Effect of soil disturbance on recharging fluxes: case study on the Snake River Plain,Idaho National Laboratory,USA

Soil structural disturbance influences the downward flow of water that percolates deep enough to become aquifer recharge. Data from identical experiments in an undisturbed silt-loam soil and in an adjacent simulated waste trench composed of the same soil material, but disturbed, included (1) laboratory- and field-measured unsaturated hydraulic properties and (2) field-measured transient water content profiles through 24 h of ponded infiltration and 75 d of redistribution. In undisturbed soil, wetting fronts were highly diffuse above 2 m depth, and did not go much deeper than 2 m. Darcian analysis suggests an average recharge rate less than 2 mm/year. In disturbed soil, wetting fronts were sharp and initial infiltration slower; water moved slowly below 2 m without obvious impediment. Richards’ equation simulations with realistic conditions predicted sharp wetting fronts, as observed for disturbed soil. Such simulations were adequate for undisturbed soil only if started from a post-initial moisture distribution that included about 3 h of infiltration. These late-started simulations remained good, however, through the 76 d of data. Overall results suggest the net effect of soil disturbance, although it reduces preferential flow, may be to increase recharge by disrupting layer contrasts.     

Estimating hydraulic conductivity from specific capacity for Hawaii aquifers,USA

Site-specific relationships between specific capacity and hydraulic parameters (transmissivity and hydraulic conductivity) were investigated for volcanic rocks in Maui, Hawaii, USA. Details about well construction were commonly ignored in previous studies. To improve on such efforts, specific-capacity values were normalized by the open interval of the well. Correcting specific capacity for turbulent head losses using step-drawdown tests and including aquifer penetration length improved the correlation between specific capacity and hydraulic conductivity and reduced uncertainty in the prediction of hydraulic parameters. The relationships provide estimates of aquifer parameters with correlation coefficients between 0.81 and 0.99. The relationships for Maui can probably be extended to other Hawaii islands, given the similarity of aquifer formations and a reasonable fit to step-drawdown data from Oahu. Hydraulic conductivity was estimated from 1,257 specific-capacity values in the Hawaii’s well database. Hydraulic-conductivity estimates for dike-free volcanic rocks are consistent on different islands. For all islands, the estimates range from 3 to 8,200 m/d, with a geometric-mean and median value of 272 and 291 m/d, respectively. A geostatistical approach was applied to Maui and Oahu to generate island-wide hydraulic-conductivity maps to facilitate groundwater management efforts.     

余杭区房产基础地理信息系统的设计和建设

本文介绍了余杭区房地产基础地理信息系统的概况,系统设计思想和应用功能。对房地产行业的GIS应用、系统设计与建设中的一些普遍性问题做一些简要分析和探讨。     

Transitive Geostatistics for Stepwise Modeling Across Boundaries between Rock Regions

A single intrinsic stationary random field may not account for transitional heterogeneity and abrupt dissimilarity of geological properties across boundaries between rock type regions. This paper proposes the stepwise construction of transitive covariance models for modeling continuous properties correlated across boundaries of multiple disjoint physical domains such as rock type bodies. Modeling in geology is usually simplified by splitting the geological space into rock type geo-domains (e.g., strata, sedimentary facies, soil series, diagenetic regions and alteration zones). Due to the limitations of simultaneous solutions, a simplification is to model each domain independently at the cost of losing the conditioning of properties across domains. This paper proposes to organize the modeling process in a triangular array which follows events in the geological time domain; for example, the younger formations are at the top of the pyramid and the older formation at the base. The estimation may go from top to base by assuming that younger events have perturbed older formations. Geology shows the scars of events that cumulate in rock formations before they are finally eroded. In some cases, older formations may be parent material for younger formations. The continuous property within each geo-domain has a conditional covariance in the main diagonal of the array which may belong to a specific event in the geological time. This sequence leads to transitive estimation and simulations in the physical space. If a simultaneous solution is sought (i.e., the future and past are correlated both ways), the complex covariance functions can be constructed stepwise from conditional spectra.     

山东招远-平度断裂带南段地球物理特征及找矿预测

以招平断裂带南段为研究对象,综合利用招平断裂带的地质、重力、磁法、大地电磁等资料总结了研究区的重磁场特征及岩石的物性特征,并通过5条典型剖面开展可控源音频大地电磁测深（CSAMT）,进一步查明了研究区的成矿条件和找矿前景。根据CSAMT实测数据,反演及推断了招平断裂带南段深部的延深及变化情况,推测脆性断裂是招平断裂带南段金矿找矿的关键因素并据此在实测剖面上圈定了8处成矿有利靶区。本文认为研究区的北部具有较好的成矿条件和找矿潜力。     

Diagenesis and reservoir properties of Middle Jurassic sandstones,Traill Ø, East Greenland: The influence of magmatism and faulting

