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101.
Osmar Carvalho Junior Renato Guimaraes Leonardo Freitas Daniel Gomes‐Loebmann Roberto Arnaldo Gomes Eder Martins David R. Montgomery 《地球表面变化过程与地形》2010,35(5):611-617
Urbanization can change catchment hydrology, accelerating gully erosion and causing serious damage to urban structures like roads, bridges and buildings. Increased impervious surfaces lead to large, rapid increases in surface runoff in urban catchments during storm events, as well as changes in the upslope contributing area due to rerouting of urban runoff that can exacerbate erosion. Accounting for changes in surface drainage patterns Gama City, Brazil, is used to predict areas prone to accelerate gullying and develop a method of assessing the potential for gully erosion produced by urbanization. The method is based on the analysis and comparison of detailed digital elevation models (DEMs) of the natural condition before urbanization and the topography after urbanization. The study site is located in an area where changes in drainage patterns associated with rapid urbanization in the last 30 years have resulted in severe gullying. Our analysis identifies areas potentially susceptible to gullying and highlights the erosional influence of increased flow concentration caused by urban occupation, a finding that has implications and applications for strategies to prevent gully development in cities or areas undergoing urban expansion. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
102.
Quantification of Metals and Semimetals in Carbon‐Rich Rocks: A New Sequential Protocol Including Extraction from Humic Substances
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Renato Henrique‐Pinto Sarah‐Jane Barnes Dany Savard Sadia Mehdi 《Geostandards and Geoanalytical Research》2017,41(1):41-62
We have developed a new sequential extraction technique that does not require complex procedures and is efficient in determining metal and semimetal contents of carbon‐rich rocks. Six geological reference materials (SBC‐1, SCHS‐1, SCo‐1, SDO‐1, SGR‐1b and SLg‐1) and an in‐house black shale (SH‐1) were selected to test the method, which consists of four main digestion steps involving: (a) dilute HCl acid; (b) NaOH; (c) aqua regia; and (d) hydrofluoric acid. Compared with traditional aqua regia + hydrofluoric acid attack, this new protocol recovers more of the moderately volatile elements during early extraction of humic substances. In addition when compared with reference values, those for most elements are in agreement within uncertainty. Furthermore, this new protocol reveals important information on the partitioning of elements; for instance, steps one and two indicate which elements are associated with carbonates and organic phases from fulvic and humic acid extractions, whereas step three provides results for which elements are associated with sulfide minerals and step four indicates which elements remained in the silicate and oxide phases. 相似文献
103.
To obtain the shear wave velocity profile for engineering application to near-subsurface, many geophysical techniques are used. The dispersion curve alone is unable to provide deeper shear wave velocity information for deep soil deposit; therefore, a joint inversion of dispersion curves with the horizontal over vertical (H/V) (i.e., apparently ellipticity) curve is recommended. The H/V curve obtained from the microtremor recording contains a major part of Love wave contribution to the noise wavefield horizontal component. Due to this presence of Love wave fraction, the H/V curve does not completely replicate the ellipticity of Rayleigh wave. In this study, we try to compare the Rayleigh wave ellipticity obtained from the borehole velocity model to the H/V curve obtained at the same locality from seismic ambient noise recording. Two different techniques available for the Love effect minimization are tested and compared with the borehole ellipticity. Finally, the joint inversion of H/V and dispersion curve is made, which shows great correspondence with the previous measurement at the site. 相似文献
104.
When performing the seismic risk assessment of new or existing buildings, the definition of compact indexes able to measure the damaging and safety level of structures is essential, also in view of the economic considerations on buildings rehabilitation. This paper proposes two series of indexes, named, respectively, Global Damage Indexes (GDIs), which are representative of the overall structure performance, and Section Damage Indexes (SDIs), which assess the conditions of reinforced concrete (RC) beam‐column sections. Such indexes are evaluated by means of an efficient numerical model able to perform nonlinear analyses of the RC frame, based on the continuum damage mechanics theory and fiber approach. An improvement of a two‐parameter damage model for concrete, developed by some of the authors, which guarantees a better correlation between the Local Damage Indexes (LDIs) and the material's mechanical characteristics, is also presented. For the reinforcement, a specific LDI, named ‘steel damage index’, which takes into account the plastic strain development and the bar buckling effect, is proposed. The numerical model has been employed to simulate several experimental tests, in order to verify the accuracy of the proposed approach in predicting the RC member's behavior. Nonlinear static and dynamic analyses of two RC frames are carried out. The robustness of the method, as well as the effectiveness of the GDIs in assessing the structural conditions, are demonstrated here. Finally, comparisons between the evolution of GDIs and the achievement of the performance levels as proposed in FEMA 356 are reported. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
105.
