不同环境条件下的土壤侵蚀分析——以重庆市为例

为了探讨土壤侵蚀与温度、降雨量、植被指数、地形指数、水热指数和环境质量综合指数的关系,本文对重庆市不同环境条件下的土壤侵蚀进行了分析.在定义土壤侵蚀综合指数的基础上,将年平均温度、大于0°积温,大于10°积温,年降雨量,干燥度、湿润度,地形综合指数、植被指数、热量指数、水分指数,水热指数,和环境质量综合指数等分级数据统一成格网大小为100 m*100 m的栅格(grid)数据.然后,利用GIS的叠加统计分析功能,将这些数据与100 m*100 m格网大小的土壤侵蚀栅格(grid)数据进行叠加统计分析,从而揭示出了土壤侵蚀与这些环境因子之间的关系.     

基于ArcGIS Server的土壤资源环境信息共享平台研究

为实现土壤资源环境信息共享,本文提出了一种利用ArcGIS Server技术实现土壤资源环境信息共享的方案,详细阐述了共享平台的整体框架结构,能有效地实现土壤资源环境信息的共享,具有良好的可扩展性。     

Decision Support System for Microtunneling Applications

Microtunneling is a trenchless technology method used for installing new pipelines. The inherent advantages of this method over open-cut trenching have led to its increasing use since its first introduction into North America in the early 1980s. With this technology, surface disruption can be minimized, especially in urban areas, and high accuracy of installation (usually less than 2?cm over 100?m) can be achieved in both line and grade. But microtunneling machines are very expensive and few contractors have extensive experience with this technology. Microtunneling can also be risky when unexpected obstacles or soil changes occur. Careful constructability analysis is needed, and an appropriate microtunneling method should be selected in order to achieve successful completion of microtunneling projects. A computerized decision support system (DSS) for microtunneling was developed to support decision making for contractors who want to bid on microtunneling projects. This paper discusses the decision-making process for microtunneling and the development of the DSS. When the user enters basic information about the potential project such as drive length, installation depth, pipe diameter, and soil condition, the DSS evaluates whether microtunneling will be economically feasible and suggests appropriate types of microtunneling methods. The user can then select microtunneling machines, types of pipes, and types of shaft construction methods. This DSS is most beneficial when used at the preplanning stage by utility contractors.     

Study of the Potential for Bioremediation of Petroleum Hydrocarbons within Smear Zone Soils

A bench-scale study was completed to assess the potential for the bioremediation of smear zone soils at a leaking underground storage tank site in Fort Drum, N.Y. The study demonstrated that the vertical distribution of total petroleum hydrocarbons (TPHs) within the smear zone corresponded to differences in microbial biomass and activity. The soil core featured the lowest TPH and highest biomass levels at the top of the smear zone, and the highest TPH and median biomass levels at the bottom of the smear zone. Phospholipid fatty acid biomarkers indicate that gram-positive bacteria and fungi were associated with the in situ TPH biodegradation. The microcosm study shows that microbial respiration at the top of the smear zone was much stronger than that at the bottom of the smear zone. At the top of the smear zone, microbial mineralization was faster under the saturated condition, whereas at the bottom of the smear zone, microbial mineralization was faster under the unsaturated condition. The column study shows that the biodegradation rates of bioventing and biosparging for the specific site did not differ substantially.     

Reaction Kinetics of Ozone in Variably Saturated Porous Media

A kinetic model based on the mass balance principle with equilibrium partitioning of gaseous ozone into pore water was developed to delineate the reactions of ozone in variably saturated porous media contaminated with phenanthrene. Dimensionless fraction factors were used in the kinetic model to account for the reactions of ozone with soil organic matter (SOM), metal oxide (MO), and phenanthrene as a function of water saturation. The enhanced removal of phenanthrene resulting from heterogeneous catalytic reactions between ozone and soil organic matter and metal oxide was incorporated as lumped parameters in the reaction rate coefficients of gaseous and dissolved ozone with phenanthrene. Laboratory experiments employing 5 cm long mini column reactor systems were conducted to estimate the reaction constants for three porous medium types (glass beads, baked field soil, and field soil) at various water-saturation levels. Water saturation and SOM were found to significantly affect the decomposition of gaseous ozone in both uncontaminated and contaminated porous media. It was found that water saturation over 75% completely eliminates gas-to-solid interfacial ozone reactions with SOM and MO. The kinetic model, with the reaction parameters estimated in this study, predicted reasonably well the experimental data obtained from both the mini column reactor and 20 cm long columns packed with field soil, suggesting that the kinetic model would be suitable for describing the fate and reactions of ozone in variably saturated porous media for soil types and experimental conditions similar to those tested in this study.     

