清镇顽辉石球粒陨石（EH3）不透明相的岩石,矿物学研究

通过对最新鲜、最原始的ＥＨ３型损石－清镇员石不透明矿物的岩石学、矿物学研究，揭示了不透明矿物化学组成与产状的成因关系，提出了星云冷凝，金属与星去气相组分的硫化反应，矿物出熔及矿物分解等四种形成机制。对不透明物的各种环带结构及闪锌矿、矿镁矿等矿物温度计的研究，揭示了该陨石在星云阶段和母体中的热历史，与Ｙａｍａｔｏ－６９１（ＥＨ３）的对比表明，清镇陨石不透明矿物形成于更加还原的星云条件。     

Search for extinct Cl: Vigarano CAIs, the Pink Angel from Allende, and a Ningqiang chondrule

We have searched for excesses of ³⁶S derived from the decay of extinct ³⁶Cl in sodalite, a secondary Cl-rich mineral, in Ca-Al-rich inclusions (CAIs) from the Vigarano and Allende CV3 chondrites and in a chondrule from the Ningqiang carbonaceous chondrite. The presence of sodalite in two CAIs from Vigarano and its absence from surrounding CAI fragments suggests sodalite formation after CAI fragmentation. As for sodalite in the Allende Pink Angel CAI, oxygen isotopic compositions have been interpreted as indicative of high temperature interactions, thus suggesting formation prior to accretion to the parent body, probably in a nebular setting. Sodalite in the Ningqiang chondrule is considered to have formed via alkali-Ca exchange, which is believed to have occurred before accretion to the parent body.Sodalites in the Vigarano CAIs and in the Ningqiang chondrule show no clear evidence for the presence of radiogenic ³⁶S. The inferred 2σ upper limits for ³⁶Cl/³⁵Cl at the time of sodalite formation are 1.6 × 10⁻⁶ (Vigarano CAIs) and 3.3 × 10⁻⁶ (Ningqiang chondrule), respectively. In the Pink Angel CAI sodalite exhibits small ³⁶S excesses which weakly correlate with ³⁵Cl/³⁴S ratios. The inferred ³⁶Cl/³⁵Cl ratio of (1.8 ± 2.2) × 10⁻⁶ (2σ error) is lower than that found by Hsu et al. [Hsu, W., Guan, Y., Leshin, L. A., Ushikubo, T. and Wasserburg, G. J. (2006) A late episode of irradiation in the early solar system: Evidence from extinct ³⁶Cl and ²⁶Al in meteorites. Astrophys. J. 640, 525-529], thus indicative of heterogeneous distribution of ³⁶Cl in this CAI. Spallation reactions induced by energetic particles from the young Sun are suggested for the origin of ³⁶Cl, similar to the case of ¹⁰Be. While ¹⁰Be appears to be present in roughly equal abundance in all studied CAIs, our study indicates the level of ³⁶Cl abundances to be variable so that there seems to be no simple relationship between ¹⁰Be and ³⁶Cl. This would be expected if trapped cosmic rays rather than Early Solar System spallation were the dominant source of ¹⁰Be in the Early Solar System, since their contribution to ³⁶Cl would have been tiny.If the variability of ³⁶Cl abundances is caused by temporal differences in the alteration that formed sodalite, sodalite in the Vigarano CAIs and in the Ningqiang chondrule may have formed ?0.5 and ?0.2 Ma after formation of the sodalite in the Ningqiang CAI analyzed by Lin et al. [Lin, Y., Guan, Y., Leshin, L. A., Ouyang, Z. and Wang, D. (2005) Short-lived chlorine-36 in a Ca- and Al-rich inclusion from the Ningqiang carbonaceous chondrite. Proc. Natl. Acad. Sci. USA 102, 1306-1311]. The Pink Angel sodalite that we analyzed may have formed ∼0.3 Ma after formation of the sodalite in the Pink Angel analyzed by Hsu et al. [Hsu, W., Guan, Y., Leshin, L. A., Ushikubo, T. and Wasserburg G. J. (2006) A late episode of irradiation in the early solar system: Evidence from extinct ³⁶Cl and ²⁶Al in meteorites. Astrophys. J. 640, 525-529]. The estimated temporal differences suggest that alteration extended over at least 0.5 Ma. If previous works showing very low initial ³⁶Cl/³⁵Cl in the Allende CAIs and a H3 chondrite CAI are also considered, then alteration processes may have been more than 1.7 Ma.     

