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681.
Complex substrates are degraded in anoxic sediments by the concerted activities of diverse microbial communities. To explore the effects of substrate complexity on carbon transformations in permanently cold anoxic sediments, four substrates—Spirulina cells, Isochrysis cells, and soluble high molecular weight carbohydrate-rich extracts of these cells (Spir-Ex and Iso-Ex)—were added to sediments collected from Svalbard. The sediments were homogenized, incubated anaerobically in gas-tight bags at 0°C, and enzyme activities, fermentation, and terminal respiration were monitored over a 1134 h time course. All substrate additions yielded a fraction (8%-13%) of carbon that was metabolized to CO2 over the first 384 h of incubation. The timecourse of VFA (volatile fatty acid) production and consumption, as well as the suite of VFAs produced, was similar for all substrates. After this phase, pathways of carbon degradation diverged, with an additional 43%, 32%, 33%, and 8% of Isochrysis, Iso-Ex, Spirulina, and Spir-Ex carbon respired to CO2 over the next 750 h of incubation. Somewhat surprisingly, the soluble, carbohydrate-rich extracts did not prove to be more labile substrates than the whole cells from which they were derived. Although Spirulina and Iso-Ex differed in physical and chemical characteristics (solid/soluble, C/N ratio, lipid and carbohydrate content), nearly identical quantities of carbon were respired to CO2. In contrast, only 15% of Spir-Ex carbon was respired, despite the initial burst of activity that it fueled, its soluble nature, and its relatively high (50%) carbohydrate content. The microbial community in these cold anoxic sediments clearly has the capacity to react rapidly to carbon input; extent and timecourse of remineralization of added carbon is similar to observations made at much higher temperatures in temperate sediments. The extent of carbon remineralization from these specific substrates, however, would not likely have been predicted on the basis of general substrate characteristics. 相似文献
682.
683.
Estuaries, the interface of interaction of fluvial discharge and marine action serve as temporary repositories of materials (solid and dissolved) before finally exporting them to sea. This interchange of material is dependant on a range of factors such as those due to tidal variation, fluvial flows and estuarine morphodynamics. The efficacy of transfer of materials to the marine environment is important for estuarine health particularly in estuaries located in highly developed areas such as the major coastal metropolitan areas of many countries. This study assesses this efficacy for three estuaries of the eThekwini Municipality (TM) of the city of Durban, South Africa which maintains an open mouth status, ensuring tidal exchange through the year. The net flux of nitrates was measured for these estuaries on a seasonal basis for both spring and neap tides. Results indicate that although there is a net export of nitrates to the nearshore, there were instances, particularly on the spring tide, when a net import of nitrates into the estuary occurred. Data analysis reveal summer and neap tide flux dominance for the Tongati and Mgeni estuaries whilst the Isipingo Estuary exhibited larger flux variance for spring tides and the spring season. The origin of the latter is likely derived from unusually high biotic decomposition at sea and/or the longshore transport of decomposing sewage outfall. This creates an added dimension for consideration in estuarine management plans. Taking all three estuaries studied into consideration, a net export of nitrates for all seasons for the TM was measured with a clear seasonal influence detected where high rainfall seasons led to greater export as a consequence of greater fluvial flows, erosion and leaching of agricultural lands and, longer ebb duration and flows. 相似文献
684.
Assessment of cement’s dust impact on the soil using principal component analysis and GIS 总被引:1,自引:1,他引:1
Z. Zerrouqi M. Sbaa Ph.D. M. Oujidi Ph.D. M. Elkharmouz S. Bengamra A. Zerrouqi 《International Journal of Environmental Science and Technology》2008,5(1):125-134
To evaluate the impact of the cement’s dust emitted by the eastern Moroccan cement factory (Oujda Holcim) and deposited on the soil of the Ain Lahjar commune, 58 samples of soil were collected around the factory on a radius of 3 km approximately. The physicochemical analyses of the upper 3 cm of the soil surface samples correspond to the pH, electrical conductivity, the chlorides and the oxides of Ca, Al, Fe, K, Mn, S and Si which were analyzed by the fluorescence of X-rays. The preliminary results demonstrate that this dust are especially basic and contain a high free lime (43% CaO). The principal component analysis (applied on the 58 samples of soil) allows deducting that the free lime and the sulfur oxide are the tracer elements of this form of pollution. Furthermore, the spatial projection of the factor scores of the principal component analysis using the geographical information system permits to determine the spatial distribution of more polluted areas of soils as well as to estimate their surface (63.3% of the survey zone). 相似文献
685.
T. A. Myskova N. M. Ivanov M. A. Korsakova R. I. Mil’kevich N. G. Berezhnaya S. L. Presnyakov 《Stratigraphy and Geological Correlation》2013,21(4):337-358
The geological, geochemical, and isotopic-geochronological data obtained for Sumian moderate-basic metavolcanites of Shombozero and Lekhta structures of the Panayarvi-Vygozero belt shows that the Tunguda Formation is confined to the Paleoproterozoic structural and material complex. This formation is represented by the complex of weakly differentiated andesitobasalts and andesites of calc-alkaline series with higher contents of MgO and moderate contents of Al2O3 and rare earth elements. The rocks of the Tunguda Formation are different from the Late Archean basic rocks of the Hiziyarvi Formation represented mainly by tholeiitic basalts with low REE contents and undifferentiated spectrum of REE distribution. The age of volcanites of the Tunguda Formation was determined to be 2439 ± 21 Ma. The xenogenic zircons from metaandesites of the Tunguda Formation have Neoarchean age according to the 207Pb/206Pb ratio (from 2536 ± 4 to 2825 ± 7 Ma). The Neoarchean zircons, a negative value of ?Nd (?3.8), and indicative geochemical parameters are evidence that the crustal component took part in formation of the protolith of the studied rocks. 相似文献
686.
