Distribution of diagenetic alterations within depositional facies and sequence stratigraphic framework of fluvial sandstones: Evidence from the Petrohan Terrigenous Group,Lower Triassic,NW Bulgaria     

Mohamed Ali Kalefa El-Ghali  Sadoon Morad  Howri Mansurbeg  Miguel Angel Caja  George Ajdanlijsky  Neil Ogle  Ihsan Al-Aasm  Manhal Sirat 《Marine and Petroleum Geology》2009

Sequence stratigraphy of fluvial deposits is a controversial topic because changes in relative sea level will eventually have indirect impact on the spatial and temporal distribution of depositional facies. Changes in the relative sea level may influence the accommodation space in fluvial plains, and hence have impact on types of fluvial system, frequency of avulsion, and style of vertical and lateral accretion. This study aims to investigate whether depositional facies and changes in the fluvial system of the Lower Triassic Petrohan Terrigenous Group sandstones (NW Bulgaria) in response to changes in the relative sea level have an impact on the spatial and temporal distribution of diagenetic alterations.  相似文献   

Assessing fish quality status in transitional waters,within the European Water Framework Directive: Setting boundary classes and responding to anthropogenic pressures     

Ainhize Uriarte  Angel Borja 《Estuarine, Coastal and Shelf Science》2009

Validation of the AZTI's Fish Index (AFI), proposed for the Basque Country (northern Spain), in assessing fish quality within the Water Framework Directive (WFD), is undertaken. The response to anthropogenic pressure is investigated, in setting the boundaries between the different quality status classes. Hence, 12 estuaries were sampled, at different frequencies, between 1989 and 2007, by means of a beam trawl. Significant (p < 0.0001) correlations were found between the AFI and oxygen saturation and ammonia. Oxygen quality standards are used to set boundaries between quality classes. Then, the AFIs obtained are compared with different anthropogenic pressures, including urban and industrial discharges, engineering works and dredging. The effects of the removal of some of these pressures are also studied. The total number of pressures within an estuary shows significant (p < 0.009) negative correlation with AFI, explaining between 51 and 62% of the variability in fish quality. The impact of pressures upon fish and demersal assemblages is detected as required by the WFD. Nonetheless, further investigation and intercalibration of the methods used, are necessary.  相似文献   

Assessing the benthic quality status of the Bohai Bay (China) with proposed modifications of M-AMBI   总被引：1，自引：1，他引：0  

CAI Wenqian  BORJA Angel  LIN Kuixuan  ZHU Yanzhong  ZHOU Juan  LIU Lusan 《海洋学报(英文版)》2015,34(10):111-121

Multivariate AZTI's Marine Biotic Index (M-AMBI) was designed to indicate the ecological status of European coastal areas. Based upon samples collected from 2009 to 2012 in the Bohai Bay, we have tested the response of variations of M-AMBI, using biomass (M-BAMBI) in the calculations, with different transformations of the raw data. The results showed that the ecological quality of most areas in the study indicated by M-AMBI was from moderate to bad status with the worse status in the coastal areas, especially around the estuaries, harbors and outfalls, and better status in the offshore areas except the area close to oil platforms or disposal sites. Despite large variations in nature of the input data, all variations of M-AMBI gave similar spatial and temporal distribution patterns of the ecological status within the bay, and showed high correlation between them. The agreement of new ecological status obtained from all M-AMBI variations, which were calculated according to linear regression, was almost perfect. The benthic quality, assessed using different input data, could be related to human pressures in the bay, such as water discharges, land reclamation, dredged sediment and drilling cuts disposal sites. It seems that M-BAMBI were more effective than M-NABMI (M-AMBI calculated using abundance data) in indicating human pressures of the Bay. Finally, indices calculated with more severe transformations, such as presence/absence data, could not indicate the higher density of human pressures in the coastal areas of the north part of our study area, but those calculated using mild transformation (i.e., square root) did.  相似文献   

Measuring and managing changes in estuaries and lagoons: morphological and eco-toxicological aspects   总被引：1，自引：0，他引：1  

Zonta R  Guerzoni S  Pérez-Ruzafa A  de Jonge VN 《Marine pollution bulletin》2007,55(10-12):403-406

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Trends in Abundance Indices of Fishes in Maryland’s Coastal Bays During 1972–2009     

Jennifer Pincin  Michael J. Wilberg  Lora Harris  Angel Willey 《Estuaries and Coasts》2014,37(4):791-800

