长期施钾对湖北省几种土壤粘土矿物组成影响的初步研究

对耕层土壤的粘粒进行X 射线衍射分析结果表明,无论是10 年不施钾或是10 年连续施钾,同一土壤的粘土矿物组成表现出相同的变化趋势:麻砂泥田粘土矿物组成中,水云母含量下降,1-4 nm 矿物含量相应上升,类型由以蛭石为主转变为以1-4 nm 过渡矿物为主,且1-4 nm 过渡矿物的热稳定性有所增强,这主要是由于土壤钾、镁等营养元素长期“入不敷出”所致;白散泥田土壤粘土矿物组成变化不明显;灰油砂土粘粒中,水云母含量上升,1-4 nm 矿物相应下降,这可能主要是粗粒云母类矿物在表层风化的结果。

秦川盆地土壤粘土矿物特征与土壤质地的关系

以灰钙土、耕种灰钙土、砂田灰钙土、砂田盐化灰钙土和旱盐土5种土壤为研究对象,研究了矿物特征和土壤质地的关系。结果表明5种土壤的粒度成分都比较细,以细砂为主,铺砂对土壤质地的影响不显著,土壤质地特征主要是由土壤母质、成土作用决定的。土壤粘土矿物含量最多的样品,也是质地最粘重,或粒度组成最细的样品。而粘土矿物含量较低的样品,粉砂的含量均小于细砂的含量,而且随着粉砂与细砂之间含量差异的扩大,粘土矿物含量逐渐降低。由于秦川盆地土壤的成土环境和成土作用是相似的,因此,虽然它们的质地特征不同,但土壤粘土矿物的类型是相同的,土壤粘土矿物含量的不同,反映的是成土作用进行的阶段或程度的差异。

灵台红粘土-黄土-古土壤序列频率磁化率的古气候意义

通过对甘肃灵台晚新生代红粘土 -黄土 -古土壤序列的磁化率测量和频率磁化率分析 ,发现红粘土及黄土 -古土壤的磁化率和频率磁化率存有良好的正相关关系 ,表明两套沉积在成壤过程中由生物作用或化学作用而形成的超顺磁性矿物含量 ,对磁化率和频率磁化率增大有重要的贡献。相比磁化率而言 ,受影响因素较少的频率磁化率变化 ,反映了不同气候条件下形成的超顺磁粒级铁磁性矿物的相对含量 ,能更真实、敏感地记录不同时间尺度的古气候波动。灵台红粘土 -黄土 -古土壤序列的频率磁化率在 2 .6MaBP前后不同的变率特征 ,揭示了大冰期来临前后黄土高原的冷暖、干湿反差产生了显著变化 ,而与此相关的冬。

基于RWEQ模型的土壤风蚀模数影响因素研究

RWEQ模型是定量研究土壤风蚀的关键模型,为深刻分析该模型在建模过程中各引入变量与土壤风蚀的关系,以土壤最大转移容量(Qmax)为描述变量,探究植被盖度、土壤粘粒含量与Qmax的关系,对植被盖度、土壤粘粒含量分段赋值,产生9898组变量组合,计算了气象因子为17、可蚀性因子为0.456、土壤粗糙因子为0.68、有机质含量为2%前提条件下的Qmax值,分析了各种组合条件下三者的关系,结果表明:1) Qmax值与植被盖度存在较明显的负相关关系,且40%植被盖度是抑制风蚀作用的重要节点盖度,在达到此盖度前植被具有剧烈的抗风蚀作用;2) 与上述方法相同,土壤粘粒含量也与Qmax值呈负相关关系,且土壤粘粒含量阈值达到30%后抗风蚀作用明显减弱;3) RWEQ模型中各因子对于Qmax值的耦合作用、以及不同分蚀阶段的主导因素不同。低阈值阶段,土壤粘粒含量对于Qmax值的影响较明显;高阈值阶段,植被盖度又对Qmax值的影响较为明显。

