Benthic mucilaginous aggregates in the Mediterranean Sea: Origin, chemical composition and polysaccharide characterization     

Gianfranco Sartoni  Ranieri Urbani  Paola Sist  Daniela Berto  Caterina Nuccio  Michele Giani   《Marine Chemistry》2008,111(3-4):184-198

Benthic mucilaginous aggregates are frequently formed in various parts of the Mediterranean basin, as in the Tyrrhenian and Adriatic Seas. Notwithstanding their wide spatial distribution, the role played by these aggregates in the biogeochemical cycling of organic matter is still largely unknown.The characteristics of the benthic aggregates examined in the present study showed that they are different from other mucilaginous aggregates, such as the “pelagic” ones that can form in the same areas in the water column and subsequently sediment to the seafloor. The aggregates are usually formed of structures of the filamentous macroalgae Acinetospora crinita, Chrysonephos lewisii and Nematochrysopsis marina. The elemental composition of the aggregates showed a marine macrophyte origin on the basis of the bulk organic matter content of the aggregates. Carbohydrates and proteins account for 26.6 to 55.9% of the organic carbon in the mucilage, respectively. Monosaccharide composition of exopolysaccharides in the mucilage aggregates revealed a characteristic pattern, with galactose, xylose or mannose and fucose as the major components. The relatively high content of deoxysugars is another distinctive feature. The abundant sulphate and uronic groups present in the polysaccharides in addition to their macromolecular dimensions and elongation contribute to inter-chain aggregation. Electron microscopic observations suggest that the polysaccharide fraction is the main macromolecular component in the formation of the persistent gel network in the aggregates.  相似文献   

The role of land surface versus drainage network characteristics in controlling water quality and quantity in a small urban watershed          下载免费PDF全文

Katherine L. Meierdiercks  Mary Beth Kolozsvary  Kevin P. Rhoads  Michele Golden  Nicholas F. McCloskey 《水文研究》2017,31(24):4384-4397

The processes that control run‐off quantity and quality in urban watersheds are complex and not well understood. Although impervious surface coverage has traditionally been used to examine altered hydrologic response in urban watersheds, several studies suggest that other elements of the urban landscape, particularly those associated with urban infrastructure and the drainage system, play an equally important role. The relative importance of impervious surfaces, stormwater ponds, expansion of the drainage network, and drainage network structures in controlling hydrologic response was examined in the subwatersheds of the Kromma Kill, an urban watershed located in Albany County, NY. In this study, geographic information systems was used to compute geospatial land surface and drainage network properties of 5 Kromma Kill subwatersheds. In these same subwatersheds, water quantity (rainfall and run‐off) and quality (macroinvertebrates, nitrate, total nitrogen, dissolved oxygen, total dissolved solids, and nonpurgable organic carbon) parameters were measured. Strong and significant correlations were identified between land surface and drainage network properties and field observations. Causal relationships were then tested using the Environmental Protection Agency's Stormwater Management Model. Field and model analyses suggest that whereas percent imperviousness is a dominant control on water quality, drainage density and slope are equally important. However, for water quantity, whereas imperviousness is positively correlated with increased run‐off volumes, drainage network properties and slope are the dominant controls on run‐off volumes. Results have important implications for stormwater management plans, especially those aimed at reducing the effective impervious surface coverage of urban watersheds. Reducing the percentage of effective imperviousness in a watershed is not a “one size fits all” solution and can help to meet some management objectives, such as reducing nitrogen concentrations and improving water quality, but may not serve as the most effective, and therefore economical, solution for every management objective including reducing run‐off volumes.  相似文献   

Stellar velocity profiles and line strengths out to four effective radii in the early-type galaxies NGC 3379 and 821     

Anne-Marie Weijmans  Michele Cappellari  Roland Bacon  P. T. de Zeeuw  Eric Emsellem  Jesús Falcón-Barroso  Harald Kuntschner  Richard M. McDermid  Remco C. E. van den Bosch  Glenn van de Ven † 《Monthly notices of the Royal Astronomical Society》2009,398(2):561-574

