Variation in transparent exopolymer particles in relation to biological and chemical factors in two contrasting lake districts     

Inmaculada de Vicente  Eva Ortega-Retuerta  Ignacio P. Mazuecos  Michael L. Pace  Jonathan J. Cole  Isabel Reche 《Aquatic Sciences - Research Across Boundaries》2010,72(4):443-453

In inland waters, transparent exopolymer particles (TEP) can affect carbon export and sequestration in sediments with consequences for lake C budgets. We measured TEP concentration in 32 lakes from two contrasting lake districts covering wide ranges in biological and chemical characteristics. North temperate lakes, located in a wet region, have low to moderate ionic strength and low to high dissolved organic carbon with corresponding variation in color (light absorbance). Mediterranean lakes located in a semiarid region were characterized by high ionic strength and high concentrations of dissolved organic carbon but low color. TEP concentrations were large relative to the living portion of the particulate organic carbon pool in both Mediterranean (36%) and north temperate (33%) lakes. TEP concentrations ranged from 36 to 1,462 μg [as Gum Xanthan equivalents (GX eq)] L⁻¹ in north temperate lakes. In the Mediterranean lakes, concentrations were higher that previously reported for other systems and ranged from 66 to 9,038 μg GX eq L⁻¹. TEP concentration was positive and significantly related to chlorophyll a (chl a) in north temperate lakes and in the entire data set. Although a significant and positive relationship between TEP and chl a was also detected in the Mediterranean lakes, bacterial abundance was most strongly related to TEP. In contrast with the positive influence of phytoplankton and bacteria on TEP, there were weaker relationships between TEP and the chemical variables tested. We observed a significant and positive relationship between pH and TEP (for all lakes) but this relationship was indirectly driven by a co-variation of pH with phytoplankton biomass based on multiple regression analysis. For the Mediterranean lakes, the negative (but not significant) trends between TEP and both conductivity and divalent cations suggest thresholds above which TEP will likely be destabilized. Under these conditions, TEP may flocculate or disperse in the water column.  相似文献   

Impacts of human activities on recharge in a multilayered semiarid aquifer (Campo de Cartagena,SE Spain)   总被引：1，自引：0，他引：1       下载免费PDF全文

Paul Baudron  Florent Barbecot  José Luis García Aróstegui  Christian Leduc  Yves Travi  David Martinez‐Vicente 《水文研究》2014,28(4):2223-2236

The development of intense agriculture in semiarid areas modifies intensity and spatial distribution of groundwater recharge by summing irrigation return flow to limited rainfall infiltration. Environmental tracers provide key information, but their interpretation is complicated by more complex groundwater flow patterns. In multilayered aquifers, the real origin of the groundwater samples is hard to assess because of local mixing processes occurring inside long‐screened boreholes. We use environmental tracers (¹⁴C, ¹³C, ²H, ¹⁸O, ³H) to investigate the long‐term evolution of recharge in the five‐layer Campo de Cartagena aquifer in South‐Eastern Spain, in addition to high‐resolution temperature loggings to identify the depth of origin of groundwater. Despite the complex background, this methodology allowed a reliable interpretation of the geochemistry and provided a better understanding of the groundwater flow patterns. The tritium method did not give good quantitative results because of the high variability of the recharge signal but remained an excellent indicator of recent recharge. Nonetheless, both pre‐anthropization and post‐anthropization recharge regime could be identified and quantified by radiocarbon. Before the development of agriculture, recharge varied from 17 mm.year^‐1 at the mountain ranges to 6 mm.year^‐1 in the plain, whereas the mean annual rainfall is about 300 mm. In response to the increase of agricultural activity, recharge fluxes to the plain were amplified and nowadays reach up to 210 mm.year^‐1 in irrigated areas. These values are strengthened by global water budget and local unsaturated zone studies. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Thermal structure and energy budget in a small high mountain lake: La Caldera,Sierra Nevada,Spain     

Miguel Rodríguez‐Rodríguez  Enrique Moreno‐Ostos  Inmaculada De Vicente  Luis Cruz‐Pizarro  Sergio Luiz Rodrigues Da Silva 《新西兰海洋与淡水研究杂志》2013,47(5):879-894

This work examines the diel change of energy storage and its associated patterns of thermal stratification during the ice‐free period in a high mountain lake (La Caldera Lake, Sierra Nevada, Spain), in response to meteorological conditions. Bihourly data have been implemented to a standard methodology of surface heat exchange calculations in lakes. Strong variations have been observed on the diverse components of the energy budget at different time scales, ranging from diel to seasonal. Additionally, time‐series analyses have been applied to reveal the underlying periodicities involved in relation to the different variables studied. The results obtained from this study provided realistic conditions for the environmental modelling of such processes, which are very sensitive in time scale.  相似文献   

