Phosphorus fractions and sorption dynamics in the sediments of two Ca-SO4 water reservoirs in the central Argentine Andes     

Jos&#; Gabriel Le&#;n  Fernando Luis Pedrozo  Pedro F&#;lix Temporetti 《国际泥沙研究》2017,32(3)

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Stable isotope paleohydrology and chemostratigraphy of the Albian Wayan Formation from the wedge-top depozone,North American Western Interior Basin     

Jeffrey B. Ross  Greg A. Ludvigson  Andreas Möller  Luis A. Gonzalez  J. D. Walker 《中国科学:地球科学(英文版)》2017,60(1):44-57

Understanding of the role of atmospheric moisture and heat transport in the climate system of the Cretaceous greenhouse world represents a major challenge in Earth system science.Stable isotopic paleohydrologic data from mid-Cretaceous paleosols in North America,from paleoequatorial to paleoArctic latitudes,have been used to constrain the oxygen isotope mass balance of the Albian hydrologic cycle.Over the range from 40°-50°N paleolatitude,sideritic paleosols predominate,indicating paleoenvironments with positive precipitation-evaporation(P-E)balances.Local exceptions occur on leeward side of the Sevier Orogen,where calcic paleosols in the wedge-top depozone record paleoenvironments with negative P-E balances in the orographic rain shadow.Stratigraphic sections in the Wayan Formation of Idaho(WF)were sampled from the wedge-top depozone.The units consist of stacked m-scale mudstone paleosols separated by m-scale sandstone-siltstone beds.Sections were sampled for organic carbon isotope profiles,and B-horizons from 6 well-developed paleosols were sampled for detrital zircons to determine maximum depositional ages.The first of these from the WF has produced a U-Pb concordia age of 101.0±1.1 Ma.This same WF section has produced a stratigraphic trend of upwardly decreasingδ~(13)C values ranging from-24‰upwards to-27‰VPDB,suggesting correlation to the late Albian C15 C-isotope segment.Pedogenic carbonates from the WF principally consist of micritic calcite,with carbon-oxygen isotope values that array along meteoric calcite lines(MCLs)withδ~(18)O values that range from-9.47‰up to-8.39‰VPDB.At approximately 42°N paleolatitude,these MCL values produce calculated paleoprecipitation values of-8.12‰to-7.04‰VSMOW,a range that is consistent with the estimates produced from other proxies at the same paleolatitudes across North America.These results indicate that despite the orographic rain shadow effect,the processes of meridional atmospheric moisture transport in this locale were similar to those in more humid mid-latitude paleoenvironments elsewhere in the continent.  相似文献   

Trend analysis of nutrient loadings in a large prairie catchment     

Luis Alejandro Morales-Marín  Kwok Pan Chun  Howard Simon Wheater  Karl-Erich Lindenschmidt 《水文科学杂志》2017,62(4):657-679

Nutrient loadings in many river catchments continue to increase due to rapid expansion of agriculture, urban and industrial development, and population growth. Nutrient enrichment of water bodies has intensified eutrophication which degrades water quality and ecosystem health. In this study, we carried out a trend analysis of total phosphorus and total nitrogen loads in the South Saskatchewan River (SSR) catchment using a novel approach to analyse nutrient time series. Seasonal analysis of trends at each of the water quality stations was performed to determine the relationships between annual flow regimes and nutrient loads in the catchment, in particular, the influence of the high spring runoff on nutrient export. Decadal analysis was also performed to determine the long-term relationships of nutrients with anthropogenic changes in the catchment. Although it was found that seasonal and historical variability of nutrient load trends is mainly determined by streamflow regime changes, there is evidence that increases in nitrogen concentration can also be attributed to anthropogenic changes.  相似文献   

Uncertainty analysis and probabilistic segmentation of electrical resistivity images: the 2D inverse problem          下载免费PDF全文

Juan Luis Fernández‐Martínez  Shan Xu  Colette Sirieix  Zulima Fernández‐Muniz  Joëlle Riss 《Geophysical Prospecting》2017,65(Z1):112-130

In this paper, we present the uncertainty analysis of the 2D electrical tomography inverse problem using model reduction and performing the sampling via an explorative member of the Particle Swarm Optimization family, called the Regressive‐Regressive Particle Swarm Optimization. The procedure begins with a local inversion to find a good resistivity model located in the nonlinear equivalence region of the set of plausible solutions. The dimension of this geophysical model is then reduced using spectral decomposition, and the uncertainty space is explored via Particle Swarm Optimization. Using this approach, we show that it is possible to sample the uncertainty space of the electrical tomography inverse problem. We illustrate this methodology with the application to a synthetic and a real dataset coming from a karstic geological set‐up. By computing the uncertainty of the inverse solution, it is possible to perform the segmentation of the resistivity images issued from inversion. This segmentation is based on the set of equivalent models that have been sampled, and makes it possible to answer geophysical questions in a probabilistic way, performing risk analysis.  相似文献   

Influence of earthquake ground‐motion duration on damage estimation: application to steel moment resisting frames          下载免费PDF全文

Andre R. Barbosa  Filipe L. A. Ribeiro  Luis A. C. Neves 《地震工程与结构动力学》2017,46(1):27-49

