Responses to a warming trend and “El Niño” events in a tropical lake in western Mexico     

Margarita Caballero  Gabriela Vázquez  Beatriz Ortega  Mario E. Favila  Socorro Lozano-García 《Aquatic Sciences - Research Across Boundaries》2016,78(3):591-604

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Hydrodynamic conditions associated with the formation,maintenance and dissipation of a phytoplankton thin layer in a coastal upwelling system     

Lourdes Velo-Suárez  Liam Fernand  Patrick Gentien  Beatriz Reguera 《Continental Shelf Research》2010

During May–June 2005, a 17-d cruise was carried out in Ría de Pontevedra (Galician Rías Baixas) to study the physical–biological interactions that may lead to subsurface aggregations of phytoplankton organisms in thin layers (TLs). Physical processes governed the initiation and development, maintenance, and decline of a diatom (toxin producing Pseudo-nitzschia spp. and Chaetoceros socialis) TL during an upwelling relaxation-upwelling–downwelling sequence. Differences in shear profiles appeared to lead to the formation of a TL during upwelling events. These results reveal that the coupling between maximum values of shear and buoyancy frequency can shape a subsurface chlorophyll maximum (SCM) into a TL. The effect of shear upon phytoplankton patches, which has been predicted on the basis of theoretical studies, has been corroborated in this study in which the vertical distribution of an observed TL was controlled by physical processes.  相似文献   

Radial velocities in the open cluster Trumpler 14     

Hugo Levato  Stella Malaroda  Beatriz García  Nidia Morrell  Gladys Solivella  Monica Grosso 《Astrophysics and Space Science》1991,183(1):147-153

Spatially-homogenous and anisotropic Bianchi type-II and III cosmological models are obtained in Barber's second self-creation theory of gravitation both in vacuum and in the presence of perfect fluid with pressure equal to energy density. Some properties of the models are discussed.  相似文献   

Products and Mechanism of the NO<Subscript>3</Subscript> Reaction with Thiophene     

B.?Caba?asEmail author  M.?T.?Baeza  P.?Martín  S.?Salgado  F.?Villanueva  E.?Monedero  K.?Wirtz 《Journal of Atmospheric Chemistry》2005,51(3):317-335

Products of the gas-phase reaction of the NO₃ radical with thiophene have been investigated using different experimental systems. On the one hand, experiments have been conducted in our laboratory using two different methods, a Teflon static reactor coupled to a gas chromatograph combined with mass-spectrometry (GC-MS) and a discharge flow tube with direct MS spectroscopic detection. A qualitative analysis in these cases indicates that possible products for the reaction of thiophene+NO₃ at room temperature include: sulphur dioxide, acetic and formic acids, a short-chain aldehyde, 2-nitrothiophene and 3-nitrothiophene. On the other hand, quantitative experiments have been performed in the European Photoreactor (EUPHORE) in Valencia, Spain. In this case, the major products were: HNO₃ (≈80%), nitrothiophenes (≈30%), SO₂ (≈20%), propanal (3%) and a fraction of particles (≈10%). The results obtained indicate that at least 70% of the reaction of NO₃ with thiophene proceeds by an H-abstraction process at room temperature. The mechanism of the reaction studied is proposed on the basis of experimental results.  相似文献   

Paleoecological and climatic changes of the Upper Lerma Basin, Central Mexico during the Holocene     

Beatriz Ludlow-Wiechers  Lucia Almeida-Leero  Gerald Islebe 《Quaternary Research》2005,64(3):318-332

The record of Almoloya Lake in the Upper Lerma basin starts with the deposition of the late Pleistocene Upper Toluca Pumice layer. The data from this interval indicate a period of climatic instability that lasted until 8500 cal yr B.P., when temperature conditions stabilized, although moisture fluctuations continued until 8000 cal yr B.P. Between 8500 and 5000 cal yr B.P. a temperate climate is indicated by dominance of Pinus. From 5000 to 3000 cal yr B.P. Quercus forest expanded, suggesting a warm temperate climate: a first indication of drier environmental conditions is an increase in grassland between 4200 and 3500 cal yr B.P. During the Late Holocene (3300 to 500 cal yr B.P.) the increase of Pinus and grassland indicates temperate dry conditions, with a considerable increase of Pinus between 1100 and 950 cal yr B.P. At the end of this period, humidity increased. The main tendency during the Holocene was a change from humid to dry conditions. During the Early Holocene, Almoloya Lake was larger and deeper; the changing humidity regime resulted in a fragmented marshland, with the presence of aquatic and subaquatic vegetation types.  相似文献   

