Spatial trends in the geochemical composition of sediments in the Panuco River discharge area, Gulf of Mexico.     

L. Rosales Hoz  A. Carranza Edwards  S. Santiago Perez  E. Morales De La Garza 《Environmental Geology》2005,48(4-5):496-506

Major and trace elements, organic matter, carbonates, loss of ignition, grain size, gravel, sand, silt, clay, and qualitative mineralogical composition were determined on surficial marine sediments sampled during the stormy (February), dry (May), and rainy (September) seasons in the coastal area adjacent to Panuco River discharges into the Gulf of Mexico. The sediments supplied by the river move in a north-east direction, and are deposited in the north-east extreme of the studied area. Terrigenous sediments show a strong association of Al₂O₃ with Fe₂O₃, Na₂O, K₂O, P₂O₅, Rb, Cu, Zn, organic matter, clay, and grain size (Mz). Mineralogical analysis shows that they are formed by quartz, kaolinite, montmorillonite, illite-montmorillonite and biotite. The highest metal concentration of Cu (25 mg/kg), Zn (155 mg/kg), Pb (50 mg/kg) and organic matter (1.26%) was observed in the sampling points located very close to the river mouth. A statistical analysis was done with the information contained in the variables. Five significant factors explain 77% of the total variance: factor 1 is due to sediments from a terrigenous source, factor 2 corresponds to sediments from a biogenous source, factor 3 is associated to sediments with heavy minerals, factor 4 is due to Co concentration, and factor 5 is due to Ni concentration. The sediments supplied from the river had a short-term local impact on the sediment distribution, as observed by the carbonate and heavy mineral concentration of the sediments.  相似文献   

Contexte lithostructural, âges 40K40Ar et géochimie du volcanisme calco-alcalin tertiaire de Cap-d'Ail dans le tunnel ferroviaire de Monaco     

Jean-Pierre Ivaldi  Hervé Bellon  Pierre Guardia  Christian Mangan  Carla Müller  Jean-Louis Perez  Serge Terramorsi 《Comptes Rendus Geoscience》2003,335(4):411-421

Lithostratigraphic and structural framework, chronology and geochemistry of the Tertiary calc-alkaline volcanism of Cap-d'Ail (French Maritime Alps) are specified according to the new data collected during the earthworks of the recent railway tunnel built between Cap-d'Ail and Monaco. Two different magmatic events were dated: the first one, to Palaeogene, the other one, to Neogene. To cite this article: J.-P. Ivaldi et al., C. R. Geoscience 335 (2003).  相似文献   

Nitrogen and phosphorus transport between Fourleague Bay, LA, and the Gulf of Mexico: the role of winter cold fronts and Atchafalaya River discharge     

Brian C. Perez  John W. Day  Jr.  Dubravko Justic  Robert R. Twilley 《Estuarine, Coastal and Shelf Science》2003,57(5-6):1065-1078

Nutrient fluxes were measured between Fourleague Bay, a shallow Louisiana estuary, and the Gulf of Mexico every 3 h between February 1 and April 30, 1994 to determine how high velocity winds associated with cold fronts and peak Atchafalaya River discharge influenced transport. Net water fluxes were ebb-dominated throughout the study because of wind forcing and high volumes of water entering the northern Bay from the Atchafalaya River. Flushing time of the Bay averaged <8 days; however, more rapid flushing occurred in response to northerly winds with approximately 56% of the volume of the Bay exported to the Gulf in 1 day during the strongest flushing event. Higher nitrate+nitrite (NO₂+NO₃), total nitrogen (TN), and total phosphorus (TP) concentrations were indicative of Atchafalaya River input and fluxes were greater when influenced by high velocity northerly winds associated with frontal passage. Net exports of NO₂+NO₃, TN, and TP were 43.5, 98.5, and 13.6 g s⁻¹, respectively, for the 89-day study. An average of 10.6 g s⁻¹ of ammonium (NH₄) was exported to the Gulf over the study; however, concentrations were lower when associated with riverine influence and wind-driven exports suggesting the importance of biological processes. Phosphate (PO₄) fluxes were nearly balanced over the study with fairly stable concentrations indicating a well-buffered system. The results indicate that the high energy subsidy provided by natural pulsing events such as atmospheric cold fronts and seasonal river discharge are efficient mechanisms of nutrient delivery to adjacent wetlands and nearshore coastal ecosystems and are important in maintaining coastal sustainability.  相似文献   

