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1.
DFeRB和SRB对冰封期铁与硫还原的影响研究 总被引：1，自引：1，他引：0
铁硫还原对环境中碳、氮、磷等生源要素的环境地球化学行为及重金属等污染物的形态和生物有效性有重要影响,而微生物在铁硫还原过程中起关键控制作用。本文针对北方寒旱区冰封期较长的特点,采用室内模拟研究,重点探究了冰封期异化铁还原菌(Dissimilatory iron reducing bacteria,DFeRB)和硫酸盐还原菌(Sulfate reducing bacteria,SRB)介导的还原过程对铁硫行为的影响以及铁硫还原的耦合关系。结果表明,铁硫共存时,DFeRB和SRB的存在影响铁硫自身的电子传递,使铁和硫的还原过程更为复杂。DFeRB和SRB的还原倾向性存在明显差异。铁硫共存时,DFeRB更有利于铁的异化还原,DFeRB对铁的影响程度强于SRB。无论是DFeRB还是SRB,铁和还原菌同时存在时对硫酸盐还原的促进作用更强。DFeRB和SRB介导下的异化铁还原和硫酸盐还原存在明显的耦合关系,且存在显著的阶段性差异。研究表明冰封期DFeRB和SRB仍具有生物活性及还原能力,且对异化铁还原和硫酸盐还原有明显促进作用。 相似文献
2.
利用基因芯片技术在转录水平上对过铁胁迫条件下酵母中硫转运体系进行了分析。结果表明,在铁过量的时候,酵母硫转运系统相关基因上调表达。认为酵母在过铁条件下会增加细胞中的硫转运,以便维持细胞的铁稳态,降低过量铁对细胞的毒害作用。 相似文献
3.
A Ni-Fe-Cu center in a bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase 总被引：1，自引：0，他引：1
Doukov TI Iverson TM Seravalli J Ragsdale SW Drennan CL 《Science (New York, N.Y.)》2002,298(5593):567-572
A metallocofactor containing iron, sulfur, copper, and nickel has been discovered in the enzyme carbon monoxide dehydrogenase/acetyl-CoA (coenzyme A) synthase from Moorella thermoacetica (f. Clostridium thermoaceticum). Our structure at 2.2 angstrom resolution reveals that the cofactor responsible for the assembly of acetyl-CoA contains a [Fe4S4] cubane bridged to a copper-nickel binuclear site. The presence of these three metals together in one cluster was unanticipated and suggests a newly discovered role for copper in biology. The different active sites of this bifunctional enzyme complex are connected via a channel, 138 angstroms long, that provides a conduit for carbon monoxide generated at the C-cluster on one subunit to be incorporated into acetyl-CoA at the A-cluster on the other subunit. 相似文献
4.
The segregation of sulfur in liquid cast iron was studied under conditions of microgravity on Spacelab 1. A rod of cast iron containing carbon, silicon, sulfur, and phosphorus was unidirectionally solidified at four different rates. The influence of sulfur on the graphite structure and the stability of an aluminum oxide skin deposited on the surface of the specimen were investigated. 相似文献
5.
Coal combustion is the largest single source of sulfur oxide pollution. Treatment of some major representative U.S. coals with aqueous ferric solution removes 40 to 75 percent of the sulfur content through near quantitative oxidation of the pyritic sulfur contained in the coal matrix. Elemental sulfur and iron sulfate are recovered as products of the reaction. Engineering assessment indicates that the system, when fully developed, offers high potential for the economic abatement of sulfur oxide pollution. 相似文献
6.
Carter JL 《Science (New York, N.Y.)》1973,181(4102):841-842
A probable vapor-liquid-solid (VLS) type of growth has been discovered for the first time in nature on the surface of lunar rock 15015. Scanning electron microprobe and energy dispersive x-ray data indicate that the growth occurs as metallic iron stalks from about 0.015 to 0.15 micrometer in diameter, with bulbous tips consisting of a mixture of iron and sulfur and measuring from about 0.03 to 0.2 micrometer in diameter. The stalk length is two to ten times the bulb diameter. 相似文献
7.
Rieder R Gellert R Anderson RC Brückner J Clark BC Dreibus G Economou T Klingelhöfer G Lugmair GW Ming DW Squyres SW d'Uston C Wänke H Yen A Zipfel J 《Science (New York, N.Y.)》2004,306(5702):1746-1749
The Alpha Particle X-ray Spectrometer on the Opportunity rover determined major and minor elements of soils and rocks in Meridiani Planum. Chemical compositions differentiate between basaltic rocks, evaporite-rich rocks, basaltic soils, and hematite-rich soils. Although soils are compositionally similar to those at previous landing sites, differences in iron and some minor element concentrations signify the addition of local components. Rocky outcrops are rich in sulfur and variably enriched in bromine relative to chlorine. The interaction with water in the past is indicated by the chemical features in rocks and soils at this site. 相似文献
8.
