Intrinsic aquifer vulnerability assessment: validation by environmental tracers in San Miguel de Allende, Mexico   总被引：1，自引：0，他引：1  

Jürgen Mahlknecht  Ma. Guadalupe Medina-Mejía  Jaime Gárfias-Solis  Irene Cano-Aguilera 《Environmental Geology》2006,51(3):477-491

Vulnerability maps are important tools for water decision makers and land-use planners for protection of aquifers against contamination. The vulnerability map, according to the parametric method SINTACX for assessing intrinsic aquifer vulnerability, was validated in a case study with chlorofluorocarbon tracer technologies (CFC-11, CFC-12, and CFC-113) of groundwater. The tested area was the 1,295 km² volcano-sedimentary area of San Miguel de Allende (SMA), Mexico. From the results of this area, it appears that the vulnerability map is in parts inconsistent with the underlying groundwater flow system. Thus, the vulnerability map was corrected with tracer information. The validated vulnerability map indicates that the degree of vulnerability varies from low to moderate-high. Low vulnerability values are found in the graben extending from north to south along the SMA fault system and high values in recharge areas southeast and northwest of the study area. The investigation is a demonstration that the scientific reliability of results of the parametric method can be improved by validation with tracer techniques representing the groundwater dynamics. The flexible structure of SINTACX allows revising and adjusting scores and weights of the parameter maps to rebuild a new vulnerability map consistent with the hydrological system.  相似文献   

Magnetic fabrics, rock magnetism, cathodoluminescence and petrography of apparently undeformed Bambui carbonates from São Francisco Basin (Minas Gerais State, SE Brazil): An integrated study     

M. Irene B. Raposo  Ian McReath  Manoel S. D'Agrella-Filho   《Tectonophysics》2006,418(1-2):111

Magnetic measurements were performed on apparently undeformed limestones and carbonate shales from 44 sites in nearly horizontal stratigraphic layers mainly from the basal units of the Neoproterozoic Bambui Group in the southern part of the São Francisco Basin. Rock magnetism, cathodoluminescence, transmitted and reflected light microscopy analyses reveal that there is a mix of ferromagnetic minerals, mainly magnetite and pyrrhotite, in most sites. In some sites, however, the ferromagnetic minerals are magnetite and hematite. Fine-grained pyrrhotite and pyrite accompany rare fine-grained graphite and probably amorphous carbon in some of stylolites, while pyrrhotite is also present as larger interstitial masses in coarse-grained domains outside, but close to the stylolites. Magnetic fabrics were determined applying both anisotropy of low-field magnetic susceptibility (AMS) and anisotropy of anhysteretic remanence magnetization (AAR). The AAR tensor was less well defined than the AMS fabric due to the low ferromagnetic mineral content. The analysis at the individual-site scale defines three AMS fabric types. The first type (two sites) shows K_min perpendicular to the bedding plane, while K_max and K_int are scattered within bedding plane itself. This fabric is usually interpreted as primary (sedimentary-compactional), typical of totally undeformed sediments. The second type shows the three well-clustered AMS axes with K_min still perpendicular to the bedding plane. This fabric is the most important since it was found in the majority of the sites. The third type (two sites) is characterized by well-clustered K_max in the bedding plane, while K_min and K_int are distributed along a girdle. The second and third fabric types are interpreted as combinations of sedimentary-compactional and tectonic contributions at the earliest, and at a slightly later stage of deformation, respectively. AMS represents the contribution of all the rock-forming minerals, while AAR isolates the contribution of remanence-bearing minerals from the matrix minerals. However, rock magnetism shown that anhysteretic remanence only reaches grains with coercivity < 100 mT because the maximum AF in the majority of the available instruments is 100 mT. Therefore, hematite and pyrrhotite probably do not contribute to AAR, which is due to the shape-preferred orientation of magnetite grains. For some sites, the AMS and AAR fabric orientations are different, mainly with respect to the lineation orientations (K_max and A_max, respectively). In general, K_max is well developed and follows the trend of the main regional thrusts, fold axes and faults generated in the first deformational phase, while A_max follows both this trend and that of structural lineaments formed during the second deformational phase. These deformation phases arose from the compression, which occurred during the evolution of the Brasília fold belt during the last stages of the Brasiliano event. The magnetic fabrics of the apparently undeformed Bambui limestones are typical of very weakly deformed sediments, in which the depositional-compaction fabric has been partly overprinted by a tectonic one, with minimum susceptibility direction remaining perpendicular to bedding. This result is in agreement with the textures given by the petrographic observations.  相似文献   