Characterization of spatial relationships between three remotely sensed indirect indicators of biodiversity and climate: a 21years' data series review across the Canadian boreal forest     

Liliana Perez  Trisalyn Nelson  Nicholas C. Coops  Fabio Fontana  C. Ronnie Drever 《International Journal of Digital Earth》2016,9(7):676-696

Climate drives ecosystem processes and impacts biodiversity. Biodiversity patterns over large areas, such as Canada's boreal, can be monitored using indirect indicators derived from remotely sensed imagery. In this paper, we characterized the historical space–time relationships between climate and a suite of indirect indicators of biodiversity, known as the Dynamic Habitat Index (DHI) to identify where climate variability is co-occurring with changes in biodiversity indicators. We represented biodiversity using three indirect indicators generated from 1987 to 2007 National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer images. By quantifying and clustering temporal variability in climate data, we defined eight homogeneous climate variability zones, where we then analyzed the DHI. Results identified unique areas of change in climate, such as the Hudson Plains, that explain significant variations in DHI. Past variability in temperatures and growing season index had a strong influence on observed vegetation productivity and seasonality changes throughout Canada's boreal. Variation in precipitation, for most of the area, was not associated with DHI changes. The methodology presented here enables assessment of spatial–temporal relationships between biodiversity and climate variability and characterizes distinctive zones of variation that may be used for prioritization and planning to ensure long-term biodiversity conservation in Canada.  相似文献   

Magma characterization of the Mexican volcanic belt (Mexico)     

S. Pal  M. Lopez  J. Perez  D. J. Terrell 《Bulletin of Volcanology》1978,41(4):379-389

Over 330 bulk chemical analyses of rocks (Oligocene or Miocene to Recent) from the Mexican Volcanic Belt (MVB) have been compiled. These analyses all together represent a calc-alkaline sequence of continental margin type. The North-Eastern part of the Belt seems to overlap with another volcanic province, namely. Eastern Cordillera in which magmas are mostly of alkaline sequence. A model involving fractional crystallization as the principal mechanism is proposed for magma genesis in the MVB.  相似文献   

K---Ar and Rb---Sr geochronology og igneous rocks from the Sierra de Paiman, northwestern Argentina     

W.A Perez  K Kawashita 《Journal of South American Earth Sciences》1992,5(3-4)

Epizonal igneous and metamorphic rocks in northwestern Argentina are exposed in the Sierra de Paiman. The metamorphic rocks are quartzites, phyllites, and slates with soft-body impressions and fossil traces that suggest a late Precambrian-Cambrian age. The igneous rocks were intruded during two major magmatic events according to K---Ar and Rb---Sr data. The older event is represented by different kinds of granitoids and gabbroids, intruded 437–459 Ma. These rocks were emplaced syntectonically in a shear zone that remained active after emplacement, causing extensive mylonitization on the east side of the range. The granitoids show Sr isotopic disturbances possibly related to magma mixing events. Petrologic, geochemical, and isotopic data for these rocks suggest a volcanic-arc setting, probably related to the back arc of the eastward-dipping continental arc of the Famatina Belt. During the younger event (ca. 379 Ma) stocks and dikes of leucogranites were emplaced post-tectonically with respect to the last episode of mylonitization. The leucogranites have syn-collisional signatures and may thus represent the culmination of the volcanic arc of the Famatina Belt.  相似文献   

Threshold of motion and settling velocities of mollusc shell debris: Influence of faunal composition     

Alissia Rieux  Pierre Weill  Dominique Mouaze  Clement Poirier  Farid Nechenache  Laurent Perez  Bernadette Tessier 《Sedimentology》2019,66(3):895-916

Bioclastic particles derived from mollusc shell debris can represent a significant fraction of sandy to gravelly sediments in temperate and cool‐water regions with high carbonate productivity. Their reworking and subsequent transport and deposition by waves and currents is highly dependent on the shape and density of the particles. In this study, the hydrodynamic behaviour of shell debris produced by eight mollusc species is investigated for several grain sizes in terms of settling velocity (measurements in a settling tube) and threshold of motion under unidirectional current (flume experiments using an acoustic profiler). Consistent interspecific differences in settling velocity and critical bed shear stress are found, related to differences in shell density, shell structure imaged by scanning electron microscopy and grain shape. Drag coefficients are proposed for each mollusc species, based on an interpolation of settling velocity data. Depending on the shell species, the critical bed shear stress values obtained for bioclastic particles fall within or slightly below empirical envelopes established for siliciclastic particles, despite very low settling velocity values. The results suggest that settling velocity, often used to describe the entrainment of sediment particles through the equivalent diameter, is not a suitable parameter to predict the initiation of motion of shell debris. The influence of the flat shape of bioclastic particles on the initiation of motion under oscillatory flows and during bedload and saltation transport is yet to be elucidated.  相似文献   

