U-Th-Pb systematics of selected samples from Apollo 17, Boulder 1, Station 2     

P. D. Nunes  M. Tatsumoto 《Earth, Moon, and Planets》1975,14(3-4):463-471

Nine U-Th-Pb whole-rock analyses of selected brecciated materials from sample 72215 and one analysis of a pigeonite basalt clast from 72275 are presented. Both samples are from Boulder 1, Apollo 17. These data supplement previous Boulder 1 U-Th-Pb analyses of samples 72275 and 72255. U and Th concentrations indicate that most of the samples contain a moderate to large KREEP component. Samples containing the least KREEP are a noritic clast (72255,49; Civet Cat clast) and an anorthositic clast (72275,117). Evidence for the migration of Pb from Pb-rich matrix material into relatively Pb-poor clasts is presented for two clasts. Most of the Boulder 1 data define a linear trend that intersects concordia at ～ 3.9 and 4.4 b.y. when plotted on a U-Pb concordia diagram. The presence of one anorthositic clast distinctly off this trend indicates that a simple two-stage U-Pb evolution history is inadequate to explain all the data. Accordingly physical significance is only attached to the lower concordia intercept age of 3.9–4.0 b.y. The older concordia intercept age of ～ 4.4 b.y. is interpreted to reflect an averaging of events both older and younger than 4.4 b.y. The data suggest that significant differentiation and/or metamorphism occurred ～ 4.2 b.y. ago. The age of this event, however, is not accurately defined by these data.  相似文献   

Copper complexing capacity of phytoplanktonic cell exudates     

Alfredo Seritti  David Pellegrini  Elisabetta Morelli  Corrado Barghigiani  Romano Ferrara 《Marine Chemistry》1986,18(2-4)

Copper complexing capacity of cell exudates of Dunaliella salina in natural seawater culture medium was investigated in order to evaluate the influence of this organism on speciation of trace metals in seawater.Seawater samples were collected at 200 m and 2 miles off the coast and immediately filtered. Copper complexing capacity (CC_Cu) and stability constants (K′) of related cupric complexes were then measured. They were, respectively, 27.1 × 10⁻⁸ mol l⁻¹ and 0.56 × 10⁷ l mol⁻¹ for the samples collected at 200 m and 12.8 × 10⁻⁸ mol l⁻¹ and 6.10 × 10⁷ l mol⁻¹ for those collected 2 miles off the coast. A stock culture (20 ml, 10⁶ cells ml⁻¹) in log-phase was inoculated in 2 l of each sample of filtered natural seawater. The trend of cell influence was estimated on filtered culture medium by measuring CC_Cu and K′ after 1 h, 3 and 7 days. From the results it appears that CC_Cu increased with respect to time and this was related to the growth rate, indicating a certain relationship with cell metabolic activity.It can be concluded that a comparison between the culture referring to 200 m and 2 miles, respectively, shows that the former presents a CC_Cu two times higher than the latter while the K′ is ten times higher at 2 miles than that at 200 m.  相似文献   

On the relation between GDOP and the volume described by the user-to-satellite unit vectors for GNSS positioning     

Blanco-Delgado  Nuria  Duarte Nunes  Fernando  Seco-Granados  Gonzalo 《GPS Solutions》2017,21(3):1139-1147

GPS Solutions - The geometric dilution of precision (GDOP) is related to the satellite geometry. Thus far, research has focused on minimizing the GDOP by selecting a set of satellites that...  相似文献   

Erratum to: Effects of alkaline hydrolysis and autoclaving on inorganic components present in healthcare waste     

S. C. Pinho  M. F. Almeida  O. C. Nunes 《International Journal of Environmental Science and Technology》2016,13(2):761-761

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Instrumental neutron activation analysis,gamma spectrometry and geographic information system techniques in the determination and mapping of rare earth element in phosphogypsum stacks     

Renata Coura Borges  Déborah Inês Teixeira Fávaro  Vanessa Godoy Caldas  Dejanira da Costa Lauria  Alfredo Victor Bellido Bernedo 《Environmental Earth Sciences》2016,75(8):705

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Quality indices of groundwater for agricultural use in the region of Tierra Nueva,San Luis Potosi,Mexico     

José Alfredo Ramos-Leal  B. López-Álvarez  G. Santacruz-De León  O. Almanza-Tovar  J. Morán-Ramírez  D. A. Padilla-Reyes  Z. I. González-Acevedo 《Arabian Journal of Geosciences》2016,9(19):736

The paper evaluates the quality of groundwater for agricultural use in Tierra Nueva, San Luis Potosi, Mexico, where the agricultural productivity zone presents problems of salinity soil. Twenty groundwater samples and 11 soil samples at 2 depths at each point were collected and analyzed. In this type of water quality study, Wilcox classification diagram and the method of Salinity Laboratory United States for the quality of agricultural land were used. However, in some cases, these rankings do not reflect the actual condition, as in the case of Tierra Nueva, where the soil is classified as normal while water is classified at intermediate good. To analyze the real conditions of soil and water quality indicators of water for agricultural use risk of salinization, sodium adsorption ratio, adsorption ratio magnesium, permeability index, sodium percentage, soluble sodium percentage, residual sodium carbonate, and Kelly ratio were used. Sodicity rates including sodium adsorption ratio indicate no problem in soil extract. However, 25% of water samples are dangerous, with levels ranging from medium to high. For indexes of sodium percentage, residual sodium carbonate, and Kelly ratio, a distribution of classes ranging from questionable to inadequate was applied. Salinity levels show that effective salinity has good classification; potential salinity (PS) is conditional and therefore not recommended; and osmotic potential and electrical conductivity are classified as high in saline water, which is an increasingly important problem. The combination of different indices emphasized serious problems of salinity conditions, particularly sodicity.  相似文献   

