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181.
José R. Martínez Catalán Ricardo Arenas Jacobo Abati Sonia Sánchez Martínez Florentino Díaz García Javier Fernández Suárez Pablo González Cuadra Pedro Castiñeiras Juan Gómez Barreiro Alejandro Díez Montes Emilio González Clavijo Francisco J. Rubio Pascual Pilar Andonaegui Teresa E. Jeffries James E. Alcock Rubén Díez Fernández Alicia López Carmona 《Comptes Rendus Geoscience》2009,341(2-3):114-126
Ophiolites of different Paleozoic ages occur in North-West (NW) Iberia in a rootless suture representing the remnants of the Rheic Ocean. Associated allochthonous terranes in the hanging- and foot-walls of the suture derive from the former margins, whereas the relative autochthon corresponds to the Paleozoic passive margin of northern Gondwana. The Paleozoic tectonic evolution of this part of the circum-Atlantic region is deduced from the stratigraphical, petrological, structural and metamorphic evolution of the different units and their ages. The tectonic reconstruction covers from Cambro-Ordovician continental rifting and the opening of the Rheic Ocean to its Middle to Upper Devonian closure. Then, the Variscan Laurussia–Gondwana convergence and collision is briefly described, from its onset to the late stages of collapse associated with the demise of the orogenic roots. 相似文献
182.
Juan Bellas Liliana Saco-lvarez
scar Nieto Ricardo Beiras 《Marine pollution bulletin》2008,57(6-12):493
The toxicity of polycyclic aromatic hydrocarbons (PAHs) was determined using mussel, sea-urchin and ascidian embryo–larval bioassays. Fluorescent light exposure enhanced phenanthrene, fluoranthene, pyrene and hydroxypyrene toxicity in comparison with dark conditions, but not naphthalene and fluorene toxicity. The toxicity of PAHs was inversely related to their KOW values following QSAR models derived for baseline toxicity of general narcotics, whereas the obtained regression using toxicity data from photoactivated PAHs significantly departed from the general narcosis model. Also, the mixture toxicity of five PAHs to the larval growth of the sea-urchin was compared with predictions derived from the concentration addition concept, indicating less than additive effects. Finally, we compared our toxicity data with worst-case environmental concentrations in order to provide a preliminary estimate of the risk to the marine environment. Naphthalene, fluorene and pyrene are not considered to pose a risk to sea-urchin, mussel or ascidian larvae, whilst phenanthrene and fluoranthene may pose a risk for mussel and sea-urchin. Moreover, a higher risk for those species is expected when we consider the photoactivation of the PAHs. 相似文献
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184.
Ezer Tal Carniel Sandro Amin Chabchoub de Camargo Ricardo Estrada-Allis Sheila N. Gao Guoping Greatbatch Richard J. Lermusiaux Pierre F. J. Liu Zhiyu Miyazawa Yasumasa Forster Alejandro Orfila Panickal Swapna Phillips Helen Pinones Andrea Stanev Emil Volker Christoph Xu Fanghua Young Emma 《Ocean Dynamics》2023,73(1):35-38
185.
Marcos Almeida Bezerra Ricardo Erthal Santelli Valfredo Azevedo Lemos Juscelia Pereira dos Santos Alves Bernardo Ferreira Braz Luana Bastos Santos 《洁净——土壤、空气、水》2020,48(7-8)
The implementation of flow injection analysis (FIA) systems and correlated techniques in the laboratory routine provides an increase of analytical throughput and the reduction of risks of analyte losses and contamination. Naturally, it contributes to the reduction of reagent consumption and minimization of waste generation. This paper presents and discusses an overview of the main strategies adopted to make methods based on FIA systems more environmentally friendly, and offers a review of these methods that covers the period from January 2002 to December 2019. Strategies based on reagent management (adoption of procedures without reagents, replacement of toxic reagents, recycling and reuse of reagents and, use of immobilized reagents), the online waste treatment, and the improvements of FIA systems (flow system configurations that avoid reagent wastage, use of green detectors, automation, and miniaturization) are approached in this perspective. 相似文献
186.
