The impact of hydrological conditions on salinisation and nitrate concentration in the coastal Velez River aquifer (southern Spain)     

Azzurra Lentini  Claus Kohfahl  Jose Benavente  José Luis García-Aróstegui  Inaki Vadillo  Hanno Meyer  Asaf Pekdeger 《Environmental Geology》2009,58(8):1785-1795

This study reports the impact of hydrological conditions on salinisation and nitrate concentrations of a coastal aquifer located at the Mediterranean Sea, southern Spain. Eighty-two samples of ground- and surface water taken during two extreme hydrological events between 1994 and 1996 at 25 different wells were evaluated with regard to hydrochemistry, focusing on nitrate concentrations and salinisation, which constitute the main hazard of this aquifer. Furthermore, hydrochemical data were analysed by principal component analysis (PCA). Additionally, in 2007 13 ground- and surface water samples taken at 12 different locations were analysed for stable isotopes of D/¹⁸O, and one sample was analysed for ¹⁵N. Since 1993 until present saltwater intrusion was observed only during dry hydrological conditions in 1994; it showed an irregular salinisation pattern probably related to locally elevated hydraulic conductivities. Nitrate concentrations increase significantly during wet hydrologic conditions owing to uptake of nitrate by rising groundwater. Stable isotopes of groundwater reveal an Atlantic origin of the precipitation that recharges the aquifer and a minor amount of groundwater recharge by the water coming from the La Viñuela reservoir, which is used for irrigation over the aquifer. ¹⁵N isotopes point to a considerable input of nitrates derived from organic fertilisers.  相似文献   

Estimation of actual evapotranspiration by numerical modeling of water flow in the unsaturated zone: a case study in Buenos Aires, Argentina     

Andrés Cesanelli  Luis Guarracino 《Hydrogeology Journal》2009,17(2):299-306

A method is presented to estimate actual evapotranspiration (ET_A) from potential evapotranspiration (ET_P) by numerical modeling of water flow in the unsaturated zone. Water flow is described by the Richards equation with a sink term representing the root water uptake. Evaporation is included in the model as a Neumann boundary condition at the soil surface. The Richards equation is solved in a one-dimensional domain using a mixed finite element method. The values of ET_A are obtained by applying a water stress factor to ET_P to account for soil moisture changes during the simulation period. The proposed numerical model is used to estimate ET_A in an experimental plot located in a flatland area in Buenos Aires (Argentina). Numerical results show that the proposed model is a useful tool for evaluating evapotranspiration under different scenarios.  相似文献   

Recovery of Normal Cytogenetic Records in Mussels After Cessation of Pollutant Effluents in Puerto Madryn (Patagonia,Argentina)     

Gonzalo Machado-Schiaffino  Luis O. Bala  Eva Garcia-Vazquez 《Estuaries and Coasts》2009,32(4):813-818

The capacity of coast recovering after interruption of pollution sources has been explored employing mussels as biomarkers. In an area polluted by sewage sludge in Puerto Madryn (Argentina), abnormally high cytogenetic records (micronuclei) had been detected in the mussel Mytilus edulis, even higher than those obtained in this and other mussel species (Brachydontes rodriguezi, Aulacomya atra atra, Perumytilus purpuratus) sampled from heavily polluted industrial areas, and much higher than those recorded in samples from unpolluted areas of the same region. Normal cytogenetic patterns were recovered in Puerto Madryn less than 1 year after cessation of sewage sludge discharges, without additional treatment of the affected area. This discovery opens the possibility of considering restored coastal areas for aquaculture purposes instead of endangering natural populations in virgin areas.  相似文献   

The δ Scuti star 38 o¹ Eri     

Luis A. Balona 《Monthly notices of the Royal Astronomical Society》2000,318(1):289-293

We present and discuss 247 high dispersion échelle spectra of the δ Scuti star 38 o ¹ Eri. We find at least three periods, but all are affected by aliasing problems. We attempt to identify the modes by a technique involving both temporal and spatial pre-whitening. All modes are of high degree, probably ℓ≈4 and ℓ≈7.  相似文献   

海洋中尺度涡与内波的地震图像   总被引：10，自引：5，他引：5       下载免费PDF全文

宋海斌  Luis Pinheiro  王东晓  董崇志  宋洋  拜阳 《地球物理学报》2009,52(11):2775-2780

海洋反射地震通常用于调查、研究海底地质构造,勘探油气与天然气水合物资源.近期研究表明多道反射地震方法也可以对水柱的热盐细结构成像.中尺度涡与内波是重要的物理海洋现象,但是常规的物理海洋调查是在间隔若干公里的离散测站上进行的,水平分辨率较低,因此对中尺度涡的结构与内波的横向分布了解较差.本文利用在大西洋东部、南海采集的地震数据给出了低频反射地震可以对中尺度涡与内波清晰成像的新的证据.反射地震方法较传统海洋观测手段,具有明显的优势,主要体现在高的水平分辨率和短时间内对整个海水剖面进行成像方面．从地震剖面上,能够清楚地观测到中尺度涡、内波造成的反射特征变化,从而有助于改进对能量在不同尺度的海水运动之间传递过程的认识.  相似文献   