Francine A. Kalas Renato S. Carreira Stephen A. Macko Angela L. R. Wagener 《Continental Shelf Research》2009
The present work aimed at studying the origin of particulate organic matter in Guanabara Bay and in some rivers of the Guanabara basin by using elemental composition, isotopic ratios (δ13C and δ15N) and molecular markers (sterols) in samples collected in two periods (winter and summer). Elemental and isotopic compositions were determined by dry combustion and mass spectrometry, respectively, while sterols were investigated by GC–FID and GC–MS. Higher sterol concentrations were present in the north-western part of the bay in winter (5.10–23.5 μg L–1). The high abundance of algal sterols (26–57% of total sterols), the elemental composition (C/N=6–8) and the isotopic signatures (δ13C=−21.3‰ to −15.1‰ and δ15N=+7.3‰ to +11.1‰) suggested the predominance of autochthonous organic matter, as expected for an eutrophic bay, although seasonal variation in phytoplankton activity was observed. Coprostanol concentration (fecal sterol) was at least one order of magnitude higher in the particulate material from fluvial samples (4.65–55.98 μg L–1) than in the bay waters (<0.33 μg L–1). This could be ascribed to a combination of factors including efficient particle removal to sediments in the estuarine transition zone, dilution with bay water and bacterial degradation during particle transport in the water column. 相似文献
106.
Petrology and geochemistry of Camiguin Island, southern Philippines: insights to the source of adakites and other lavas in a complex arc setting 总被引:72,自引:1,他引:71
Paterno R. Castillo Philip E. Janney Renato U. Solidum 《Contributions to Mineralogy and Petrology》1999,134(1):33-51
Camiguin is a small volcanic island located 12 km north of Mindanao Island in southern Philippines. The island consists of
four volcanic centers which have erupted basaltic to rhyolitic calcalkaline lavas during the last ∼400 ka. Major element,
trace element and Sr, Nd and Pb isotopic data indicate that the volcanic centers have produced a single lava series from a
common mantle source. Modeling results indicate that Camiguin lavas were produced by periodic injection of a parental magma
into shallow magma chambers allowing assimilation and fractional crystallization (AFC) processes to take place. The chemical
and isotopic composition of Camiguin lavas bears strong resemblance to the majority of lavas from the central Mindanao volcanic
field confirming that Camiguin is an extension of the tectonically complex Central Mindanao Arc (CMA). The most likely source
of Camiguin and most CMA magmas is the mantle wedge metasomatized by fluids dehydrated from a subducted slab. Some Camiguin
high-silica lavas are similar to high-silica lavas from Mindanao, which have been identified as “adakites” derived from direct
melting of a subducted basaltic crust. More detailed comparison of Camiguin and Mindanao adakites with silicic slab-derived
melts and magnesian andesites from the western Aleutians, southernmost Chile and Batan Island in northern Philippines indicates
that the Mindanao adakites are not pure slab melts. Rather, the CMA adakites are similar to Camiguin high-silica lavas which
are products of an AFC process and have negligible connection to melting of subducted basaltic crust.
Received: 27 February 1998 / Accepted: 27 August 1998 相似文献
107.
Mount Etna volcano was shaken during the summer 2001 by one of the most singular eruptive episodes of the last centuries.
