“Matrix effects” in Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy are the spectroscopic changes induced by intermolecular interactions, providing sensitivity to local structure and order in solids and liquids. This project aims to identify the effect of intermolecular interactions caused by different n-alkane solid state structures on their NEXAFS spectra. Changes to the carbon 1s NEXAFS spectra are studied as a function of their solid state structure and organization. Two experimental approaches were proposed in this project. In the first approach, different n-alkane crystal structures (orthorhombic, monoclinic, etc.) are examined which arise as a function of n-alkane chain length. In the second approach, changes observed through the pre-melting point order-disorder phase transition found in n-alkanes are examined. This work will explore the characteristic spectroscopic differences observed between n-alkanes in different crystalline forms as well as in the disordered phase below the melting points. In this project, well-ordered diamond shape n-alkane single crystals were obtained by solution casting, using experimental conditions optimized for each n-alkane. As circularly polarized radiation will average the effect of molecular orientation, circularly polarized radiation was used to obtain the NEXAFS spectra of n-alkanes. However, in the analysis of the NEXAFS spectra of n-alkanes recorded with the left circularly polarized X-rays, a significant linear polarization contamination was found. Therefore, linearly polarized X-rays were used to acquire angle dependent NEXAFS spectra, where the X-ray polarization was deliberately aligned along the principal axes (X, Y) of the n-alkane crystal. It was observed that the room temperature carbon 1s NEXAFS spectrum of n-octacosane (C28H58) was different from that of the other n-alkanes, n-tetracosane (C24H50), n-tricosane (C23H48) and n-tetracontane (C40H82). This difference can be attributed due to the different crystal packing of n-octacosane (C28H58 - monoclinic) relative to the other n-alkanes (triclinic and orthorhombic), suggesting different intermolecular interactions (matrix effects) in n-octacosane (C28H58). The analysis of the temperature dependent NEXAFS spectra of n-alkanes reveals that samples of the short chain n-alkane crystals, specially n-tricosane (C23H48), n-tetracosane (C24H50) and n-octacosane (C28H58), sublimed in the STXM microscope. Changes observed in the carbon 1s NEXAFS spectra of n-tetracontane (C40H82) with temperature were attributed to the order-disorder transition. This further illustrates the existence of matrix effects in the NEXAFS spectra of n-alkanes.

In the first experiment, forage samples (n = 39) were collected during 4 years (2006 ? 2009) from pastures grazed by Santa Gertrudis cattle at the King Ranch, TX. The in vitro gas production technique (IVGP) was performed to understand the pattern of fermentation parameters of the forage and obtain fractional digestion rate (kd) values to predict total digestible nutrients (TDN). The best nonlinear model to describe the IVGP values of the forages was the two-pool logistic equation. The passage rate (kp) of 4%/h was used.. The kp predicted by the Large Nutrient Ruminant System (LNRS) model was 3.66%/h. The average TDN was 55.9% compared to 53.8% using a theoretical equation. In the second experiment, Brahman bulls (n = 16) grazed Coastal bermudagrass pastures [Cynodon dactylon (L.) Pers.] and stocked at a moderate to low grazing pressure. Three periods of fecal collections were made within each period. Bulls were individually fed at 0700 and 1900 h of 400 g of corn gluten pellets containing C32 n-alkanes. Each period was divided in 2 sub periods in which fecal samples were collected 4 times a day (0700, 1100, 1500 and 1900 h). N-alkanes in the forage and feces were determined using gas chromatography. In the third experiment, four methods were used to estimate dry matter intake (DMI): C31 or C33 with or without adjustment for forage C32 (C31_0 and C33_0, respectively). There was a difference between morning (0700 and 1100 h) and afternoon fecal collections (1500 and 1900 h) on the predicted DMI using C31 (P = 0.0010), C33 (P = 0.0001), C31_0 (P = 0.0010), or C33_0 (P < 0.0001). There was no difference in average daily gain (ADG) between low and high residual feed intake (RFI) (P = 0.5709). The nonparametric analysis indicated that preranking animals for efficiency under confinement conditions does not guarantee (P < 0.0001) similar ranking under grazing conditions when using the alkane technique to determine forage DMI. In order to estimate DMI at least 5 d of fecal collection and 2 times a day of collection (0700 and 1500h) are needed to decrease the variability.