Ricardo?A.?OleaEmail author 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(2):481-491
Spatial data are commonly minimal and may have been collected in the process of confirming the profitability of a mining venture or investigating a contaminated site. In such situations, it is common to have measurements preferentially taken in the most critical areas (sweet spots, allegedly contaminated areas), thus conditionally biasing the sample. While preferential sampling makes good practical sense, its direct use leads to distorted sample moments and percentiles. Spatial clusters are a problem that has been identified in the past and solved with approaches ranging from ad hoc solutions to highly elaborate mathematical formulations, covering mostly the effect of clustering on the cumulative frequency distribution. The method proposed here is a form of resample, free of special assumptions, does not use weights to ponder the measurements, does not find solutions by successive approximation and provides variability in the results. The new method is illustrated with a synthetic dataset with an exponential semivariogram and purposely generated to follow a lognormal distribution. The lognormal distribution is both difficult to work with and typical of many attributes of practical interest. Testing of the new solution shows that sample subsets derived from resampled datasets can closely approximate the true probability distribution and the semivariogram, clearly outperforming the original preferentially sampled data. 相似文献
187.
Lucas O. Bianchi Juan Antonio Rivera Facundo Rojas Mauro Britos Navarro Ricardo Villalba 《水文科学杂志》2017,62(4):533-545
In the Central Andes of Argentina (30–37°S), snowmelt is the main source of freshwater, an essential natural resource for ~2.2 million people in the adjacent arid lowlands. In this region, Laguna Llancanelo collects the water inputs from the Malargüe endorheic basin. Previous studies concerning the annual and intra-annual variations of this lagoon and its relationship with regional climate are rare. We obtained a monthly record for the Laguna Llancanelo area (LLA, 1984–2013) using the modified normalized difference water index derived from Landsat images. Monthly LLA ranges between 35 km2 and 411 km2 and is significantly related to variations of the Río Malargüe, the main snow-fed tributary to the lagoon. There is no long-term relationship between LLA and local rainfall, but rapid increases in LLA result from heavy rainfall around the lagoon. Conversely, rapid reductions in LLA encompass periods with both reduced discharge from the Río Malargüe and low local rainfall. The LLA integrates moisture of both Pacific (snowfall in the upper Andes) and Atlantic (lowland rainfall) origins; therefore, we propose using LLA as an indicator of regional water balance. 相似文献
188.
Ricardo N. Szupiany Cecilia Lopez Weibel Massimo Guerrero Francisco Latosinski Molly Wood Lucas Dominguez Ruben Kevin Oberg 《地球表面变化过程与地形》2019,44(6):1295-1308
Quantifying sediment flux within rivers is a challenge for many disciplines due, mainly, to difficulties inherent to traditional sediment sampling methods. These methods are operationally complex, high cost, and high risk. Additionally, the resulting data provide a low spatial and temporal resolution estimate of the total sediment flux, which has impeded advances in the understanding of the hydro-geomorphic characteristics of rivers. Acoustic technologies have been recognized as a leading tool for increasing the resolution of sediment data by relating their echo intensity level measurements to suspended sediment. Further effort is required to robustly test and develop these techniques across a wide range of conditions found in natural river systems. This article aims to evaluate the application of acoustic inversion techniques using commercially available, down-looking acoustic Doppler current profilers (ADCPs) in quantifying suspended sediment in a large sand bed river with varying bi-modal particle size distributions, wash load and suspended-sand ratios, and water stages. To achieve this objective, suspended sediment was physically sampled along the Paraná River, Argentina, under various hydro-sedimentological regimes. Two ADCPs emitting different sound frequencies were used to simultaneously profile echo intensity level within the water column. Using the sonar equation, calibrations were determined between suspended-sand concentrations and acoustic backscatter to solve the inverse problem. The study also analyzed the roles played by each term of the sonar equation, such as ADCP frequency, power supply, instrument constants, and particle size distributions typically found in sand bed rivers, on sediment attenuation and backscatter. Calibrations were successfully developed between corrected backscatter and suspended-sand concentrations for all sites and ADCP frequencies, resulting in mean suspended-sand concentration estimates within about 40% of the mean sampled concentrations. Noise values, calculated using the sonar equation and sediment sample characteristics, were fairly constant across evaluations, suggesting that they could be applied to other sand bed rivers. © 2018 John Wiley & Sons, Ltd. 相似文献
189.
190.
To consolidate knowledge of some aspects of the partitioning of incident rainfall into throughfall, stemflow and interception loss, a study was made in a typical cocoa (Theobroma cacao Lour.) plantation in south-east Bahia, Brazil. The samples were collected, on a per shower basis, from locations at different levels in the canopy over a period of two and a half years. During the period studied, of the amount of incident rainfall reaching the cocoa plantation, on average 16% was retained by shelter trees, 19% by cocoa trees and 9% by the ground litter. Losses due to interception caused some variations and were mainly regulated by temporal variations and by the amount and intensity of rainfall in the plantation. The amount of rainfall intercepted, as determined in this study, is comparable with other tropical stands, but important differences do exist and are believed to be influenced by the previous level of moisture availability within the cocoa plantation. 相似文献