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1.
Cells of Nostoc muscorum and Rhodopseudomonas spherodes have been subjected to thermal alteration over varying periods of time. Experiments were conducted using both unextracted and extracted cells in the absence and presence of montmorillonite. The isoprenoid hydrocarbons produced in these experiments have been examined. The major hydrocarbons produced were phytane and five isomeric phytenes. Phytane was observed to form faster from the unextracted cells than from the extracted cells. Montmorillonite increased the amount of phytane formed from the unextracted cells of Nostoc muscorum but not from the cells of Rhodopseudomonas spheroides. No phytadienes, pristane or pristenes were detected in the products of any of these experiments.  相似文献   

2.
Visible light induced, type II (i.e. involving singlet oxygen, 1O2) photosensitized oxidation of mono-, di-, tri- and tetraunsaturated C25 highly branched (HBI) alkenes in solution was investigated. The photodegradation rate was shown to be dependent on the number and nature of the double bonds, especially the number of trisubstituted ones. HBI alkenes with at least one trisubstituted double bond were photodegraded at similar or higher rates than some other lipids (e.g. vitamin E) known to be very reactive towards 1O2. The 1O2 mediated photo-oxidation of HBI alkenes likely involves direct reaction of 1O2 with the trisubstituted double bond via a concerted ‘ene’ addition, leading to formation of a hydroperoxide at each carbon of the original double bond. The enhanced photoreactivity of HBI alkenes with at least one trisubstituted double bond was confirmed in dead cells of the diatom Haslea ostrearia. In addition, since HBI alkenes with such double bonds were photodegraded at similar or higher rates compared to polyunsaturated fatty acids, vitamin E and chlorophyll a, they should be significantly photochemically altered within the euphotic zone of the ocean. In contrast, HBIs with only di- and monosubstituted double bonds seem to be relatively inert with respect to type II photoprocesses. The results support the apparent good preservation of the monoene IP25 in sediments, while the interpretation of sedimentary occurrences of HBI trienes may need further consideration.  相似文献   

3.
Capillary gas chromatography-mass spectrometry (C-GC-MS) and Iatroscan thin layer chromatography-flame ionisation detection (TLC-FID) were used to study hydrocarbon distributions in a sediment core from Ace Lake, a saline, meromictic lake in the Vestfold Hills of Antarctica. Hydrocarbons were abundant in most core sections (up to 125/μg/g dry wt), particularly in near-surface samples, and the distributions were very complex. Major constituents were identified as phytane, 2,6,10,15,19-pentamethyleicosane, tetrahydrosqualene, a mixture of phytenes, cholesta-3,5-diene and fern-7-ene. Smaller amounts of sterenes and hopenes were also present. The predominance of the first 3 acyclic isoprenoids in sediments buried less than 30 cm is consistent with high populations of methanogenic bacteria known to be present.Phytenes were abundant in all core sections, and there was no relationship between their abundance and that of phytane which suggests that they were not derived from methanogenic bacteria. Phytadienes were minor constituents at all depths studied. An unusual feature of some distributions was the high concentrations of fern-7-ene which was the major hydrocarbon in the 20–25 cm core section. This alkene was only abundant in sediments which contained high concentrations of methanogen markers suggesting that it may also be indicative of anoxic depositional environments. A possible source might be from purple non-sulphur bacteria. High concentrations of straight-chain C29 and C34 alkenes were also found in these sediments but their origin has not been determined. Major changes in the hydrocarbon distributions with depth indicate that the depositional environment in the lake has altered dramatically since the lake was formed less than 8000 years ago. The present condition of permanent anoxic bottom waters probably developed only in the last 1000 years.  相似文献   

