência de poros. Os espectros FTIR de bio-óleos produzidos sob fluxo de nitrogênio apresentaram um aumento da intensidade relativa das bandas cerca de 1700 cm-1 (&nu; C=O) e 1230 cm-1 (&nu; C-O) em comparação com os produzidos sob fluxo de ar, o que sugere a presença de grandes quantidades de compostos oxigenados de carbono, como aldeídos, cetonas e ácidos carboxílicos. As análises das fases gás mostraram a predominância de CO2 e CO a temperaturas inferiores a 400ºC e a formação preferencial de H2 acima desta temperatura. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP