Measuring and modeling vertical gradients in suspended sediments in the Solimões/Amazon River          下载免费PDF全文

E. Armijos  A. Crave  R. Espinoza  P. Fraizy  A.L.M.R. Dos Santos  F. Sampaio  E. De Oliveira  W. Santini  J.M. Martinez  P. Autin  N. Pantoja  M. Oliveira  N. Filizola 《水文研究》2017,31(3):654-667

Accurately measuring sediment flux in large rivers remains a challenge due to the spatial and temporal cross‐sectional variability of suspended sediment concentrations in conjunction with sampling procedures that fail to accurately quantify these differences. This study presents a field campaign methodology that can be used to improve the measurement of suspended sediment concentrations in the Amazon River or similarly large rivers. The turbidity signal and Rouse model are together used in this study to define the spatial distribution of suspended sediment concentrations in a river cross‐section, taking into account the different size fractions of the sediment. With this methodology, suspended sediment fluxes corresponding to each sediment class are defined with less uncertainty than with manual samples. This paper presents an application of this methodology during a field campaign at different gauging stations along a 3,000‐km stretch of the Solimões/Amazon River during low water and flood periods. Vertical concentration profiles and Rouse model applications for distinctive sediment sizes are explored to determine concentration gradients throughout a cross‐section of the river. The results show that coupling both turbidity technology and the Rouse model may improve our understanding of the spatial distribution of different sediments fractions sizes in the Solimões/Amazon River. These data are very useful in defining a pertinent monitoring strategy for suspended sediment concentrations in the challenging context of large rivers.  相似文献   

Analyzing the commercial activities of a street network by ranking their nodes: a case study in Murcia,Spain     

Taras Agryzkov  Jose L. Oliver  Leandro Tortosa 《International journal of geographical information science》2014,28(3):479-495

Urban researchers and planners are often interested in understanding how economic activities are distributed in urban regions, what forces influence their special pattern and how urban structure and functions are mutually dependent. In this paper, we want to show how an algorithm for ranking the nodes in a network can be used to understand and visualize certain commercial activities of a city. The first part of the method consists of collecting real information about different types of commercial activities at each location in the urban network of the city of Murcia, Spain. Four clearly differentiated commercial activities are studied, such as restaurants and bars, shops, banks and supermarkets or department stores, but obviously we can study other. The information collected is then quantified by means of a data matrix, which is used as the basis for the implementation of a PageRank algorithm which produces a ranking of all the nodes in the network, according to their significance within it. Finally, we visualize the resulting classification using a colour scale that helps us to represent the business network.  相似文献   

Benthic habitat mapping: Concerns using a combined approach (acoustic, sediment and biological data)     

Rosa Freitas  Fernando Ricardo  Fbio Pereira  Leandro Sampaio  Susana Carvalho  Miguel Gaspar  Victor Quintino  Ana Maria Rodrigues 《Estuarine, Coastal and Shelf Science》2011,92(4):72

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Soil discrimination using diffuse reflectance Vis–NIR spectroscopy in a local toposequence     

José Francirlei Oliveira  Michel Brossard  Pedro Rodolfo Siqueira Vendrame  Stanislas Mayi III  Edemar Joaquim Corazza  Robélio Leandro Marchão  Maria de Fátima Guimarães 《Comptes Rendus Geoscience》2013,345(11-12):446-453

Vis–NIR spectroscopy is nowadays presented as a possible routine method for soil sample analysis. However, there is still no consensus on which is the best multivariate statistical method to use. We propose to use principal component analysis to complete the spectral data treatment. The soil samples came from a pedological cover made up of red–yellow Latosols: 88 samples of 11 soil profiles on four toposequences were collected; clay, organic matter, silica, iron, aluminum and titanium total contents were determined; the contents of goethite, hematite, gibbsite, and kaolinite were calculated. Diffuse reflectance Vis–NIR spectroscopy at wavelengths from 400 to 2400 nm combined with principal component analysis (PCA) was sufficiently sensitive to discriminate different Latosols. Wavelengths of 700 nm and 2200 to 2300 nm were influenced by content ratios of organic matter and iron oxides (700 nm), and kaolinite and gibbsite absorption (2200 and 2300 nm). The spectral responses were affected not only by the content of these constituents, but also by the composition of the minerals, so that the same class of Latosol may have different or similar spectral responses. The role of microaggregation is discussed.  相似文献   

Response by the Authors to S. R. Hencher’s Discussion of the Paper “Comparison of Different Techniques of Tilt Testing and Basic Friction Angle Variability Assessment     

Leandro R. Alejano  Javier González  José Muralha 《Rock Mechanics and Rock Engineering》2012,45(6):1141-1143

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Measurement of runoff and soil loss from two differently sized plots in a subtropical environment (Brazil)     

Edivaldo L. Thomaz  Leandro R. Vestena 《地球表面变化过程与地形》2012,37(4):363-373

Studies of soil erosion on small plots present upscaling problems. The results in the literature on the effect of slope length (i.e. scale) on runoff and soil erosion are contradictory. Furthermore, most studies that examine scale effects measured through erosion plots have been conducted in Mediterranean environments. The objective of this study was to assess the effects of plot size on runoff and soil loss in a subtropical environment. Other measurements were taken to appraise the topsoil property changes inside the plots. The soil was ploughed twice, the surface was leveled with a hoe and it was kept bare during the experiment. Data were collected from 10 paired plots, five plots measuring 10 m × 1 m and five plots measuring 1 m × 1 m, installed in the same pedo‐geomorphologic unit. Measurements were carried out from November 2008 to November 2009. During this period, 97 natural storms were registered. The results indicate that the small plots tended to have higher runoff (30% higher) compared to larger plots, especially during periods of greater rainfall volume, duration and intensity. The soil loss was similar in both the 1 m² plots (6·33 kg/m²) and the 10 m² plots (6·26 kg/m²). Moreover, the dynamics of the soil loss during the experiment was relatively similar across both plot sizes. The large plots tended to have a greater internal complexity. In these plots, the steps retreat were higher, the overland flow scars were more frequent, and points of rill initiation and protochannels emerged in several parts of the plots. The results of the small plots were comparable to the results obtained on the large plots, especially in relation to soil loss. These plots were useful for short‐term assessments of soil erosion. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

The role of snow melting upon landslides in the central Argentinean Andes     

Stella Moreiras  Maria Sol Lisboa  Leandro Mastrantonio 《地球表面变化过程与地形》2012,37(10):1106-1119

This paper focuses on the historical range of variability of landslide activity and its relation to climate in the Aconcagua Park, Argentina. Landslide frequency data are obtained through historic compilation, including the review of more than 85 data sources and personal interviews with members of the local community. Based on these records, the study analyzes major landslide triggering mechanisms and evaluates the role of climate. Slope instability in Aconcagua Park appears to be mainly forced by the melting of snow accumulated during the winter season, which in turn promotes soil saturation and landslide occurrence the following spring–summer (December–February). This finding is supported by a strong correlation between landslides and stream flows of Andean rivers. These peaks occur during warmer seasons, fed by snow and ice‐glacier melting. In contrast, the correlation between landslide frequency and precipitation (diary/accumulative/monthly/annual) is less certain; and the relationship of landslide to temperature records (mean annual temperature/mean temperature during November–February period) is weak. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Carbon and nitrogen stable isotopes in coastal benthic populations under multiple organic enrichment sources     

Leandro Sampaio 《Marine pollution bulletin》2010,60(10):1790-1802

In a dispersive coastal area under multiple organic enrichment sources, stable isotopes were used to trace organic sources of carbon and nitrogen in sediments and benthic macrofauna. The Bivalve Abra alba and the Polychaetes Nephtys sp. and Pectinaria (Lagis) koreni were reliable indicators of the input of terrestrial-derived organic matter into this coastal area, either originated in outfall sewage discharges or estuarine outflow. An isotopic depletion was observed up to 250 m from the outfall branches, much stronger in the biota than in the sediments. An enrichment of 2‰ in the sediments, and 2-6‰ in the species was noticed in sites located farther than 1500 m from the outfall. Depositivores and carnivores/omnivores gave the best picture of the extension of the sewage dispersion and incorporation into the food web.  相似文献   

Particulate matter geochemistry of a highly industrialized region in the Caribbean:Basis for future toxicological studies     

Luis F.O.Silva  Ismael L.Schneider  Paulo Artaxo  Yuleisy Núñez-Blanco  Diana Pinto  Érico M.M.Flores  Leandro Gómez-Plata  Omar Ramírez  Guilherme L.Dotto 《地学前缘(英文版)》2022,(1):376-387

Air pollution has become an important issue,especially in Caribbean urban areas,and,particulate matter(PM)emitted by different natural and anthropogenic sources causes environmental and health issues.In this work,we studied the concentrations of PM₁₀ and PM_2.5 sources in an industrial and port urban area in the Caribbean region of Colombia.PM samples were collected within 48-h periods between April and October 2018 by using a Partisol 2000 i-D sampler.Elemental geochemical characterization was performed by X-ray fluorescence(XRF)analysis.Further,ionic species and black carbon(BC)were quantified by ion chromatography and reflectance spectroscopy,respectively.Using the Positive Matrix Factorization(PMF)receptor model,the contributions of PM sources were quantified.The average concentration of PM₁₀ was 46.6±16.2μg/m³,with high concentrations of Cl and Ca.For PM_2.5,the average concentration was 12.0±3.2μg/m³,and the most abundant components were BC,S,and Cl.The receptor model identified five sources for PM₁₀ and PM_2.5.For both fractions,the contributions of marine sea spray,re-suspended soil,and vehicular traffic were observed.In addition,PM_2.5 included two mixed sources were found to be fuel oil combustion with fertilizer industry emissions,and secondary aerosol sources with building construction emissions.Further,PM₁₀ was found to also include building construction emissions with re-suspended soil,and metallurgical industry emissions.These obtained geochemical atmospheric results are important for the implementation of strategies for the continuous improvement of the air quality of the Caribbean region.  相似文献   

Impact of intensive fish farming on methane emission in a tropical hydropower reservoir     

Marcelo Gomes da Silva  Ana Paula Packer  Fernanda G. Sampaio  Luciano Marani  Ericka V. C. Mariano  Ricardo A. A. Pazianotto  Willian J. Ferreira  Plínio C. Alvalá 《Climatic change》2018,150(3-4):195-210

Fisheries and aquaculture are important sources of food for hundreds of millions of people around the world. World fish production is projected to increase by 15% in the next 10 years, reaching around 200 million tonnes per year. The main driver of this increase will be based on fish farming management in developing countries. In Brazil, fish farming is increasing due to the climate conditions and large supply of water resources, with the production system based on Nile tilapia (Oreochromis niloticus) farming in reservoirs. Inland waters like reservoirs are a natural source of methane (CH₄) to the atmosphere. However, knowledge of the impact from intensive fish production in net cages on CH₄ fluxes is not well known. This paper presents in situ measurements of CH₄ fluxes and dissolved CH₄ (DM) in the Furnas Hydroelectric Reservoir in order to evaluate the impact of fish farming on methane emissions. Measurements were taken in a control area without fish production and three areas with fish farming. The overall mean of diffusive methane flux (DMF) (5.9?±?4.5 mg CH₄ m^?2 day^?1) was significantly lower when compared to the overall mean of bubble methane flux (BMF) (552.9?±?1003.9 mg CH₄ m^?2 day^?1). The DMF and DM were significantly higher in the two areas with fish farming, whereas the BMF was not significantly different. The DMF and DM were correlated to depth and chlorophyll-a. However, the low production of BMF did not allow the comparison with the limnological parameters measured. This case study shows that CH₄ emissions are influenced more by reservoir characteristics than fish production. Further investigation is necessary to assess the impact of fish farming on the greenhouse gas emissions.  相似文献