Research on soil salt transfer under freeze-thawing condition

Soil salt transformation plays an important role in the freeze-thawing process,which is also one of basic problems of cryopedology. The very special law is made up of the two time salt-moisture transfer under freeze-thawing condition. Based on the latest research at home and abroad,through the investigation of soil moisture-salt change in the freeze-thawing process,the conclusion is made that the soil water potential gradient is the main driving force of soil salt movement and the factors are of quantities. The research shows that,when freezing,temperature drops,salt and moisture move towards frozen layer. All make the salinity content of the frozen layer increase significantly. In the thawing process,salinity and moisture in the soil move up again with evaporation and makes the salt second migration.     

西宁地区次生盐渍土的分布特征及地基处理方法

西宁地区次生盐渍土主要分布于山麓斜坡带高阶地和河谷高漫滩,前者属中～弱硫酸、亚硫酸盐渍土,且多具中等～强烈湿陷性,盐份主要来自斜坡后缘含盐碎屑岩风化物及易溶盐;后者为中等亚氯、亚硫酸盐渍土,溶于土中的盐份系浅层咸地下水常年毛细上升蒸发所致。其次生盐渍土的松胀性、溶陷性、腐蚀性较强,工程建设要引起重视。     

天津滨海绿地土壤水分特征曲线的拟合与比较分析

土壤水分特征曲线是定量研究土壤水运动和溶质运移的重要参数,对滨海地区盐碱土绿化建设有重要的作用。通过对天津滨海盐碱地绿化土进行脱水试验,选取Gardner模型和VG模型对实测数据进行拟合。运用对数简化方法对Gardner模型变形后进行回归分析,另外,采用软件Matlab的非线性拟合函数lsqcurvefit对VG模型进行了参数求解。结果表明:Gardner模型和VG模型都可以用于天津滨海盐碱地绿化土水分特征曲线的拟合。Gardner模型的参数求解过程简单,但用VG模型计算出的残差平方和较Gardner模型小,拟合效果优于Gardner模型。同时,该区绿地土断面上各层之间的拟合曲线相近,持水能力相当,说明了该区绿化土断面上各土层的土壤质地和结构差异不大。     

L波段对不同盐类土壤的微波介电特性分析

 土壤盐碱化是世界面临的一大难题。微波遥感探测土壤具有优势,L波段对土壤含水量和含盐量较为敏感。为了分析不同盐类对土壤介电特性的影响,本文利用L波段(1.43 GHz)微波谐振腔测量了我国盐碱土中普遍存在的3种盐类(NaCl,Na₂SO₄,NaHCO₃)土壤样品的介电常数,研究了土壤介电常数与含水量、含盐量和盐种类的关系。得出结论:实部主要由土壤的含水量决定,含盐量对实部的影响无明显规律;虚部值随含水量和含盐量的增加而增大;3种盐类土壤介电常数虚部随含盐量变化呈现不同的递增趋势,在含盐浓度一定的条件下,虚部值是ε″ _NaCI>ε″ _NaHCO3>ε″ _Na2SO4;在某一含盐量点3种盐类土壤虚部随含水量变化的斜率不同,以此能将3种盐类区分。该研究为建立含不同盐类土壤介电常数模型和微波遥感监测土壤盐碱化提供了实验的依据。     

Experimental study on dispersive soil in western Jilin

In order to research engineering geological properties of the soil in Zhenlai of western Jilin, especially the dispersivity of soil, the authors carried out the basic physicochemical test and dispersivity identification test. The results show that the dispersivity of the soil increases with the increase of depth within 0-30 cm ( surface soil) ; it decreases as the depth increases within in 30-100 cm. Furthermore, the statistical analysis of the dispersivity indexes and physicochemical propertity indexes show that the DP is positively linear correlated with total soluble salt content, sodium ion content, ESP, pH and organic matter content. Meanwhile, it is negatively linear correlated with clay content, and the linear relationship is better. Through the study of the dispersion mechanism of soil samples, it can be concluded that sodium montmorillonite, higher percentage of exchangeable sodium and high pH are the main reasons for the dispersion of soils in western Jilin.     