4.
Concentration profiles of five C25 and C30 biogenic alkenes in a sediment core collected from the upper anoxic basin of the Pettaquamscutt River have been determined. The five alkenes were identified usin gas chromatography/mass spectrometry as three isomeric C25 dienes, a C25 triene and a bicyclic C30 diene. All five compounds exhibit subsurface concentration maxima, thought to result from either preservation of a past increase in alkene production or a current bacterial in situ production at depth. Similarities exist in the concentrations of two alkenes common to this core and a core from upper Narragansett Bay, despite significant differences in the origin and content of sedimentary organic matter (as inferred from organic carbon and δ 13C measurements) at each location. These observations support the proposed bacterial in situ synthesis of alkenes. Other alkenes, whose concentration in sediments had been previously correlated with the incidence of marine organic matter, were not detected in the upper basin sediments. Their absence is consistent with the range of organic carbon δ 13C values measured, which indicate that the component originating from marine sources is small. A comparison of organic carbon and δ 13C values in this core with those previously reported from a core collected in an adjoining basin indicate that the sedimentary regimes at the two sites differ despite their close proximity and similar hydrography.  相似文献   

5.
Recent sediments from Bransfield Strait, Antarctica have been analyzed for triterpenoid and steroid hydrocarbons, sterols and steroid ketones to consider the effects of hydrothermal fluids on the sedimentary organic matter. The steroid distributions in unaltered and altered sediments are controlled more by inputs from source organisms than by the effects of hydrothermal activity, which is suggested to be limited to low temperature alteration. Nevertheless, chemical reactions occurred in altered sediments and include dehydration of sterols to sterenes, isomerization of triterpenes and sterenes, rearrangement of sterenes to diasterenes and reductive processes leading to generation of phytane from phytol via phytenes.  相似文献   

6.
From the surface sediment of a eutrophic lake (Japan), the double bond position in the monounsaturated fatty acids (C15-C26) has been determined by combined gas chromatography-mass spectrometry of the methoxylated derivatives. The relative abundance of 11-octadecenoic acid, suggested to be of bacterial origin, is higher in the chloroform-methanol extract than the extract by saponification.  相似文献   

7.
Equilibrium 2H/1H fractionation factors (αeq) for various H positions in alkanes, alkenes, ketones, carboxylic acids, esters, alcohols, and ethers were calculated between 0 and 100 °C using vibrational frequencies from ab initio QM calculations (B3LYP/6-311G**). Results were then corrected using a temperature-dependent linear calibration curve based on experimental data for Hα in ketones (Wang et al., 2009). The total uncertainty in reported αeq values is estimated at 10–20‰. The effects of functional groups were found to increase the value of αeq for H next to electron-donating groups, e.g. OR, OH or O(CO)R, and to decrease the value of αeq for H next to electron-withdrawing groups, e.g. (CO)R or (CO)OR. Smaller but significant functional group effects are also observed for Hβ and sometimes Hγ. By summing over individual H positions, we estimate the equilibrium fractionation relative to water to be −90‰ to −70‰ for n-alkanes and around −100‰ for pristane and phytane. The temperature dependence of these fractionations is very weak between 0 and 100 °C. Our estimates of αeq agree well with field data for thermally mature hydrocarbons (δ2H values between −80‰ and −110‰ relative to water). Therefore the observed δ2H increase of individual hydrocarbons and the disappearance of the biosynthetic δ2H offset between n-alkyl and linear isoprenoid lipids during maturation of organic matter can be confidently attributed to H exchange towards an equilibrium state. Our results also indicate that many n-alkyl lipids are biosynthesized with δ2H values that are close to equilibrium with water. In these cases, constant down-core δ2H values for n-alkyl lipids cannot be reliably used to infer a lack of isotopic exchange.  相似文献   

8.
Methyltrimethyltridecylchromans (MTTCs) have been widely detected in sediments and crude oils from various depositional settings and are established markers for palaeosalinities. A likely origin of these compounds, which show a distinctive isoprenoid substituted aromatic structure, seems to be condensation reactions of phytol with higher plant derived alkyl phenols during early diagenesis. However, a direct biological origin from phytoplanktonic organisms cannot be excluded. To further investigate the potential origin from condensation reactions, an online pyrolysis–gas chromatography–isotope ratio mass spectrometry (PY–GC–irMS) method with the capacity to measure δ13C in fragments (trimethylphenol and pristenes) generated from 5,7,8-trimethyl-MTTC was developed in this study. This straight forward technique poses a great potential for the elucidation of chroman formation in geological samples as it possibly enables the distinction between the different proposed sources of isoprenoid and alkyl-phenol fragments (mainly phytoplankton and higher plants, respectively) based on their stable isotopic compositions. Furthermore, it might be useful for the investigation of products generated from MTTCs during thermal maturation of geological samples.  相似文献   

