Numerical modeling assessment of three-gate structures for capturing contaminated groundwater

This modeling study evaluated the capability of alternative funnel-and-gate structures with three gates for capturing contaminated groundwater in a hypothetical unconfined aquifer. Simulated interceptor structures were linear and 45 m wide, consisting of three gates and two funnels (walls). One gate occupied the center and two gates occupied the ends of the interceptor structures. The structures, positioned perpendicular to regional groundwater flow, traversed the entire thickness of the aquifer. A total of four structures were evaluated (numbers designate widths of end, center, and end gates, respectively, in meters): 3-3-3, 2-5-2, 1-7-1, and 4-1-4. Particle tracking and zonal water budgets identified shapes of capture zones and discharge patterns for each interceptor structure. A mass transport model, accounting for advection and hydrodynamic dispersion, tested the capability of each structure for capturing a contaminant plume. Results suggest that: time-dependent capture zones underestimate the amount of time to capture a contaminant plume, wide center gates facilitate plume capture, and wide end gates facilitate lateral containment of contaminants. Of the structures simulated, the 2-5-2 configuration was relatively efficient at processing and containing the simulated contaminant plume.     

Variation of infiltration rate through karstic surfaces due to land use changes: A case study in Murgia (SE-Italy)

Groundwaters of the Murgia carbonate aquifer represent the main groundwater resource of the Apulia region (SE Italy). In the highlands (Alta Murgia) karst crops out in different forms and textures which have been preserved up to the 1970s: little evolved agriculture and sheep rearing produced only a marginal modification of the epikarst while a high degree of division into parcels by drystone walls helped in preserving soils from erosion. In the last years the original scenery of the Alta Murgia changed due to widespread transformations of surface karstic textures for agricultural purposes, with undeniable negative consequences on the hydrogeological balance, concerning both the infiltration and the runoff terms. Stone shattering led to flattening and deep alteration of a large part of the original karstic landscape and to demolition of drystone walls.In a study area of about 139 km² located in the Alta Murgia, the comparison of aerial photos related to the period 1950–2001 indicated that stone shattering had occurred for about 42% of the area.The hydrological behaviour of the first soil layer of experimental parcels representing both shattered stone and natural karstic surface textures was analysed by using the numerical model Hydrus-2D with the aim of estimating the variation on infiltration rate due to stone shattering. Intensive field and laboratory measurements concerned soil texture, soil water content, pressure head, saturated hydraulic conductivity, pan evaporation and meteorological parameters.     

攀西地区铂族元素地球化学异常分布及其筛选

攀西地区不同时代地层的水系沉积物中铂族元素地球化学背景值具有明显的规律性分布.笔者通过对该地区铂族元素含量在各地层中的分布以及地球化学异常的圈定、归并和分类,结合有关铂族矿床地球化学特征的认识,通过对水系沉积物中Pt、Pd综合异常的筛选,在铂族元素综合衬值异常图的基础上共划分出Ⅰ类异常4个、Ⅱ类异常19个、Ⅲ类异常23个以及Ⅳ类异常14个.初步筛选出的19个Ⅱ类异常子区可为进一步开展铂族矿床找矿工作提供依据.     

Identifying China’s leading world city: a network approach

This paper reports our research on China’s world cities. Formal network analysis of air passenger linkages for recent years among China’s most populous cities and among many of the world’s largest cities allows us to identify the country’s leading world city from among the leading Mainland candidates, Beijing, Shanghai and Guangzhou. We theorize our findings about China’s world cities in relation to both global forces (and China’s increasing entanglement with them) and the policies and actions of the national state. We examine the national and global urban network through a longitudinal, two-level analysis of airline passenger travel for four time points between about 1990 and 2005. We show that Beijing was China’s leading world city at the beginning of the time period, a status it lost nationally in as early as 1995, and then globally 10 years later. On the other hand Shanghai became China’s leading world city, and it acquired this status first nationally in 2000, and then globally in 2005. The changing status of the Chinese capital corresponds to the country’s increasing involvement with the capitalist world economy. Shanghai’s ascendance as the leading world city in China may indicate that global forces have come to play an increasingly important role relative to that of the developmental state.

深水沉积层序特点及构成要素

本文在回顾当前国际上深水沉积研究热点的基础上,结合在墨西哥湾深水研究的成果系统描述了深水沉积的定义、形成机理、深水沉积层序及深水沉积构成要素的特点.深水沉积主要是在重力流作用下深水环境的沉积,主要形成于相对水平面下降和早期上升的时期,主要分布在低位体系域中.深水层序以凝缩段为边界,块状搬运沉积最早形成并直接位于层序界面上,其上被河道-天然堤沉积所覆盖.典型深水沉积的要素主要由河道、天然堤及越岸沉积、板状砂、块状搬运沉积等构成,这些沉积要素时空上有序地分布.深水河道是物源的主要通道和沉积的重要场所,从上游至下游河道弯曲度增加,能量逐渐减弱.侧向迁移明显,垂向上由富砂的顺直河道演化为相对富泥的弯曲河道.天然堤及越岸沉积以泥质为主,天然堤沿河道呈楔状分布,其近端砂岩含量高,地层厚且倾角较陡;远端砂岩含量低,地层薄且平缓,侧向连续性好但垂向连续性差.板状砂主要为深水扇前缘非限制性沉积,可分为块型和层型.块型侧向连续性好,同时垂向连通性高.层型侧向连续性好,垂向连通性差.块状搬运沉积主要是低水位期坡上沉积物失稳形成的各类滑塌体及碎屑流,其对下伏地层侵蚀明显,分布广泛,变形构造常见,可作为油气良好的封盖层.     