Method for Estimating Dynamic Compaction Effect on Sand

This paper proposes a method for estimating the degree and depth of improvement resulting from dynamic compaction on sand. The method is based on extensive two-dimensional finite element analyses, which are benchmarked using centrifuge model results. By appropriately normalizing the results from a wide range of soil properties, initial conditions and operating parameters such as momentum per blow, energy per blow, and number of blows, the results for numerous cases can be summarized into a relatively small number of plots, which can be used for predictive purposes. A preliminary assessment of the reliability of these curves was conducted using results from a centrifuge and a field study. The results of this comparative exercise indicate that the predictions using the method are reasonably realistic.     

Soil-Water Characteristic Curve Equation with Independent Properties

The soil-water characteristic curve (SWCC) has traditionally been represented using equations whose fitting parameters do not individually correspond to clearly defined soil properties or to features of the curve. As a result, unique sets of parameters are often nonexistent, and sensitivity analyses and statistical assessments of SWCC parameters become difficult. In order to overcome these difficulties, a new class of equations to represent unimodal and bimodal SWCCs is proposed. The chosen fitting parameters are the air-entry value, the residual suction, the residual degree of saturation, and a parameter that controls the sharpness of the curvatures. The physical meaning for the soil parameters is discussed for different soil types. A unique relation between each of the equation parameters and the individual features of SWCCs is assured. The proposed equations are fitted to data corresponding to a variety of soil types and a good fit is observed.     

Shear Strength of Compacted Soil under Infiltration Condition

Landslides in residual soil slopes are commonly induced by rainfall infiltration. These residual soils are typically in an unsaturated state with negative pore-water pressures or matric suctions since the groundwater tables in steep slopes are often deep. The net normal and shear stresses of the soil remain essentially constant during rainwater infiltration into the slope. Failure of the slope during rainfall can be primarily associated with the decrease in the matric suction of the soil. The objective of the study was to investigate the strength and deformation characteristics of a residual soil of the Bukit Timah Granitic Formation during infiltration that leads to slope failure. There were two modified direct shear apparatuses used. One apparatus was used for the determination of shear strength under controlled suction conditions while the other apparatus was used for shearing-infiltration tests. The shearing-infiltration test results were compared with the shear strength values obtained from the shearing tests under constant suction. The shearing-infiltration test results indicate a close relationship between the decreasing matric suction and the increasing displacement rate of the soil specimen. At the initial part of the infiltration process, there is a rapid reduction in matric suction that is accompanied by little movement in the soil. When failure of the soil is imminent, the soil movement will accelerate.     

Temporal dynamics of PSR-based soil moisture across spatial scales in an agricultural landscape during SMEX02: A wavelet approach

In this study, we examined the characteristics of soil moisture dynamics of wet and dry fields across hierarchical spatial scales within the region of Soil Moisture Experiment 2002 (SMEX02) hydrology campaign in Iowa. The Polarimetric Scanning Radiometer (PSR)-based remotely sensed surface (∼ 0-5 cm) soil moisture at 800 m × 800 m resolution was used in this study. Wavelet-based multiresolution technique decomposed the soil moisture into large-scale mean soil moisture fields and fluctuations in horizontal, diagonal, and vertical directions at hierarchical spatial resolutions. Results suggested linearity in the log-log dependency of the variance of soil moisture up to a resolution of 6400 m × 6400 m on PSR sampling dates during SMEX02. The wet fields (with high soil moisture) show almost similar variance for all the resolutions signifying the strong spatial correlation. Analysis of the dry fields (with low soil moisture) indicated a log-log linearity of moments with various scales, and the slopes of these relationships exhibit a concave functional form with the order of moments, typically representing a multiscaling process. The scaling exponent of soil moisture during dry-down suggests a transition from simple scaling (in wet fields) to multiscaling (in dry fields) behavior. The fluctuation components of multiresolution analysis in the horizontal, diagonal, and vertical directions for dry and wet fields exhibited self-similarity. Another important finding of this study is the increase of subpixel soil moisture variability with increasing resolution, especially for the wet fields. These findings will help develop appropriate up-and down-scaling schemes of remotely sensed soil moisture data for various hydrologic and environmental modeling applications.     

基于GIS的云南省土壤环境质量数据管理系统

为了揭示云南省1718个采样点的土壤环境质量统计、评价与对比分析结果数据之间的空间关系和空间分布模式,设计和实现了云南省土壤环境质量数据管理系统,该系统采用GIS进行基于GIS组件的二次开发,以C#作为开发语言,SQLServer作为数据库,来实现信息的输入、维护、查询、分析、专题制图、管理等基本功能,以空间可视化的方法实现了空间信息和属性信息的集成管理,并完善地建立了二者之间的联系。