不同耕作措施对南方壤粘土的侵蚀产流产沙影响

通过微径流场模拟降雨试验,研究了我国南方暴雨条件下不同旱地耕作措施的坡耕地产流产沙情况,并设置了秸秆覆盖、横坡起垄、免耕和纵坡起垄4种南方最为常见的旱地表土耕作方式。在320mm/h的稳定降雨强度下,观测到华南保护性耕作研究区域壤质粘土的产流量与降雨时间符合线次或二次函数关系。由各处理的径流含沙量可知:秸秆覆盖是最有效的防治土壤侵蚀的方式;免耕其次;横坡垄作在降雨初期有一定程度的防治效果,但暴雨依旧会造成土壤结构的破坏;顺坡起垄的水土流失程度最大。分析土壤质地可知:流失的土壤大多为粒径小的粉粒和黏粒,暴雨不仅造成水土流失,也造成表层土壤质地的改变。该研究可为华南地区受暴雨侵蚀的坡耕地提供耕作模式价值相关参考。

Effects of Organic Acids on Adsorption of Cadmium onto Kaolinite, Goethite, and Bayerite

Effects of organic acids (oxalic, acetic, and citric) on adsorption characteristics of Cadmium (Cd) on soil clay minerals (kaolinite, goethite, and bayerite) were studied under different concentrations and different pH values. Although the types of organic acids and minerals were different, the effects of the organic acids on the adsorption of Cd on the minerals were similar, i.e., the amount of adsorbed Cd with an initial solution pH of 5.0 and initial Cd concentration of 35 mg L-1 increased with increasing concentration of the organic acid in solution at lower concentrations, and decreased at higher concentrations. The percentage of Cd adsorbed on the minerals in the presence of the organic acids increased considerably with increasing pH of the solution. Meanwhile, different Cd adsorption in the presence of the organic acids, due to different properties on both organic acids and clay minerals, on kaolinite, goethite, or bayerite for different pHs or organic acid concentrations was found.

A Preliminary Stndy on Identification of Clay Minerals in Soils with Reference to Reflectance Spectra

The characteristics of the reflectance spectra of clay minerals and their influences on the reflectancespectra of soils are dealt with in the paper. The results showed that dominant clay minerals in soils couldbe distinguished in light of the spectral-form parameters of the reflectance spectra of soils, thus making itpossible to develop a quick method to determine clay minerals by means of reflectance spectra of soils in thelab. and providing a theoretic basis for retnote sensing of clay minerals in soils with a high resolution imagingspectrometer.

Short-term Effects of Tillage Practices on Organic Carbon in Clay Loam Soil of Northeast China

A tillage experiment, consisting of moldboard plow （MP）, ridge tillage （RT）, and no-tillage （NT）, was performed in a randomized complete block design with four replicates to study the effect of 3-year tillage management on SOC content and its distribution in surface layer （30 cm） of a clay loam soil in northeast China. NT did not lead to significant increase of SOC in topsoil （0-5 cm） compared with MP and RT; however, the SOC content in NT soil was remarkably reduced at a depth of 5-20 cm. Accordingly, short-term （3-year） NT management tended to stratify SOC concentration, but not necessarily increase its storage in the plow layer for the soil.

Analysis of phreatic evaporation law and influence factors of typical lithology in Hebei Plain

Based on three typical mediums(sandy loam, loam and sandy clay loam) in Hebei Plain, this paper designs phreatic evaporation experiments under different lithology and phreatic depth. Based on the analysis of experimental data, the phreatic evaporation law and influencing factors of three mediums were studied. The results showed that:(1) The shallower the phreatic depth, the larger the phreatic evaporation.(2) Sandy clay loam has the biggest response to the increase of the phreatic depth, sandy loam is the second and loam is the smallest.(3) The limit depth of phreatic evaporation of sandy clay loam is about 3 m and that of loam and sandy loam is about 2 m and 3 m, seperately.(4) By fitting the daily evaporation of phreatic water and phreatic depth, the results showed that sandy loam and sandy clay loam are exponential functions and loam is power functions.

