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91.
Sujittra Youngme Pongthipun Phuengphai Gerard A. van Albada Jan Reedijk 《Inorganica chimica acta》2005,358(3):849-853
A novel tetranuclear μ3,η3- Cu(II) complex with a new coordination mode of a hydrogenphosphato bridge, [Cu4(di-2-pyridylamine)4(μ3,η3-HPO4)2(H2O)2(NO3)2](NO3)2(H2O)2 has been synthesised and characterised structurally, spectroscopically and magnetically. The geometry around the Cu(II) ions is distorted square pyramidal for Cu(1) and an intermediate between square pyramidal and trigonal pyramidal. The magnetic susceptibility measurements have been fit for a weak antiferromagnetic interaction of J = −10.3(1) cm−1 between outer Cu ions and J = −5.3(2) cm−1 between inner Cu atoms. 相似文献
92.
A multichannel microcalorimeter of the heat-conduction type was equipped with a prototype of a perfusion vessel and was used to measure the total activity during long time periods in natural, aquatic sedimnet samples from aerobic environments. The effect of addition of organic substances, a pollutant and bacteria was studied. The water phase of the sediment phase of the sediment samples was aerated with humidified air and stirred uring measurements. The total activity of the actual sediment was also measured in an ampoule system, for comparison. Aeration of the samples led to an increased heat production rate. 相似文献
93.
Anaerobic and aerobic oxidation of ferrous iron at neutral pH by chemoheterotrophic nitrate-reducing bacteria 总被引:11,自引:0,他引:11
Nine out of ten anaerobic enrichment cultures inoculated with sediment samples from various freshwater, brackish-water, and
marine sediments exhibited ferrous iron oxidation in mineral media with nitrate and an organic cosubstrate at pH 7.2 and 30° C.
Anaerobic nitrate-dependent ferrous iron oxidation was a biological process. One strain isolated from brackish-water sediment
(strain HidR2, a motile, nonsporeforming, gram-negative rod) was chosen for further investigation of ferrous iron oxidation
in the presence of acetate as cosubstrate. Strain HidR2 oxidized between 0.7 and 4.9 mM ferrous iron aerobically and anaerobically
at pH 7.2 and 30° C in the presence of small amounts of acetate (between 0.2 and 1.1 mM). The strain gained energy for growth
from anaerobic ferrous iron oxidation with nitrate, and the ratio of iron oxidized to acetate provided was constant at limiting
acetate supply. The ability to oxidize ferrous iron anaerobically with nitrate at approximately pH 7 appears to be a widespread
capacity among mesophilic denitrifying bacteria. Since nitrate-dependent iron oxidation closes the iron cycle within the anoxic
zone of sediments and aerobic iron oxidation enhances the reoxidation of ferrous to ferric iron in the oxic zone, both processes
increase the importance of iron as a transient electron carrier in the turnover of organic matter in natural sediments.
Received: 24 April 1997 / Accepted: 22 September 1997 相似文献
94.
K. Bester 《Helgoland Marine Research》2000,54(2-3):95-98
In the German Wadden Sea there has been a remarkable decline in seagrass beds. It was the aim of this study to test whether
herbicide contamination could be a reason for this. Concentrations of triazine herbicides such as atrazine, simazine and terbutylazine
as well as phenylurea herbicides were measured in Wadden Sea sediments within or in the neighbourhood of seagrass meadows.
Sediments were thus used as a marker for medium-term contamination of the Wadden Sea. The respective concentrations were examined
in relation to the density and status of the seagrass meadows. Preliminary results show that there may be a connection between
seagrass decline and herbicide contamination in the parts of the Wadden Sea sampled. A comparison with other contamination
is also given.
Received: 11 January 1999 / Received in revised form: 1 December 1999 / Accepted: 8 December 1999 相似文献
95.
This study provides some results about microbial activity in salt marsh sediments. Microbial activity was determined by profiling
extracellular enzyme activities in three Tagus estuary marshes and in two sediments horizons: surface layer (0–2 cm) and depth
(8–10 cm). Five enzymatic activities were examined (β-glucosidase, cellulase, alkaline phosphatase, potential nitrification and nitrate reductase). All extracellular enzymatic
activities were highest in the surface layer and decreased with depth. β-glucosidase and alkaline phosphatase prevailed both in surface sediments (1150 and 1200 ηmol h−1 g−1, respectively) and in deeper sediments (150 and 200 ηmol h−1 g−1, respectively). Microbial activities differed significantly between salt marshes. The marsh location in the estuary seemed
to contribute to these differences: marshes located in the proximity of urbanised and industrial areas had higher microbial
activities. 相似文献
96.