Free-surface formulation of mantle convection—II. Implication for subduction-zone observables     

Michael Gurnis  Christophe Eloy  Shijie Zhong 《Geophysical Journal International》1996,127(3):719-727

Viscous and viscoelastic models for a subduction zone with a faulted lithosphere and internal buoyancy can self-consistently and simultaneously predict long-wavelength geoid highs over slabs, short-wavelength gravity lows over trenches, trench-forebulge morphology, and explain the high apparent strength of oceanic lithosphere in trench environments. The models use two different free-surface formulations of buoyancy-driven flows (see, for example, Part I): Lagrangian viscoelastic and pseudo-free-surface viscous formulations. The lower mantle must be stronger than the upper in order to obtain geoid highs at long wavelengths. Trenches are a simple consequence of the negative buoyancy of slabs and a large thrust fault, decoupling the overriding from underthrusting plates. The lower oceanic lithosphere must have a viscosity of less than to²⁴ Pa s in order to be consistent with the flexural wavelength of forebulges. Forebulges are dynamically maintained by viscous flow in the lower lithosphere and mantle, and give rise to apparently stiffer oceanic lithosphere at trenches. With purely viscous models using a pseudo-free-surface formulation, we find that viscous relaxation of oceanic lithosphere, in the presence of rapid trench rollback, leads to wider and shallower back-arc basins when compared to cases without viscous relaxation. Moreover, in agreement with earlier studies, the stresses necessary to generate forebulges are small (∼ 100 bars) compared to the unrealistically high stresses needed in classic thin elastic plate models.  相似文献   

COMPARISON　OF　SEDIMENT　DISCHARGE　PREDICTIONS　FOR　SMALL　WATERSREDS　IN　THE　SOUTRWESTERN　UNITED　STATES     

Yakov WIGDOR  Vicente L.LOPES  Peter F.FFOLLIOTT 《国际泥沙研究》1996,(1)

ＣＯＭＰＡＲＩＳＯＮ　ＯＦ　ＳＥＤＩＭＥＮＴ　ＤＩＳＣＨＡＲＧＥ　ＰＲＥＤＩＣＴＩＯＮＳ　ＦＯＲ　ＳＭＡＬＬ　ＷＡＴＥＲＳＲＥＤＳ　ＩＮ　ＴＨＥ　ＳＯＵＴＲＷＥＳＴＥＲＮ　ＵＮＩＴＥＤ　ＳＴＡＴＥＳＹａｋｏｖＷＩＧＤＯＲ；ＶｉｃｅｎｔｅＬ．ＬＯＰＥＳ...  相似文献   

Essai d'organisation paléogéographique et structurale du PaléozoÏque des Andes Méridionales     

Prof. Jean -Claude Vicente 《International Journal of Earth Sciences》1975,64(1):343-394

Hercynian absolute ages obtained from many plutonites and metamorphites of the Sierras Pampeanas compel to consider this polymetamorphic domain rather as an intermediate hinterland and axis of divergent symmetry between the two elementary geosyncline ranges (Cuyanides and Bolivianides) of the south america hercynian orogen. Attempt of Cuyanides paleogeographic organization indice to define during the geosyncline period (Cambrian to Devonian):

the Pampean zone which consist of:

1. an internal sub-zone (eastern) or pampean s. st. with hinterland significance
2. a more external sub-zone (western) or transpampean or Umango sub-zone with intermediate features between eugeanticlinal ridge and eugeosynclinal furrow;
3. the Calingasta zone as a typical eugeosynclinal furrow with pelagic-terrigenous ordovician sedimentation and ophiolitic magmatism followed by early silurian than devonian Flyschs;
4. the Zonda zone as an external ridge with neritic cambro-ordovician facies and devonian flyschs.

The unwonted position of Zonda no metamorphic Facies surrounded by Calingasta and Umango metamorphic Facies, suggest its window situation and wide allochthonous structures for the internal zones. An eastward origin of the nappes is discussed in relation with pampean syntectonic metamorphism and plutonism. Essentially, structures are referred to the Acadian phase (= bretonic) but early paleo-hercynian phases are also emphasized to explain Flyschs sequences and some pampean plutonic cycles. Tardi- and Post-hercynian organization is briefly sketched with related molasses, neomolasses and magmatism. The remarquable geosyncline pattern of the Cuyanides is emphasizes in all stages of its evolution and under aspects however tectonic, magmatic and metamorphic. Finally, the fundamentally western polarity of the Cuyanides is replaced into the most general framework of Gondwanides organization.  相似文献   

Landscape evolution and geodynamic controls in the Gulf of Cadiz (Huelva coast, SW Spain) during the Late Quaternary     