Parameterization,sensitivity analysis,and inversion: an investigation using groundwater modeling of the surface-mined Tivoli-Guidonia basin (Metropolitan City of Rome,Italy)   总被引：1，自引：1，他引：0  

Francesco La Vigna  Mary C. Hill  Rudy Rossetto  Roberto Mazza 《Hydrogeology Journal》2016,24(6):1423-1441

With respect to model parameterization and sensitivity analysis, this work uses a practical example to suggest that methods that start with simple models and use computationally frugal model analysis methods remain valuable in any toolbox of model development methods. In this work, groundwater model calibration starts with a simple parameterization that evolves into a moderately complex model. The model is developed for a water management study of the Tivoli-Guidonia basin (Rome, Italy) where surface mining has been conducted in conjunction with substantial dewatering. The approach to model development used in this work employs repeated analysis using sensitivity and inverse methods, including use of a new observation-stacked parameter importance graph. The methods are highly parallelizable and require few model runs, which make the repeated analyses and attendant insights possible. The success of a model development design can be measured by insights attained and demonstrated model accuracy relevant to predictions. Example insights were obtained: (1) A long-held belief that, except for a few distinct fractures, the travertine is homogeneous was found to be inadequate, and (2) The dewatering pumping rate is more critical to model accuracy than expected. The latter insight motivated additional data collection and improved pumpage estimates. Validation tests using three other recharge and pumpage conditions suggest good accuracy for the predictions considered. The model was used to evaluate management scenarios and showed that similar dewatering results could be achieved using 20 % less pumped water, but would require installing newly positioned wells and cooperation between mine owners.  相似文献   

Progress and Challenges in Coupled Hydrodynamic-Ecological Estuarine Modeling     

Neil K. Ganju  Mark J. Brush  Brenda Rashleigh  Alfredo L. Aretxabaleta  Pilar del Barrio  Jason S. Grear  Lora A. Harris  Samuel J. Lake  Grant McCardell  James O’Donnell  David K. Ralston  Richard P. Signell  Jeremy M. Testa  Jamie M. P. Vaudrey 《Estuaries and Coasts》2016,39(2):311-332

Numerical modeling has emerged over the last several decades as a widely accepted tool for investigations in environmental sciences. In estuarine research, hydrodynamic and ecological models have moved along parallel tracks with regard to complexity, refinement, computational power, and incorporation of uncertainty. Coupled hydrodynamic-ecological models have been used to assess ecosystem processes and interactions, simulate future scenarios, and evaluate remedial actions in response to eutrophication, habitat loss, and freshwater diversion. The need to couple hydrodynamic and ecological models to address research and management questions is clear because dynamic feedbacks between biotic and physical processes are critical interactions within ecosystems. In this review, we present historical and modern perspectives on estuarine hydrodynamic and ecological modeling, consider model limitations, and address aspects of model linkage, skill assessment, and complexity. We discuss the balance between spatial and temporal resolution and present examples using different spatiotemporal scales. Finally, we recommend future lines of inquiry, approaches to balance complexity and uncertainty, and model transparency and utility. It is idealistic to think we can pursue a “theory of everything” for estuarine models, but recent advances suggest that models for both scientific investigations and management applications will continue to improve in terms of realism, precision, and accuracy.  相似文献   

Sr and Nd isotope composition of the metamorphic,sedimentary and ultramafic xenoliths of Lanzarote (Canary Islands): Implications for magma sources     

Alfredo Aparicio  Colombo C.G. Tassinari  Roberto García  Vicente Araña 《Journal of Volcanology and Geothermal Research》2010,189(1-2):143-150

The lavas produced by the Timanfaya eruption of 1730–1736 (Lanzarote, Canary Islands) contain a great many sedimentary and metamorphic (metasedimentary), and mafic and ultramafic plutonic xenoliths. Among the metamorphosed carbonate rocks (calc-silicate rocks [CSRs]) are monomineral rocks with forsterite or wollastonite, as well as rocks containing olivine ± orthopyroxene ± clinopyroxene ± plagioclase; their mineralogical compositions are identical to those of the mafic (gabbros) and ultramafic (dunite, wherlite and lherzolite) xenoliths. The ⁸⁷Sr/⁸⁶Sr (around 0.703) and ¹⁴³Nd/¹⁴⁴Nd (around 0.512) isotope ratios of the ultramafic and metasedimentary xenoliths are similar, while the ¹⁴⁷Sm/¹⁴⁴Nd ratios show crustal values (0.13–0.16) in the ultramafic xenoliths and mantle values (0.18–0.25) in some CSRs. The apparent isotopic anomaly of the metamorphic xenoliths can be explained in terms of the heat source (basaltic intrusion) inducing strong isotopic exchange (⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd) between metasedimentary and basaltic rocks. Petrofabric analysis also showed a possible relationship between the ultramafic and metamorphic xenoliths.  相似文献   

Comparison of building damage scales and damage descriptions for use in earthquake loss modelling in Europe   总被引：1，自引：1，他引：0  

Marc Hill  Tiziana Rossetto 《Bulletin of Earthquake Engineering》2008,6(2):335-365

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