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991.
Lana Xavier Serra C. Casas-Castillo M. C. Rodríguez-Solà R. Redaño A. Burgueño A. 《Theoretical and Applied Climatology》2018,133(1-2):385-403
Theoretical and Applied Climatology - An analysis of the normalised rainfall intensity curves in Barcelona (NE Spain) has been undertaken from 41 selected rain rate episodes recorded by an urban... 相似文献
992.
Gonzalo Gurrea Vicente Blanca-Giménez Vicente Pérez María-Antonia Serrano Juan-Carlos Moreno Solar Radiation Group of the Universitat Politècnica de València 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(4):599-610
The goal of this study was to statistically analyse the variability of global irradiance and ultraviolet erythemal (UVER) irradiance and their interrelationships with global and UVER irradiance, global clearness indices and ozone. A prediction of short-term UVER solar irradiance values was also obtained. Extreme values of UVER irradiance were included in the data set, as well as a time series of ultraviolet irradiance variability (UIV). The study period was from 2005 to 2014 and approximately 250,000 readings were taken at 5-min intervals. The effect of the clearness indices on global irradiance variability (GIV) and UIV was also recorded and bi-dimensional distributions were used to gather information on the two measured variables. With regard to daily GIV and UIV, it is also shown that for global clearness index (kt) values lower than 0.6 both global and UVER irradiance had greater variability and that UIV on cloud-free days (kt higher than 0.65) exceeds GIV. To study the dependence between UIV and GIV the χ2 statistical method was used. It can be concluded that there is a 95% probability of a clear dependency between the variabilities. A connection between high kt (corresponding to cloudless days) and low variabilities was found in the analysis of bi-dimensional distributions. Extreme values of UVER irradiance were also analyzed and it was possible to calculate the probable future values of UVER irradiance by extrapolating the values of the adjustment curve obtained from the Gumbel distribution. 相似文献
993.
Interaction of freshly precipitated silica gel with aqueous solutions was studied at laboratory batch experiments under ambient
and near neutral pH-conditions. The overall process showed excellent reversibility: gel growth could be considered as an opposite
process to dissolution and a linear rate law could be applied to experimental data. Depending on the used rate law form, the
resulting rate constants were sensitive to errors in parameters/variables such as gel surface area, equilibrium constants,
Si-fluxes, and reaction quotients. The application of an Integrated Exponential Model appeared to be the best approach for
dissolution data evaluation. It yielded the rate constants k
dissol ∼ (4.50 ± 0.68) × 10−12 and k
growth ∼ (2.58 ± 0.39) × 10−9 mol m−2 s−1 for zero ionic strength. In contrast, a Differential Model gave best results for growth data modeling. It yielded the rate
constants k
dissol ∼ (1.14 ± 0.44) × 10−11 and k
growth ∼ (6.08 ± 2.37) × 10−9 mol m−2 s−1 for higher ionic strength (I ∼ 0.04 to 0.11 mol L−1). The found silica gel solubility at zero ionic strength was somewhat lower than the generally accepted value. Based on the
and standard Gibbs free energy of silica gel formation was calculated as and −850,318 ± 20 J mol−1, respectively. Activation energies for silica gel dissolution and growth were determined as and respectively. An universal value for growth of any silica polymorph, is not consistent with the value for silica gel growth, which questions the hypothesis about one unique activated complex
controlling the silica polymorph growth. 相似文献
994.
Methodology for groundwater recharge assessment in carbonate aquifers: application to pilot sites in southern Spain 总被引:1,自引:0,他引:1
B. Andreo J. Vías J. J. Durán P. Jiménez J. A. López-Geta F. Carrasco 《Hydrogeology Journal》2008,16(5):911-925
Aquifer recharge can be determined by conventional methods such as hydrodynamic or hydrologic balance calculations, or numerical, hydrochemical or isotopic models. Such methods are usually developed with respect to detrital aquifers and are then used on carbonate aquifers without taking into consideration their hydrogeological particularities. Moreover, such methods are not always easy to apply, sometimes requiring data that are not available. Neither do they enable determination of the spatial distribution of the recharge. For eight regions in southern Spain, the APLIS method has been used to estimate the mean annual recharge in carbonate aquifers, expressed as a percentage of precipitation, based on the variables altitude, slope, lithology, infiltration landform, and soil type. The aquifers are representative of a broad range of climatic and geologic conditions. Maps of the above variables have been drawn for each aquifer, using a geographic information system; thus they can be superimposed to obtain the mean value and spatial distribution of the recharge. The recharge values for the eight aquifers are similar to those previously calculated by conventional methods and confirmed by discharge values, which corroborates the validity of the method. 相似文献
995.
