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101.
102.
Boris F. Ochoa‐Tocachi Wouter Buytaert Bert De Bièvre Rolando Célleri Patricio Crespo Marcos Villacís Carlos A. Llerena Luis Acosta Mauricio Villazón Mario Guallpa Junior Gil‐Ríos Paola Fuentes Dimas Olaya Paúl Viñas Gerver Rojas Sandro Arias 《水文研究》2016,30(22):4074-4089
Changes in land use and land cover are major drivers of hydrological alteration in the tropical Andes. However, quantifying their impacts is fraught with difficulties because of the extreme diversity in meteorological boundary conditions, which contrasts strongly with the lack of knowledge about local hydrological processes. Although local studies have reduced data scarcity in certain regions, the complexity of the tropical Andes poses a big challenge to regional hydrological prediction. This study analyses data generated from a participatory monitoring network of 25 headwater catchments covering three of the major Andean biomes (páramo, jalca and puna) and links their hydrological responses to main types of human interventions (cultivation, afforestation and grazing). A paired catchment setup was implemented to evaluate the impacts of change using a ‘trading space‐for‐time’ approach. Catchments were selected based on regional representativeness and contrasting land use types. Precipitation and discharge have been monitored and analysed at high temporal resolution for a time period between 1 and 5 years. The observed catchment responses clearly reflect the extraordinarily wide spectrum of hydrological processes of the tropical Andes. They range from perennially humid páramos in Ecuador and northern Peru with extremely large specific discharge and baseflows, to highly seasonal, flashy catchments in the drier punas of southern Peru and Bolivia. The impacts of land use are similarly diverse and their magnitudes are a function of catchment properties, original and replacement vegetation and management type. Cultivation and afforestation consistently affect the entire range of discharges, particularly low flows. The impacts of grazing are more variable but have the largest effect on the catchment hydrological regulation. Overall, anthropogenic interventions result in increased streamflow variability and significant reductions in catchment regulation capacity and water yield, irrespective of the hydrological properties of the original biome. Copyright © 2016 The Authors. Hydrological Processes. Published by John Wiley & Sons Ltd. 相似文献
103.
Narjess El Euch-El Koundi Serge Ferry Jean-Pierre Suc Georges Clauzon Mihaela Carmen Melinte-Dobrinescu Christian Gorini Anissa Safra Fouad Zargouni 《地学学报》2009,21(1):41-48
Outcrops, offshore wells, electric logs and seismic profiles from northern Tunisia provide an opportunity to decipher the Messinian Salinity Crisis in the Strait of Sicily. Messinian deposits (including gypsum beds) near the Tellian Range reveal two successive subaerial erosional surfaces overlain by breccias and marine Zanclean clays, respectively. In the Gulf of Tunis, Messinian thick evaporites (mostly halite) are strongly eroded by a fluvial canyon infilled with Zanclean clays. The first erosional phase is referred to the intra-Messinian tectonic phase and is analogous to that found in Sicily. The second phase corresponds to the Messinian Erosional Surface that postdates the marginal evaporites, to which the entire Sicilian evaporitic series must refer. The Western and Eastern Mediterranean basins were separated during deposition of the central evaporites. 相似文献
104.
Vicente G. Ruiz de Argandoa Lope Calleja ngel Rodríguez-Rey Luis Miguel Surez del Río Carmen Celorio 《Engineering Geology》2009,103(3-4):69-75
X-ray Computed Tomography (X-ray CT) has been used to study the petrophysical characteristics of a Jurassic sandstone from Asturias (Northern Spain) used as building stone in several monuments in the region. CT monitoring of water capillarity tests has made it possible to visualize the movement of water inside the samples, to relate this movement with texture characteristics, and to measure the height reached in successive images, thereby determining the capillary penetration coefficient; based on this coefficient, the effective capillary pore radius has also been estimated. An advantage of the use of CT is that, as the information comes from the sample interior, border effects that can be generated in the external faces can be avoided.The CT was also used to visualize how a commercial organosilicon consolidant penetrates inside the rock by means of capillarity, a usual way of consolidant application in stone restoration processes. The coefficient of capillary penetration of the product, determined on the basis of the measurements made on the tomographic images, is 53% less than that of water. The influence of rock texture characteristics on the capillarity both of the consolidant and the water was also observed.The samples underwent CT water capillarity studies before and after the consolidant application, proving that the treatment improves the rock's hydric properties. The coefficient of capillary penetration decreased by 24% following the application of the consolidant, whereas the effective pore radius decreased by more than 40%. 相似文献
105.