Assessing rheological properties of fluid mud samples through tuning fork data     

Fonseca  Diego Luiz  Marroig  Patrícia Cunha  Carneiro  Juliane Castro  Gallo  Marcos Nicolás  Vinzón  Susana Beatriz 《Ocean Dynamics》2019,69(1):51-57

Ocean Dynamics - At the nautical bottom approach, part of the fluid mud layers can be included in the available depth if they present favorable rheology. As it is difficult to perform in situ...  相似文献   

Impacts of Holocene and modern sea-level changes on estuarine mangroves from northeastern Brazil     

Marcelo C.L. Cohen  Beatriz L. Figueiredo  Nedra N. Oliveira  Neuza A. Fontes  Marlon Carlos França  Luiz C.R. Pessenda  Adriana V. de Souza  Kita Macario  Paulo C.F. Giannini  José A. Bendassolli  Paula Lima 《地球表面变化过程与地形》2020,45(2):375-392

Projections of the impacts of modern Relative Sea Level (RSL) rise on estuarine mangroves should be supported by coastal topographic data and records of mangrove dynamics under past RSL change. This work identified inland and seaward mangrove migrations along the Jucuruçu River (Bahia, Northeastern Brazil), during the Holocene based on sedimentary features, palynological and geochemical (δ¹³C, δ¹⁵N, C/N) data integrated with digital elevation models. During the Middle Holocene, in response to RSL rise, the estuary saw mangrove forest establish up to ~37 km inland. RSL stood between -1.4 (+0.36/-2.2 m) and +1 (2.19/0.2 m) around 7400 cal yr BP, and rose to a highest position of +3.25 (4.22/2.45 m) reached around 5350 cal yr BP. That marine incursion caused the inland replacement of freshwater vegetation by mangroves on tidal flats. Since then, the estuary experienced RSL fall, reducing inland tidal water salinity towards the Late Holocene, making that the mangroves were replaced by freshwater floodplain vegetation. Today, in the seaward part of the estuary near its mouth, mangroves occupy an area of ~10 km² along tidal channels. Considering a RSL rise of 98 cm up to the end of the 21^st century, at a rate significantly higher than that of Middle Holocene RSL rise (1.5 mm/yr) and fall (0.6 mm/yr), the current mangrove substrates are expected to drown and/or eroded near the coast, while new mangroves may establish inland, at topographically higher tidal flats in nowadays freshwater-tidal zones. Mangrove area could expand over 13 km² of coastal and flood plain. Following the same interaction between RSL/climate changes and Holocene mangrove dynamics, such upstream mangrove migration may be attenuated or intensified by changes in fluvial discharge. © 2019 John Wiley & Sons, Ltd.  相似文献   

Homogeneous Catalytic Ozonation of Lipids Involving Fe2+ and Mn2+: An Experimental and Modeling Study     

Rúbia Martins Bernardes Ramos  Ana Paula Biz  Deolinda Alvarez Tavares  Mnica Beatriz Kolicheski  Tirzh Lins Porto Dantas 《洁净——土壤、空气、水》2020,48(7-8)