9.
Messinian marls from evaporitic cycle IV of the Gessoso-solfifera formation (Italy) are known to contain in high abundance the diaromatic carotenoid isorenieratene of green sulfur bacterial (Chlorobiaceae) origin along with a second diaromatic carotenoid. The previous tentative assignment of the latter as a cis diastereomer of isorenieratene has now been confirmed; this indicates that double bond isomerization occurs during early diagenesis and provides further evidence for the pathway proposed previously to link isorenieratene to a number of aromatic isoprenoid hydrocarbon biomarkers. Stable carbon isotopic data confirm the Chlorobiaceae origin of the intact all-trans isorenieratene isomer and indicate that the isomerization is accompanied by little or no kinetic isotope effect. Comparison of the δ13C values of each of the isolated carotenoids (measured as isorenieratane after hydrogenation) with those of their sulfide-bound counterpart in the polar fraction of the extracts (also measured as isorenieratane) indicates that sulfurization resulted in little depletion in 13C.  相似文献   

10.
Young kerogens isolated from seven freshwater lakes, six river mouths and four marine surface sediments were subjected to pyrolysis in vacuo. Their pyrolysates were trapped and separated subsequently for determination of hydrocarbons, fatty acids and alcohols. The abundances, carbon number distributions of long (C12) polymethylene chain lipid compounds and relative abundances of pristenes are proposed as possible indices applicable to discrimination between young kerogens from freshwater lacustrine and marine sediments. Some oil-shale kerogens of Eocene and Permian age were pyrolyzed in the same way, where the chain-length distributions of the pyrolysis products showed similar trends as those observed for the pyrolysis of young kerogens.  相似文献   

11.
在多级折流板反应器生物处理装置中,采用活性炭为载体人工固定化生物处理合成染料废水,出水水质稳定, 出水中的烷烃肽链变短;其对CODCr和BOD5的去除率可达96.46%、99.77% ;对SO2-4和钙镁总量的去除效率超过80.37%、78.66%;折流板反应器的容积负荷率Nv可达2.8 kg COD/(d•m3)。活性炭经生物固定化后,不仅不会影响它的处理效果,还会延长活性炭的使用寿命;当冲击性有机负荷发生时,固定化生物活性炭能够承受并能很快恢复。  相似文献   

12.
Exchange of carbon bound hydrogen has been observed when alkenes, saturated and aromatic hydrocarbons are heated at moderate temperatures on carbonaceous surfaces (activated carbon and coal). Isomerisation of alkenes and the formation of hydrogenated/dehydrogenated products from the saturated and aromatic reactants resulted. A suite of crude oils from the Carnarvon Basin (Western Australia) have been analysed with a view to comparing their relative abundances of structurally similar hydrocarbons. The consistent relationships between hydrocarbons in crude oils that are chemically related via hydrogenation/dehydrogenation reactions suggest that a hydrogen exchange process similar to that demonstrated in laboratory experiments occurs during crude oil formation in sedimentary rocks.  相似文献   

13.
潘志清  林壬子 《沉积学报》1991,9(2):106-113
笔者首次在华北晋县高硫原油和含硫膏泥岩的饱和烃馏份中检测出丰富的短链甾类化合物(C20-C26),它们包括甾烷、甾烯、4-甲基甾烷和4,4-二甲基甾烷。同时,样品中还检测出C23-C25类异戊二烯烷烃。这此化合物是盐湖相沉积环境中细菌输入和降解作用的产物。  相似文献   