We use the integral-field spectrograph SAURON to measure the stellar line-of-sight velocity distribution and absorption line strengths out to four effective radii ( R _e) in the early-type galaxies NGC 3379 and 821. With our newly developed observing technique, we can now probe these faint regions in galaxies that were previously not accessible with traditional long-slit spectroscopy. We make optimal use of the large field-of-view and high throughput of the spectrograph: by adding the signal of all ∼1400 lenslets into one spectrum, we obtain sufficient signal-to-noise in a few hours of observing time to reliably measure the absorption line kinematics and line strengths out to large radius.
We find that the line strength gradients previously observed within 1 R _e remain constant out to at least 4 R _e, which puts constraints on the merger histories of these galaxies. The stellar halo populations are old and metal poor. By constructing orbit-based Schwarzschild dynamical models, we find that dark matter is necessary to explain the observed kinematics in NGC 3379 and 821, with 30–50 per cent of the total matter being dark within 4 R _e. The radial anisotropy in our best-fitting halo models is less than in our models without halo, due to differences in orbital structure. The halo also has an effect on the  Mg  b – V _esc  relation: its slope is steeper when a dark matter halo is added to the model.  相似文献   

高精度地下水示踪技术及其应用——以毛村地下河流域为例   总被引：9，自引：0，他引：9  

何师意  Michele L  章程  汪进良  李强 《地球学报》2009,30(5):673-678

笔者以桂林毛村岩溶地下河流域的示踪试验为例, 探索高精度地下水示踪方法在岩溶水文地质研究中的应用。实践证明, 该方法较传统示踪方法具有较大优势。试验中, 从地下河主出口回收I号示踪剂为34%, 地下水平均流速为35.3 m/h, 全部回收率约为60%~70%。示踪结果证实毛村地下河流域具有典型河间地块特征, 存在多个排泄出口, 水文地质边界较复杂; 主出口处示踪剂浓度变化呈宽域多峰, 说明具有多管道、沿途多个较大溶潭特征; II号示踪剂在所有接收点都没有收到, 其原因较为复杂和不确定。枯季部分地下水有沿西南方向断层排泄迹象, 雨季是否存在较大径流, 还需用示踪试验来证实; 流量不均衡, 排泄区可能存在潜流。  相似文献   

Clinopyroxene/liquid trace element partitioning in natural trachyte–trachyphonolite systems: insights from Campi Flegrei (southern Italy)     

Lorenzo Fedele  Alberto Zanetti  Vincenzo Morra  Michele Lustrino  Leone Melluso  Riccardo Vannucci 《Contributions to Mineralogy and Petrology》2009,158(3):337-356

Trace element partition coefficients between clinopyroxenes and associated glassy matrix (^Cpx/L D) have been determined for 13 REE, HFSE^4+,5+, U, Th, Sr, Pb, Sc and V from combined LA-ICP-MS/EMP analyses in selected trachytes and trachyphonolites from Campi Flegrei. Composition of clinopyroxene and glass is pretty homogeneous in the trachyphonolites, pointing to an overall attainment of the equilibrium conditions. In trachytes, conversely, phases show some compositional heterogeneity (due to the presence of clinopyroxene xenocrysts) that requested a more careful petrographic and geochemical inspection of the samples to assess the equilibrium clinopyroxene composition. In the trachyte clinopyroxenes, REE are compatible from Nd to Lu (^Cpx/L D up to 2.9), like Y, Ti, Sc and V. The ^Cpx/L D for Eu is lower than those of the adjacent REE, highlighting Eu²⁺ contribution. High D values are also shown by U, Th, Pb, Zr, Hf, Nb and Ta relatively to basaltic and andesitic systems, whereas the D _Sr is roughly similar to that found for less evolved magmas. Trachyphonolites are characterized by an overall decrease of the ^Cpx/L D for highly-charged cations (with the exception of V), and by a slight increase of D _Sr. REE are still compatible from Nd to Lu (^Cpx/L D up to 2.1), like Ti, Y, Sc and V. This variation is also predicted for REE and Y by models based on the elastic strain theory, being consistent with the slightly lower polymerization degree estimated for the trachyphonolites. However, the observed ^Cpx/L D _(REE,Y) are matched by the modelled ones only considering very low T (≤825°C), which are believed unlikely. This mismatch cannot be attributed to effects induced by the water-rich composition of the trachyte–trachyphonolite suite, since they would lower the observed ^Cpx/L D _(REE,Y). Moreover, the anomalous inflections of measured ^Cpx/L D for HREE suggests some crystal-chemical control, such as the entrance of these elements in a site distinct from M2. It is concluded that the large ^Cpx/L D determined for trachytes and trachyphonolites are likely induced by hitherto unconstrained changes of the Z³⁺ activities related to the composition of melt and/or solid. All these considerations strongly highlight the importance of a direct characterization of trace element partitioning in natural samples from magmatic systems poorly characterized by experimental studies. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Density distribution functions and correlations of earthquake parameters     