Cari Zazo  Norbert Mercier  Pablo G. Silva  Cristino J. Dabrio  Jos Luis Goy  Elvira Roquero  Vicente Soler  Francisco Borja  Javier Lario  Dolores Polo  Luis de Luque 《Geomorphology》2005,68(3-4):269-290

The coastal evolution of the El Abalario area (Huelva, southern Spain) during the Late Pleistocene and Holocene is reinterpreted after a refinement of the available geochronology by means of optically stimulated luminescence (OSL) dating. New data come from the analysis of soft sediment deformation, palaeosols, geomorphological mapping, and published seismic surveys on the onshore and offshore Gulf of Cadiz.The present structure of El Abalario dome resulted from the complex interaction of littoral-catchment processes and sea-level changes upon an emergent coastal plain, conditioned by the upwarping of the underlying Pliocene–Pleistocene prograding deltaic sequence. Upwarping is probably related to escape of over-pressurized fluids, accompanied by dewatering, prior to (?) and during OIS (Oxygen Isotopic Stage) 5. Continued upwarping produced the large NW–SE gravitational fault of Torre del Loro (TLF) in the southwestern flank of the dome, roughly parallel to the present coastline during OIS 5–OIS 4. The resulting escarpment favoured the accumulation of aeolian sand dunes (units U1, U2, and U3) from OIS 5 to early OIS 1. Unit U1 (OIS 5) ends upwards in a supersurface with a thick weathering profile that suggests moist and temperate climatic conditions. Unit U2 accumulated mainly during OIS 4 and OIS 3 with prevailing W/E winds. The supersurface between U2 and U3 records a part of OIS 2, with relative low sea level. Sedimentation of unit U3 took place during the Last Deglaciation (radiocarbon and OSL ages) with prevailing W/SW winds, under a temperate moist climate, that became more arid towards the top (Holocene). A major supersurface with an iron crust-like layer (SsFe) developed during the Holocene Climatic Optimum (OIS 1) under wetter and more temperate conditions than before, fossilizing the TLF. The supersurface is covered by younger aeolian dunes (U4, U5, U6, and U7) transported by W–SW winds since the Late Neolithic–Chalcolithic cultural period (5.0 ky cal BP).  相似文献   

Detection of displacements on Tenerife Island, Canaries, using radar interferometry   总被引：1，自引：0，他引：1  

José Fernández  Rosana Romero  Daniel Carrasco  Kristy F. Tiampo  Gema Rodríguez-Velasco  Alfredo Aparicio  Vicente Araña  F. J. González-Matesanz 《Geophysical Journal International》2005,160(1):33-45

  相似文献   

MODELING SEDIMENT PROCESSES ON SMALL WATERSHEDS: A CONCEPTUAL FRAMEWORK Ⅱ. CONCENTRATED FLOW PROCESSES     

Vicente L. LOPES  Peter F. FFOLLIOTT Assistant Professor  School of Renewable Natural Resources  The University of Arizona. Tucson. Arizona. Professor  School of Renewable Natural Resources. The University of Arizona  Tucson. Arizona. 《国际泥沙研究》1993,(1)

L INTRODUCTIONThe purpose of this paper is to present a general modeling framework that can serveas a conceptual basis for developing sediment process models by concentrated flow systems on small watersheds. A survey of fundamental principles for developing sedimentprocess models is made with particular emphasis on the effects of space and time averaging on the governing equations. Starting from the most general one--dimensional,unsteady model of sediment processes, simpler model structur…  相似文献   

Remanent magnetization of andesitic and dacitic pumice from the 1985 eruption of Nevado del Ruiz (Colombia) reversed due to self-reversal     

Maja Haag  Friedrich Heller  Juan Carlos Carracedo  Vicente Soler 《Journal of Volcanology and Geothermal Research》1990,41(1-4)

The natural remanent magnetization of andesitic pumice emitted during the 1985 eruption of the Nevado del Ruiz volcano (Colombia) has a direction opposite to the present geomagnetic field. The self-reversing mechanism can be re-activated in the laboratory during cycles of heating and subsequent cooling in air and zero magnetic field. Laboratory-produced thermoremanent magnetization is dominated by the same self-reversal process in fields up to several mT. Microchemical, optical and Curie temperature analyses indicate that the ferromagnetic minerals are members of the magnetite-ulvöspinel and hematite-ilmenite series with average compositions of Fe_2.73Ti_0.27O₄ and Fe_1.38Ti_0.62O₃, respectively. In analogy with the magnetic behaviour of synthetically grown antiferromagnetic-ferromagnetic FeMn-FeNi films, the self-reversal can probably be interpreted in terms of an exchange field acting between a Ti-poor canted antiferromagnetic and a Ti-rich ferrimagnetic phase in the hemoilmenite grains.  相似文献