Diasporic connections: case studies of Asian women in business     

Irene Hardill  Parvati Raghuram 《Area》1998,30(3):255-261

Summary In this paper, we use a case-study approach in order to explore the ways in which diasporic connections are being used by four Asian¹ businesswomen who serve an emerging niche market for clothing, which is defined by class and gender.  相似文献   

Book reviews     

Anne E. McElroy  Stephen Tennenbaum  James D. Felley  Carl H. Hobbs  James D. Felley  Carl H. Hobbs  Irene H. Stuckey  Ning Labbish Chao 《Estuaries and Coasts》1988,11(1):73-77

  相似文献   

Estimation of hypocentral parameters of local earthquakes when crustal layers have constantP-velocities and dipping interfaces     

Irene Sarkar  R. Chander  K. N. Khattri  V. K. Gaur 《Journal of Earth System Science》1987,96(3):229-238

The paper describes an algorithm for estimating the hypocentral coordinates and origin time of local earthquakes when the wave speed model to be employed is a layered one with dipping interfaces. A constrained least-squared error problem has been solved using the penalty function approach, in conjunction with the sequential unconstrained optimization technique of Fiacco and McCormick. Joint confidence intervals for the computed parameters are estimated using the approach of Bard for nonlinear problems. These results show that when a hypocentre lies outside the array of recording stations and head waves from a dipping interface are involved, then its inclination must be taken into account for dip angles exceeding 5°.  相似文献   

The influence of oxic degradation on the sedimentary biomarker record I: evidence from Madeira Abyssal Plain turbidites     

Marcel J.L. HoefsW.Irene C. Rijpstra  Jaap S. Sinninghe Damsté 《Geochimica et cosmochimica acta》2002,66(15):2719-2735

Free and ester-bound lipid biomarkers were analysed in oxidised and unoxidised parts of four distinct turbidites from the Madeira Abyssal Plain (MAP), which contained 1 to 2% organic carbon homogeneously distributed throughout the turbidites at the time they were deposited. These turbidites are well suited to study the effects of oxic degradation on lipid biomarkers without the complicating influence of varying organic matter sources, sedimentation rates, or bioturbation. One sample from the oxidised turbidite was compared with two samples from the unoxidised part of each turbidite. Postdepositional oxic degradation decreased concentrations of biomarkers by several orders of magnitude. The ester-bound lipids were degraded to a far lesser extent than their free counterparts were. The extent of degradation of different compounds differed substantially. Within a specific class of biomarkers, degradation also took place to a different extent, altering their distributions. This study shows that oxic degradation of the organic matter may have a profound effect on the biomarker fingerprint and may result in a severe bias in, for example, the interpretation of organic matter sources and the estimation of the palaeoproductivity of specific groups of phytoplankton.  相似文献   

The Energy Balance Experiment EBEX-2000. Part I: overview and energy balance   总被引：2，自引：1，他引：2  

Steven P. Oncley  Thomas Foken  Roland Vogt  Wim Kohsiek  H. A. R. DeBruin  Christian Bernhofer  Andreas Christen  Eva van Gorsel  David Grantz  Christian Feigenwinter  Irene Lehner  Claudia Liebethal  Heping Liu  Matthias Mauder  Andrea Pitacco  Luis Ribeiro  Tamas Weidinger 《Boundary-Layer Meteorology》2007,123(1):1-28

An overview of the Energy Balance Experiment (EBEX-2000) is given. This experiment studied the ability of state-of-the-art measurements to close the surface energy balance over a surface (a vegetative canopy with large evapotranspiration) where closure has been difficult to obtain. A flood-irrigated cotton field over uniform terrain was used, though aerial imagery and direct flux measurements showed that the surface still was inhomogeneous. All major terms of the surface energy balance were measured at nine sites to characterize the spatial variability across the field. Included in these observations was an estimate of heat storage in the plant canopy. The resultant imbalance still was 10%, which exceeds the estimated measurement error. We speculate that horizontal advection in the layer between the canopy top and our flux measurement height may cause this imbalance, though our estimates of this term using our measurements resulted in values less than what would be required to balance the budget. The National Center for Atmospheric Research is supported by the National Science Foundation  相似文献   

Application of LPW and SAI SAFNWC/MSG satellite products in pre-convective environments     

Miguel A. Martinez  Mercedes Velazquez  Marcelino Manso  Irene Mas 《Atmospheric Research》2007,83(2-4):366-379

