Temporal Trends of Dissolved Trace Metals in Jamaica Bay,NY: Importance of Wastewater Input and Submarine Groundwater Discharge in an Urban Estuary   总被引：1，自引：0，他引：1  

Aaron J. Beck  J. Kirk Cochran  Sergio A. Sañudo-Wilhelmy 《Estuaries and Coasts》2009,32(3):535-550

Jamaica Bay, NY, is a highly urbanized estuary within the boroughs of New York City conspicuously lacking published information on dissolved trace metal concentrations. The current study examines the distribution and cycling of trace metals in that embayment with data gathered during cruises in November 2004, April 2005, and June 2006. Most of the metal distributions (Fe, Zn, Co, Ag, Cu, Pb, Ni) in the water column are explained by the input of substantial volumes of treated wastewater effluent. However, several lines of evidence suggest that submarine groundwater discharge (SGD) is also an important source of dissolved Fe, Zn, Co, Ni, and isotopically distinct stable Pb ratios (²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb) in the Bay. Conversely, the recirculated seawater component of SGD is an apparent sink for dissolved Mo. This study provides the first measurements of dissolved trace metals in the Jamaica Bay water column and subterranean estuary and provides evidence for trace metal input due to SGD.  相似文献   

An improved correlation model for sediment delivery ratio assessment   总被引：3，自引：1，他引：2  

Nazzareno Diodato  Sergio Grauso 《Environmental Earth Sciences》2009,59(1):223-231

In the present work, a new simplified model approach for sediment delivery ratio (SDR) assessment is proposed. Modelling and assessing SDR is still an open question. Difficulties rise from the lack of sufficient data availability, on one side, and, on the other, from the inherent uncertainties including spatial variability and temporal discontinuity of the land cover, climatic, hydrological and geomorphological variables involved. The proposed SDR_SIM model tries to skip over the limitations observed in other models generally adopted. A comparison with two different selected models amongst the most widespread simplified models, i.e. the area-model and the slope-model, is showed in application to a wide range of catchments extensions across different landscapes of Italy. The SDR_SIM estimates were also evaluated against observed SDR over a validation dataset of 11 basins sparse over different regions of the world. The results showed the effectiveness of the proposed model approach based on easily available catchment parameters.  相似文献   

Landscape evolution and origin of Lake Fúquene (Colombia): Tectonics, erosion and sedimentation processes during the Pleistocene     

Gustavo Sarmiento  Sergio Gaviria  Henry Hooghiemstra  Juan Carlos Berrio  Thomas Van der Hammen 《Geomorphology》2008,100(3-4):563-575

The Basin of Ubaté–Chichinquirá (5°28′N, 73°45′ W, c. 2580 m altitude) includes the Fúquene Valley and is located in the central part of the Eastern Cordillera of Colombia. Rocks and sediments were folded and faulted during the Miocene, uplifted during the (late) Pliocene, and affected by glaciers during the Pleistocene. Successive glacial and interglacial periods left significant marks in the landscape which were used to reconstruct six stages in the development of the landscape along a relative chronology. During early Pleistocene episode 1 glaciers formed U-shape valleys. Evidence of the impact of ice sheets has been found as far downslope as ca. 2900 m elevation. During episode 2 moraines developed which were cut by the present San José River. During episode 3 abundant sediment was produced by glacial erosion. It accentuated the sculpturing of hard rock and deepening of the drainage basin. The ancestral Ubaté–Suarez River constituted a dynamic erosive system that gave rise to deep V-shaped valleys and progressively formed a set of intricate valleys with a high sediment production. Finally, intense glacial and fluvio-glacial erosion led to a geomorphological system with high energy levels and intensive sediment transport leading to wide valleys. During episode 4 the Ubaté–Suarez River eroded and deepened its valley until it captured the old El Hato–San José Valley. It caused intense erosion of the moraine and the fluvio-glacial gravels. Deep V-shaped valleys stabilized in the high areas of the main drainage system and these valleys form the present-day fluvial sub-basins. During episode 5 the deep valley in the northern part of the Basin of Ubaté–Chichinquirá developed. During middle Pleistocene episode 6 colluvial sediments formed the Saboya dam and a lake was formed in the river valley of which the present Lake Fúquene is only a small remnant. Lithological changes indicate fluctuating water levels and Lake Fúquene must have expanded periodically up to an area 5 to 10 times the present-day surface.  相似文献   

