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31.
Tritep Vichkovitten Marianne Holmer 《Journal of experimental marine biology and ecology》2005,316(2):183-201
The influence of seagrass Zostera marina on sediment characteristics was examined in two contrasting sediments, one organic-rich and one organic-poor. The presence of plants leads to reduced sediment redox potential in both sediment types compared to bare sediment with the largest effects in the organic-poor sediment. Z. marina stimulated the sulfate reduction rates in organic-poor sediment with ∼50% and higher pools of dissolved organic carbon (DOC) were found. In contrast, sulfate reduction rates were lower in vegetated compared to bare sites in the organic-rich sediment. Despite a low contribution of dissolved carbohydrate (DCHO) to the DOC pool (<5%), the seagrass vegetation was responsible for an increase of ∼50% in DCHO pools with a peak in the root zone suggesting that Z. marina supplied DCHO to the pore waters. The Z. marina meadows also enhanced the contribution of particulate carbohydrate (PCHO) to sedimentary particulate organic carbon (POC) pools by 6-14% compared to bare sediment. Although the PCHO pools were higher in organic-rich than organic-poor sediments, the analyses of carbohydrate composition revealed that three groups of neutral sugars including glucose, galactose and mannose+xylose were the major compounds of PCHO and contributed with >60% to sedimentary carbohydrate pools at both sites. Only glucose showed depletion with depth in the vegetated sediments, whereas the percentage of ribose and rhamnose increased indicating a selective degradation of labile carbohydrates in the meadows. Galactose and mannose+xylose appeared to represent a refractory part of carbohydrate that remained after degradation of the more labile components. The sugar content was rather constant with depth at the bare organic-rich sediment indicating that only recalcitrant carbohydrate pools were buried. There was less difference in the PCHO composition profiles between vegetated and bare organic-poor sediments. 相似文献
32.
Iveta Ondrejkovi?ová Jerzy Mroziński Julia K?ak Zofia Olejnik 《Inorganica chimica acta》2008,361(8):2483-2490
The iron(II) compound of formula [Fe(NCS)2(dena)2]n (dena = N,N′-diethylnicotinamide) has been prepared by the reaction between iron(III) thiocyanate and dena in ethanol solution. The complex was characterized by elemental analysis, spectral and magnetic measurements. Single-crystal X-ray diffraction methods show that the complex, crystallizing in the triclinic space group, undergoes a phase transition between 220 K and 230 K, connected with the doubling of cell volume. Crystal structures at 230 K (1a; HT phase) and 150 K (1b; LT phase) are described and a transition mechanism is discussed. In both phases the compound has an extended chain structure, in which the neutral molecule of N,N′-diethylnicotinamide acts as a bridging ligand binding through pyridine N atom to one centre and through amide O atom to the neighbouring Fe centre. The Fe2+ ion has a slightly distorted trans-octahedral environment with FeO2N4 chromophore, and all Fe-O and Fe-N bonds in the typical for high-spin iron(II) compounds range. Variable-temperature magnetic susceptibility data in the temperature range 1.8-300 K show that iron(II) is high-spin S = 2(5T2g) and as a result effects due to zero-field splitting are anticipated at low temperatures. The IR spectrum suggested the coordination of N,N′-diethylnicotinamide to the central atom of iron(II) as a bridging ligand and NCS group as a monodentate ligand. 相似文献
33.
A copper(II) coordination polymer {[Cu2(cpa)2]}n (1) (cpaH2 = 4-carboxyphenoxyacetic acid) has been synthesized by hydrothermal technique. The X-ray structure of the compound shows that it is a 2D coordination polymer where Cu(II) ions are pentacoordinated in a square pyramidal fashion. The magnetic measurement of 1 in different magnetic fields suggest a weak ferromagnetic ordering taking place below 20 K, arising from spin canting phenomenon due to the non-coplanar basal planes of copper ions. 相似文献
34.
Four one-dimensional coordination polymers, [Ln(H2O)4(HTDA)(H2TDA)] · H2O [Ln = Sm (1) and Eu (2)]; (H3TDA = 1H-[1,2,3]-triazole-4,5-dicarboxylic acid), [Ln(H2O)4(HTDA)] · (H2TDA) · H2O [Ln = Tb (3) and Dy (4)] were prepared and characterized by IR, elemental analysis, PXRD and single-crystal X-ray diffraction. The powder and single-crystal X-ray crystallographic studies of 1-4 reveal that all compounds are one-dimensional zigzag chain structures. Luminescent studies reveal that they are potential luminescent materials. Moreover, in solution, the emission intensity of 2 increases upon the addition of Ca2+ ions, while introduction of other metal ions leads to either unchanged or decreased intensity, which indicates that 2 may be applied as a promising Ca2+-ion-selective luminescent probe. The basic magnetic properties of 1-4 were also studied. 相似文献
35.