Twenty-two sediment samples were collected from Kaohsiung Harbour, and it¡¦s neighboring coastal area, Taiwan and analysed for a suite of n-C10-C35 aliphatic hydrocarbons and fifteen polycycilc aromatic hydrocarbons (PAHs). The average total concentration of n-alkanes was 4.327 £gg/g dry wt. (0.461-22.601 £gg/g dry wt.) and PAHs was 0.588 £gg/g dry wt. (0.088-1.75 £gg/g dry wt.). The highest n-alkanes and PAHs concentrations were recorded in samples from D and A stations in Kaohsiung Harbour ; stations D and A are near the outlets of Chyan-Jenn and Jen-Ai rivers, respectively. The sources of n-alkanes are probably contributed form origins of petrogenic, biogenic and higher plants according to the value of CPI (carbon preference index), chromatogram of UCM (unresolved complex materials), and n-C16 ratio etc.; while PAHs were contributed mainly from combustion in coastal areas and petrogenic in harbour areas based on the ratios of total combustion and LMW/HMW ratios. Overall, sediment concentrations of n-alkanes and PAHs in Kaohsiung coastal area were similar to literature in the world. The potential for biological effects due to PAHs is found to be low based as their individual PAHs concentrations are in general lower than effects most existed sediment quality guidelines, except Acenaphthaene, Anthracene, Benzo[a]anthracene, and Fluorene.

Geological Society of China Cenozoic climatic and environmental changes in the arid Asian interior, and their possible relations with global climatic changes and the Tibetan Plateau uplift, have been intensively investigated and debated over past decades. Here we present 40-Myr (million years)-long n-alkane records from a continuous Cenozoic sediment sequence in the Dahonggou Section, Qaidam Basin, northern Tibetan Plateau, to infer environmental changes in the northern basin. A set of n-alkane indexes, including ACL, CPI and Paq, vary substantially and consistently throughout the records, which are interpreted to reflect relative contributions from terrestrial vascular plants vs. aquatic macrophytes, and thus indicate depositional environments. ACL values vary between 21 and 30; CPI values range from 1.0 to 8.0; and Paq values change from <0.1 to 0.8 over the past 40-Myr. We have roughly identified two periods, at 25.8–21.0 Ma (million years ago) and 13.0–17.5 Ma, with higher ACL and CPI and lower Paq values indicating predominant lacustrine environments. Lower ACL and CPI values, together with higher Paq values, occurred at >25.8 Ma, 17.5–21.0 Ma, and <13.0 Ma, corresponding to alluvial fan/river deltaic deposits and shallow lacustrine settings, consistent with the observed features in sedimentological facies. The inferred Cenozoic environmental changes in the northern Qaidam Basin appear to correspond to global climatic changes.

No description available.

Os marcadores orgânicos moleculares (hidrocarbonetos alifáticos, esteróis e álcoois) em amostras de sedimentos superficiais e de testemunhos curtos coletados em diápiros e pockmarks localizados no talude sul do Brasil, foram utilizados para identificar as possíveis contribuições biogênicas (autóctones / alóctones). De modo geral, tanto nas amostras superficiais como ao longo dos testemunhos, o maior acúmulo de carbono orgânico total nos pockmarks foi observado, indicando o possível aprisionamento de sedimentos e de matéria orgânica no interior das concavidades. A presença de &#946;-sitosterol, campesterol, álcoois e n-alcanos pesados, indicaram contribuições terrígenas para a área de estudo, que pode ser advinda da descarga continental do Rio da Prata, uma vez que a predominância terrígena é proveniente das pradarias, típica vegetação do Uruguai e do sul do Rio Grande do Sul. O transporte de sedimentos terrígenos ocorre em direção ao norte, ao longo da plataforma continental sul brasileira, pela Corrente Costeira do Brasil. A presença de detritos de fitoplâncton e zooplâncton também ocorre devido à influência dos nutrientes do Rio da Prata. As possíveis liberações de gás/fluido, que sustentaram ecossistemas quimiossintéticos em diferentes intervalos de dois testemunhos em pockmark e diápiro foram constatadas através da presença relativamente maior de n-alcanos leves com número par de carbonos. / Organic molecular markers (aliphatic hydrocarbons, sterols and alcohols) in superficial and short cores sediment samples collected in diapirs and pockmarks located in the southern slope of Brazil were used in order to identify the possible biogenic contributions (autochthonous / allochthonous). In general, in surface samples and throughout the cores samples, the greatest accumulation of total organic carbon in the pockmarks was observed, indicating the possible entrapment of sediments and organic matter inside the concavities. The presence of &#946;-sitosterol, campesterol, alcohols and heavy n-alkanes indicated terrigenous contributions to the study area, which may be due to the continental discharge of Río de la Plata, since the terrigenous predominance is due to the prairies, a typical vegetation of Uruguay and the south of Rio Grande do Sul. The terrigenous sediments transport is carried through the North, along the Brazilian continental shelf, by the Coastal Stream of Brazil. The presence of phytoplankton and zooplankton debris is also due to the influence of the nutrients contribution from Río de la Plata. Possible gas / fluid releases, which sustained chemosynthetic ecosystems at different intervals of two pockmark and diaper cores, were verified by the relative predominance of even-numbered carbon n-alkanes.