687.
N. V. Chukanov R. K. Rastsvetaeva S. M. Aksenov I. V. Pekov D. I. Belakovskiy G. Blass G. Möhn 《Geology of Ore Deposits》2013,55(8):663-668
A new mineral, lahnsteinite, has been found in the dump of the Friedrichssegen Mine, Bad Ems district, Rhineland-Palatinate (Rheinland-Pfalz), Germany. Lahnsteinite, occurring as colorless tabular crystals in the cavities of goethite, is associated with pyromorphite, hydrozincite, quartz, and native copper. The Mohs’ hardness is 1.5; the cleavage is perfect parallel to (001). D calc = 2.995 g/cm3, D meas = 2.98(2) g/cm3. The IR spectrum is given. The new mineral is optically biaxial, negative, α = 1.568(2), β = 1.612(2), γ = 1.613(2), 2V meas = 18(3)°, 2V calc = 17°. The chemical composition (wt %, electron microprobe data; H2O was determined by gas chromatography of ignition products) is as follows: 3.87 FeO, 1.68 CuO, 57.85 ZnO, 15.83 SO3, 22.3 H2O, total is 101.53. The empirical formula is (Zn3.3Fe0.27Cu0.11)Σ3.91(S0.98O4)(OH)5 · 3H2.10O. The crystal structure has been studied on a single crystal. Lahnsteinite is triclinic, space group P1, a = 8.3125(6), b = 14.545(1), c = 18.504(2) Å, α = 89.71(1), β = 90.05(1), γ = 90.13(1)°, V = 2237.2(3) Å3, Z = 8. The strong reflections in the X-ray powder diffraction pattern [d, Å (I, %)] are: 9.30 (100), 4.175 (18), 3.476 (19), 3.290 (19), 2.723 (57), 2.624 (36), 2.503 (35), 1.574 (23). The mineral has been named after its type locality near the town of Lahnstein. The type specimen of lahnsteinite is deposited in the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, registration number 4252/1. 相似文献
688.
V. F. Rudnitsky K. B. Aleshin A. Zh. Kuznetsov V. S. Ivanchenko 《Geology of Ore Deposits》2013,55(6):467-481
The structure of magnetite lodes is determined by iron and sulfur distribution, as well as texture and structure of ore. These features have been revealed by documentation of cores from ore intervals in exploration boreholes penetrating two main lodes 21 and 22 of the Estyunino iron deposit. The documentation of cores was accompanied by sampling for microscopic examination of texture and structure of ore and selection of Fe and S contents in ore. Then these data were summarized as sections of the lodes. It was established that the structure of magnetite lodes is characterized by conformable ore layers distinguished by texture, structure, and Fe and S contents. Banded and spotty ores containing less than 50% magnetite are predominant. Layers of homogeneous massive ore are infrequent. The textural pattern indicates a volcaniclastic nature of host rocks. The spotty texture is characteristic of hyaloclastites with vitreous shards. The banded texture with oriented distribution of fiamme is inherent to volcaniclastic rocks. In both cases, magnetite selectively replaces dark-colored vitreous fragments and is also dispersed in the salic matrix and lava fragments. No indications of crosscutting superposed relationships are observed. The available data can be satisfactorily explained by an impregnation-metasomatic mode of ore deposition. 相似文献
689.
690.
P. M. Nikolić S. Ðurić D. M. Todorović D. Vasiljević-Radović V. Blagojević P. Mihajlović J. Elazar K. T. Radulović A. I. Bojičić D. Urošević 《Physics and Chemistry of Minerals》2001,28(1):44-51
Electron transport properties of single crystal and polycrystalline natural mineral galena (PbS) samples from the Trep?a mine, Yugoslavia, were determined using the photoacoustic frequency transmission technique. Their thermal diffusivity (D T≈0.16 × 10?5 m2 s?1), the coefficient of diffusion (D between 0.15×10?2 0.16×10?2 m2 s?1) and lifetime of the excess carrier (τ≈35 μs and the front and rear recombination velocity (s g≈65.5 m s?1 and s b≈66.4 m s?1, respectively), were calculated by comparing the experimental results and the theoretical photoacoustic amplitude and phase signals. The lattice parameter obtained by X-ray work was a?=5.936?Å. The free carrier concentration of these single-crystal samples was measured using the Hall method (N?=?3×1018 cm?3). Measurements of the optical reflectivity of the same samples, as a function of wavelength, in the infrared and far infrared ranges, were performed. In the far infrared range a free electron plasma frequency was observed and numerically analyzed, using the least-squares fitting procedure. The values of optical parameters were calculated and the value of the free carrier concentration obtained by the Hall method was confirmed. 相似文献