Geoeffectiveness of solar flares in magnetic crochet (sfe) production: II—Dependence on the detection method     

Juan José Curto  Luis R. Gaya-Piqué 《Journal of Atmospheric and Solar》2009,71(17-18):1705-1710

During magnetic active periods, disturbances in the geomagnetic field can act as natural noise masking other magnetic variations of small amplitude. In this paper, the influence of these perturbations on the observation of the effects on Earth of solar flares (sfe) has been studied. The diurnal and monthly values of detected sfe have been obtained, as well as the temporal variation of the relative occurrence of events. These numbers show how the irregular distribution of the magnetic observatories is an important limitation in the efficiency of the detection method. Some considerations about the actual method used at the International Service on Rapid Magnetic Variations are finally presented.  相似文献   

Geoeffectiveness of solar flares in magnetic crochet (sfe) production: I—Dependence on their spectral nature and position on the solar disk     

Juan José Curto  Luis R. Gaya-Piqué 《Journal of Atmospheric and Solar》2009,71(17-18):1695-1704

The influence of the spectral nature and position on the solar disk of solar flares related to the production of magnetic effects on earth (from now on, sfe) over a more than 30-year period has been studied. Regarding the spectral issue, we found that the probability of a flare to produce sfe depends on the spectral band in which we observe it, being higher when the flare is important both in Hα and X-ray emissions. On the other hand, Hα and X-ray emissions have been considered in many different divisions of the solar surface and their effectiveness on sfe production have been compared. We found that there is not any privileged region on the solar disk for sfe production. These results end with the controversy generated by distinct conclusions obtained in classical studies on the subject.  相似文献   

Chemical residues in lime‐plastered archaeological floors     

Luis Barba 《Geoarchaeology》2007,22(4):439-452

In addition to research carried out on soils and sediments, there is a parallel field of research applying the same analytical techniques to the study of chemical residues in stuccoes. The most common material used to build floors in Mesoamerica after the Classic period was lime plaster. The study of residues in stuccoes becomes, therefore, a very promising study area. In last 25 years the Archaeological Prospection Laboratory at Mexico's National Autonomous University has developed a research strategy to study human activities based on ethnoarchaeological studies to interpret the distribution of chemical residues in archaeological floors. The most successful applications have been in lime‐plastered surfaces; this article presents a brief review of these works. © 2007 Wiley Periodicals, Inc.  相似文献   

Seismic damage evaluation in urban areas using the capacity spectrum method: Application to Barcelona   总被引：8，自引：0，他引：8  

Alex H. Barbat  Luis G. Pujades  Nieves Lantada 《Soil Dynamics and Earthquake Engineering》2008,28(10-11):851

Conceptual aspects related to seismic vulnerability, damage and risk evaluation are discussed first, together with a short review of the most widely used possibilities for seismic evaluation of structures. The capacity spectrum method and the way of obtaining seismic damage scenarios for urban areas starting from capacity and fragility curves are then discussed. The determination of capacity curves for buildings using non-linear structural analysis tools is then explained, together with a simplified expeditious procedure allowing the development of fragility curves. The seismic risk of the buildings of Barcelona, Spain, is analyzed in the paper, based on the application of the capacity spectrum method. The seismic hazard in the area of the city is described by means of the reduced 5% damped elastic response spectrum. The information on the buildings was obtained by collecting, arranging, improving and completing a broad database of the dwellings and current buildings. The buildings existing in Barcelona are mainly of two types: unreinforced masonry structures and reinforced concrete buildings with waffled-slab floors. The ArcView software was used to create a GIS tool for managing the collected information in order to develop seismic risk scenarios. This study shows that the vulnerability of the buildings is significant in Barcelona and, therefore, in spite of the low-to-moderate seismic hazard in the region, the expected seismic risk is considerable.  相似文献   

Copper speciation in continental inputs to the Vigo Ria: sewage discharges versus river fluxes   总被引：1，自引：0，他引：1  

Santos-Echeandia J  Laglera LM  Prego R  van den Berg CM 《Marine pollution bulletin》2008,56(2):308-317

Continental inputs of copper via rivers and sewage into the Vigo Ria were evaluated. The main fluvial input is not contaminated and the most degraded discharges occur on the southern margin of the middle ria. Continental inputs of copper and ligands to the ria are dominated by sewage treatment plants (136 mol Cu day(-1), 124 mol L day(-1)) supported by rivers (15 mol Cu day(-1), 21 mol L day(-1)). The dissolved fraction is the main channel of discharge for rivers (66%) with particulate matter being predominant in sewage (63%). Dissolved copper is organically complexed both in rivers (99.8%) and sewage (99.9%). This minor difference may be attributed to the fact that the stability of sewage complexes is greater than those in rivers. Moreover, ligand concentrations are higher in sewage than in rivers. Thus, the natural continental inputs of copper and ligands into the ria are magnified by anthropogenic inputs (5-15 and 3-5 times higher for copper and ligands, respectively).  相似文献