The Spinning Enhanced Visible and Infrared Imagery (SEVIRI) instrument, on board the Meteosat Second Generation (MSG), is a radiometer with eight infrared (IR) spectral bands. Seven of these channels are used to retrieve Layer Precipitable Water (LPW) and Stability Analysis Imagery (SAI). Both products are the PGE07 and the PGE08 of SAFNWC (Satellite Application Facility on support to Nowcasting and Very Short-Range Forecasting). The authors at Instituto Nacional de Meteorología (INM) have developed the LPW and SAI algorithms, in the SAFNWC framework. Both products are retrieved using statistical retrieval based on neural networks. The main advantage of these algorithms versus physical retrieval algorithms is the independence from the Numerical Weather Prediction (NWP) models. The LPW provides information on the water vapor contained in a vertical column of unit cross-section area in three layers in the troposphere (low, middle and high) and in the total layer in cloud free areas. The SAI provides estimations of the atmospheric instability in cloud free areas, in particular the Lifted Index (LI).The stability and precipitable water obtained with both products are routinely generated every 15 min at a satellite horizontal resolution of 3 km in NADIR. A significant advantage of these MSG products, compared to traditional measurements such as radiosondes, is their ability to measure high resolution temporal and spatial variations of atmospheric stability and moisture in pre-convective environments. The main disadvantage is that they do not have the vertical resolution of radiosonde. The MSG moisture and stability time trend fields are especially useful during the period preceding the outbreak of convection due to the high resolution. Once the outbreak of convection occurs, the products calculated in the clear air pixels surrounding the convective system will allow to foresee the evolution of the convection.  相似文献   

Barriers perceived to engaging with climate change among the UK public and their policy implications   总被引：6，自引：2，他引：6  

Irene Lorenzoni  Sophie Nicholson-Cole  Lorraine Whitmarsh 《Global Environmental Change》2007,17(3-4):445-459

This paper reports on the barriers that members of the UK public perceive to engaging with climate change. It draws upon three mixed-method studies, with an emphasis on the qualitative data which offer an in-depth insight into how people make sense of climate change. The paper defines engagement as an individual's state, comprising three elements: cognitive, affective and behavioural. A number of common barriers emerge from the three studies, which operate broadly at ‘individual’ and ‘social’ levels. These major constraints to individual engagement with climate change have implications for achieving significant reductions in greenhouse gases in the UK. We argue that targeted and tailored information provision should be supported by wider structural change to enable citizens and communities to reduce their carbon dependency. Policy implications for effective engagement are discussed.  相似文献   

Quantitative antimony speciation in shooting-range soils by EXAFS spectroscopy   总被引：1，自引：0，他引：1  

Andreas C. Scheinost  Andre Rossberg  Irene Xifra  Ann-Kathrin Leuz  C. Annette Johnson 《Geochimica et cosmochimica acta》2006,70(13):3299-3312

The Sb speciation in soil samples from Swiss shooting ranges was determined using Sb K-edge X-ray absorption spectroscopy (XAS) and advanced statistical data analysis methods (iterative transformation factor analysis, ITFA). The XAS analysis was supported by a spectral data set of 13 Sb minerals and 4 sorption complexes. In spite of a high variability in geology, soil pH (3.1-7.5), Sb concentrations (1000-17,000 mg/kg) and shooting-range history, only two Sb species were identified. In the first species, Sb is surrounded solely by other Sb atoms at radial distances of 2.90, 3.35, 4.30 and 4.51 Å, indicative of metallic Sb(0). While part of this Sb(0) may be hosted by unweathered bullet fragments consisting of PbSb alloy, Pb L_III-edge XAS of the soil with the highest fraction (0.75) of Sb(0) showed no metallic Pb, but only Pb²⁺ bound to soil organic matter. This suggests a preferential oxidation of Pb in the alloy, driven by the higher standard reduction potential of Sb. In the second species, Sb is coordinated to 6 O-atoms at a distance of 1.98 Å, indicative of Sb(V). This oxidation state is further supported by an edge energy of 30,496-30,497 eV for the soil samples with <10% Sb(0). Iron atoms at radial distances of 3.10 and 3.56 Å from Sb atoms are in line with edge-sharing and bidentate corner-sharing linkages between Sb(O,OH)₆ and Fe(O,OH)₆ octahedra. While similar structural units exist in tripuhyite, the absence of Sb neighbors contradicts formation of this Fe antimonate. Hence the second species most likely consists of inner-sphere sorption complexes on Fe oxides, with edge and corner-sharing configuration occurring simultaneously. This pentavalent Sb species was present in all samples, suggesting that it is the prevailing species after weathering of metallic Sb(0) in oxic soils. No indication of Sb(III) was found.  相似文献