For about 3 weeks, several eruptive fractures developed, emitting lava flows and tephra that significantly modified the landscape
of the southern flank of the volcano. This event stimulated the attention of the scientific community especially for the simultaneous
emission of petrologically distinct magmas, recognized as coming from different segments of the plumbing system. A stratigraphically
controlled sampling of tephra layers was performed at the most active vents of the eruption, in particular at the 2,100 m
(CAL) and at the 2,550 m (LAG) scoria cones. Detailed scanning electron microscope and energy dispersive x-ray spectrometer
(SEM-EDS) analyses performed on glasses found in tephra and comparison with lava whole rock compositions indicate an anomalous
increase in Ti, Fe, P, and particularly of K and Cl in the upper layers of the LAG sequence. Mass balance and thermodynamic
calculations have shown that this enrichment cannot be accounted for by “classical” differentiation processes, such as crystal
fractionation and magma mixing. The analysis of petrological features of the magmas involved in the event, integrated with
the volcanological evolution, has evidenced the role played by volatiles in controlling the magmatic evolution within the
crustal portion of the plumbing system. Volatiles, constituted of H2O, CO2, and Cl-complexes, originated from a deeply seated magma body (DBM). Their upward migration occurred through a fracture network
possibly developed by the seismic swarms during the period preceding the event. In the upper portion of the plumbing system,
a shallower residing magma body (ABT) had chemical and physical conditions to receive migrating volatiles, which hence dissolved
the mobilized elements producing the observed selective enrichment. This volatile-induced differentiation involved exclusively
the lowest erupted portion of the ABT magma due to the low velocity of volatiles diffusion within a crystallizing magma body
and/or to the short time between volatiles migration and the onset of the eruption. Furthermore, the increased amount of volatiles
in this level of the chamber strongly affected the eruptive behavior. In fact, the emission of these products at the LAG vent,
towards the end of the eruption, modified the eruptive style from classical strombolian to strongly explosive. 相似文献
108.
Renato L. Prado Isabel C. Espin Fenoll Irfan Ullah Gianna C. Maciel Miura Alvaro P. Crsta Roberto P. Zanon dos Santos Wolf Uwe Reimold Vagner R. Elis Erico Imbernon Claudio Riccomini Liliana Alcazar Diogo 《Meteoritics & planetary science》2019,54(10):2357-2372
The origin of the nearly circular Colônia structure, located at the southwestern edge of the city of São Paulo, Brazil, has been the subject of a long‐standing debate, ever since the 1960s when the structure was first investigated by geophysical methods. The structure still raises interest for geological research, as its sedimentary infill holds important paleoclimatic information about the evolution of the tropical rainforest, as well as the interplay between the South American summer monsoon, the Intertropical Convergence Zone, and the southern Westerly wind belt—for possibly as long as several million years. In addition, the search for evidence to conclusively establish the origin of this structure continues, and the answer most likely lies in the lower portions of the basin's sedimentary infill, which also holds a significant potential for underground water resources. Here, we present the results from recent seismic (reflection and HVSR), gravimetric, and geoelectrical surveys. They have provided a reliable image of the sedimentary infill, and the maximum depth to basement within the structure has been constrained consistently by the different methods to approximately ?400 m. The geophysical data have also allowed to map the lateral contact between the crystalline basement rocks and the sedimentary infill, which indicates a diameter of approximately 2.8 km for the sedimentary basin, with 3.6 km being the diameter of the outermost limit of the structure. A total of six seismic stratigraphic boundaries were identified within the sedimentary infill, providing a framework for the planning of a deep drilling campaign and subsequent sampling program aimed at geological and paleoclimatology studies. 相似文献
109.
110.
Di Franco A Graziano M Franzitta G Felline S Chemello R Milazzo M 《Marine pollution bulletin》2011,62(5):926-933
Many human activities add new structures to the marine landscape. Despite the fact that human structures cause some inevitable impacts, surprisingly little information exists on the effects of marina on natural marine assemblages. The aim of this paper is to assess habitat-specific response of benthic sessile organisms of rocky shores in relation to the presence of a small marina. Sampling was carried out at three coastal habitats (midshore, lowshore and subtidal) by means of visual censuses adopting an after-control-impact (ACI) experimental design. It appears that the marina affects the structure and composition of benthic communities of both the midshore and the lowshore. Little effect was evident on shallow subtidal assemblage structure. The results of the present study clearly show habitat-specific responses of coastal benthic assemblages to the presence of infrastructure. 相似文献