电磁感应仪EM38用于土壤盐渍剖面分类与评价研究

结合电磁感应仪EM38测量与田间采样,文章分析了黄河三角洲典型区域土壤电导率的剖面分布特征,建立了磁感式表观电导率与土壤电导率间的(多元)回归解译模型,探讨了不同分类方法对土壤盐渍剖面分类结果的准确性,并对典型盐渍剖面类型进行了评价。结果表明:研究区土壤盐分具有较强的表聚性与变异强度;土壤电导率与磁感表观电导率EMh、EMv间呈极显著的相关关系,EMh对浅层土壤电导率的解译精度较高,而EMv对深层土壤电导率的解译精度较高;EMv/EMh法和理论函数法对土壤盐渍剖面的分类结果均具有较高的精度,且理论函数法分类结果的准确性明显优于EMv/EMh法;研究区土壤盐渍剖面可划分为表聚型、底聚型与均匀型,在数量上以表聚型及底聚型为主,其中表聚型与均匀型属于积盐型剖面,底聚型属于脱盐型剖面。该结果对研究黄河三角洲地区土壤盐渍化的发生、机理、预测与评估该地区土壤盐渍化的发生、发展具有重要意义。     

基于电磁感应仪的表聚型土壤盐渍剖面特征解译研究

针对目前黄河三角洲地区存在的土壤盐渍化问题,以该地区分布最广泛的表聚型盐分剖面类型为研究对象,运用磁感大地电导率仪EM38,建立了磁感式表观电导率和土壤盐分之间的(多元)回归模型,在分析土壤盐分剖面分布特征的基础上提出了指数衰减模型,并运用该模型对盐分剖面进行了参数拟合和验证.结果表明:磁感式表观电导率EMh和EMv呈极显著的线性相关,土壤盐分在垂直方向上的变异主要表现在表层0～25cm的深度范围内.统计分析和Friedman检验结果表明,回归模型和指数衰减模型均具有较好的拟合结果和预测效果,二者的预测精度差异也不显著,表明本文提出的指数衰减模型不仅能降低待估参数的数量、提高土壤盐分剖面磁感式解译的实用性,同时还具有较高的预测精度.该研究结果为利用电磁感应仪快速、精确地进行土壤盐分预测以及盐分剖面解译提供了一定的理论参考和实践依据.     

Detecting a salinity plume in an unconfined sandy aquifer and assessing secondary soil salinization using electromagnetic induction techniques, North Dakota, USA

 Land-use changes on the Sheyenne Delta in southeastern North Dakota, USA, have prompted research on impacts to the unconfined Sheyenne Delta aquifer (SDA). This study examines effects of the saline discharge of a flowing artesian well that taps the Dakota aquifer (DAK) on SDA groundwater chemistry and soil salinity. Objectives were to map the saline plume in the SDA using induction techniques, to assess chloride migration in the SDA, and to evaluate induction sensitivity to moderately saline sands. Induction data, collected in a 2.9-ha grid, were compared to 31 soil profiles analyzed for gravimetric moisture, electrical conductivity, and chloride. Soil salinization is widespread, but only 7% of the area meets the 4-dS/m threshold for saline soils. SDA chloride distribution was determined on transects oriented with and perpendicular to the flow path determined from induction readings. Chloride was detected in the aquifer 550 m from the source, indicating a transport rate of 21 m/yr. Complex recharge and discharge patterns and hummocky relief contribute to a wide chloride plume at this site. A mass balance based on soil-water content and chloride concentration shows that only 4% of the chloride from the DAK well remains in the grid volume. Received, January 1998 · Revised, January 1999 · Accepted, March 1999     

Propagation of electromagnetic waves from an induction source in media with time-dependent conductivity and permittivity

Electromagnetic wave propagation from an induction source (a transmitter coil) in media with time-dependent conductivity and permittivity is simulated using the vector finite-element method. A special algorithm is suggested for source approximation.     

