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1.
Stuart G. Wakeham 《Geochimica et cosmochimica acta》1982,46(11):2239-2257
The vertical flux and composition of wax esters, steryl esters, triacylglycerols, and alkyldiacylglycerols in particulate matter was determined in the equatorial Atlantic Ocean by deploying sediment traps at 389, 988, 3,755 and 5,068 m. Detailed compositional analyses of these lipids were carried out by high temperature glass capillary gas chromatography and gas chromatography/mass spectrometry.The distributions of these lipids are discussed in terms of potential biological sources. Zooplankton fecal matter and intact zooplankters may represent the most important input of these compounds to the shallower two traps, while the material in the deeper two traps appears to have been biogeochemically altered. The finding of these biochemically important compounds, often unsaturated, indicates that particle transit through the water column must be relatively fast.Wax esters were most abundant in the 389 m sediment trap and decreased with increasing trap depth. Compounds ranging from C28–C44 were present at all depths. The major homologs were C32, C34 and C36, most often monounsaturated. The dominant alcohol/acid combinations in the 389 m trap were and , but in the 988 m sample, was the major wax ester. A flux maximum was observed for steryl esters at 988 m. Cholesteryl esters of C14:0, C16:1 and C16:0, and fatty acids were the dominant steryl esters. For triacylglycerols, fluxes in the 389 and 988 m traps were similar, while the deeper pair of traps contained much less triacylglycerol. C46, C48, C50 and C52 compounds were the major triacylglycerols. Constituent fatty acids in the 389 m and 988 m samples were mainly C14:0, C16:1, C16:0, C18:1 and C18:0. In the 988 m material, C20:5 and C22:6 were also dominant. A homologous series of alkyldiacylglycerols was abundant in the 389 m trap material. The alkyldiacylglycerols consisted of C46–C56 compounds composed of C16:0 alkyl moieties and C14:0, C16:0, C18:1, and C18:0 fatty acids. 相似文献
2.
Water samples collected from a slope station and two deep stations in the western basin of the Black Sea were analyzed for stenols and stanols by glass capillary gas chromatography. These results were used in conjuction with hydrographic, particulate organic carbon, and chlorophyll a data to better understand sterol sources and their transport and transformation mechanisms in anoxic basins.The total free sterol concentrations found in the surface waters were 450–500 ng/l dropping rapidly to values well below 100 ng/l at depths below the interface. In the upper 200 m of the water column a strong association of sterols with particulate matter is suggested. Structural elucidation by a gas chromatograph-mass spectrometer-computer system revealed the presence of at least sixteen different stenols and stanols in the surface waters of the Black Sea. Cholesterol, 24-methylenecholesterol and 24-methylcholesta-5,22-dien-3β-ol were the major sterols in the surface waters. Cholesterol and 24-ethylcholesterol both exhibited a subsurface maximum at the interface. In the anoxic deep waters (200–2000 m) only cholesterol and 24-ethylcholesterol were found. Two stenols were found that have not been reported in seawater: a C26 stenol with a saturated C7H15 side chain (presumably 24-norcholesterol) and 24-ketocholesterol. At least six 5α-stanols could be identified in the surface samples, each of them comprising about 10–20% of the concentration of the corresponding Δ5-stenol. From these comparatively high surface values the stanol concentrations drop rapidly to values near zero at the interface. Except for very low concentrations of 5α-cholestanol (< 4ng/l) no other stanols could be detected in the anoxic zone.From this data it appears that no detectable stenol → stanol conversion is occurring at the interface or in the deep anoxic waters of the Black Sea. 相似文献
3.