Application of principal component analysis to evaluation of black soil degradation in Jilin

Principal Component Analysis(PCA) can simplify the structure of database by replacing multi-dimensional parameters with relatively less comprehensive variables in order to ensure the minimum lost in initial data.In this paper,eighteen black soil samples from different sites were tested and thirteen distinctive indexes were chosen to evaluate the degeneration of black soil.By using principal component analysis,variables of thirteen dimensions can be diminished to six unrelated principal indexes.Analysis shows that the soluble salt content,Fulvic acids(FA) and aggregation degree have a high weighing coefficient,indicating these three indexes are the major parts for the evaluation of black soil degradation.It also provides a new path to the degenerated black soil treatment in Northeast China.     

PRIMARY ANALYSIS ON GROUNDWATER, SOIL MOISTURE AND SALINITY IN FUKANG OASIS OF SOUTHERN JUNGGAR BASIN

１INTRODUCTIONSoilandlandformarethemoreimportantenviron－mentalfactorsaffectingthedistributionofvegetationinabasinwhenthemeteorologicconditionissimilaronalargescale，especiallyspatialandtemporalvariationsofthesoilmoistureandsaltcontent．Inaridareasthesoil…     

镉在棕壤上的吸附过程及其对土壤酶活性的影响

土壤对镉的吸附过程是影响镉在土壤溶液中的浓度、迁移性、潜在毒性的重要因素。土壤微生物活性作为土壤质量的重要指标之一,对土壤重金属的含量具有较好的指示作用。该文研究了重金属镉在棕壤中的吸附过程,及在此过程中土壤酶活性的变化。结果表明,随着溶液中Cd2+含量的增大,两种土壤对Cd2+吸附量逐渐增大,且吸附反应符合Freundlich模型。随着镉初始浓度的增加,土壤中脲酶和过氧化氢酶的活性均出现抑制现象,其中脲酶对镉的反应更加敏感。     

FACTORS AFFECTING SOIL RESPIRATION IN REFERENCE WITH TEMPERATURE'S ROLE IN THE GLOBAL SCALE

Ｉ．ＩＮＴＲＯＤＵＣＴＩＯＮＳｏｉｌｒｅｓｐｉｒａｔｉｏｎｉｓＣＯ２ｅｖｏｌｕｔｉｏｎｐｒｏｃｅｓｓｆｒｏｍｓｏｉｌｔｏａｔｍｏｓｐｈｅｒｅ．Ｉｔｉｓｍａｉｎｌｙｐｒｏｄｕｃｅｄｂｙｏｘｉｄｉｚｉｎｇｏｒｇａｎｉｃｍａｔｅｒｂｙｍｉｃｒｏｏｒｇａｎ...     

盐溶液入渗过程的电阻率成像法时空监测

采用电阻率成像法探讨了室内实验尺度上岩体中盐溶液的入渗过程。在岩柱试样上进行蒸馏水和盐溶液的入渗实验,在入渗过程中通过多通道高密度电阻率勘测系统对岩柱的电性特征在三维空间上进行动态监测。然后对入渗过程岩柱进行电阻率成像,从而获得不同时刻岩柱中的电阻率分布。各勘测截面上电阻率的分布和变化基本反映了岩柱内盐溶液的时空变化特征,表明电阻率成像法动态监测室内实验尺度岩石中盐溶液的入渗是可行的,岩柱5个截面的电阻率图像表明溶液的入渗是不均匀的。     

ECO-ENVIRONMENT CHANGE AND SOIL EROSION PROCESS IN THE RECLAIMED FORESTLAND OF THE LOESS PLATEAU

1INTRODUCTIONSerioussoilerosionhasmadetheeco-environmentfragileintheLoessPlateau.InthemodernsoilerosionoftheLoessPlateau,theman-madeerosionwasthedominanterosionpattern (TANGetal.,1993a,1993b).Manyhumanactivitiesacceleratesoilerosion,butthemostinfluentialactivitiesaretodestroyforestandgrass,eventodestroyallvegetation.Reclamationbydestroyingforestlandandgrasslandartificiallycouldrapidlyincreasesoilerosionintensityinshorttimeandenlargeerosionspacegradually,evenchangeerosiondirectionandwor…     