Delineation of areas with different temporal behavior of soil properties at a landslide affected Alpine hillside using time-lapse electromagnetic data

Landslide activity is largely controlled by changes in soil properties, particularly soil moisture and the corresponding changes in pore pressure within the vadose zone. While knowledge of changes in soil conditions is of utmost importance for the prediction of landslides, it is difficult to obtain reliable information on the field scale. A possibility of filling that information gap is the monitoring of changes in soil properties by time-lapse electromagnetic induction (EMI) data. Given the relative stability of soil properties, changes in apparent electric conductivity (ECa) are mainly related to changes in soil water content and its mineralization. Thus, we use time-lapse ECa data over a nine-month period from different investigation depths (0.75, 1.5, 3, and 6 m) to separate areas with different temporal behavior of soil properties. However, working with time-lapse EMI data raised the comparability problem since the recoded ECa is also affected by several day-specific survey conditions (e.g., instrument temperature, operator). Consequently, the reproducibility of accurate ECa measurements is difficult due to potential dynamic shifts which hinders a direct comparing. We introduce in this study a straightforward method for comparability of ECa values from different time steps by normalization of data ranges assuming that the majority of shifts of measured data originate from field calibration. We identify the intensity of spatial changes by means of the standard deviation (SD) as an indication for the intensity of soil properties variability. To obtain the temporal changes and its progression over time, we separate the dynamic signal from the background. A two-layer system could be identified: one shallow more dynamic layer with an east–west-oriented structure and a deeper, more stationary layer with a north–south-oriented structure. The ECa dynamics of the shallow layer is related to the altitude (R ² = 0.84) while the deeper dynamics follow a different regime. The decreasing of ECa dynamics with depth was consistent with the decreasing of SWC dynamics observed by previous studies.     

Evaluation of watershed soil erosion hazard using combination weight and GIS: a case study from eroded soil in Southern China

Natural Hazards - On September 20, 2017, Maria, the eleventh-most intense Atlantic hurricane ever recorded, made landfall at 6:15 am local time, the second category 5 hurricane to strike the island...     

Automatic sorting of scrap metals with a combined electromagnetic and dual energy X-ray transmission sensor

The combination of an electromagnetic and a dual energy X-ray transmission sensor is a new method for automatic sorting of scrap non-ferrous metals. It allows classification of metals based on differences in electrical conductivity and atomic number. Both sensors were developed and tested at Delft University of Technology. In a number of experiments non-ferrous metals from post-shredder scrap were identified and sorted based on the combined sensor output. The results and possible industrial applications in automatic sorting of scrap metals are discussed. A sorting system that includes both sensors allows replacement of conventional ferro-silicon based dense medium systems by an entirely dry process that does not require any washing.     

Application of a novel laser sensor volume measurement system to the triaxial testing of an unsaturated lime-treated soil

The paper reviews the common techniques of volume change measurement during unsaturated soil testing, focusing in particular on a newly developed system by the authors. The advantages and accuracy of the system compared to other available volume measurement techniques are discussed. This is followed by the application of the system to the volume change measurement of a lime-treated clay soil during suction-controlled triaxial testing, and a discussion on the behaviour of the soil during shearing.     

Geoarchaeological evidence of a Chola‐period tsunami from an ancient port at Kaveripattinam on the southeastern coast of India

Literature of the ancient Chola Dynasty (A.D. 9th–11th centuries) of South India and recent archaeological excavations allude to a sea flood that crippled the ancient port at Kaveripattinam, a trading hub for Southeast Asia, and probably affected the entire South Indian coast, analogous to the 2004 Indian Ocean tsunami impact. We present sedimentary evidence from an archaeological site to validate the textual references to this early medieval event. A sandy layer showing bed forms representing high‐energy conditions, possibly generated by a seaborne wave, was identified at the Kaveripattinam coast of Tamil Nadu, South India. Its sedimentary characteristics include hummocky cross‐stratification, convolute lamination with heavy minerals, rip‐up clasts, an erosional contact with the underlying mud bed, and a landward thinning geometry. Admixed with 1000‐year‐old Chola period artifacts, it provided an optically stimulated luminescence age of 1091 ± 66 yr and a thermoluminescence age of 993 ± 73 yr for the embedded pottery sherds. The dates of these proxies converge around 1000 yr B.P., correlative of an ancient tsunami reported from elsewhere along the Indian Ocean coasts. © 2011 Wiley Periodicals, Inc.     