Given the issue of lipids in effluent treatment systems and their negative impact on the environment, this study aimed to examine lipid degradation by homogenous catalytic ozonation with the aid of iron and manganese ions. This technology presents the possibility of completely mineralizing pollutants using hydroxyl radicals. Milk is chosen as the lipid source because of the high concentration of triglycerides in its matrix, this kind of lipid being the one found most frequently in food and, consequently, in effluent treatment systems. The milk pH value is controlled, and acidic, neutral, and basic conditions are evaluated. The rates of pseudo‐first‐order reactions and the effective value are estimated. It is shown that under acidic conditions low catalyst dosages are enough to cause the complete degradation of lipids. Under neutral conditions, a similar behavior is observed. Under basic conditions, higher catalyst dosages give higher reaction rates. The order of effectiveness of the catalysts under acidic and basic conditions is Fe²⁺ > Mn²⁺, with Mn²⁺ > Fe²⁺ under neutral conditions. Homogeneous catalytic ozonation is therefore efficient at lipid degradation. This technique is viable economically, since the lipid removal occurred at low ozone levels. In addition, the ions used as catalysts are naturally abundant.  相似文献   

Can climate variability information constrain a hydrological model for an ungauged Costa Rican catchment?          下载免费PDF全文

Beatriz Quesada‐Montano  Ida K. Westerberg  Diana Fuentes‐Andino  Hugo G. Hidalgo  Sven Halldin 《水文研究》2018,32(6):830-846

Long‐term hydrological data are key to understanding catchment behaviour and for decision making within water management and planning. Given the lack of observed data in many regions worldwide, such as Central America, hydrological models are an alternative for reproducing historical streamflow series. Additional types of information—to locally observed discharge—can be used to constrain model parameter uncertainty for ungauged catchments. Given the strong influence that climatic large‐scale processes exert on streamflow variability in the Central American region, we explored the use of climate variability knowledge as process constraints to constrain the simulated discharge uncertainty for a Costa Rican catchment, assumed to be ungauged. To reduce model uncertainty, we first rejected parameter relationships that disagreed with our understanding of the system. Then, based on this reduced parameter space, we applied the climate‐based process constraints at long‐term, inter‐annual, and intra‐annual timescales. In the first step, we reduced the initial number of parameters by 52%, and then, we further reduced the number of parameters by 3% with the climate constraints. Finally, we compared the climate‐based constraints with a constraint based on global maps of low‐flow statistics. This latter constraint proved to be more restrictive than those based on climate variability (further reducing the number of parameters by 66% compared with 3%). Even so, the climate‐based constraints rejected inconsistent model simulations that were not rejected by the low‐flow statistics constraint. When taken all together, the constraints produced constrained simulation uncertainty bands, and the median simulated discharge followed the observed time series to a similar level as an optimized model. All the constraints were found useful in constraining model uncertainty for an—assumed to be—ungauged basin. This shows that our method is promising for modelling long‐term flow data for ungauged catchments on the Pacific side of Central America and that similar methods can be developed for ungauged basins in other regions where climate variability exerts a strong control on streamflow variability.  相似文献   

Forced oscillation measurements of seismic wave attenuation and stiffness moduli dispersion in glycerine-saturated Berea sandstone     

Samuel Chapman  Jan V. M. Borgomano  Hanjun Yin  Jerome Fortin  Beatriz Quintal 《Geophysical Prospecting》2019,67(4):956-968

Fluid pressure diffusion occurring on the microscopic scale is believed to be a significant source of intrinsic attenuation of mechanical waves propagating through fully saturated porous rocks. The so-called squirt flow arises from compressibility heterogeneities in the microstructure of the rocks. To study squirt flow experimentally at seismic frequencies the forced oscillation method is the most adequate, but such studies are still scarce. Here we present the results of forced hydrostatic and axial oscillation experiments on dry and glycerine-saturated Berea sandstone, from which we determine the dynamic stiffness moduli and attenuation at micro-seismic and seismic frequencies (0.004–30 Hz). We observe frequency-dependent attenuation and the associated moduli dispersion in response to the drained–undrained transition (∼0.1 Hz) and squirt flow (>3 Hz), which are in fairly good agreement with the results of the corresponding analytical solutions. The comparison with very similar experiments performed also on Berea sandstone in addition shows that squirt flow can potentially be a source of wave attenuation across a wide range of frequencies because of its sensitivity to small variations in the rock microstructure, especially in the aspect ratio of micro-cracks or grain contacts.  相似文献