The germinability of Chara vulgaris oospores collected from the sediments of four Ontario lakes varies considerably, ranging in germination percentage from 7% to 54%. Chemical analysis of the interstitial water of the sediments indicated that oospores with low germination occurred in lakes which have high acid volatile sulfides (H2S, FeS, HS−) and high soluble Fe2+. The inhibitory effects of sediment on oospore germination were demonstrated by transplant experiments, and suggested that sulfide was the toxic agent. Exposure of high-germinating sedimentary oospores to free sulfide concentrations greater than 2.0 mM caused a greater than 30% reduction in oospore germination. The presence of sulfide in sediments was shown to result from sulfate reduction by bacteria in sediment pore water of those lakes where oospore viability was lowest. Differences in oospore germination percentage appear, therefore, to be due to the toxicity of H2S produced in the sediment, either by a direct effect on the oospore, or on the parent plants. 相似文献
36.
Hiroshi Sakiyama Akihiko Sugawara Masatomi Sakamoto Kei Unoura Katsuya Inoue Mikio Yamasaki 《Inorganica chimica acta》2000,310(2):163-168
Dinuclear manganese(II) complexes [Mn2(bomp)(PhCO2)2]BPh4 (1), [Mn2(bomp)(MeCO2)2]BPh4 (2), and [Mn2(bomp)(PhCO2)2]PF6 (3) were synthesized with a dinucleating ligand 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenol [H(bomp)]. Dinuclear zinc complex [Zn2(bomp)(PhCO2)2]PF6 (4) was also synthesized for the purpose of comparison. X-ray analysis revealed that the complex 1·CHCl3 contains two manganese ions bridged by the phenolic oxygen and two benzoate groups, forming a μ-phenoxo-bis(μ-benzoato)dimanganese(II) core. Magnetic susceptibility measurements of 1–3 over the temperature range 1.8–300 K indicated antiferromagnetic interaction (J=−4 to −6 cm−1). Cyclic voltammograms of 3 showed a quasi-reversible oxidation process at +0.9 V versus a saturated sodium chloride calomel reference electrode, assigned to MnIIMnII/MnIIMnIII. 相似文献
37.
正厌氧氨氧化作用(Anaerobic Ammonia Oxidation,Anammox)是细菌在厌氧条件下,以NO_2~-为电子受体,以铵离子为电子供体的氧化还原反应[1]。厌氧氨氧化细菌的生长极为缓慢,只能在高菌体浓度时才显示其氨氧化活性,且对氧的存在十分敏感,所以传统的微生物纯化、分离和培养的方法并不适用于厌氧氨氧化细菌。由于微生物可培养技术的局限性,因此实时荧光定量PCR技术成为定量描述难培养微生物分布和丰度的有力手段[2]。宋亚娜等[3]。利用荧光定量PCR方法对土壤中厌氧氨氧化细菌进行了检测,但对于高原湖泊底泥中厌氧氨氧化细 相似文献
38.
Abstract Microhabitats and survival of sulfate-reducing bacteria (SRB) in an oxic surface sediment of a seawater lake were examined. The size of fractionation of the sediment suspension showed that most of SRB were associated with sediment particles larger than 10 μm. The D values (time in h required to destroy 90% of the initial viable population) for SRB in the whole sediment suspension and for SRB i n the < μ m and the < 5 μ m fractions were, respectively, 23.7, 10 and 4 when the SRB were exposed to air. Survival of the FeS-associated Desulfovibrio desulfuricans ( D value, 9.3) was higher than that of the free-living ones ( D value, 1.8). These results show that particle-associated SRB are more protected against oxygen than free-living ones in oxic sediments. 相似文献
39.
Critical review of the IMO international convention on the management of ships’ ballast water and sediments 总被引:2,自引:0,他引:2
Stephan Gollasch Matej David Matthias Voigt Egil Dragsund Chad Hewitt Yasuwo Fukuyo 《Harmful algae》2007,6(4):585-600
The International Maritime Organization (IMO), the United Nations body which administers the international regulatory regime for shipping, noted the negative impact of non-indigenous organisms transported in the ballast water of ships already in the early 1970s. Consequently, measures were taken with the aim to minimize ballast water mediated species invasions through IMO Marine Environmental Protection Committee (MEPC) Resolutions. As a result of long-term IMO efforts, it was determined that an international convention would best meet the needs of the global community, hence the International Convention for the Control and Management of Ships’ Ballast Water and Sediments was adopted in a Diplomatic Conference in 2004 and is now open for signature by IMO Member States. This very complex (and by no means “simple”) Convention aims to reduce the transfer and subsequent impact of aquatic organisms in the ballast water and sediment of ships by acting to reduce the load of these organisms in discharged ballast water. A set of 15 guidelines provides technical guidance for the implementation of the Convention principles. This review considers critical aspects of this Convention and selected guidelines seen from perspectives of biological, shipping and regulatory concerns. 相似文献
40.
Extensive chemical data for the Lake Biwa sediments were examined with statistical factor analysis to find any correlation
patterns among elements and among samples. Based on those patterns, a series of x-y correlation plots of the concentrations of selected elements was constructed to see in detail how the concentrations of elements
vary among different sample groups and explain the observed variation patterns. 相似文献