Hydrostratigraphic analysis of the Darling River valley (Australia) using electromagnetic induction data and a spatially constrained algorithm for quasi-three-dimensional electrical conductivity imaging

Efforts are being made to improve the irrigation efficiency in the Murray-Darling River Basin, Australia, to deal with predicted rainfall decline and to reduce the incidence of secondary soil and water salinization. The latter commonly occurs as a result of locating water reservoirs upon relic drainage channels. To better manage irrigation, information is required about the spatial distribution of soil type and the stratigraphic features capable of redistributing deep-draining water. In previous research, electromagnetic (EM) induction instruments (e.g. EM38 and EM34) have been used to map the distribution of soil type, hydrological processes (e.g. deep drainage) and vadose-zone features. The aim of this research is to demonstrate how a joint inversion of EM38 and EM34 data, using a one-dimensional spatially constrained algorithm for quasi three-dimensional (quasi-3D) electrical conductivity imaging, can be used to infer the areal distribution of soil types and physiographic and hydrogeological units. The quasi-3D modeling of true electrical conductivity provides a framework for future environmental monitoring and management to mitigate the hydrological processes that drive localized secondary salinization in the study area.     

基于主成分聚类法的典型黑土区土壤地球化学分类

土壤地球化学分类对农业区划和生态区划具有指导意义。本文基于多目标区域地球化学调查获取的土壤常量元素数据,利用主成分分析和K均值聚类组合方法——主成分聚类法,对东北典型黑土区进行地球化学分类研究。结果显示:成土母质是土壤常量元素特征的主要控制因素,利用主成分聚类法将典型黑土区土壤样品划分为5类最为合理,各类样品的常量元素含量具有显著性差异(P<0.05)。土壤地球化学分类结果与第四纪地质单元有一定的对应关系,而分类结果更能反映成土母质的真实分布情况。同时,松花江南部黑土区较高的SiO2含量指示了黑土的沙化生态问题,在黑土地保护中应给予重视。     

Modeling of electromagnetic waves in axisymmetric geometry using a Laguerre spectral method

A spectral method for modeling high-frequency electromagnetic waves in axisymmetric geometry is proposed.The method is based on the expansion of the solutions of Maxwell’s equations in Laguerre functions in the time region.The spectral method is used to solve Maxwell’s equations for both 2D media and stratified media. In the case of stratified media, a Fourier–Bessel expansion in the radial variable is used. The effectiveness of the spectral and finite-difference methods is compared. Harmonic solutions and solitary solutions by the Laguerre method are considered, and the dynamics of monochromatic and broadband electromagnetic pulses are examined.     

Volatile organic compounds decomposition using nonthermal plasma coupled with a combination of catalysts

A series of experiments were performed for toluene decomposition from a gaseous influent at normal temperature and atmospheric pressure by nonthermal plasma coupled with a combination of catalysts technology. Nonthermal plasma was generated by dielectric barrier discharge. γ-Al₂O₃ was used to be a sorbent and a catalyst carrier. Nanocatalysts were MnO₂/γ-Al₂O₃ coupled with modified ferroelectric of nano-Ba_0.8Sr_0.2Zr_0.1Ti_0.9O₃. γ-Al₂O₃ played an important role in prolonging reaction time of nonthermal plasma with volatile organic compounds molecules. MnO₂/γ-Al₂O₃ has an advantage for ozone removal, while nano-Ba_0.8Sr_0.2Zr_0.1Ti_0.9O₃ is a kind of good ferroelectric material for improving energy efficiency. Thus these packed materials were incorporated together to strengthen nonthermal plasma power for volatile organic compounds decomposition. The results showed the synergistic technology resulted in greater enhancement of toluene removal and energy efficiencies and a better inhibition for ozone formation in the gas exhaust. Based on the data analysis of the Fourier transforms infrared spectrum, the reaction process of toluene decomposition and the mechanism of synergistic effect are discussed. The results showed in a complex oxidation mechanism of toluene via several pathways, producing either ringretaining or ringopening products. The final products were carbon dioxide and water.     