Characteristics of Channeling Flow in Cultivated Horizon of Saline Rice Soil

1 Introduction The preferential flow tends to result in the loss of irriga- tion water and nutrients. The formation of the preferen- tial flow was caused by various factors, such as soil structure, tillage, worm cavity and root channeling rup- ture (Pot et al., 2005). Besides, frozen rupture can not be ignored in the northeastern China where the lowest tem- perature reaches -40℃ (Wang et al., 1993). There are several types of preferential flow, such as bypass flow, channeling flow and macro…     

The effect of land use changes on soil conditions in arid region

Biography:CHEN Fu(1974－ ), male,a native of Sheyang County, Jiangsu Province, doctoral candidate.His research interests include land use management.1 INTRODUCTION Land use change may influence a variety of natural and ecological processes, including soil nutrient, soil moisture, soil erosion, land productivity (FU et al., 1999), biodiversity, cycle of biographical geochemistry, and so on (VITOUSEK, 1994). So, it is very important that the studies of land use changes understand re…     

A two-parameter exponential recession model for simulating cropland soil moisture dynamics

To simulate the soil moisture variation in cropland, a two-parameter exponential recession model was derived to depict the recession process of soil moisture in the root zone. The model is based on the assumption that the recession rate of soil water is propor- tional to the potential evapotranspiration rate and the difference of soil water content and steady soil water content. Two parameters in this model are soil texture-dependent recession constant and steady soil water content. The model was calibrated and validated with measured soil water data at two experiment sites in North China with different soil textures and cropping systems. Coefficients of de- termination between measured and model simulated soil water content were all greater than 0.7, indicating that both models gave satis- factory simulation results. Results showed that values of two parameters mentioned above are both larger for finer soil than those for coarser soil. At the same potential evapotranspiration rate and soil water content, the recession rate of finer soil is usually lower than that of coarser soil. The proposed model can be used in irrigation management to predict approximate date for irrigation, as well as be em- bedded into watershed hydrological models to estimate the antecedent precipitation index.     

Effects of plant types on physico-chemical properties of reclaimed mining soil in Inner Mongolia,China

A field experiment was conducted in Jungar Banner, Inner Mongolia, China to study the effects of plant types on the physical structure and chemical properties of open-cast mining soils reclaimed for 15 years, and to analyze the triggering factors of the soil formation. Results indicate that plant types affect soil-forming process especially in the upper layer (0–20 cm), and the spatial structure of reclaimed plant is the main reason for variability of the soil-forming process. In the upper soil layer at the site reclaimed with mixed plants, the concentrations of soil organic matter (SOM) and soil organic carbon (SOC) are the highest, and they were significantly higher at the sites reclaimed with Leymus chinensis, Caragana sinica, which is mainly due to a large amount of litter fall and root exudation in herbages and shrubs. However, the concentrations of SOM and SOC in the soils at the reclaimed sites are quite low comparing with those in local primary soil, which indicates the importance of using organic amendments during the ecological restoration in the study area.     

SUSTAINABLE AGRICULTURE DEVELOPMENT IN SALINE—ALKALI SOIL AREA OF SONGNEN PLAIN, NORTHEAST CHINA NORTHEAST CHINA

There is great potential for agriculture in saline-alkali soil area in Songnen Plain, Northeast China. Butthe sustainable crop production in this area has been restricted by a few of main factors, such as less precipitation, higherevaporation and frequent drought, high salinity and alkalinity, high exchangeable sodium content and poor infiltration ofthe soil, and insufficiency and low availability in nutrition. It is also considered that there are a few of favorable condi-tions for agricultural development in this region, such as sufficient light and heat resources, rich ground water resources,plenty of manure produced by livestock, and so on. At the same time, scientific management and measurements havebeen employed; rational irrigation and drainage system has been established; reclamation, amendment and fertilization ofsoil, and suitable strategies of cropping practices have been made for the sustainable development of agriculture. Great progress has been made during 1996- 2000.     

