Long-Term Changes in Water Quality and Productivity in the Patuxent River Estuary: 1985 to 2003     

Jeremy M. Testa  W. Michael Kemp  Walter R. Boynton  James D. Hagy III 《Estuaries and Coasts》2008,31(6):1021-1037

We conducted a quantitative assessment of estuarine ecosystem responses to reduced phosphorus and nitrogen loading from sewage treatment facilities and to variability in freshwater flow and nonpoint nutrient inputs to the Patuxent River estuary. We analyzed a 19-year dataset of water quality conditions, nutrient loading, and climatic forcing for three estuarine regions and also computed monthly rates of net production of dissolved O₂ and physical transport of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) using a salt- and water-balance model. Point-source loading of DIN and DIP to the estuary declined by 40–60% following upgrades to sewage treatment plants and correlated with parallel decreases in DIN and DIP concentrations throughout the Patuxent. Reduced point-source nutrient loading and concentration resulted in declines in phytoplankton chlorophyll-a (chl-a) and light-saturated carbon fixation, as well as in bottom-layer O₂ consumption for upper regions of the estuary. Despite significant reductions in seaward N transport from the middle to lower estuary, chl-a, turbidity, and surface-layer net O₂ production increased in the lower estuary, especially during summer. This degradation of water quality in the lower estuary appears to be linked to a trend of increasing net inputs of DIN into the estuary from Chesapeake Bay and to above-average river flow during the mid-1990s. In addition, increased abundance of Mnemiopsis leidyi significantly reduced copepod abundance during summer from 1990 to 2002, which favored increases in chl-a and allowed a shift in total N partitioning from DIN to particulate organic nitrogen. These analyses illustrate (1) the value of long-term monitoring data, (2) the need for regional scale nutrient management that includes integrated estuarine systems, and (3) the potential water quality impacts of altered coastal food webs.  相似文献   

Evidence of magmatic CO2-rich fluids in peraluminous graphite-bearing leucogranites from Deep Freeze Range (northern Victoria Land,Antarctica)     

Maria Luce Frezzotti  Gianfranco Di Vincenzo  Claudio Ghezzo  Ernst A. J. Burke 《Contributions to Mineralogy and Petrology》1994,117(2):111-123

Fine-grained peraluminous synkinematic leuco-monzogranites (SKG), of Cambro-Ordovician age, occur as veins and sills (up to 20–30 m thick) in the Deep Freeze Range, within the medium to high-grade metamorphics of the Wilson Terrane. Secondary fibrolite + graphite intergrowths occur in feldspars and subordinately in quartz. Four main solid and fluid inclusion populations are observed: primary mixed CO₂+H₂O inclusions + Al₂SiO₅ ± brines in garnet (type 1); early CO₂-rich inclusions (± brines) in quartz (type 2); early CO₂+CH₄ (up to 4 mol%)±H₂O inclusions + graphite + fibrolite in quartz (type 3); late CH₄+CO₂+N₂ inclusions and H₂O inclusions in quartz (type 4). Densities of type 1 inclusions are consistent with the crystallization conditions of SKG (750°C and 3 kbar). The other types are post-magmatic: densities of type 2 and 3 inclusions suggest isobaric cooling at high temperature (700–550°C). Type 4 inclusions were trapped below 500°C. The SKG crystallized from a magma that was at some stage vapour-saturated; fluids were CO₂-rich, possibly with immiscible brines. CO₂-rich fluids (±brines) characterize the transition from magmatic to post-magmatic stages; progressive isobaric cooling (T<670°C) led to a continuous decrease off _{O 2} can entering in the graphite stability field; at the same time, the feldspars reacted with CO₂-rich fluids to give secondary fibrolite + graphite. Decrease ofT andf _{O 2} can explain the progressive variation in the fluid composition from CO₂-rich to CH₄ and water dominated in a closed system (in situ evolution). The presence of N₂ the late stages indicates interaction with external metamorphic fluids.Contribution within the network Hydrothermal/metamorphic water-rock interactions in crystalline rocks: a multidisciplinary approach on paleofluid analysis. CEC program: Human Capital and Mobility  相似文献   

Asteroid “clans”: Super-families or multiple events?     

Alberto Cellino  Vincenzo Zappalà 《Celestial Mechanics and Dynamical Astronomy》1993,57(1-2):37-47

Among the recently determined asteroid families (Zappala' et al., 1992) a number of very large clusterings are recognized. Some of them agglomerate few families previously identified as single groupings. In most cases, the new big families (called clans) seem to be composed by different sub-clusterings connected each other by very narrow bridges. In the present paper we analyze their possible origin and evolution: a primordial single event followed by subsequent collisions of the fragments, a super-catastrophic original impact or different collisional events overlapping by chance.  相似文献   

A semi-analytic method for pole determination of asteroids     

Vincenzo Zappala' 《Earth, Moon, and Planets》1981,24(3):319-325

A semi-analytic method, obtained collecting amplitude-aspect and magnitude-aspect relations, is given in order to deduce the pole coordinates of asteroids. The accuracy of this method (5–10°), which needs some restrictive hypotheses, seems to be sufficient for statistical purposes. Possible ambiguities on the results could be resolved by comparison with other methods (like photometric astrometry), which start from different observational data and follow different procedures.  相似文献   