Key Variables Explaining Soil Organic Carbon Content Variations in Croplands and Non-Croplands in Chinese Provinces

Soil organic carbon (SOC) plays an important role in global carbon cycles.Large spatial variations in SOC contents result in uncertain estimates of the SOC pool and its changes.In the present study,the key variables explaining the SOC contents of croplands (CPs) and non-croplands (NCPs) in Chinese provinces were investigated.Data on SOC and other soil properties (obtained from the Second National Soil Survey conducted in the late 1970s to the early 1990s),climate parameters,as well as the proportion of the CP to the total land area (Pcp) were used.SOC content variations within a province were larger than those among provinces.Soil clay and total phosphorus content,ratio of annual precipitation to mean temperature,as well as Pcp were able to explain 75% of the SOC content variations in whole soil samples.Soil pH,mean temperature during the growing season from May to October,and mean annual wind velocity were able to explain 63% of the SOC content variations in NCP soils.Compared with NCP soils,CP soils had lower SOC contents,with smaller variations within and among provinces and lower C/N ratios.Stepwise regression showed that the soil clay content was a unique factor significantly correlated with the SOC content of CP soils.However,this factor only explained 24% of the variations.This result suggested that variables related to human activities had greater effects on SOC content variations in CP soils than soil properties and climate parameters.Based on SOC contents directly averaged from soil samples and estimated by regression equations,the total SOC pool in the topsoil (0-20 cm) of China was estimated at 60.02 Pg and 57.6 Pg.Thousands of years of intensive cultivation in China resulted in CP topsoil SOC loss of 4.34-4.98 Pg.

Bio-Mobilization of Potassium from Clay Minerals: Ⅱ. By Ectomycorrhizal Fungi

Ectomycorrhizal fungi, including Cenococcum geophilum SIV (Cg SIV), and Pisolithus tinctorius 2144 (Pt 2144), 441 (Pt 441) and XC1 (Pt XC1), were cultured in Pachlewski liquid medium with H2KPO4,KCl- saturated vermiculite and mica as K sources, respectively, to investigate the mechanism of K absorption and mobilization by the fungi. Fungal growth rate, K absorption and mobilization varied significantly among the fungal species. Faster growth and greater K accumulation in Pt XC1 than Pt 2 144, Pt 441 and Cg siv were observed. Ectomycorrhizal fungi depressed HCl-soluble K in minerals after successive extractions by water and NH4OAc. Ratio of the total amount of K, including water-, NH4OAc- and HCI-soluble K, lost from substrates to the K accumulated in fungal colonies was less than 60%. These reveal that the ectomycorrhizal fungi could utilize K in interlayer and structural pools, which are usually unavailable for plants in short period. Large differences in the depletion of K in interlayer and structural pools by fungi were observed at fungal harvest. Taking into account the nutrient absorption by ectomycorrhizal fungi in symbionts and the direct contact between hyphae and soils, the fungi species colonized on the root surfaces seemed to be related to the effectiveness of mycorrhizas to utilize K in soils. Ectomycorrhizal fungi differed in the efflux of protons and oxalate. Pt XC1 was observed to have greatest ability to effuse protons and oxalate among the fungi adopted in the experiment. Furthermore, the higher the concentrations of protons and oxalate in the liquid culture solutions, the larger the depletion of K in interlayer and structural pools in minerals by fungi. Protons could replace interlayer K and chelation of oxalate with Fe and Al in crystal lattice could cause weathering of clay minerals. So, protons and oxalate produced by ectomycorrhizal fungi might play an important role in K mobilization in these two pools.

Viscous property of dried clay

One dimensional and triaxial compression tests of air-dried and oven-dried Fujinomori clay and Pisa clay were carried out. Water content is less than 4.5% and 1.0% for air-dried and oven-dried clay specimens, respectively. In all tests, axial strain rate was changed stepwise many times and drained creep tests were performed several times during monotonic loading at a constant strain rate. Global unloading (and also reloading in some tests) was applied during which creep loading tests were performed several times. Cyclic loading with small stress amplitude and several cycles was also performed to calculate the modulus of elasticity of the clay in tests. Local displacement transducer was used in triaxial compression test to increase measuring accuracy of axial strain. The results show that air-dried and oven-dried clay have noticeable viscous properties; during global unloading, creep deformation changes from positive to negative, i.e. there exist neutral points (zero creep deformation or no creep deformation point) in global unloading part of strain-stress curve; viscous property of Fujinomori clay decreases when water content decreases, i.e. viscous property of air-dried Fujinomori clay is more significant than that of oven-dried Fujinomori clay.