The c. 500 m thick Middle Jurassic sandstones of the fluvial Bristol Elv and marine Pelion Formations of the East Greenland Basin are evaluated here in order to improve the understanding of the processes that influenced the diagenetic evolution. The study may help to predict the reservoir properties of sandstones affected by magmatism and faulting, both in general and specifically in undrilled areas on- and offshore East Greenland and, in the Vøring Basin on the Mid-Norwegian shelf. The study shows a variety of authigenic mineral phases dominated by quartz cement, carbonate cement, illite and iron-oxide. One of the clear differences between the two formations is the presence of early carbonate-cemented horizons in the marine sandstones; these horizons are inferred to reflect a primary concentration of biogenic clasts and fossil shells. Intense quartz cementation occurs primarily in the fluvial sandstones but the marine sandstones are also highly quartz-cemented. Two episodes of burial and uplift are recorded in the diagenetic sequence and widespread grain-crushing in coarse-grained intervals is believed to result from overpressure and subsequent compaction due to sudden pressure release along major faults. Maximum burial depths may only have been around 2000–2500 m. Cathodoluminescence analyses show that grain crushing was followed by intense quartz cementation. The quartz cement is to a great deal believed to have formed due to increased surface area from crushing of detrital quartz grains, creating fresh nucleation sites for the quartz. Cathodoluminescence investigations also show that only minor pressure dissolution has taken place between detrital quartz grains and that the ubiquitous quartz cementation displays several growth zones, and was thus in part the result of the introduction of silica-rich extra-formational fluids related to the flow of hot fluids along reactivated faults and increased heat flow and temperature due to magmatism. This interpretation is supported by fluid inclusion homogenization temperatures between 117 and 158 °C in quartz cements. In one of the two study areas, the development of macroscopic stylolites has significantly enhanced quartz cementation, probably in connection with thermal convection flow. As a result of the magmatic and fault-related quartz cementation and illitization, the reservoir quality of the sandstone formations deteriorated and changed drastically.     

Geotechnical and Geoacoustic Properties of Volcanic Soil in Ulleung Island,East Sea of Korea

The unique material properties of volcanic soils may cause stability problems within the soil. However, few studies have examined the composition and engineering characteristics of volcanic soils below sea level. The objective of this study is to investigate the engineering properties of volcanic soils sampled from Ulleung Island. For the volcanic soils, the index properties, particle geometry, and mineralogy are analyzed in the laboratory. An oedometer cell incorporated with bender elements is used to measure the small-strain stiffness and compressibility of the volcanic soils. To obtain the large strain strength parameter and hydraulic conductivity of the volcanic soils, direct shear tests, and constant head permeability tests are performed. The experimental results show that the basic index properties of volcanic soils sampled from Ulleung Island are very similar to the values of previously published reference data: poorly graded with a median grain size, very low fine fraction, and slightly high specific gravity. In addition, the particle surface texture features and elementary analysis indicates a dark grain color, small pits or holes in the grain, and relatively low SiO₂ and high Fe₂O₃ contents. The friction angle of the volcanic soils depends on the relative density, and the hydraulic conductivity varies according to e³/(1 + e) and D₁₀². The characterization of the electrical properties in Ulleung Island needs to be conducted with caution due to the high Fe₂O₃ content in the volcanic soils.     

华北香河站一次霾污染事件的综合观测研究

利用激光雷达、太阳光度计、系留气艇低空探测数据及MODIS卫星数据等多源资料,对2007年2月初发生在我国中东部地区的一次大范围霾污染事件进行了综合分析,重点分析了华北香河站垂直向气溶胶光学特性的变化特征,并初步讨论了气溶胶区域输送。分析结果表明:霾污染中心位于大城市、城市群或者盆地等污染物源排放强度大或者地形不利于污染物扩散的地区,形成了6个污染中心;2日霾最严重时,近地面气溶胶消光系数(355nm)达到1.8 km~(-1),是霾发生前的3倍;霾最严重时气溶胶光学厚度(340 nm)为1.4,较前后日的高;随着边界层高度的下降,底层气溶胶快速积累;香河站气溶胶在垂直向存在明显的分层现象,上层600—1000 m高度气溶胶受区域输送的影响,其光学厚度占整层气溶胶的比值能达到43.6%,甚至更高;本次霾过程以细粒子为主;弱高压系统、低至100 m左右的逆温层高度及低风速等气象条件对此次霾的形成起到了重要的作用;而3日出现的大风则很可能是驱散霾的重要因子。     

有向拓扑的河系渐变自动绘制算法

河系渐变绘制是地图制图中水系要素表达的重要方面。针对全自动河系渐变研究较少的现状,该文提出一种基于树状约束stroke特征的河系渐变自动绘制算法。该方法在深入分析有向拓扑的数据结构基础上,重点解决河口模式识别、树状约束stroke特征构建、河系层次关系建立、主支流分级渐变等问题,实现全自动河系渐变,并进行实践测试。结果表明,该算法在地图制图过程中无须对河系河源、河口识别、河系分层和河系渐变进行人工干预,自动化程度高,大幅度提升制图效率,渐变效果优于人工绘制效果。