Structural setting of the Bay of Naples (Italy) seismic reflection data: implications for Campanian volcanism: [Tectonophysics 372 (2003) 193–213]     

Pier Paolo G. Bruno  Antonio Rapolla  Vincenzo Di Fiore 《Tectonophysics》2003,376(3-4)

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Reply to Comment on “Impact of groundwater withdrawals on the interaction of multi-layered aquifers in the Viterbo geothermal area (central Italy)”: report published in Hydrogeology Journal (2013) 21:1339–1353, by Antonella Baiocchi,Francesca Lotti and Vincenzo Piscopo     

Baiocchi  Antonella  Lotti  Francesca  Piscopo  Vincenzo 《Hydrogeology Journal》2016,24(2):541-545

Hydrogeology Journal -  相似文献   

Oxygen and Nutrient Exchanges at the Sediment-Water Interface: a Global Synthesis and Critique of Estuarine and Coastal Data     

W. R. Boynton  M. A. C. Ceballos  E. M. Bailey  C. L. S. Hodgkins  J. L. Humphrey  J. M. Testa 《Estuaries and Coasts》2018,41(2):301-333

Estuarine and coastal marine sediment-water fluxes are considered to be important ecological features, but a global-scale assessment has yet to be developed. Goals of this work were to assemble a global-scale database of net sediment-water flux measurements, examine measurement techniques, characterize the geographic distribution and magnitude of sediment fluxes, explore the data for controls on sediment flux magnitude, and assess the importance of sediment fluxes in ecosystem-level metabolism and primary production. We examined 480 peer-reviewed sources and found sediment flux data for 167 estuarine and coastal systems. Most measurements were made in North America, Europe, and Australia. Fluxes varied widely among systems, some by several orders of magnitude. Inter-annual variability within sites was less than an order of magnitude but time series flux data to evaluate this were rare. However, limited time series data exhibited large and rapid responses to decreased external nutrient loading rates, climate change effects (possible temperature effects), and variability in trophic conditions. Comparative analyses indicated organic matter supply to sediments set the upper limits of flux magnitude, with other factors playing secondary roles. Two metrics were developed to assess ecosystem-level importance of sediment-water fluxes. Sediments represented 30% or more of depth-integrated rates of aerobic system respiration at depths of <10 m. An annual phytoplankton production data set was used to estimate N and P demand; sediments supplied an average of 15–32% of N and 17–100% of P demand and, in some cases, was as large or larger than external nutrient inputs. The percent of demand supplied by sediments was highest in temperate latitudes and lower in high and tropical latitudes.  相似文献   

Indentation of a Sensitive Clay by a Flat-Ended Axisymmetrical Punch     

Mireille Sandrine Ewane  Vincenzo Silvestri  Michael James 《Geotechnical and Geological Engineering》2018,36(6):3601-3625

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Deformation patterns of upper Quaternary strata and their relation to active tectonics,Po Basin,Italy     

Alessandro Amorosi  Luigi Bruno  Bruno Campo  Bianca Costagli  Wan Hong  Vincenzo Picotti  Stefano Claudio Vaiani 《Sedimentology》2021,68(1):402-424

Despite increased application of subsurface datasets below the limits of seismic resolution, reconstructing near‐surface deformation of shallow key stratigraphic markers beneath modern alluvial and coastal plains through sediment core analysis has received little attention. Highly resolved stratigraphy of Upper Pleistocene to Holocene (Marine Isotope Stage 5e to Marine Isotope Stage 1) alluvial, deltaic and coastal depositional systems across the southern Po Plain, down to 150 m depth, provides an unambiguous documentation on the deformation of previously flat‐lying strata that goes back in time beyond the limits of morphological, historical and palaeoseismic records. Five prominent key horizons, accurately selected on the basis of their sedimentological characteristics and typified for their fossil content, were used as highly effective stratigraphic markers (M1 to M5) that can be tracked for tens of kilometres across the basin. A facies‐controlled approach tied to a robust chronology (102 radiocarbon dates) reveals considerable deformation of laterally extensive nearshore (M1), continental (M2 and M3) and lagoon (M4 and M5) marker beds originally deposited in a horizontal position (M1, M4 and M5). The areas where antiformal geometries are best observed are remarkably coincident with the axes of buried ramp anticlines, across which new seismic images reveal substantially warped stratal geometries of Lower Pleistocene strata. The striking spatial coincidence of fold crests with the epicentres of historic and instrumental seismicity suggests that deformation of marker beds M1 to M5 might reflect, in part at least, syntectonically generated relief and, thus, active tectonism. Precise identification and lateral tracing of chronologically constrained stratigraphic markers in the ¹⁴C time window through combined sedimentological and palaeoecological data may delineate late Quaternary subsurface stratigraphic architecture at an unprecedented level of detail, outlining cryptic stratal geometries at the sub‐seismic scale. This approach is highly reproducible in tectonically active Quaternary depositional systems and can help to assess patterns of active deformation in the subsurface of modern alluvial and coastal plains worldwide.  相似文献   

Multifractal analysis of earthquake catalogues   总被引：1，自引：0，他引：1  

Cataldo Godano  Vincenzo Caruso 《Geophysical Journal International》1995,121(2):385-392

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