Micheal J. Gehron John D. Davis Glen A. Smith David C. White 《Journal of microbiological methods》1984,2(3):165-176
Many gram-positive bacteria form substituted polymers of glycerol and ribitol phosphate esters known as teichoic acids. Utilizing the relative specificity of cold concentrated hydroflouric acid in the hydrolysis of polyphosphate esters it proved possible to quantitatively assay the teichoic acid-derived glycerol and ribitol from gram-positive bacteria added to various soils and sediments. The lipids are first removed from the soils or sediments with a one phase chloroform-methanol extraction and the lipid extracted residue is hydrolyzed with cold concentrated hydrofluoric acid. To achieve maximum recovery of the teichoic acid ribitol, a second acid hydrolysis of the aqueous extract is required. The glycerol and ribitol are then acetylated after neutralization and analyzed by capillary gas-liquid chromatography. This technique together with measures of the total phospholipid, the phospholipid fatty acid, the muramic acid and the hydroxy fatty acids of the lipopolysaccharide lipid A of the gram-negative bacteria makes it possible to describe the community structure of environmental samples. The proportion of gram-positive bacteria measured as the teichoic acid glycerol and ribitol is higher in soils than in sediments and increases with depth in both. 相似文献
97.
To investigate the impact of water impoundment on the metal contamination in sediments cores from the three tributaries of Three Gorges Reservoir (TGR), the concentrations, distribution, bioavailability, and potential risk of eight trace metals between summer and winter were analyzed using sequential analysis. The mean contents of all studied metals were higher than the geochemical background value, and were higher in summer than in winter. The results of the partitioning study indicated that Cr and Ni prevailed in the residual fraction, while a small proportion was found in the easily soluble fractions. Cu and Zn were distributed mainly in the residual and reducible fraction, while Cd and Pb were predominantly associated with non-residual fractions. These observations suggested that the most easily mobilized metals in the study area were Cd and Pb. The mean enrichment factors (EF) of Cu, Zn, Cd and Hg were higher than 1.5, revealing the potential anthropogenic inputs, whilst the EF of other metals remained within the range of natural variability. The positive correlation between non-residual Cu, Zn and Cd and their EF values further indicated that anthropogenic inputs were the potentially major contributor for the enrichment of Cu, Zn and Cd in TGR sediments. The results evaluated by both potential ecological risk index and modified risk assessment code (mRAC) of all sampling sites demonstrated the relatively high potential risk of sediment contamination effect in TGR. 相似文献
98.
Kirsten Küsel Tanja Trinkwalter Richard Devereux 《Journal of experimental marine biology and ecology》2006,337(1):49-58
Sediment microbial communities are important for seagrass growth and carbon cycling, however relatively few studies have addressed the composition of prokaryotic communities in seagrass bed sediments. Selective media were used enumerate culturable anaerobic bacteria associated with the roots of the seagrass, Halodule wrightii, the fresh to brackish water plant, Vallisneria americana, and the respective vegetated and unvegetated sediments. H. wrightii roots and sediments had high numbers of sulfate-reducing bacteria whereas iron-reducing bacteria appeared to have a more significant role in V. americana roots and sediments. Numbers of glucose-utilizing but not acetate-utilizing iron reducers were higher on the roots of both plants relative to the vegetated sediments indicating a difference within the iron reducing bacterial community. H. wrightii roots had lower glucose-utilizing iron reducers, and higher acetogenic bacteria than did V. americana roots suggesting different aquatic plants support different anaerobic microbial communities. Sulfur-disproportionating and sulfide-oxidizing bacteria were also cultured from the roots and sediments. These results provide evidence of the potential importance of sulfur cycle bacteria, in addition to sulfate-reducing bacteria, in seagrass bed sediments. 相似文献
99.
Selective substitution of the chlorine atom coordinated to cobalt in the paramagnetic Mo3(CoCl)S4(dmpe)3Cl3 (dmpe = 1,2-bis(dimethylphosphanyl) ethane) complex with a S = 1/2 ground state has been achieved by iodine oxidation to afford the also paramagnetic [Mo3(CoI)S4(dmpe)3Cl3]I ([1]I) salt with a S = 1 ground state in almost quantitative yield. Replacement of chorine by iodine has no significant effect on the structural and electrochemical properties of the Mo3CoS4 system. Metathesis of the [1]I salt with the paramagnetic nickel anionic dithiolate [Ni(mnt)2]− (mnt = maleonitrilodithiolate) affords [1]2[Ni(mnt)2]. The stoichiometry evidenced by X-ray analysis reveals that reduction of the [Ni(mnt)2]− radical to the corresponding diamagnetic closed shell [Ni(mnt)2]2− dianion, presumably via dismutation, has occurred during the metathesis process. The crystal structure of [1]2[Ni(mnt)2] consists of [Ni(mnt)2]2− dianions sandwiched by two cluster 1+ cations which yield {1+·[Ni(mnt)2]2−·1+} subunits arranged along the crystallographic c axis. Magnetic susceptibility measurements for [1]2[Ni(mnt)2] show a χT product of 0.99 emu K/mol largely unchanged in the 10-300 K range. This behavior agrees with the presence of an S = 1 cluster 1+ cation while the Ni(mnt)2 moiety does not contribute to the paramagnetism of the sample. 相似文献
100.