14.
The distributions of a series of structurally related C25 and C30 biogenic alkenes in sediments of the Narragansett Bay estuary have been determined. The suite of alkenes detected differs both quantitatively and qualitatively from those previously reported in other estuanne and coastal regions. Four C25 mono- and dienes and one C30 diene comprise 73–91% of the total alkenes in all surface (upper 2.5–5 cm) sediments analyzed. However, significant geographic variations exist in the relative abundance of these five compounds throughout the estuary. A comparison of alkene concentrations with δ13C of the bulk sedimentary organic matter has shown that the geographic variations of some alkenes reflect the distribution of marine organic matter, suggesting a marine source for these compounds. The distributions of other alkenes are not similarly correlated. In particular, concentrations of the C30 diene are relatively constant and exhibit no dependence on the origin of organic matter in these sediments. This distribution implies an in situ production of this alkene throughout the estuary. Analysis of several sediment cores reveals that alkene concentrations are generally highest at the surface and decrease to low, constant values within the upper 25 cm. An exception is the subsurface concentration of one C25 diene, which exhibits an increase at the same depth in two separate upper bay cores.  相似文献   

15.
The chemical structure of the resin from an Australian soft brown coal (Yallourn) has been investigated by cross-polarization nuclear magnetic resonance spectroscopy with magic angle spinning (13C CP MAS NMR). Some additional solution 1H and 13C data were also obtained. Solid-state experiments were performed with and without a delay period before data acquisition. The resulting free induction decays were Fourier transformed with respect to acquisition time and delay period to produce two-dimensional solid-state spectra. Assignments made from the spectra clearly demonstrate that the gross chemical structure of the Yallourn resin is best described as a polymerized diterpenoid with one axial carboxylic group and two double bonds. One double bond is trisubstituted, the other is monosubstituted. After consideration of various mechanisms for polymerization of diterpenoid units during biogenesis and coalification, it was concluded that polymerization occurs at the C15 carbon atoms in the diterpenoids without cyclization of the methylene units at C8.  相似文献   

16.
In this study, Raman scattering measurements were obtained for momo corals covering their typical range of colors. Three different excitation wavelengths (785, 633, 514 nm) are used for the same samples at the same points. All the samples show the two major Raman features of polyenic compounds assigned to double carbon-carbon (C=C) stretching vibration at approximately 1 500 cm-1 and single carbon-carbon (C--C) stretching vibration at approximately 1 130 cm-1 bond stretching mode. These peaks are not detected in the corresponding white parts of momo corals. However, somechanges in intensities, shape, and position of C=C stretching vibrations of the same point are observed by using different excitation wavelengths. The exact position of C-C stretching vibration of polyenic molecules depends strongly on the number of double bonds contained in their polyenic chain. In addition, the number of double bonds contained in the polyenic chains shows that different colors of the red momo coral are caused by different mixtures of polyenic compounds.  相似文献   

17.
The O 1s spectrum is examined for 19 uranyl minerals of different composition and structure. Spectra from single crystals were measured with a Kratos Axis Ultra X-ray Photoelectron Spectrometer with a magnetic-confinement charge-compensation system. Well-resolved spectra with distinct maxima, shoulders and inflections points, in combination with reported and measured binding energies for specific O2− species and structural data of the uranyl minerals are used to resolve the fine structure of the O 1s envelope. The resolution of the O 1s spectra includes, for the first time, different O2− bands, which are assigned to O atoms linking uranyl with uranyl polyhedra (UOU) and O atoms of uranyl groups (OUO). The resolved bands in the O 1s spectrum occur at distinct ranges in binding energy: bands for (UOU) occur at 529.6-530.4 eV, bands for (OUO) occur at 530.6-531.4 eV, bands for O2− in the equatorial plane of the uranyl polyhedra linking uranyl polyhedra with (TOn) groups (T = Si, S, C, P, Se) (TO) occur at 530.9-532.2 eV; bands for (OH) groups in the equatorial plane of the uranyl polyhedra (OH) occur at 532.0-532.5 eV, bands of (H2O) groups in the interstitial complex of the uranyl minerals (H2Ointerst) occur at 533.0-533.8 eV and bands of physisorbed (H2O) groups on the surface of uranyl minerals (H2Oadsorb) occur at 534.8-535.2 eV. Treatment of uranyl minerals with acidic solutions results in a decrease in UOU and an increase in OH. Differences in the ratio of OH : OUO between the surface and bulk structure is larger for uranyl minerals with a high number of UOU and TO species in the bulk structure which is explained by protonation of underbonded UO, UOU and TO terminations on the surface. The difference in the ratio of H2Ointerst : OUO between the bulk and surface structures is larger for uranyl minerals with higher percentages of H2Ointerst as well as, with a higher number of interstitial H2O groups that are not bonded to interstitial cations, resulting in easier dehydration of interstitial H2O groups in uranyl minerals during exposure to a vacuum.  相似文献   