Introduction     

Sergio Vinciguerra  Yves Bernabé 《Pure and Applied Geophysics》2009,166(5-7):737-739

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Assemblages of megabenthic gastropods from Uruguayan and northern Argentinean shelf: Spatial structure and environmental controls     

Alvar Carranza  Fabrizio Scarabino  Alejandro Brazeiro  Leonardo Ortega  Sergio Martínez 《Continental Shelf Research》2008

We analyzed the structure of the megabenthic gastropod assemblages on the Uruguayan and northern Argentinean shelf and slope. Our analysis determined that there are two major biologically distinct assemblages which occurred in a 210,000 km² area showing conspicuous environmental gradients and large frontal areas: (a) an assemblage associated with the zone under the influence of the freshwater discharge of Río de la Plata and the shallow waters of the inner shelf and (b) an assemblage associated with marine zone in the outer shelf, which includes Magellanic (Subantarctic) and subtropical faunas. A multivariate analysis demonstrated a significant correlation between the environmental and biological matrix. This evidence suggests a noticeable effect of the physical environment on the spatial structure of the assemblage. We suggest that the current distribution patterns are caused by two different processes operating together: while processes operating at ecological time scales (e.g. differential tolerances to salinity and depth) determine most of the structure observed at the inner shelf, the presence of two contrasting water masses over the outer shelf determine a biogeographic boundary for the benthic fauna, linked to shifting climatic factors influencing species niche dynamics over evolutionary time scales. Thus, at the spatial scale here considered, ecological and historical processes must be considered when attempting to understand which factors determine the current structure of benthic assemblages at regional scales.  相似文献   

Application of a barrier island translation model to the millennial-scale evolution of Sand Key,Florida     

Riccardo Masetti  Sergio Fagherazzi  Alberto Montanari 《Continental Shelf Research》2008

The evolution of a barrier island and its stratigraphic architecture is investigated with the numerical model BIT (barrier island translation). The model simulates, with simplified equations, the effects of various processes (wind waves, storm surges, sea-level oscillations) on sediment location and characteristics. The presented formulation is able to reproduce both the cross-shore profile and the distribution of sediment facies in time.  相似文献   

Valentinagraptus a new genus of plectograptid graptoloid from the lower Ludlow (Silurian) of Barrandian,Bohemia     

Sergio Piras 《Geological Journal》2006,41(5):581-590

The new plectograptid—Valentinagraptus simplex gen. nov., sp. nov.,—(Family Retiolitidae) was recovered from the nilssoni and progenitor biozones (early Gorstian, Ludlow) of the Barrandian area of central Bohemia, Czech Republic. The new taxon is characterized by a sub‐oval form and considerably reduced rhabdosome framework. The rhabdosome is similar to Plectograptus, with a simple ancora umbrella with large proximal orifices, but has a simple ancora sleeve with horizontal lateral lists connecting ladder‐like ventral walls. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Seismic performance of a block of buildings representative of the typical construction in the Eixample district in Barcelona (Spain)     

L. G. Pujades  A. H. Barbat  R. González-Drigo  J. Avila  S. Lagomarsino 《Bulletin of Earthquake Engineering》2012,10(1):331-349

Between the late nineteenth century and the early twentieth century, Barcelona was expanded, occupying the terrains connecting the old walled city and the nearby towns of the plateau of Barcelona. At that time, a large number of unreinforced masonry buildings were constructed and nowadays many of them are still used as dwellings. Though built individually, these buildings are connected to adjacent buildings, forming blocks composed of aggregates. In order to analyze the seismic behavior of isolated buildings and aggregates, two typical central buildings and one typical corner building have been chosen. The two central buildings and the corner building are referred as C1, C2, and E buildings. Two corner buildings and two central buildings have been connected in order to simulate a block side. This aggregate is referred as AGG and it is composed by the following sequence of individual buildings: E-C1-C2-E. Original plans and drawings of existing buildings are then used to model these buildings. The modeled buildings have five stories. Standard pushover analyses lead to evaluate their seismic performance by means of capacity spectra and fragility curves. The analysis has been carried out in the parallel (Ux) and transversal (Uy) directions to the street. Then, a capacity spectrum based method is used to analyze the seismic behavior of these buildings considered as individual buildings and as an aggregate. Two earthquake scenarios are considered. The first one is a deterministic scenario which is based on a historical earthquake occurred in 1,824, 25 km away from the city and the second one is a probabilistic scenario, which represents the ground motion with a probability of occurrence of 10% in 50 years. The soil local effects have been also considered and both scenarios have been used to assess the expected damage. Four non-null damage states are considered: slight (1), moderate (2), severe (3) and extensive-to-collapse (4). For the type of soil where most of the buildings are, and in the Ux direction, the four buildings show a similar behavior. The mean damage grade is 2.3 for the deterministic scenario and 2.7 for the probabilistic one. This means that moderate to severe damage is expected in both cases; furthermore, in the case of the deterministic scenario more than 10% of the buildings would suffer extensive-to-collapse damage and nearly 20% for the probabilistic scenario, confirming the high vulnerability of such buildings. The differences in the expected damage are due to the significant different characteristics of the response spectra of the earthquake scenarios in the range of the fundamental periods of the buildings.  相似文献   