Alejandro?D.?Canepuccia Maria?S.?Fanjul Eugenia?Fanjul Florencia?Botto Oscar?O.?Iribarne Consejo Nacional de Investigaciones Científicas y Técnicas Departamento de Biología Universidad Nacional de Mar del Plata Mar del Plata Argentina 《Estuaries and Coasts》2008,31(5):920-930
The role of positive and indirect interactions is often crucial in communities with intense abiotic stress such as salt marshes.
The burrowing crab, Neohelice (=Chasmagnathus) granulata, is the dominant benthic macroinvertebrate of southwest Atlantic marshes (southern Brazil to Northern Argentinean Patagonia),
having strong direct and indirect effects on marsh soil and, in consequence, on marsh vegetation and primary consumers. In
this work, we investigate if this crab indirectly modifies habitat use by the granivorous rodents, Akodon azarae and Oligoryzomys flavescens, by increasing nutrient availability and thus enhancing seed production by the marsh plant Spartina densiflora. The study was conducted at the Mar Chiquita Coastal Lagoon, Argentina (37°32′ S). Rodent frequencies in S. densiflora were positively correlated with crab densities throughout the low and middle marsh. Additionally, the highest quality of
S. densiflora and inflorescence density was recorded at the highest crab densities. Experimental manipulation of crab densities shows that
N. granulata indirectly enhances the performance of S. densiflora (e.g., decreased fiber content and C/N ratios) and increases density of seeds. Moreover, N. granulata also facilitates S. densiflora seed availability to rodents by concentrating them in sediment mound at their burrows entrances. Experimental rodent exclusions
showed that rodent species used S. densiflora seeds, a variable positively related to crab burrow density. Thus, our results show that N. granulata drives the granivorous rodent distribution and the intensity of seeds–rodent interaction trough facilitative and indirect
interactions in marsh community. 相似文献
996.
Kamil Zágoršek Katarína Holcová Tomáš Třasoň 《International Journal of Earth Sciences》2008,97(4):835-850
Fossil Bryozoa occurs usually in shallow-water environments. One of the rare deep-water associations of Bryozoa has been studied
in a profile at Kralice nad Oslavou. According to studies of foraminifera, the paleodepth was more than 150 m and less than
500 m. The bryozoan assemblages are poor, consisting of four species only, dominated by Tervia irregularis (Cyclostomatida) and Reteporella kralicensis sp.n. (Cheilostomatida), a new species being described in detail. 相似文献
997.
F. Gutiérrez J. M. Calaforra F. Cardona F. Ortí J. J. Durán P. Garay 《Environmental Geology》2008,53(5):951-965
In Spain, evaporite outcrops cover approximately 7% of the total area of the country. Most of the evaporitic formations are made up of Ca-sulfates (gypsum/anhydrite) or Ca-sulfates and halite. Certain Paleogene marine evaporites also contain K-Mg-chlorides, and some Tertiary continental formations bear substantial amounts of Na-sulfates in the subsurface (glauberite and thenardite). Mesozoic evaporitic formations commonly wedge out towards the ground surface, passing into condensed sequences and dissolution-collapse breccias. Some of these highly porous breccias constitute major regional aquifers. In several areas, interstratal karstification of the evaporites has given rise to gravitational deformations such as basin structures, monoclines, and collapse structures covering several square kilometers that record a cumulative subsidence in excess of 200 m (Teruel and Calatayud Grabens). A widespread consequence of evaporite dissolution processes in Spain is the hydrochemical degradation of surface waters. Some of the largest and most outstanding lake systems, from an environmental perspective, occur in karstic depressions developed in evaporitic formations (Fuente de Piedra, Gallocanta, Bujaraloz, and Bañolas lakes). Sinkhole activity is a major geohazard in several evaporite karst areas. The sinkhole risk has a particularly high impact in sectors where Tertiary evaporites are overlain by Quaternary alluvial aquifers (Calatayud, Zaragoza, and Madrid areas). Some of the detrimental effects of subsidence include severe damage to historical monuments (Calatayud), the demolition of a whole village (Puilatos), or the derailment of a freight train (Zaragoza area). The deepest gypsum caves are found in Triassic diapiric structures (El Sumidor Cave, 210 m deep), and the longest ones are developed in horizontally lying Neogene sequences (Sorbas caves, and Estremera maze cave). The Cardona diapir hosts salt caves up to 4,300 m long whose genesis is related to flooding of mine galleries caused by the interception of a phreatic conduit. The main anthropogenic impacts on the endokarstic systems are related to the disposal of wastewaters and the destruction of caves by quarrying. The fluvial valleys that cross Tertiary evaporitic outcrops commonly show peculiar geological characteristics related to dissolution-induced synsedimentary subsidence phenomena: (1) Thickened alluvium filling dissolution basins up to several tens of kilometers long and more than 100 m deep. The largest thickenings are found in areas where the bedrock contains halite and glauberite. (2) Superimposed alluvial units locally bounded by angular unconformities. (3) Abundant deformational structures and paleosinkholes related to the rockhead and/or interstratal karstification of the substratum. These fluvial valleys typically are flanked by a prominent gypsum escarpment. Rock-falls favored by the dissolutional enlargement of joints derived from these scarps are the type of mass movement which has caused the highest number of casualties in Spain. 相似文献
998.