中国东部浅水湖泊参照状态确定的非参数方法

根据中国东部浅水湖泊受人类活动影响较严重的情况,将季节分解的非参数局部线性回归模型、频率分析和几何分块自助法有机结合,提出了一种基于非参数方法的湖泊参照状态确定的新方法。该方法首先将季节分解模型用于湖泊营养盐及其响应物的观测值,选取出适合用于推断参照状态的时间段;其次使用频率分析法分析此时间段内的观测值,并给出湖泊总氮、总磷和叶绿素a的参照状态值;最后用几何分块自助法给出各自的置信区间。该方法能有效克服前人提出方法的缺点。以太湖为例,采用该方法推断了参照状态浓度,总氮为0.78mg/L,总磷为0.030mg/L,叶绿素a为2.63μg/L;给出相应的95%置信区间分别为0.57~0.83mg/L、0.025~0.046mg/L和1.86~2.65μg/L。该方法也可适用受人类活动影响较大的中国东部其他浅水湖泊。     

Simulation of chloride transport in an aggregated soil using three conceptual models

Breakthrough curves (BTCs) of chloride displaced through columns of loessial soil aggregates of different sizes were measured under saturated steady flow conditions. The data were simulated using three conceptual models. Model I (CDE) assumed that all soil water was mobile and physical equilibrium existed in the system. Model II (two-region model) partitioned the soil water into mobile and immobile regions, and convective diffusive solute transport was limited to the mobile water region. Model III (two-flow region model) also divided the soil water into two regions based on their flow velocities, but both of the regions had a non-zero flow rate. Transfer of the chloride solute between the two soil water regions was assumed to occur at a rate proportional to the difference in solute concentration. The two unknown parameters in model I, three in model II, and four in model III were estimated by fitting the experimental data. The three models could well describe all the BTCs measured for columns packed with all the aggregate sizes at the low pore water velocity (0.68 cm/h); however, the values of the fitted parameters varied greatly. The Peclet numbers derived from both the two-region (model II) and two-flow region (model III) models behaved similarly and increased with increases in aggregate size. But the Peclet numbers derived from the convection dispersion equation (model I) were about two orders of magnitude greater than those derived from the other two models. The mobile water fraction obtained for the two-flow region model decreased with increases of aggregate size. The mass transfer coefficient decreased with an increase in pore water velocity due to the shorter residence time of the chloride solute in the soil columns.     

Petrography and decay of a marly limestone in the cloister of a medieval cathedral in Sicily

This paper deals with a significant process of decohesion of a marly limestone, taking place in the cloister of the medieval Cathedral of Cefalù, a pleasant town on the northern coast of Sicily. After desalination with deionised water and consolidation with ethyl silicate, the decay of the stone became faster. The aim of our study is to characterise the stony material and investigate the observed decay phenomena. The stone, that is a poor building material indeed, is characterised by means of petrographical, chemical and physical analyses on samples taken from the monument. Furthermore, experimental tests are performed in the laboratory in order to highlight the causes of incompatibility between the stone and the applied treatments.     

Delineating and defining the boundaries of an active landslide in the rainforest of Puerto Rico using a combination of airborne and terrestrial LIDAR data

Light detection and ranging (LIDAR) is a remote sensing technique that uses light, often using pulses from a laser to measure the distance to a target. Both terrestrial- and airborne-based LIDAR techniques have been frequently used to map landslides. Airborne LIDAR has the advantage of identifying large scarps of landslides covered by tree canopies and is widely applied in identifying historical and current active landslides hidden in forested areas. However, because landslides naturally have relatively small vertical surface deformation in the foot area, it is practically difficult to identify the margins of landslide foot area with the limited spatial resolution (few decimeters) of airborne LIDAR. Alternatively, ground-based LIDAR can achieve resolution of several centimeters and also has the advantages of being portable, repeatable, and less costly. Thus, ground-based LIDAR can be used to identify small deformations in landslide foot areas by differencing repeated terrestrial laser scanning surveys. This study demonstrates a method of identifying the superficial boundaries as well as the bottom boundary (sliding plane) of an active landslide in National Rainforest Park, Puerto Rico, USA, using the combination of ground-based and airborne LIDAR data. The method of combining terrestrial and airborne LIDAR data can be used to study landslides in other regions. This study also indicates that intensity and density of laser point clouds are remarkably useful in identifying superficial boundaries of landslides.     

Characterising soil property in an area with limited measurement: a Bayesian approach

The Bayesian approach has been proved useful to geotechnical engineering especially when project-specific data/measurements are very limited. In this paper, we introduced a new Bayesian algorithm to estimate soil properties at each location of a study area, with very limited project-specific data. In addition to the proposed methodology and algorithms, we also conducted a model application to estimate soil permeability for each of the 64 locations within a 4-by-4 m² area, based on very limited project-specific data, that is, one measurement from each location.