The legacy of initial conditions in landscape evolution     

J. Taylor Perron  Sergio Fagherazzi 《地球表面变化过程与地形》2012,37(1):52-63

Landscapes subject to constant forcing tend to evolve toward equilibrium states in which individual landforms have similar characteristics. Yet, even in landscapes at or near equilibrium, there can be significant variability among individual landforms. Furthermore, sites subject to similar processes and conditions can have different mean landform characteristics. This variability is often ascribed to on‐going transient evolution, or to heterogeneity in processes, material properties, forcing, or boundary conditions. Three surprising outcomes of landform evolution models suggest, however, that such variability could arise in equilibrium landscapes without any heterogeneity in the physical processes shaping the topography. First, homogeneous systems subjected to constant forcing can generate a heterogeneous distribution of equilibrium landforms. Second, even simple non‐linear systems can have multiple stable equilibrium states. Third, evolving landscapes can exhibit path dependence and hysteresis. We show how these three mechanisms can produce variability in landforms that arises from the characteristics of the initial topographic surface rather than from heterogeneity in geomorphic processes. Numerical experiments on the formation of low‐order fluvial valleys and transportational cyclic steps in erodible streambeds illustrate why it is important to consider the influence of initial conditions when comparing models with natural topography, estimating the uncertainty of model predictions, and studying how landscapes respond to disturbances. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Growth discontinuity in males of the deep-water giant red shrimp Aristaeomorpha foliacea in the Mediterranean Sea     

Sergio Ragonese  Sergio Vitale  Mark Dimech  Alberto De Santi 《Marine Ecology》2012,33(3):386-392

The deep-water giant red shrimp, Aristaeomorpha foliacea (Risso, 1827) (Decapoda, Aristeidae), represents a highly valuable resource for bottom trawling in the Mediterranean Sea. Recent assessments have described both a worsening of the status of the traditionally exploited stocks and low levels of annual-based instantaneous natural mortality (M 0.4–0.7 year⁻¹) in the unexploited stocks. The mortality (M) figures, however, are in contrast with the longevity (T_max) of 3–4-year males and 4–5-year females, estimated from classical length frequency distribution analysis. Reduced growth (after the onset of sexual maturity) and pile-up of older individuals in the larger size classes have been considered to be reasonable explanations for the contrast between M and T_max. We propose that a discontinuity of the growth models could address this contrast. Because a clear discontinuity in sexual maturity is evident only in males, length frequency distribution data for different sets of males collected from the South of Sicily and the Maltese Islands deep bottoms (400–800 m) were fitted with both the classic (c) and double-phased (d) von Bertalanffy growth formula (VBGF). According to the dVBGF, adult males sharply reduce their growth rate after reaching an age between 1.2 and 1.5 year, which corresponds to the estimates of age at sexual maturity (t_m between 1 and 1.5 years). The reduction in growth determines a higher T_max (7.3–9.5 year) and lower M (0.4–0.6 year⁻¹) than previously derived on the basis of cVBGF estimates (T_max 3–4 years and M 1.2 year⁻¹). The dVBGF results suggest that sexual dimorphism and length–sex segregation in giant red shrimps reflect an alternative life history strategy that is based mainly on growth reduction in adult males and it might be adopted for implementing more conservative assessments.  相似文献