川西前陆盆地中—新生代沉积迁移与构造转换

川西前陆盆地中—新生代各构造层的残余厚度展布和沉积特征分析发现,四川克拉通周缘的前陆盆地在晚三叠世时期发育于龙门山山前,明显属于龙门山褶皱逆冲构造载荷所形成的前渊凹陷;侏罗纪早期的沉积地层呈面状分布,没有表现出显著的挠曲沉降,指示了一个构造相对平静的阶段;中侏罗世早期前渊凹陷迁移至龙门山北段和米仓山山前,前渊沉积从晚三叠世的北东向转换为近东西向,广泛的湖泊相沉积预示了前陆盆地的欠充填状态;中侏罗世中晚期,川西盆地沉降中心又迁移到大巴山山前,相应的挠曲变形又从近东西向转化为北西向,构成了大巴山的前渊凹陷;晚侏罗世—早白垩世时期,沉降中心再次回到米仓山山前,巨厚的前渊凹陷沉积指示了米仓山冲断带的主要活动时期;白垩纪末—古近纪的前渊凹陷则跃迁至雅安—名山地区。川西前陆盆地的同造山沉降中心以四川盆地中心为核心在西部和北部呈弧形迁移,沉积序列不断更替和叠加。中生界各构造层底界构造图显示现今的构造低部位位于川西北地区和川西南地区,在川西北地区均有东西走向的等值线分布,而川西南地区等值线走向则为北东-南西向。因此分析认为,晚侏罗世至早白垩世的构造变形可能控制了川西盆地现今的地层变形,形成了川西北地区的南北向构造挤压结构,而晚期的新生代构造变形则主要体现在川西盆地的西南部,形成北东-南西向的地层展布特征。     

基于贡献权重叠加法的滑坡风险区划

贡献权重叠加法是对滑坡本底因子和承灾体因子在滑坡发育中的贡献率进行统计后,通过贡献率均值化、规一化处理,利用权重转换模型计算出每一个因子内部的权重——自权重和因子相互之间的权重——互权重。将滑坡因子、承灾体因子和两者的自权重、互权重分别相乘叠加,得到滑坡危险度和易损度区划结果,再将2项结果相乘得出滑坡风险区划结果。     

青藏高原西北缘祁漫塔格山中新世快速抬升的磷灰石裂变径迹证据

对祁漫塔格山体不同海拔高度所取的9个磷灰石样品的裂变径迹分析结果表明,东昆仑西段中新世早中期为主要的隆升期且隆升速率较高,早期隆升速率为111m／Ma,晚期隆升速率为98m／Ma,总体隆升速率为100m／Ma。样品显示出磷灰石裂变径迹长度大致分2类,一类磷灰石裂变径迹长度为（12．21±10．20）-（13．75±0．30）μm,径迹长度分布图基本上为窄而对称的正态分布,反映具有快的剥露冷却速率,未受到后期热事件的干扰。另一类磷灰石裂变径迹长度为（11．88±0．33）～（13．32±0．27）μm,较前一类具有稍慢的剥露冷却速率,并且受到了后期热事件的干扰。     

东菲律宾海深水铁锰结壳发育站位沉积物的粒度及黏土矿物学特征

大洋铁锰结壳是潜在的重要海洋资源,多年来世界各国对此已作了大量调查.传统意义上的铁锰结壳均分布于3000m水深以浅的海山基岩上.中国科学院海洋研究所在对东菲律宾海的地质调查中采集到大量褐黑色深水铁锰结壳.在300多个站位的取样中,在44个站位采集到结壳样品,可见结壳在研究区的分布较为广泛.该结壳发育于4000~5000m水深的致密至半固结沉积物的表层,厚度一般为2~3cm,最厚可达7cm.结壳为板(层)状.     

Numerical Experiment on Two-Dimensional Line Thermal

The time evolution of a two-dimensional line thermal-a turbulent flow produced by an initial element with signifi-cant buoyancy released in a large water body, is numerically studied with the two-equation k - e model for turbulence closure. The numerical results show that the thermal is characterized by a vortex pair flow and a kidney shaped concentra-tion structure with double peak maxima; the computed flow details and scalar mixing characteristics can be described by self-similar relations beyond a dimensionless time around 10. There are two regions in the flow field of a line thermal: a mixing region where the concentration of tracer fluid is high and the flow is turbulent and rotational with a pair of vortex eyes, and an ambient region where the concentration is zero and the flow is potential and well-described by a model of doublet with strength very close to those given by early experimental and analytical studies. The added virtual mass coeffi-cient of the thermal motion is found to be approximat