Determination of Water Colltent in Clayey Red Soil Using Techniques Based on Measurement of Dielectric Constant

Two time-domain reflectometry (TDR) systems and a new impedance measuring instrument, Thetaprobe,which are based on determination of soil dielectric constant, were used to measure water content of clayeyred soil to eraluate the accuracy of these instruments. The results indicated that these instruments shouldbe carefUlly re-calibrated before being applied in clayey red soil. With a new calibration curve fed into one ofthe TDR systems tested, nase system, the measured data compared well with tho8e by standard oven-dryingmethod.

Main Clay Minerals in Soils of Fujian Province, China

The clay minerals of more than 200 soil samples collected from various sites of Fujian Province were studied by the X-ray diffraction method and transmission electron microscopy to study their distribution and evolution. Montmorillonite was found in coastal solonchak, paddy soils derived from marine deposit, lacustrine deposit and river deposit, and some latentic red soil, red soil and yellow soil with a low weathering degree. Chlorite existed mainly in coastal solonchak and paddy soil developed from marine deposit. 1.4 nm intergradient mineral appeared frequently in yellow soil, red soil and latentic red soil. The content of l.4 nm intergradient mineral increased with the decrease of weathering degree from latentic red soil to red soil to yellow soil. Hydrous micas were more in coastal solonchak, paddy soils derived from marine deposit, lacustrine deposit and river deposit, and purple soil from purple shale than in other soils. Kaolinite was the most important clay mineral in the soils in this province. The higher the soil weathering degree, the more the kaolinite existed. From yellow soil to red soil to latentic red soil, kaolinite increased gradually. Kaolinite was the predominant clay mineral accompanied by few other minerals in typical latentic red soil. Tubular halloysite was a widespread clay mineral in soils of Fujian Province with varying quantities. The soil derived from the parent rocks rich in feldspar contained more tubular halloysite. Spheroidal halloysite was found in a red soil and a paddy soil developed from olivine basalt. Gibbsite in the soils in this district was largely 'primary gibbsite' which formed in the early weathering stage. Gibbsite decreased with the increase of weathering degree from yellow soil to red soil to latentic red soil. Goethite also decreased in the same sequence while hematite increased.

Estimation of the van Genuchten Soil Water Retention Properties from Soil Textural Data

The van Genuchten (vG) function is often used to describe the soil water retention curve (SWRC) of unsaturated soils and fractured rock. The objective of this study was to develop a method to determine the vG model parameter m from the fractal dimension. We compared two approaches previously proposed by van Genuchten and Lenhard et al. for estimating m from the pore size distribution index of the Brooks and Corey (BC) model. In both approaches we used a relationship between the pore size distribution index of the BC model and the fractal dimension of the SWRC. A dataset containing 75 samples from the UNSODA unsaturated soil hydraulic database was used to evaluate the two approaches. The statistical parameters showed that the approach by Lenhard et al. provided better estimates of the parameter m. Another dataset containing 72 samples from the literature was used to validate Lenhard's approach in which the SWRC fractal dimension was estimated from the clay content. The estimated SWRC of the second dataset was compared with those obtained with the Rosetta model using sand, silt, and clay contents. Root mean square error values of the proposed fractal approach and Rosetta were 0.081 and 0.136, respectively, indicating that the proposed fractal approach performed better than the Rosetta model.

Parametric Study on the Effects of Pile Inclination Angle on the Response of Batter Piles in Offshore Jacket Platforms

Offshore jacket-type platforms are attached to the seabed by long batter piles. In this paper, results from a finite element analysis, verified against experimental data, are used to study the effect of the pile＇s inclination angle, and its interaction with the geometrical properties of the pile and the geotechnical characteristics of the surrounding soil on the behavior of the inclined piles supporting the jacket platforms. Results show that the inclination angle is one of the main parameters affecting the behavior of an offshore pile. We investigated the effect of the inclination angle on the maximum von Mises stress, maximum von Mises elastic strain, maximum displacement vector sum, maximum displacement in the horizontal direction, and maximum displacement in the vertical direction. Results indicate that the pile＇s operationally optimal degree of inclination is approximately 5°. By exceeding this value, the instability in the surrounding soil under applied loads grows extensively in all the geotechnical properties considered. Cohesive soils tend to display poorer results compared to grained soils.