Optimization of photovoltaic solar power plant locations in northern Chile     

Anna Suuronen  Anssi Lensu  Markku Kuitunen  Rodrigo Andrade-Alvear  Natalia Guajardo Celis  Marcelo Miranda  Marcelo Perez  Jussi V. K. Kukkonen 《Environmental Earth Sciences》2017,76(24):824

The optimization of photovoltaic solar power plants location in Atacama Desert, Chile, is presented in this study. The study considers three objectives: (1) Find sites with the highest solar energy potential, (2) determine sites with the least impact on the environment, and (3) locate the areas which produce small social impact. To solve this task, multi-criteria decision analyses (MCDAs) such as analytical hierarchy process and ordered weighted averaging were applied in a GIS environment. In addition, survey results of social impacts were analyzed and included into the decision-making process, including landscape values. The most suitable sites for solar energy projects were found near roads and power lines throughout the study area. Large suitable areas were found also from central valley from Arica and Parinacota to the north edge of Atacama region. In Atacama region, most suitable sites were found in the Andes. On the contrary, Andes were also found to have high environmental values and scenically valuable landscapes. Moderate and low suitability were found on the coast, especially in Atacama region. Factors such as slope and distance to power lines and roads influenced largely the sensitivity analysis. Area of high suitability increased by 15% when distance to roads was excluded and 18% when distance to power lines or slope was removed. MCDA-GIS method was found to be useful and applicable to the optimization of solar power plant locations in northern Chile.  相似文献   

委内瑞拉1999年特大泥石流灾害   总被引：10，自引：2，他引：8  

韦方强  谢洪  Jose L.Lopez  David Perez 《山地学报》2000,18(6):580-582

受娜尼拉现象的影响,１９９９－１２－１５～１６委内拉北部阿维拉册区加勒比海沿岸的８个州连降特大暴雨,造成山体大面积滑塌,数十条沟谷同时暴发大规模的泥石流。泥石流造成３万人死亡、经济损失高达１００亿美元,成为本基纪最严重的泥石流灾害,这次泥石汉灾害具有群发性、规模大、低频率和直接入海等特点,对这类泥石流进行泥石流成因、活动规律、预测预报、泥石流与异常气候现象关系和直接入海型泥石流运动规律,沉积特征、  相似文献   

The influence of halo assembly on galaxies and galaxy groups     

Tatiana Zapata  Josefa Perez  Nelson Padilla  Patricia Tissera 《Monthly notices of the Royal Astronomical Society》2009,394(4):2229-2237

In this paper, we study the variations of group galaxy properties according to the assembly history in Sloan Digital Sky Survey Data Release 6 (SDSS-DR6) selected groups. Using mock SDSS group catalogues, we find two suitable indicators of group formation time: (i) the isolation of the group, defined as the distance to the nearest neighbour in terms of its virial radius and (ii) the concentration, measured as the group inner density calculated using the fifth nearest bright galaxy to the group centre. Groups within narrow ranges of mass in the mock catalogue show increasing group age with isolation and concentration. However, in the observational data the stellar age, as indicated by the spectral type, only shows a correlation with concentration.
We study groups of similar mass and different assembly history, finding important differences in their galaxy population. Particularly, in high-mass SDSS groups, the number of members, mass-to-light ratios, red galaxy fractions and the magnitude difference between the brightest and second-brightest group galaxies, show different trends as a function of isolation and concentration, even when it is expected that the latter two quantities correlate with group age. Conversely, low-mass SDSS groups appear to be less sensitive to their assembly history.
The correlations detected in the SDSS are not consistent with the trends measured in the mock catalogues. However, discrepancies can be explained in terms of the disagreement found in the age-isolation trends, suggesting that the model might be overestimating the effects of environment. We discuss how the modelling of the cold gas in satellite galaxies could be responsible for this problem. These results can be used to improve our understanding of the evolution of galaxies in high-density environments.  相似文献