18.
《Applied Geochemistry》1996,11(4):541-554
In the acidic stream (pH 2.2–4) of the Carnoulès Pb-(Zn) mine, Gard, France, very high As contents (from 9 to 20%) can be accumulated as ferric arsenate and arsenate-sulphate precipitates in rapidly growing bacteria-made structures. The main bacterial forms are rod-shaped and sheathed, their sheath is made of Fe-As-rich material and is coated with ferric arsenate colloidal particles or may be partially included in authigenic crystals. Living forms ofThiobacillus-type bacteria have been recognized in the precipitates. The cyclic development of bacterial colonies alternating with sand deposition and erosive episodes results in the formation of As-rich ferruginous accretions. These laminated and dome-shaped bacterial constructions are similar to those of stromatolites. The extremely high contents of solute As in upstream flow (250 mg/1) are lowered by 2–3 order of magnitude downstream. Lead is also precipitated and concentrated in this FeAs-rich bacterial stromatolite (2500 ppm Pb). This accumulation and concentration of As and heavy metals via direct or induced microbial action limits pollution downflow. But seasonal storms could erode these FeAsPb-rich deposits and drastically increase pollution.The accumulation of ferric arsenate by bacterial stromatolites suggests that possible microbial remediation strategies may be used in acid mine drainage environments.  相似文献   

19.
This study presents molecular orbital/density functional theory (MO/DFT) calculations of the electronic structure, vibrational frequencies, and equilibrium isotope fractionation factors for iron desferrioxamine B (Fe-DFO-B) complexes in aqueous solution. In general, there was good agreement between the predicted properties of Fe(III)-DFO-B and previously published experimental and theoretical results. The predicted fractionation factor for equilibrium between Fe(III)-DFO-B and Fe(III)-catecholate at 22 °C, 0.68 ± 0.25‰, was in good agreement with a previously measured isotopic difference between bacterial cells and solution during the bacterial-mediated dissolution of hornblende [Brantley S. L., Liermann L. and Bullen T. D. (2001) Fractionation of Fe isotopes by soil microbes and organic acids. Geology29, 535-538]. Conceptually, this agreement is consistent with the notion that Fe is first removed from mineral surfaces via complexation with small organic acids (e.g., oxalate), subsequently sequestered by DFO-B in solution, and ultimately delivered to bacterial cells by Fe(III)-DFO-B complexes. The ability of DFO-B to discriminate between Fe(III) and Fe(II)/Al(III) was investigated with Natural Bond Orbital (NBO) analysis and geometry calculations of each metal-DFO-B complex. The results indicated that higher affinity for Fe(III) is not strictly a function of bond length but also the degree of Fe-O covalent bonding.  相似文献   

20.
A sample of the sediment-water column interface which lies on the continental shelf under the Peru upwelling regime, has been examined for fatty acids, fatty alcohols, ketones and hydrocarbons. Fatty acids were the most abundant compound class, ranging from C12-C24, with 16:0 as the major component (765.5 μg/g dry sediment). The alcohols were dominated by 3,7,11,15-tetramethylhexadeca-2-en-ol (phytol), with even-chain n-alcohols in the range C14-C20. The ketones consisted of C37-C39 di- and tri-unsaturated alken-2-ones and alken-3-ones. Both alkanes and alkenes were present in the hydrocarbon fraction; the alkanes ranging from C13 — C20 and comprising both straight chain and isoprenoid compounds; the alkenes consisting of isomeric pairs of C25 branched trienes and tetraenes. The data indicate that the organic content has been contributed very largely from marine sources (probably mainly from phytoplankton and bacteria), showing little terrigenous influence. The presence of labile compounds such as polyunsaturated fatty acids (with two to six double bonds), implies that the sediment has undergone very little diagenetic alteration, and the lipids are probably largely unchanged from the state in which they actually reached the sediment. They may therefore serve as a useful baseline in assessing diagenesis in older sediments, where diagenetic transformations are more advanced.  相似文献   

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