Evaluation of Risk Sechage-Humidification of a Clay Soil of Algiers： The Case Study of the Argillaceous Marnes

Consecutive differential movements of ground to the dryness and the rehydration of the sols are irregular movements of ground related to the phenomenon of withdrawal-swelling. By risk of withdrawal-swelling, one understands the phenomenon ＂natural＂ likely to occur, with a probability of more or less large occurrence. For the phenomenon of withdrawal-swelling of the argillaceous grounds, one will speak about strong, average or weak risk. This article returns within the framework＇s study of risk withdrawal-swelling or dryness-humidification of the argillaceous Mames of the area of Ouled Fayet and Cheraga of Algiers.

Changes of Clay Mineral Association After High-Gradient Magnetic Separation

The changes of clay mineral association after high-gradient magnetic separation (HGMS) treatment, and the effects of chemical and physical technologies on concentrating Fe oxides for main soils in central and southern China were investigated by means of X-ray diffraction (XRD) and chemical analysis methods. Results indicated that the concentrating times of Fe oxides by HGMS treatment were the largest for 0.2-2 μmsize fractions in the examined soils. For the soils in which 2: 1 phyllosilicates were dominant, concentrating times of iron oxides by HGMS treatment were larger than by 5 mol L-1 NaOH treatment. Phyllosili-cates were decreased after HGMS treatment; however, the decrease was less than that of kaorolinite. The goet bite / (goethite + hematie) values in Fe oxides of the soils kept virtually constant after HGMSt reatment.

Models and Optimization of Rice Husk,Ash-Clay Soil Stabilization

Soil stabilization has been found to be very effective in upgrading the bearing capacity of weak soils for construction purposes. The stabilizing agent, for cost efficiency, ought to provide a cheaper alternative to other possible processes. With the rapid industrialization efforts around the globe, enormous quantities of waste materials are generated and there has not been adequate mechanism for recycling and re-use of such wastes to reduce the consequent environmental problems and hazardous situations created as a result. The objective of the study is to upgrade expansive soils from Eke Obinagu, Ugwuaji in Enugu State and Egbede in Abia State Nigeria, as constructions material using RHA （rice husk ash）. Expansive clay soils were mixed with this ash, remolded and tested to examine the effect on the OMC （optimum moisture content） and the CBR （California Bearing Ratio）. The characterization of the soils was done in accordance with BS1377 and 1990b, with respect to their engineering properties which include OMC, MDD, Soaked CBR, Liquid Limit, Classification and Sieve Analysis. The rice husk was burnt and prepared in a cylindrical incinerator to form the ash. The results of classification showed A-7-5, A-6, A-2-7 soils for Eke Obinagu, Egbede and Ugwuaji, respectively. The CBR values showed increase from 5% to 29%, 7% to 13% and 5% to 23% for A-7-5, A-6 ~nd A-2-7 respectively at optimal value of 17.5% stabilization. There was also an appreciable increase in the OMC values from 15% to 33%, 14% to 25% and 15% to 31% for A-7-5, A-6 and A-2-7 soils respectively at 17.5% stabilization. Empirical models based on Scheffe＇s model were developed with the experimental results and the equations resulting from the second degree polynomials of Scheffe＇s models were solved using the least square method. The models developed showed close correlation with the experimental results for the A-7-5 and A-6 soils and will form good guide in pavement and foundation designs in the study areas.

Charge Properties and Clay Mineral Composition of Tianbao Mountains Soils

The clay mineral association, oxides of clay fraction and surface charge properties of 7 soils, which are developed from granite, located at different altitudes of the Tianbao Mountains were studied. Results indicate that with the increase in altitude, 1) the weathering process and desilicification of soil clay minerals became weaker, whereas the leaching depotassication and the formation process of hydroxy-aluminum interlayer got stronger; 2) the contents of amorphous and complex aluminum and iron, and the activity of aluminum and iron oxides for soil clay fraction increased; and 3) the amount of variable negative charge, anion exchange capacity and the values of PZC and PZNC also increased. The activity of aluminum and iron oxides, the accumulation of aluminum, and surface charge characteristics and their relation to clay oxides of the vertical zone soils were observed and recorded.