F. Carrasco D. Sánchez I. Vadillo B. Andreo C. Martínez L. Fernández 《Environmental Geology》2008,54(3):575-585
The water framework directive (WFD) is applied within the Guadalhorce river basin, a Western Mediterranean basin in the Málaga
province (South Spain). Criteria defining different surface and groundwater bodies are described. The basic hydrographic network
is constituted of low-mountain and low-altitude Mediterranean mineralized rivers. Heavily modified surface water bodies correspond
(1) to areas where dams regulate the main watercourses, (2) to areas downstream of reservoirs, where river flow is reduced,
and (3) to the coastal sector of the river where artificial channelling has caused morphological variations. Groundwater bodies
are related to carbonate and porous aquifers and, locally, to aquifers influenced by dissolution of evaporites. The main impacts
to water bodies are irrigated lands and livestock farming. There are also point sources of pollution, such as wastewater,
landfills, golf courses, industrial zones, quarries and petrol stations. In addition, groundwater is frequently pumped for
human supply and irrigation. Qualitative status of groundwater bodies was done by chemical analysis of samples from a monitoring
network and the quantitative status by examining variations in piezometric levels. Both revealed the existence of water bodies
at risk of not meeting the environmental objectives of the WFD. The main indicators of pollution are nitrates related to agricultural
activities, and total organic carbon (TOC), PO43− and NH4+ in relation to wastewater. 相似文献
999.
María Yanina Esper Angillieri 《Environmental Geology》2008,55(1):107-111
This work analyzes various morphometric characteristics of the Colangüil river basin in order to evaluate flash flood hazards.
Such high-water events pose a risk to the similarly named small village located at the basin’s foot area. For this purpose,
the basin is divided into seven sub-basins and some basic measurements (surface, perimeter, basin length, river beds, elevations
and slope of the main river bed, and of a number of minor river beds) are calculated. These measurements permit to predict
approximately the behavior of the basin in the presence of a series of theoretical rainstorms that may generate unusual runoff
volumes that make up such flash floods. 相似文献
1000.
Xiomara Cazañas Pura Alfonso Joan Carles Melgarejo Joaquín Antonio Proenza Anthony Edward Fallick 《Mineralium Deposita》2008,43(7):805-824
The El Cobre deposit is located in eastern Cuba within the volcanosedimentary sequence of the Sierra Maestra Paleogene arc.
The deposit is hosted by tholeiitic basalts, andesites and tuffs and comprises thick stratiform barite and anhydrite bodies,
three stratabound disseminated up to massive sulphide bodies produced by silicification and sulphidation of limestones or
sulphates, an anhydrite stockwork and a siliceous stockwork, grading downwards to quartz veins. Sulphides are mainly pyrite,
chalcopyrite and sphalerite; gold occurs in the stratabound ores. Fluid inclusions measured in sphalerite, quartz, anhydrite
and calcite show salinities between 2.3 and 5.7 wt% NaCl eq. and homogenisation temperatures between 177 and 300°C. Sulphides
from the stratabound mineralisation display δ
34S values of 0‰ to +6.0‰, whilst those from the feeder zone lie between −1.4‰ and +7.3‰. Sulphides show an intra-grain sulphur
isotope zonation of about 2‰; usually, δ
34S values increase towards the rims. Sulphate sulphur has δ
34S in the range of +17‰ to +21‰, except two samples with values of +5.9‰ and +7.7‰. Sulphur isotope data indicate that the
thermochemical reduction of sulphate from a hydrothermal fluid of seawater origin was the main source of sulphide sulphur
and that most of the sulphates precipitated by heating of seawater. The structure of the deposit, mineralogy, fluid inclusion
and isotope data suggest that the deposit formed from seawater-derived fluids with probably minor supply of magmatic fluids. 相似文献