This paper presents an analytical study evaluating the influence of ground motion duration on structural damage of 3‐story, 9‐story, and 20‐story SAC steel moment resisting frame buildings designed for downtown Seattle, WA, USA, using pre‐Northridge codes. Two‐dimensional nonlinear finite element models of the buildings are used to estimate the damage induced by the ground motions. A set of 44 ground motions is used to study the combined effect of spectral acceleration and ground motion significant duration on drift and damage measures. In addition, 10 spectrally equivalent short‐duration shallow crustal ground motions and long‐duration subduction zone records are selected to isolate duration effect and assess its effect on the response. For each ground motion pair, incremental dynamic analyses are performed at at least 20 intensity levels and response measures such as peak interstory drift ratio and energy dissipated are tracked. These response measures are combined into two damage metrics that account for the ductility and energy dissipation. Results indicate that the duration of the ground motion influences, above all, the combined damage measures, although some effect on drift‐based response measures is also observed for larger levels of drift. These results indicate that because the current assessment methodologies do not capture the effects of ground motion duration, both performance‐based and code‐based assessment methodologies should be revised to consider damage measures that are sensitive to duration. Copyright © 2016 John Wiley & Sons, Ltd  相似文献   

Depth of closure: New calculation method based on sediment data     

Luis Aragonés  Jose Ignacio Pagán  Isabel López  José C.Serra 《国际泥沙研究》2018,33(2):198-207

Obtaining depth of closure (DoC) in an accurate manner is a fundamental issue for coastal engineering, since good results for coastal structures and beach nourishment depend mainly on DoC. Currently, there are two methods for obtaining the DoC, mathematical formulations and profile surveys. However, these methods can incur important errors if one does not take into account the characteristics and morphology of the area, or if one does not have a sufficiently long time series. In this work the DoC is obtained from the break in the trend of the sediment with the depth, that is, in general with the increase of the depth a decrease in the size of the sediment takes place. However, at one point this tendency changes and the size increases, and then decreases again. When comparing the point where the minimum sediment size occurs before the increase, it is observed that the error incurred is small compared to other methods. If the Standard Deviation of Depth Change (SDDC) method is considered as the most accurate method, the error incurred by the proposed method is less than 7%. In addition, it can be seen that the dispersion of the sediment method always occurs outside the zone of bar movement. Whereas in the methods of profiles survey (using 2 cm precision profiles), sometimes the DoC is obtained within the active zone of bar movement. In addition, where the relative minimum of the median sediment size is found, and the sizes of 0.063 and 0.125 mm predominate in the composition of the sample. Therefore, this new method allows the precise location of the DoC to be obtained in a fast and simple way. Furthermore, this method has the advantage that it is not affected by the modifications that may be experienced by both the study area and the cross-shore beach profile.  相似文献   

Reconstruction of fluvio-lacustrine landscapes and settlement history in the Texcoco region,Mexico, using a modern geomorphic analog     

Kurt H. Wogau  Carlos E. Cordova  Luis Morett-Alatorre  Guillermo Acosta Ochoa 《Geoarchaeology》2024,39(2):168-182

Located in the Basin of Mexico, the eastern shore of former Lake Texcoco sustained a variety of human occupations throughout the Holocene, including preceramic hunter-gatherers, incipient agriculturalists, and a variety of settlements in the ceramic periods. Nonetheless, the environmental dynamics of occupations on the lakeshore have not been fully addressed. The Archaic preagricultural Texcoco Man site (>5000 B.C.E.) and the Late Formative TX-LF-14 site (c. 550-200 B.C.E.), among others, occupy this fluvio-lacustrine transitional environment. Few stratigraphic works in and around the sites have been performed. Consequently, it is difficult to understand the dynamics of the sedimentary system in space and time. This work highlights and describes the fluvio-lacustrine sedimentary dynamics and the resulting landscape that past societies inhabited on the eastern shore of Texcoco Lake. Because the study area has been altered by historic and modern draining, our work employs Lake Santiaguillo and its main tributary, the Tejamen River in the Durango state, as a modern analog to study their sedimentary dynamics. The analyses of surface geomorphology in the Texcoco study area were employed to corroborate the modern analog interpretation. To achieve these goals, we conducted a GIS-based morphometric analysis and LANDSAT-8 imagery to study the variations in landforms through wet and dry events. The results indicate an increase in the lake volume, low bifurcation in the active fluvial channels, few inundated surfaces, and the presence of bird-foot deltaic channels during high precipitation events. In contrast, low precipitation events are characterized by reduced lake volume, increased fluvial channel bifurcation, and expanded floodplains. This heterogeneous landscape thus provided a rich source of diverse natural resources of saline and freshwater aquatic habitats. Simultaneously, constant or recurring flooding events generated a challenging landscape for prehistoric settlers who implemented diverse technologies, such as the construction of tlateles, on the levees of deltaic channels to reduce the risk and impact of flooding events.  相似文献   

Reservoir architecture and heterogeneity distribution in floodplain sandstones: Key features in outcrop,core and wireline logs     

Luis Miguel Yeste  Augusto N. Varela  César Viseras  Neil D. Mcdougall  Fernando García-García 《Sedimentology》2020,67(7):3355-3388

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On Sinkholes and Galaxies: An Example of Fractal Universality     

Pardo-Igúzquiza  Eulogio  Dowd  Peter A.  Rizo-Decelis  Luis David 《Mathematical Geosciences》2020,52(5):639-650

Mathematical Geosciences - The universality of fractals implies that very different physical processes can give rise to similar complex spatial patterns. Sinkholes (dolines) and galaxies provide a...  相似文献   

Assessment of microscale economic flood losses in urban and agricultural areas: case study of the Santa Bárbara River,Ecuador     

Pinos  Juan  Orellana  Daniel  Timbe  Luis 《Natural Hazards》2020,103(2):2323-2337

Natural Hazards - To reduce and prevent significant economic flood losses, reliable tools are required to estimate potential river inundation effects. This paper focuses on the estimation of direct...  相似文献