M. Ángeles Martín-Lara Mª Carmen Trujillo Miranda A. Ronda Gálvez A. Pérez Muñoz M. Calero de Hoces 《International Journal of Environmental Science and Technology》2017,14(12):2661-2674
The main aim of this work is to study the effect of scaling in the biosorption of chromium(VI) onto olive stone in two different fixed-bed columns. Firstly, the effect of flow rate, bed depth and inlet concentration of Cr(VI) in both columns was analyzed. The results revealed a better operation for lower flow rates, higher bed heights and lower inlet concentrations of metal. When decreasing flow rate, the operation time of the column increases. Therefore, as the solution flow rate increased the breakthrough and the exhaustion times decreased. An increase in bed depth increases the quantity of chromium eliminated and thus, the higher sorption capacity of the system. A decrease in the inlet concentration of chromium produces a delay in exhaustion time, and larger volumes of solution could be treated. The results were fitted to the BDST model, obtaining that the adsorptive capacity of the bed depth is similar in laboratory- and pilot-scale fixed-bed columns, considering the biosorption capacity as a biosorption-coupled reduction process. Results also could indicate that scaling affects more to the reduction process than properly biosorption process. The experimental data were also fitted to Adams–Bohart, Thomas, Yoon–Nelson and dose–response models. A good fit of the biosorption process of Cr(VI) was found for dose–response and Adams–Bohart models. 相似文献
106.
Octavio Artieda Alfonso Davila Jacek Wierzchos Peter Buhler Rafael Rodríguez‐Ochoa Juan Pueyo Carmen Ascaso 《地球表面变化过程与地形》2015,40(14):1939-1950
Miocene continental saltpans are scattered in the Central Valley of the Atacama Desert, one of the driest regions on Earth. These evaporitic deposits are hydrologically inactive, and are detached from groundwater brines or aquifers. The surface of the saltpans, also known as salars, comprises desiccation polygons, commonly with nodular salt structures along their sides. The morphology and bulk mineralogy of salt polygons differs between and within salars, and the shape and internal structure of salt nodules varies between different polygon types. Based on field observation, and mineralogy and crystallography data, we generated a conceptual model for the genesis and evolution of these surface features, whereby rare rainfall events are responsible for the transformation of desiccation salt polygons and the initial formation of salt nodules along polygon borders. In addition, frequent, but less intense, deliquescence events further drive the evolution of salt nodules, resulting in a characteristic internal structure that includes laminations, and changes in porosity and crystal morphologies. As a result, and despite the extreme dryness, the surfaces of fossil salars are dynamic on timescales of several years to decades, in response to daily cycles in atmospheric moisture, and also to rare and meager rainfall events. We propose that fossil salars in the Atacama Desert represent an end stage in the evolution of evaporitic deposits under extreme and prolonged dryness. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
107.
This paper explores the relationship between disaster risk reduction and long-term adaptive capacity building in two climate vulnerable areas—the Cayman Islands in the Caribbean and Ceará, in NE Brazil. Drawing on past applications of the disaster risk reduction framework, we identify four critical factors that have led to reductions in risk: flexible, learning-based, responsive governance; committed, reform-minded and politically active actors; disaster risk reduction integrated into other social and economic policy processes; and a long-term commitment to managing risk. We find that while the presence of these factors has reduced overall risk in both regions, in Ceará, disaster response as it is currently practiced, has fallen short of addressing the fundamental causes of vulnerability that leave those prone to hazards able to cope in the short term, yet enmeshed in poverty and at risk from the longer-term changes associated with climate change. Although calls for integration of disaster risk management with poverty eradication are not new, there has been insufficient attention paid in the literature on how to foster such integration. Based on the two case studies, we argue that the adoption of good governance mechanisms (such as stakeholder participation, access to knowledge, accountability and transparency) in disaster risk reduction policy may create the policy environment that is conducive to the kind of structural reform needed to build long-term adaptive capacity to climate-driven impacts. We conclude that without a synergistic two-tiered approach that includes both disaster risk reduction and structural reform, disaster risk reduction, in the face of climate changes, will prove to be an expensive and ineffective palliative treatment of changing risks. 相似文献
108.