A model of capillary cohesion for numerical simulations of 3D polydisperse granular media

We present a 3D discrete‐element approach for numerical investigation of wet granular media. This approach relies on the basic laws of contact and Coulomb friction enriched by a capillary force law between particles. We show that the latter can be expressed as a simple explicit function of the gap and volume of the liquid bridge connecting a pair of spherical particles. The length scales involved in this expression are analyzed by comparing with direct integration of the Laplace–Young equation. We illustrate and validate this approach by application to direct shear and simple compression loadings. The shear and compression strengths obtained from simulations reproduce well the experimental measurements under similar material and boundary conditions. Our findings clearly show that the number density of liquid bonds in the bulk is a decisive parameter for the overall cohesion of wet granular materials. A homogeneous distribution of the liquid within the bridge debonding distance, even at low volume contents, leads to the highest cohesion. The latter is independent of the liquid content as far as the liquid remains in the pendular state and the number density of liquid bonds remains constant. Copyright © 2007 John Wiley & Sons, Ltd.     

Pesticides and lipids occurrence in Tangier agricultural soil (northern Morocco)

This study evaluates pesticide occurrence in Tangier agricultural soil (northern Morocco). Soil samples were measured for alpha endosulfan, beta endosulfan, endosulfan sulfate, alpha HCH, beta HCH, gamma HCH, aldrin, dieldrin, endrin, o,p′ DDT, p,p′ DDD, p,p′ DDE and p,p′ DDT. The analyses were performed by gas chromatography coupled with mass spectrometry (GC/MS). Endosulfan isomers (alpha and beta) and endosulfan sulfate were detected in soil samples, in which the beta isomer showed the highest concentrations. Some DDT metabolites (o,p′ DDT and p,p′ DDE) and alpha HCH were also detected in the analyzed soil. The lipid fraction of the soil samples was extracted by accelerated solvent extraction and fractionated using chromatographic techniques. The principal biomarkers obtained were alcohols, esters, ketones, aldehydes, fatty acids and hydrocarbons. Lipid biomarkers were characterized to determine soil organic matter sources. Experimental results showed that the organic matter was mainly of plant origin, although the bacterial contribution was significant.     

Karst groundwater resources in the countries of eastern Mediterranean: the example of Lebanon

The hydrogeological study of some karst systems in Lebanon shows important storage capacity, up to 27 billions m³ for Zarka system, the spring of Orontes River. Their geological and morphological settings, as well as their hydrodynamic function, show structures developed below the level of present springs, probably up to several hundreds meters at depth. Since Miocene, those carbonate formations were subject to a remarkable instability of their base levels. Variations of sea level, of which the Messinian salinity crisis is the major phase, and effects of the alpine orogenesis, combined with climate variations to develop complex, multiphased karst systems. Karstification occurs frequently in the whole formation, often deeply below sea level or underneath sediment filling of continental basins. The surface karst landscape is often intensely eroded. Those multiple, superimposed karst phases give the carbonate aquifers their large extension and storage capacity. These karst aquifers show the typical easy restoration of storage. They have the ability to bear large interannual recharge variations and support exploitation under high pumping rates. However, these aquifers have some disadvantages for sustainable management. In some regions, successful boreholes, which allow high pumping rates also induce uncontrolled exploitation. Another consequence is natural seawater intrusion, as well as the submarine discharge of fresh groundwater, in coastal aquifers. Those carbonate aquifers are subject to important economical stress which jeopardizes their durability. The systematic study and understanding of carbonate aquifers in Eastern Mediterranean is a preliminary condition to any integrated and sustainable management of water resources. Studies in progress in Lebanon may serve as examples to the whole region.     