Distribution and isotopic composition (δ13C) of low molecular weight hydrocarbon gases were studied in Big Soda Lake (depth = 64 m), an alkaline, meromictic lake with permanently anoxic bottom waters. Methane increased with depth in the anoxic mixolimnion (depth = 20–35 m), reached uniform concentrations (55 μM/l) in the monimolimnion (35–64 m) and again increased with depth in monimolimnion bottom sediments (>400 μM/kg below 1 m sub-bottom depth). The μ13C[CH4] values in bottom sediment below 1 m sub-bottom depth (<?70 per mil) increased with vertical distance up the core (δ13C[CH4] = ?55 per mil at sediment surface). Monimolimnion δ13C[CH4] values (?55 to ?61 per mil) were greater than most δ13C[CH4] values found in the anoxic mixolimnion (92% of samples had δ13C[CH4] values between ?20 and ?48 per mil). No significant concentrations of ethylene or propylene were found in the lake. However ethane, propane, isobutane and n-butane concentrations all increased with water column depth, with respective maximum concentrations of 260, 80, 23 and 22 nM/l encountered between 50–60 m depth. Concentrations of ethane, propane and butanes decreased with depth in the bottom sediments. Ratios of were high (250–620) in the anoxic mixolimnion, decreased to ~161 in the monimolimnion and increased with depth in the sediment to values as high as 1736. We concluded that methane has a biogenic origin in both the sediments and the anoxic water column and that C2-C4 alkanes have biogenic origins in the monimolimnion water and shallow sediments. The changes observed in δ13C[CH4] and with depth in the water column and sediments are probably caused by bacteria] processes. These might include anaerobic methane oxidation and different rates of methanogenesis and C2 to C4 alkane production by microorganisms. 相似文献
4.
Roger A. Burke James M. Brooks William M. Sackett 《Geochimica et cosmochimica acta》1981,45(5):627-634
Light hydrocarbon (C1-C3) concentrations in the water from four Red Sea brine basins (Atlantis II, Suakin, Nereus and Valdivia Deeps) and in sediment pore waters from two of these areas (Atlantis II and Suakin Deeps) are reported. The hydrocarbon gases in the Suakin Deep brine (T = ~ 25°C, , ) are apparently of biogenic origin as evidenced by ) ratios of ~ 1000. Methane concentrations (6–8 μl/l) in Suakin Deep sediments are nearly equal to those in the brine, suggesting sedimentary interstitial waters may be the source of the brine and associated methane.The Atlantis II Deep has two brine layers with significantly different light hydrocarbon concentrations indicating separate sources. The upper brine (T = ~ 50°C, , CH4 = ~ 155 μl/l) gas seems to be of biogenic origin [], whereas the lower brine (T = ~ 61°C, , CH4 = ~ 120μl/l) gas is apparently of thermogenic origin []. The thermogenic gas resulting from thermal cracking of organic matter in the sedimentary column apparently migrates into the basin with the brine, whereas the biogenic gas is produced in situ or at the seawater-brine interface. Methane concentrations in Atlantis II interstitial waters underlying the lower brine are about one half brine concentrations; this difference possibly reflects the known temporal variations of hydrothermal activity in the basin. 相似文献
5.
The following equation has been previously developed for the drag coefficient of a sphere. In this work the authors propose a power series expansion for C0 in terms of the Reynolds number: A fifth-order polynomial permits obtaining the drag coefficient and the settling velocity of a sphere, up to a Reynolds number of 3 × 105, with an average relative error of about 2%. 相似文献
6.
Lipid fraction and cell-wall materials have been separated from three types of algae (blue green, Microcystis sp.; green, Scenedesmus sp. and diatomaceous Diatoma sp.) and their KMnO4 oxidation products (aliphatic dicarboxylic acids; aliphatic normal C14–C24 monocarboxylic acids; benzoic acid and C18 isoprenoidal ketone) examined by gas chromatography and gas chromatographymass spectrometry. The results suggest that the lipid material could make a greater contribution to polymethylene chains in kerogen than the cell-wall material, when the kerogens are mainly derived from algal components. 相似文献
7.