O gênero Croton possui aproximadamente 1300 espécies amplamente distribuídas em zonas tropicais e subtropicais do novo e velho mundo e é o segundo maior gênero de Euphorbiaceae. No presente trabalho, foram analisadas a composição e a morfologia das ceras foliares cuticulares de 13 espécies de Croton. Para a maioria das espécies, foram amostrados três indivíduos. A morfologia das ceras foi analisada por microscopia eletrônica de varredura. Diversos tipos de depósitos cerosos foram observados (amorfos, plaquetas, grânulos), principalmente na face adaxial e caracterizando grupos de espécies. A observação dos padrões de depósitos cerosos de várias espécies foi prejudicada na face abaxial, devido à alta densidade de tricomas. As ceras foram extraídas por três imersões consecutivas das folhas em diclorometano e a separação das classes dos constituintes foi feita por cromatografia em camada delgada preparativa. A análise da distribuição dos constituintes foi realizada por cromatografia a gás acoplada a espectrometria de massas. n-Alcanos e álcoois primários foram detectados em todos os indivíduos analisados. Triterpenos também são muito comuns, não tendo sido detectados em apenas uma espécie. Os esteroides são constituintes raros nas espécies analisadas. Os resultados da distribuição de n-alcanos, álcoois primários e triterpenos foram utilizados para o estabelecimento de afinidades químicas por meio de análises de agrupamento pelo método UPGMA, empregando-se distâncias euclidianas (n-alcanos e álcoois) e coeficiente de DICE (triterpenos), baseando-se na distribuição de cada classe de constituinte isoladamente e combinando-se as distribuições de n-alcanos e álcoois primários. Não se notou congruência entre as topologias dos dendrogramas de afinidades químicas e a filogenia molecular do gênero. Observou-se coerência entre algumas afinidades químicas e características morfológicas, como tipos de tricomas foliares e presença de glândulas peciolares. A distribuição de n-alcanos, álcoois primários e triterpenos mostraram-se úteis como caracteres da maioria das espécies analisadas. Entre os constituintes analisados, distribuição de álcoois primários revelou-se o melhor marcador para a caracterização de espécies. A variação intraespecífica, no entanto, impede que esses caracteres sejam úteis como marcadores taxonômicos de algumas espécies de Croton / Croton comprises nearly 1300 species distributed in tropical and subtropical areas of either the New or Old Worlds, making up the largest genus of Euphorbiaceae. In the present work, the chemical composition and the morphology of the foliar cuticular waxes of 13 species of Croton were analized. Three individuals were sampled for analyses of most species. The morphology of the waxes was analyzed by scanning electron microscopy. Several types of wax deposits were observed (amorph, platlets, granules), chiefly on the adaxial side, characterizing groups of species. The observation of wax deposits on the abaxial side was hampered in several species due to the high density of trichomes. The cuticular wax was extracted by three successive immersions of the leaves in dichloromethane, and the separation of the constituent classes was achieved by preparative thin layer chromatography. The analyses of the distribution of the constituents were performed by gas chromatography coupled to mass spectrometry. n-Alkanes and primary alcohols were detected in all analyzed individuals. Triterpenes were also very common, having not been detected in only one species. Steroids are rare constituents in the analyzed species. The results of the distribution of n-alkanes, primary alcohols and triterpenes were used for the establishment of chemical affinities using cluster analysis by the UPGMA method and Euclidean distances (n-alkanes and alcohols) and DICE coefficient, based on the distribution of each constituent class alone and combining the distribution of n-alkanes and primary alcohols. No congruence was noted between the topologies of the dendrograms of chemical affinity and the molecular phylogeny of the genus. Coherence was observed between chemical affinities and morphologic characteristics, such as types of foliar trichomes and petiolar glands. The distribution of n-alkanes, primary alcohols and triterpenes were shown to be useful as characters for most analyzed species. Among the constituents analyzed, the distribution of primary alcohols was the best marker for species characterization. Intraspecific variation, however, precludes the use of these characters as taxonomic markers of some Croton species