Maryland’s coastal bays provide habitat for juveniles of many commercially and recreationally important species of shellfish and finfish. Since 1972, the Maryland Department of Natural Resources has conducted the Maryland Coastal Bays Trawl and Seine Survey to monitor the populations of key species. The survey has undergone substantial spatial and methodological changes affecting the interpretation of simple indices of abundance. We developed generalized linear models to standardize the indices of abundance of five commonly caught fish species: Atlantic menhaden Brevoortia tyrannus, weakfish Cynoscion regalis, spot Leiostomus xanthurus, bay anchovy Anchoa mitchilli, and summer flounder Paralichthys dentatus. Density declined significantly since 1972 for menhaden, bay anchovy, and spot in at least one region within the coastal bays. The northern bays had significantly higher densities than the southern bays for all species. Changes in abundance indices of the five species examined were not related to sea grass coverage, temperature, salinity, nitrogen-to-phosphorus ratios, and other habitat variables but were likely a result of stock-wide recruitment processes.  相似文献   

Nonextensive Statistical Mechanics: Some Links with Astronomical Phenomena     

Constantino Tsallis  Constantino Tsallis  Domingo Prato  Angel R. Plastino  Angel R. Plastino 《Astrophysics and Space Science》2004,290(3-4):259-274

A variety of astronomical phenomena appear to not satisfy the ergodic hypothesis in the relevant stationary state, if any. As such, there is no reason for expecting the applicability of Boltzmann–Gibbs (BG) statistical mechanics. Some of these phenomena appear to follow, instead, nonextensive statistical mechanics. In the same manner that the BG formalism is based on the entropy S _BG=?k∑ _i p _i ln p _i, the nonextensive one is based on the form S _q=k(1 ?∑ _i p _i ^q)/(q? 1) (with S ₁=S _BG). The stationary states of the former are characterized by an exponential dependence on the energy, whereas those of the latter are characterized by an (asymptotic) power law. A brief review of this theory is given here, as well as of some of its applications, such as the solar neutrino problem, polytropic self-gravitating systems, galactic peculiar velocities, cosmic rays and some cosmological aspects. In addition to these, an analogy with the Keplerian elliptic orbits versus the Ptolemaic epicycles is developed, where we show that optimizing S _q with a few constraints is equivalent to optimizing S _BG with an infinite number of constraints.  相似文献   

Geostrophic Adjustment Problems in a Polar Basin     

Maria V. Luneva  Andrew J. Willmott  Miguel Angel Morales Maqueda 《大气与海洋》2013,51(2):134-155

The geostrophic adjustment of a homogeneous fluid in a circular basin with idealized topography is addressed using a numerical ocean circulation model and analytical process models. When the basin is rotating uniformly, the adjustment takes place via excitation of boundary propagating waves and when topography is present, via topographic Rossby waves. In the numerically derived solution, the waves are damped because of bottom friction, and a quasi-steady geostrophically balanced state emerges that subsequently spins-down on a long time scale. On the f-plane, numerical quasi-steady state solutions are attained well before the system's mechanical energy is entirely dissipated by friction. It is demonstrated that the adjusted states emerging in a circular basin with a step escarpment or a top hat ridge, centred on a line of symmetry, are equivalent to that in a uniform depth semicircular basin, for a given initial condition. These quasi-steady solutions agree well with linear analytical solutions for the latter case in the inviscid limit.

On the polar plane, the high latitude equivalent to the β-plane, no quasi-steady adjusted state emerges from the adjustment process. At intermediate time scales, after the fast Poincaré and Kelvin waves are damped by friction, the solutions take the form of steady-state adjusted solutions on the f-plane. At longer time scales, planetary waves control the flow evolution. An interesting property of planetary waves on a polar plane is a nearly zero eastward group velocity for the waves with a radial mode higher than two and the resulting formation of eddy-like small-scale barotropic structures that remain trapped near the western side of topographic features.