Art F White 《Geochimica et cosmochimica acta》1977,41(5):613-625
The coprecipitation of Na and K was experimentally investigated in aragonite. The distribution functions were determined at pH 6.8 and 8.8 over aqueous Na and K concentrations of between 5 × 10?4and 2.0 M and temperatures of between 25 and 75°C.The mole fractions of Na and K in aragonite are related to the aqueous ratios of Na and Ca by a function of the form where C0 and C1 are constants at a given temperature. This equation was derived by a statistical model assuming a heterogeneous energy distribution for the sites of incorporation. The independence of the coprecipitation process from aqueous anion activities suggests that carbonate is the only anionic species in the solid solution. 相似文献
8.
Oxygen isotope exchange between BaSO4 and H2O from 110 to 350°C was studied using 1 m H2SO4-1 m NaCl and 1 m NaCl solutions to recrystallize the barite. The slow exchange rate (only 7% exchange after 1 yr at 110°C and 91% exchange after 22 days at 350°C in 1 m NaCl solution) prompted the use of the partial equilibrium technique. However, runs at 300 and 350°C were checked by complete exchange experiments. The temperature calibration curve for the isotope exchange is calculated giving most weight to the high temperature runs where the partial equilibrium technique can be tested. Oxygen isotope fractionation factors (α) in 1 m NaCl solution (110–350°C), assuming a value of 1.0407 for αCO2H2O at 25°C, are: .These data, when corrected for ion hydration effects in solution (Truesdell, 1974), give the fractionation factors in pure water: .In the 1 m H2SO4-1 m NaCl runs, sulfur isotope fractionation between HSO?4 and BaSO4 is less than the detection limit of 0.4%. A barite-sulfide geothermometer is obtained by combining HSO?4H2S and sulfide-H2S calibration data.Barite in the Derbyshire ore field, U.K., appears to have precipitated in isotopic equilibrium with water and sulfur in the ore fluid at temperatures less than 150°C. At the Tui Mine, New Zealand, the barite-water geothermometer indicates temperatures of late stage mineralization in the range 100–200°C. A temperature of 350 ± 20°C is obtained from the barite-pyrite geothermometer at the Yauricocha copper deposit, Peru, and oxygen isotope analyses of the barite are consistent with a magmatic origin for the ore fluids. 相似文献
9.
The fractionation factors () for the reduction of CO2 to CH4 by pure cultures of methane-producing bacteria are, for Methanosarcina barkeri at 40°C, 1.045 ± 0.002; for Methanobacterium strain M.o.H. at 40°C, 1.061 ± 0.002; and, for Methanobacterium thermoautotrophicum at 65°C, 1.025 ± 0.002. These observations suggest that the acetic acid used by acetate dissimilating bacteria, if they play an important role in natural methane production, must have an intramolecular isotopic fractionation () approximating the observed fractionation. 相似文献
10.
A.E. Beswick 《Geochimica et cosmochimica acta》1973,37(2):183-208
K and Rb distributions between aqueous alkali chloride vapour phase (0.7 molar) and coexisting phlogopites and sanidines have been investigated in the range 500 to 800°C at 2000 kg/cm2 total pressure.Complete solid solution of RbMg3AlSi3O10(OH)2 in KMg3AlSi3O10(OH)2 exists at and above 700°C. At 500°C a possible miscibility gap between approximately 0.2 and 0.6 mole fraction of the Rb end-member is indicated.Only limited solid solution of Rb AlSi3O8 in KAlSi3O8 has been found at all temperatures investigated.Distribution coefficients, expressed as in solid/(Rb/K) in vapour, are appreciably temperature-dependent but at each temperature are independent of composition for low Rb end-member mole fractions in the solids. The determined values and their approximate Rb end-member mole fraction () ranges of constancy are summarized as follows: (°C)
| (°C)T | ||||
| 500 | 0–0.2 | 0–0.07 | ||
| 700 | 0–0.2 | 0–0.1 | ||
| 800 | 0–0.2 | 0–0.1 |