A Consistent Soil Fatigue Framework Based on the Number of Equivalent Cycles

Cyclic soil degradation and hardening affects soil stiffness and strength, and is linked to an increase or decrease in the mean effective confining stress due to void ratio or pore pressure changes. This change of state can be explicitly modeled by using effective stress methods, or implicitly modeled using total stress methods. In the latter, this is achieved by using empirical functions based on the number of loading cycles that are derived from constant-amplitude stress or strain laboratory tests. To suite generalized loading conditions, these functions must be extrapolated to variable-amplitude loading. This falls under the general class of a fatigue-based problem. The main focus of this paper is to present a generalized consistent soil fatigue formulation for soils under cyclic loading. The paper then goes on to discuss the implementation of various cyclic soil degradation and hardening models reported in the literature, and highlights their important underlying assumptions, capabilities and limitations.     

Numerical modeling of the flow and transport of radionuclides in heterogeneous porous media

This paper is concerned with numerical methods for the modeling of flow and transport of contaminant in porous media. The numerical methods feature the mixed finite element method over triangles as a solver to the Darcy flow equation and a conservative finite volume scheme for the concentration equation. The convective term is approximated with a Godunov scheme over the dual finite volume mesh, whereas the diffusion–dispersion term is discretized by piecewise linear conforming triangular finite elements. It is shown that the scheme satisfies a discrete maximum principle. Numerical examples demonstrate the effectiveness of the methodology for a coupled system that includes an elliptic equation and a diffusion–convection–reaction equation arising when modeling flow and transport in heterogeneous porous media. The proposed scheme is robust, conservative, efficient, and stable, as confirmed by numerical simulations.      

Geographical Analysis of Agro-Environmental Measures for Reduction of Chemical Inputs in Tuscany

The agro-environmental policies included in rural development plans are getting increasing importance in European Community strategies. These policies represent the meeting point between demand and supply of positive externalities. The difficulty of assessing real environmental efficiency is one of the elements characterizing agro-environmental measures. This difficulty is related to the identification of suitable parameters for evaluating farms according to their impact on the territory. This impact is mainly related both to chemical inputs and to the territorial characteristics of the farm. Different types of fertilizers, pesticides and herbicides are currently used in production processes; however, the analysis has focused only on nitrates, as they represent the most critical types of chemicals related to soil pollution. A case study is provided by analysis of agro-environmental measures in Tuscany for the reduction of nitrates in organic and integrated farms. Using spatial multicriteria analysis, integrated and organic farms were classified according to their geographical locations and their release of nitrates into the soil. This classification permits the highlighting of farms that make the greatest economic efforts to reduce pollution and therefore it could determine environmental benefits. Considering that the trend of policy strategies is toward a reduction of monetary resources, the classification could help decision makers choose the right allocation of future resources.

     

Future projections of synoptic weather types over the Arabian Peninsula during the twenty-first century using an ensemble of CMIP5 models

An assessment of future change in synoptic conditions over the Arabian Peninsula throughout the twenty-first century was performed using 20 climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) database. We employed the mean sea level pressure (SLP) data from model output together with NCEP/NCAR reanalysis data and compared the relevant circulation types produced by the Lamb classification scheme for the base period 1975–2000. Overall, model results illustrated good agreement with the reanalysis, albeit with a tendency to underestimate cyclonic (C) and southeasterly (SE) patterns and to overestimate anticyclones and directional flows. We also investigated future projections for each circulation-type during the rainy season (December–May) using three Representative Concentration Pathways (RCPs), comprising RCP2.6, RCP4.5, and RCP8.5. Overall, two scenarios (RCP4.5 and RCP 8.5) revealed a statistically significant increase in weather types favoring above normal rainfall in the region (e.g., C and E-types). In contrast, weather types associated with lower amounts of rainfall (e.g., anticyclones) are projected to decrease in winter but increase in spring. For all scenarios, there was consistent agreement on the sign of change (i.e., positive/negative) for the most frequent patterns (e.g., C, SE, E and A-types), whereas the sign was uncertain for less recurrent types (e.g., N, NW, SE, and W). The projected changes in weather type frequencies in the region can be viewed not only as indicators of change in rainfall response but may also be used to inform impact studies pertinent to water resource planning and management, extreme weather analysis, and agricultural production.     

Spatial and temporal analysis of the drought vulnerability and risks over eight decades in a semi-arid region (Tensift basin: Morocco)

Theoretical and Applied Climatology - The multiple downscaled scenario products allow us to assess the uncertainty of the variations of precipitation and temperature in the current and future...