Os marcadores orgânicos moleculares (hidrocarbonetos alifáticos, esteróis e álcoois) em amostras de sedimentos superficiais e de testemunhos curtos coletados em diápiros e pockmarks localizados no talude sul do Brasil, foram utilizados para identificar as possíveis contribuições biogênicas (autóctones / alóctones). De modo geral, tanto nas amostras superficiais como ao longo dos testemunhos, o maior acúmulo de carbono orgânico total nos pockmarks foi observado, indicando o possível aprisionamento de sedimentos e de matéria orgânica no interior das concavidades. A presença de &#946;-sitosterol, campesterol, álcoois e n-alcanos pesados, indicaram contribuições terrígenas para a área de estudo, que pode ser advinda da descarga continental do Rio da Prata, uma vez que a predominância terrígena é proveniente das pradarias, típica vegetação do Uruguai e do sul do Rio Grande do Sul. O transporte de sedimentos terrígenos ocorre em direção ao norte, ao longo da plataforma continental sul brasileira, pela Corrente Costeira do Brasil. A presença de detritos de fitoplâncton e zooplâncton também ocorre devido à influência dos nutrientes do Rio da Prata. As possíveis liberações de gás/fluido, que sustentaram ecossistemas quimiossintéticos em diferentes intervalos de dois testemunhos em pockmark e diápiro foram constatadas através da presença relativamente maior de n-alcanos leves com número par de carbonos. / Organic molecular markers (aliphatic hydrocarbons, sterols and alcohols) in superficial and short cores sediment samples collected in diapirs and pockmarks located in the southern slope of Brazil were used in order to identify the possible biogenic contributions (autochthonous / allochthonous). In general, in surface samples and throughout the cores samples, the greatest accumulation of total organic carbon in the pockmarks was observed, indicating the possible entrapment of sediments and organic matter inside the concavities. The presence of &#946;-sitosterol, campesterol, alcohols and heavy n-alkanes indicated terrigenous contributions to the study area, which may be due to the continental discharge of Río de la Plata, since the terrigenous predominance is due to the prairies, a typical vegetation of Uruguay and the south of Rio Grande do Sul. The terrigenous sediments transport is carried through the North, along the Brazilian continental shelf, by the Coastal Stream of Brazil. The presence of phytoplankton and zooplankton debris is also due to the influence of the nutrients contribution from Río de la Plata. Possible gas / fluid releases, which sustained chemosynthetic ecosystems at different intervals of two pockmark and diaper cores, were verified by the relative predominance of even-numbered carbon n-alkanes.

Highly fluorinated organic compounds are emerging environmental contaminants of concern, due to their persistence, ubiquitous distribution, bioaccumulation potential and toxicity. Ski waxes are sources of highly fluorinated chemicals to the environment that have not been investigated so far. Some contain fluorinated additives such as semifluorinated n-alkanes (SFAs). This thesis investigated the fate of SFAs after abrasion onto snow through skiing activities. Furthermore, perfluorinated alkyl acids (PFAAs) were found to be present in fluorinated ski waxes. A lot of attention has been paid to elucidating the environmental fate of PFAAs during the past decade. However, nothing was known so far about their release from melting snow packs. Analytical methods for quantification of SFAs in different environmental matrices were developed. The methods were used to investigate the fate of SFAs during snow melt and to study their occurrence in ski areas. Laboratory snow melt experiments and model-based fate simulations suggested that SFAs will sorb to the snow grain surface and particles in the bulk snow and, after snowmelt, will end up on the underlying (soil) surface. SFAs were detected and quantified for the first time in snow and soil samples taken from a ski area in Sweden. Comparison of concentrations in snow and soil did not give any evidence for long-term accumulation of SFAs in surface soil, but suggested volatilization of shorter chain homologues during snow melt. Such a volatilization could also explain an observed SFA pattern difference between snow and soil samples. Laboratory scale snow melt experiments were also used to investigate the behavior of PFAAs during snowmelt. PFAAs were released with the melt water from the snow pack in pulses. The pulses occurred early, late or with a so far unknown peak elution in the middle of the snowmelt, depending on the hydrophobicity of the PFAAs. These peak releases were further influenced by the age of the snow pack and thus the snow surface area and to a lesser extent by pH and ion concentrations.

The Gaoping (GP) river which has the largest drainage basin and is the second longest river in Taiwan. Highly erodible sedimentary and metamorphic rocks in the drainage basin, coupled with a steep landscape, humid climate, frequent typhoons and earthquakes, provide favorable conditions for bedrock weathering and soil erosion in the GP drainage basin. Its exceptionally high sediment yield and tidal-dominated dispersal system presents a unique case for comparative study. In this study, we collected sediment and soil samples not only from estuary region but also traced up to upper stream areas of the GP drainage. We analyze the content of n-alkanes in the sediments and soils of GP river-sea system, and utilize compositional patterns to discuss the sources and process of transmission of terrigenous organic matter of GP river-sea system. Analyzed results show that the average carbon chain distribution shows same pattern for rocks, riverine and seafloor sediments but is different with soil samples. Hierarchical cluster analysis helps us to distinguish differently compositional patterns of n-alkanes. And the riverine, seafloor and rock samples have high similarity, except for soils. The spatial distribution of the carbon preference index (CPI) and temporal distribution of CPI in cores, show that values are all close to ~1, but not for soils (>2). This result indicates that for the past 150 years, lower CPI values not merely from petroleum pollutions, but also due to thermal mature terrestrial organic matter eroded from bedrock caused by tectonic and climatic events, such as typhoons and earthquakes.