Federica Magnoni  Michele Caputo   《Tectonophysics》2009,474(3-4):633-642

The statistical analysis of the source parameters of 9 earthquake sets of different types (aftershocks, scattered events, swarms) and of different seismic regions shows that the density distribution function (ddf) of the linear dimension l of a fault is represented by a negative power law, as well as the ddf of the static stress drop σ and of the scalar seismic moment M_o. It is then suggested, and tentatively verified, that also the ddf of the root mean square ground acceleration, defined as a function of l and σ, may be represented by a negative power law and that, at least in the cases examined, it scales like the ddf of σ. It is seen that the variability of the static stress drop is significant from one region to another, as is well known, but it seems remarkable also in the same seismic region (in particular in California, σ varies by several orders of magnitude) and in the different sets of events of a given region (as observed again for California). It is hypothesized that a correlation, although weak, between the stress drop and the linear dimension of a fault exists and the analyses seem not to contradict that σ may be a decreasing function of l. Finally, it is suggested that the seismicity of a region may be represented two-dimensionally as a function of the ddf of the stress drop and of the linear dimension of a fault instead of the classic b and b_o values.  相似文献   

The early instrumental warm-bias: a solution for long central European temperature series 1760–2007     

Reinhard Böhm  Philip D. Jones  Johann Hiebl  David Frank  Michele Brunetti  Maurizio Maugeri 《Climatic change》2010,101(1-2):41-67

Instrumental temperature recording in the Greater Alpine Region (GAR) began in the year 1760. Prior to the 1850–1870 period, after which screens of different types protected the instruments, thermometers were insufficiently sheltered from direct sunlight so were normally placed on north-facing walls or windows. It is likely that temperatures recorded in the summer half of the year were biased warm and those in the winter half biased cold, with the summer effect dominating. Because the changeover to screens often occurred at similar times, often coincident with the formation of National Meteorological Services (NMSs) in the GAR, it has been difficult to determine the scale of the problem, as all neighbour sites were likely to be similarly affected. This paper uses simultaneous measurements taken for eight recent years at the old and modern site at Kremsmünster, Austria to assess the issue. The temperature differences between the two locations (screened and unscreened) have caused a change in the diurnal cycle, which depends on the time of year. Starting from this specific empirical evidence from the only still existing and active early instrumental measuring site in the region, we developed three correction models for orientations NW through N to NE. Using the orientation angle of the buildings derived from metadata in the station histories of the other early instrumental sites in the region (sites across the GAR in the range from NE to NW) different adjustments to the diurnal cycle are developed for each location. The effect on the 32 sites across the GAR varies due to different formulae being used by NMSs to calculate monthly means from the two or more observations made at each site each day. These formulae also vary with time, so considerable amounts of additional metadata have had to be collected to apply the adjustments across the whole network. Overall, the results indicate that summer (April to September) average temperatures are cooled by about 0.4°C before 1850, with winters (October to March) staying much the same. The effects on monthly temperature averages are largest in June (a cooling from 0.21° to 0.93°C, depending on location) to a slight warming (up to 0.3°C) at some sites in February. In addition to revising the temperature evolution during the past centuries, the results have important implications for the calibration of proxy climatic data in the region (such as tree ring indices and documentary data such as grape harvest dates). A difference series across the 32 sites in the GAR indicates that summers since 1760 have warmed by about 1°C less than winters.  相似文献   

On Shear-Driven Ventilation of Snow   总被引：1，自引：1，他引：0  

Andrew Clifton  Costantino Manes  Jean-Daniel Rüedi  Michele Guala  Michael Lehning 《Boundary-Layer Meteorology》2008,126(2):249-261