RÉSUMÉ?Traduit par la rédaction] Nous étudions l'ajustement géostrophique d'un fluide homogène dans un bassin circulaire ayant une topographie idéalisée à l'aide d'un modèle numérique de circulation océanique et de modèles analytiques de processus. Quand le bassin est en rotation uniforme, l'ajustement se fait par l'excitation d'ondes de propagation aux limites, et en présence de topographie, par des ondes de Rossby topographiques. Dans la solution numériquement dérivée, les ondes sont amorties à cause frottement contre le fond, et un état quasi-stable géostrophiquement équilibré s’établit pour ensuite décélérer sur une longue période de temps. Sur le plan f, les solutions numériques d’états quasi-stables sont atteintes bien avant que l’énergie du système mécanique soit entièrement dissipée par le frottement. Nous démontrons que les états ajustés apparaissant dans un bassin circulaire avec un accore en forme de marche ou une crête en forme de merlon, centrés sur une ligne de symétrie, sont équivalents à ceux d'un bassin semi-circulaire de profondeur uniforme pour une condition initiale donnée. Les solutions quasi-stables s'accordent bien avec les solutions analytiques linéaires pour le dernier cas dans la limite de la non-viscosité.

Sur le plan polaire, la haute latitude équivalente au plan β, le processus d'ajustement n'aboutit à aucun état ajusté quasi-stable. Aux échelles de temps intermédiaires, après l'amortissement des ondes rapides de Poincaré et Kelvin par le frottement, les solutions prennent la forme de solutions ajustées d’états stables sur le plan f. Aux échelles de temps plus longues, les ondes planétaires déterminent l’évolution de l’écoulement. Une propriété intéressante des ondes planétaires sur un plan polaire est une vitesse de groupe presque nulle vers l'est pour les ondes ayant un mode radial plus grand que deux et la formation résultante de structures barotropiques de petite échelle de type remous qui demeurent emprisonnées près du bord ouest des caractéristiques topographiques.  相似文献   

Climate change and summer mass tourism: the case of Spanish domestic tourism   总被引：1，自引：0，他引：1  

Angel Bujosa  Jaume Rosselló 《Climatic change》2013,117(1-2):363-375

This paper investigates the impact of climate change on destination choice decisions in a context of domestic coastal tourism in Spain. Destinations are characterized in terms of travel cost and coastal ‘attractors’, such as temperature and beach-related attributes. By means of a discrete choice model based on the random utility theory, these variables are used to explain the observed pattern of interprovincial domestic trips, showing trade-offs between temperature and attractiveness in the probability of a particular destination being chosen. The model is used to investigate the impact of two climate change scenarios on the allocation of domestic tourism within Spain. The findings show that while Spain’s northern colder provinces would benefit from rising temperatures, provinces in the south would experience a decrease in the frequency of trips.  相似文献   

Analysis of the climatic constraints to maize production in the current agricultural region of Argentina—a probabilistic approach     

Gustavo Angel Maddonni 《Theoretical and Applied Climatology》2012,107(3-4):325-345

A simple method of analysis was proposed to characterize the impact of climatic conditions of a wide region of Argentina (from 27°05′S to 35°48′S, from 61°5′W to 64°21′W) on potential maize (Zea mays L.) grain yield, and the occurrence of various climatic constraints (low temperatures and low soil water content, frost, drought stress and heat stress) along the cycle. The analysis was based on previous studies of the eco-physiology of maize crops and the use of climatic records of six locations in the region under study. Results were analyzed using a probabilistic method, later organized as a checklist to consider when deciding on sowing date in a location of the region. Thus, for each production scenario (combination of location and sowing date), farmers would have a tool enabling them to pay particular attention to the restrictions more likely to occur, to include some cultural practices to avoid or mitigate the most severe climatic constraint to maize production.  相似文献   

Effect of growth on active biomonitoring with terrestrial mosses     

J. Angel Fernández  Angela Ares  Ana Rey-Asensio  Alejo Carballeira  Jesus R. Aboal 《Journal of Atmospheric Chemistry》2009,63(1):1-11

The effects of growth of autoirrigated, shaded transplants of Pseudoscleropodium purum on the quantification of tissue concentrations of Cd, Cu, Hg, V and Zn, were investigated in 4 exposure periods, each of 56 days, at 7 sampling sites (contaminated and uncontaminated). Concentrations of the elements in the basal portions of the moss shoots were compared with the concentrations in the portions of the shoots that grew during the exposure period. Mercury and V were present at lower concentrations in the new portions of the shoots than in the basal portions, whereas the opposite was true for Cd, Cu and Zn. The magnitude of error introduced by growth was not negligible, and in some cases was higher than 40%, relative to the results obtained by analysis of the whole shoot. Devitalization of moss prior to its use as transplant material is recommended to avoid growth of the plant during the exposure period.  相似文献