福建东圳库区淹没及水土流失的3D-VRGIS构建与应用

本文应用VRGIS(Virtual Reality Geographical Information System)技术,建立水库工程水土流失三维可视化动态仿真模型,实现库区的空间信息可视化。以福建省东圳水库为研究对象,建立水土流失区域三维虚拟地理信息系统(3D-VRGIS),生成水土流失现状以及库区生态环境三维场景。并结合水土流失中水淹分析要素与三维空间的数据可视化技术,实现水土流失监测预报及其区域定位监控的可视化处理,为减少水土流失危害,提供可靠的信息资源。     

陕南膨胀土加灰改良的试验研究

陕南膨胀土分布地区由于膨胀土地基的胀缩变形，常常导致建筑物开裂和毁坏。如何改良膨胀土，消除其胀缩性，加固膨胀土地基，确保工程建筑物的安全和稳定，是膨胀上分布地区工程建设实践中急待解决的重要课题。结合陕南三种类型的膨胀土，我们选取有代表性的试样进行了加灰（石灰、粉煤灰）处理的试验研究，其效果较好，消除或减弱了膨胀土的胀缩性，达到了改良膨胀上不良工程地质性质的目的．     

Weathering of pisha-sandstones in the wind-water erosion crisscross region on the Loess Plateau

Two types of pisha-sandstones of purple sandstones and gray sandstones, widely distributing in the wind-water erosion crisscross region of China, were selected and used in laboratory experiments for a better understanding of the drying-wetting-freezing weathering process resulting from the apportionment of water or salt solution to rock samples. Weathering experiments were carried out under the conditions of environment control （including temperature, moisture and salt solution）. All rock samples were frequently subjected to 140 drying-wetting-freezing cycles. The influences of weathering process were evaluated. It was found that the different treatments of moisture and salt solution applications could affect the nature of the weathering products resulting from drying-wetting-freezing. It was also observed that salt solution could effectively alleviate the weathering of pisha-sandstones. Although not all the observations could be explained, it was apparent that simulated environmental factors had both direct and indirect effects on the weathering of rocks.     

Influences of soil moisture and salt content on loess shear strength in the Xining Basin,northeastern Qinghai-Tibet Plateau

Moisture and salt content of soil are the two predominant factors influencing its shear strength. This study aims to investigate the effects of these two factors on shear strength behavior of loess in the Xining Basin of Northeast Qinghai-Tibet Plateau, where such geological hazards as soil erosion, landslides collapse and debris flows are widespread due to the highly erodible loess. Salinized loess soil collected from the test site was desalinized through salt-leaching in the laboratory. The desalinized and oven-dried loess samples were also artificially moisturized and salinized in order to examine how soil salinity affects its shear strength at different moisture levels. Soil samples prepared in different ways(moisturizing, salt-leaching, and salinized) were measured to determine soil cohesion and internal friction angle. The results show that salt-leaching up to 18 rounds almost completely removed the salt content and considerably changed the physical components of loess, but the soil type remained unchanged. As salt content increases from 0.00% to 12.00%, both the cohesion and internal friction angle exhibit an initial decrease and then increase with salt content. As moisture content is 12.00%, the salt content threshold value for both cohesion and internal friction angle is identified as 3.00%. As the moisture content rises to 16.0% and 20.00%, the salt content threshold value for cohesion is still 6.00%, but 3.00% for internal friction angle. At these thresholds soil shear strength is the lowest, below which it is inversely related to soil salinity. Beyond the thresholds, however, the relationship is positive. Dissimilar to salinity, soil moisture content exerts an adverse effect on shear strength of loess. The findings of this study can provide a valuable guidance on stabilizing the engineering properties of salinized loess to prevent slope failures during heavy rainfall events.