A series of experiments have been made in a wind tunnel to investigate the ventilation of snow by shear. We argue that the zero-plane displacement can be used as a convenient indicator of ventilation, and that this can be obtained from measurements of mean velocity profiles in conditions of zero pressure gradient. Measurements made over a natural snow surface show a zero-plane displacement depth of less than 5 mm, but practical considerations preclude extensive use of snow for these measurements. Instead, the influence of permeability is investigated using reticulated foams in place of snow. We demonstrate that the foam and snow have similar structure and flow-relevant properties. Although the surface of the foam is flat, the roughness lengths increase by two orders of magnitude as the permeability increases from 6 × 10⁻⁹ to 160 × 10⁻⁹ m². The zero-plane displacement for the least permeable foams is effectively zero, but more than 15 mm for the most permeable foams. Our data compare well to the few studies available in the literature. By analogy to conditions over snow surfaces, we suggest that shear-driven ventilation of snow is therefore limited to the upper few millimetres of snow surfaces.  相似文献   

Hydrogeological study of the intensely exploited aquifer of the Santa Croce leather-producing district, Tuscany (central Italy)   总被引：1，自引：1，他引：0  

Sergio Grassi  Marco Doveri  Gianni Cortecci  Michele Amadori 《Hydrogeology Journal》2011,19(3):671-684

A hydrogeological study was undertaken to define the groundwater circulation in the Santa Croce area (Tuscany, central Italy) where the existing multilayered aquifer has long been intensively exploited. Investigations carried out on about 150 wells revealed the existence of a deep piezometric depression (to 20?m below sea level) which drains groundwater from the entire surrounding area. Samples from about 70 water points, collected twice in 2007, were analysed for major elements and stable isotope composition. Three major groups of waters, which mix in the study area, have been distinguished: (1) waters of the Ca?CMg?CHCO₃ type mainly flowing along the Arno River Plain; (2) waters of the Na?CK?CCl/Ca?CMg?CHCO₃?CSO_4, type with SO₄ content up to 275?mg/L, inflowing from the Pisane Hills; (3) relatively high-salinity waters mainly of the Na?CHCO₃ type which, with Cl concentrations up to 750?mg/L, likely arise from a normal fault located at the foot of the northern hills. The characteristics of the different components are greatly affected by significant modifying processes such as cation exchange and sulfate reduction. The achieved conceptual model suggests the southern hills as the main recharging area of the aquifer system from which water circulation, characterized by pathways of different length and depth, develops.  相似文献   

Tremolite–calcite veins in the footwall of the Simplon Fault,Antigorio Valley,Lepontine Alps (Italy)     

Vito Meggiolaro  Michele Sapigni  Anna Maria Fioretti 《Swiss Journal of Geoscience》2011,104(3):355-365

The lowermost units of the nappe pile of the Lepontine Alps crop out in the Antigorio valley in the footwall of the Simplon Fault. The whole orthogneiss section of the Antigorio Unit is exposed on both sides of the valley, sandwiched between the Mesozoic metasedimentary sequences of the Baceno unit below and the Tèggiolo unit above. The petrography and mineral composition of tremolite–calcite veins occurring in dolomite marble in both metasedimentary sequences were investigated. Tremolite–calcite (with lesser talc and minor phlogopite) veins have rhythmic banded texture. Banding is due to cyclic differences in modal abundances and fabric of tremolite and calcite. These veins are very similar to those occurring in dolomite rafts within the Bergell granite and it is inferred that they formed by the same “fracture-reaction-seal” mechanism. Veins formed by reaction of a silica-rich aqueous fluid with the host dolomite marble along fractures. According to thermo-barometric calculations, based on electron microprobe analyses, reaction occurred at temperatures between 450 and 490°C and minimum pressure of 2–3 kbar. Such temperature conditions occurred in this footwall region of the Simplon Fault Zone around 15 Ma, during exhumation and cooling of the nappe pile and a transition to brittle behaviour. Aqueous, silica-rich fluids concentrated along fractures, forming tremolite–calcite veins in the dolomite marbles and quartz veins in the orthogneiss.  相似文献