Spiro CL Wong J Lytle FW Greegor RB Maylotte DH Lamson SH 《Science (New York, N.Y.)》1984,226(4670):48-50
High-resolution x-ray absorption spectroscopy was used to probe the chemical and structural environments of sulfur in coal. Measurement of the sulfur Kedge spectra down to 2472.0 electron volts under nonvacuum conditions was made possible in an all-helium path, and a Stern-Heald type ion chamber was used for fluorescence detection. For a number of selected sulfur-containing minerals and organic model compounds, results show that near-edge spectral features are diagnostic for sulfur in specific organic moieties such as thiols, disulfides, and various heterocyclics, as well as in mineral sulfide and sulfate phases. The spectrum of a model system containing 35 percent iron pyrite and 65 percent benzothiophene was found to match the observed spectral features of a bituminous coal from the eastern United States. 相似文献
9.
Einsle O Tezcan FA Andrade SL Schmid B Yoshida M Howard JB Rees DC 《Science (New York, N.Y.)》2002,297(5587):1696-1700
A high-resolution crystallographic analysis of the nitrogenase MoFe-protein reveals a previously unrecognized ligand coordinated to six iron atoms in the center of the catalytically essential FeMo-cofactor. The electron density for this ligand is masked in structures with resolutions lower than 1.55 angstroms, owing to Fourier series termination ripples from the surrounding iron and sulfur atoms in the cofactor. The central atom completes an approximate tetrahedral coordination for the six iron atoms, instead of the trigonal coordination proposed on the basis of lower resolution structures. The crystallographic refinement at 1.16 angstrom resolution is consistent with this newly detected component being a light element, most plausibly nitrogen. The presence of a nitrogen atom in the cofactor would have important implications for the mechanism of dinitrogen reduction by nitrogenase. 相似文献
10.
Annual growth rings from short-leaf pine trees in the Great Smoky Mountains National Park show suppressed growth and increased iron content between 1863 and 1912, a period of smelting activity and large sulfur dioxide releases at Copperhill, Tennessee, 88 kilometers upwind. Similar growth suppression and increases of iron and other metals were found in rings formed in the past 20 to 25 years, a period when regional fossil fuel combustion emissions increased about 200 percent. Metals concentrations in phloem and cambium are high, but whether they exceed toxic thresholds for these tissues is not known. 相似文献
11.
Stratigraphic records from four sediment cores collected along a transect across the Chesapeake Bay near the mouth of the Choptank River were used to reconstruct a 2000-year history of anoxia and eutrophication in the Chesapeake Bay. Variations in pollen, diatoms, concentration of organic carbon, nitrogen, sulfur, acid-soluble iron, and an estimate of the degree of pyritization of iron indicate that sedimentation rates, anoxic conditions and eutrophication have increased in the Chesapeake Bay since the time of European settlement. 相似文献
12.
Atmospheric dimethyl sulfide (DMS) measurements were made on the Atlantic Coast of the United States at Wallops Island and Cape Henry, Virginia, during June 1975. The very low concentrations, typically less than 30 parts per trillion observed at the Cape Henry site, were thought to result from the smog chemistry associated with the Norfolk metropolitan area. Atmospheric DMS concentrations at the Wallops Island site were much higher, having a geometric mean of 58 parts per trillion and a geometric standard deviation of 2.1. At this site the DMS source strength was estimated to be 6 milligrams of sulfur per square meter per year. Because of wind conditions during this experiment, the DMS source strength is thought to be representative of the DMS source strength of the ocean in the Wallops Island area and is much less than the 130 milligrams of sulfur per square meter per year needed to balance the ocean-atmosphere portion of the global sulfur budget. 相似文献
13.
Solutions of potassium chloride (pH-buffered and 1-molal) equilibrated at 350 degrees C with pyrrhotite, pyrite, and magnetite contained approximately 1 millimole of reduced sulfur and less than 0.1 millimole of oxidized sulfur per kilogram. Similar solutions equilibrated with pyrite, magnetite, and hematite contained approximately 1 millimole of reduced sulfur, but 3 to 6 millimoles of oxidized sulfur per kilogram. Both types of solutions contained less than 0.1 millimole of iron per kilogram at pH >/= 6 and approximately 100 millimoles per kilogram at pH 2. 相似文献
14.
Hayes KF Roe AL Brown GE Hodgson KO Leckie JO Parks GA 《Science (New York, N.Y.)》1987,238(4828):783-786
A novel application of x-ray absorption spectroscopy has provided structural information for ions sorbed at oxide-water interfaces. As an example, in situ extended x-ray absorption fine structure (EXAFS) measurements of adsorbed selenate and selenite ions at ah alpha-FeOOH(goethite)-water interface have been performed; these measurements show that selenate forms a weakly bonded, outer-sphere complex and that selenite forms a strongly bonded, inner-sphere complex. The selenite ion is bonded directly to the goethite surface in a bidentate fashion with two iron atoms 3.38 angstroms from the selenium atom. Adsorbed selenate has no iron atom in the second coordination shell of selenium, which indicates retention of its hydration sphere upon sorption. This method provides direct structural information for adsorbed species at solid-liquid interfaces. 相似文献
15.