Maria F. Gazulla Marta Rodrigo Monica Orduña Carmen M. Gómez 《Geostandards and Geoanalytical Research》2012,36(2):201-217
This article describes a series of methods developed for the determination of total carbon (CTotal), organic carbon (Corg), hydrogen, nitrogen and sulfur. The following elemental analysers were used: LECO model RC‐412 for the determination of organic carbon, total carbon and hydrogen; LECO model CS‐200 for the determination of total carbon and sulfur; LECO model TN‐400 for the determination of nitrogen; and LECO model TruSpec CHNS for the determination of organic carbon, total carbon, hydrogen, nitrogen and sulfur. Uncertainty and limits of detection and quantification were calculated for each method, as well as the running costs to define the most effective instrument for each material and each analyte. Accuracy was checked by the application of the Sutarno–Steger test. Finally, a compilation of the results obtained in the determination of CTotal, Corg, H, N and S in forty‐nine reference materials is presented. 相似文献
109.
The Lateglacial interstadial at the southeastern limit of the Sonoran Desert,Mexico: vegetation and climate reconstruction based on pollen sequences from Ciénega San Marcial and comparison with the subrecent record
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Carmen I. Ortega‐Rosas María C. Pealba Joel Guiot 《Boreas: An International Journal of Quaternary Research》2016,45(4):773-789
The last glacial–interglacial transition encompassed rapid climate oscillations that affected both hemispheres. At low latitudes, the pattern of oscillations is not well established. To address this issue, pollen analysis was performed at Ciénega San Marcial, a monsoon‐influenced site located on the southeastern edge of the Sonoran Desert at the limit of the tropical thornscrub. The pollen record covers the Late Wisconsinan glacial termination II, from 15 650 to 13 400 cal. a BP, including GS‐2 and the Lateglacial interstadial, and a recent historical period (AD c. 1919 to 2004). We applied the modern analogue technique, in which pollen taxa are assigned to plant functional types (PFTs), to reconstruct the past climates. At the end of GS‐2, a Juniperus–Pinus woodland is indicative of annual temperatures 10±2 °C colder than present and higher annual precipitation dominated by winter rains. The onset of the Lateglacial interstadial occurs at c. 15 500 cal. a BP, resulting in a lower sedimentation rate and the spread of a xeric grassland. This period is associated with an increase in summer insolation. A weak signal of summer monsoon intensification is dated to 14 825 cal. a BP but is associated with colder winter temperatures. A wider spread of tropical taxa occurs after 13 800 cal. a BP, along with the loss of Juniperus, suggesting a temperature increase of approximately 3 °C. In spite of the earlier Lateglacial warming, the transition from glacial to interstadial conditions seems to be related to North Atlantic atmospheric variations. We conclude that during the last glacial–interglacial transition, the Sonoran Desert at 28.5° latitude was sensitive to climate variations originating in northern latitudes. The recent historical sequence displays summer‐dominant precipitation and additional drivers of climate change, including anthropogenic factors and El Niño, thus showing a stronger Pacific circulation influence in the subrecent period. 相似文献
110.
Jorge Moreda-Piñeiro Elia Alonso-Rodríguez Isabel Turnes-Carou Carmen Moscoso-Pérez Gustavo Blanco-Heras Loreto Gómez Tellado Purificación López-Mahía Soledad Muniategui-Lorenzo Darío Prada-Rodríguez 《Journal of Atmospheric Chemistry》2017,74(1):1-21
The inorganic chemical composition (major ions and trace metals) of bulk deposition samples collected monthly with bulk collectors at seven Atlantic Coastal European cities (Galicia, Northwest of Spain) during wet season (September 2011 to March 2012) has been assessed and compared. Trace metals (Al, As, Ba, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V and Zn) were analysed in soluble fraction and non-soluble fraction (after acid extraction) of the bulk deposition by inductively coupled plasma-mass spectrometry. Major inorganic ions (Cl?, NO3 ?, SO4 2?, Na+, K+, Ca2+, Mg2+ and NH4 +) were analysed in the soluble fraction of the bulk deposition by capillary zone electrophoresis. Univariate analysis (ANOVA and Multiple Range Test) according to the location of each sampling site was performed. Results also suggest a great influence of cleaner Atlantic air masses. After partition coefficients and enrichment factor estimation, similar sources could be assigned for the ionic and metal composition of bulk deposition at seven urban sites. 相似文献