SHEN Xiao-yun 《中国农业科学(英文版)》2011,10(10):1618-1623
The clinical symptoms of a disorder which is known locally as “wool-eating ailment” in Guizhou semi-fine wool sheep in the Weining County of Guizhou Province,China,are poor weight gain,lost appetite,pica,emaciation,and wool-eating.The mineral composition of forage,and samples of blood,liver and wool from Guizhou semi-fine wool sheep in affected ranches were compared with those from the unaffected areas.The mean concentration of iron in forage from affected pasture was significantly higher than that from the unaffected pasture.The mean concentration of sulfur in forage from the affected and unaffected pasture was similar and within normal ranges.The mean concentration of sulfur in blood,liver and wool from the affected Guizhou semi-fine wool sheep was significantly lower than that from the unaffected sheep while the content of iron in blood,liver and wool from the affected sheep was significantly higher than that from the unaffected sheep.Oral administration of calcium sulfate prevented and cured the disease.We concluded that the disease of Guizhou semi-fine wool sheep in the Weining County is due to S deficiency caused by the high Fe in forages. 相似文献
16.
SUMI Katsuhiro 《东北农业大学学报(英文版)》2008,15(4):76-79
Iron sulfide is an important reductive pollutant in aquatic sediment,so that increasing attentions have been paid to it in recent years.In this paper,the formation of iron sulfide in water-body sediment was introduced.Moreover,its adverse influences upon environment were summarized,including direct contribution to deficiency of dissolved oxygen in water,association with eutrophication in water-bodies and impact on geochemical sulfur cycle.Since conventional chemical analysis for iron sulfide has several disadvantages,new technique for rapid determination of iron sulfide on-line was prospected. 相似文献
17.
T Okuchi 《Science (New York, N.Y.)》1997,278(5344):1781-1784
Because of dissolution of lighter elements such as sulfur, carbon, hydrogen, and oxygen, Earth's outer core is about 10 percent less dense than molten iron at the relevant pressure and temperature conditions. To determine whether hydrogen can account for a major part of the density deficit and is therefore an important constituent in the molten iron outer core, the hydrogen concentration in molten iron was measured at 7.5 gigapascals. From these measurements, the metal-silicate melt partitioning coefficient of hydrogen was determined as a function of temperature. If the magma ocean of primordial Earth was hydrous, more than 95 mole percent of H2O in this ocean should have reacted with iron to form FeHx, and about 60 percent of the density deficit is reconciled by adding hydrogen to the core. 相似文献
18.
Ilmenite, chrome-titanium spinel, ulv?spinel, troilite, native iron, iron-nickel alloy, and native copper are present. In addition mackinawite is provisionally identified. Three additional opaque phases are present but not identified. Modal analysis indicates that the breccia is enriched in iron relative to ilmenite and troilite, and the high nickel content of this iron suggests that it is largely of meteoritic origin. The bulk composition of liquids corresponding to iron/troilite droplets in the rocks indicates an oxygen fugacity no greater than 10(-15.5) and a sulfur fugacity of 10(-6) bar. Complete melting of rocks produced a glass containing complex iron/troilite globules and skeletal ilmenites. 相似文献
19.
Hematite nanospheres of possible colloidal origin from a precambrian banded iron formation 总被引：1，自引：0，他引：1
Exceptionally small spheres (nanospheres) of hematite (diameters between 120 and 200 nanometers) occur in the Marra Mamba Iron Formation of the Hamersley Basin, Australia. The nanospheres are clustered into small aggregates and may have formed by structural ordering and dehydration of colloidal iron hydroxide particles. Individual spheres consist of numerous thin, curved hematite platelets surrounding a central void that is approximately half the diamter of the sphere; this texture suggests that they formed by a volume reduction of the original colloidal particles by approximately 12.5%. The occurrence of hematite nanospheres supports the hypothesis that some ofthe iron was deposited colloidally during the development ofbanded iron formations, approximately 2.5 billion years ago. 相似文献
20.
In the hypothesis advanced here it is supposed that the field, in which rocks at the lunar surface acquired the remanent magnetization found through the Apollo project, arose from permanent magnetization of the deep interior of the moon. This theory involves the assumption that the moon, apart from a surface shell, accreted cold and remained below the Curie point of iron until sometime later than 3 x 10(9) years ago. The magnetization was acquired as the moon formed in a gas sphere in the strong magnetic field of the early sun. 相似文献