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1.
The mineralogical composition of clays (< 2μm) in representative profiles of all soil types of Israel was investigated. The soils were classified according to their clay mineral assemblages into three groups. I. Montmorillonitic soils. Montmorillonite is the dominant mineral and exceeds 65 per cent of the total minerals found; each of the other minerals comprises less than 15 per cent. 2. Montmorillonitic-kaolinitic soils. The soil clay fractions contain 50-60 per cent montmorillonite and 15-25 per cent kaolinite, generally adding up to more than 75 per cent of the clay fraction. 3. Montmorillonitic-calcitic soils. The clays contain more than 10 per cent calcite. Montmorillonite is the dominant clay mineral (except for one soil type, mountain rendzina, where calcite is dominant). The first and second assemblages are typical of the soils of the Mediterranean zone, whereas the soils of the desert zone are characterized by the third assemblage. The origin of montmorillonite, kaolinite, and illite, the three main clay minerals, was found to be detritic, as was the origin of palygorskite which was mainly found in the calcite rich soils of the desert zone. The cation exchange capacity of montmorillonite seems to be higher under higher precipitation. Montmorillonite content and cation exchange capacity of the clays were found to be highly correlated. The carbonate content of the clay fraction and the amount of carbonate in the soil were also highly correlated.  相似文献   

2.
Ground and surface water contamination by herbicides applied to olive groves in Spain and other Mediterranean countries is demanding strategies to prevent and remediate the environmental problems repeatedly caused by such herbicides. In this study, six different organic cations (L-carnitine, spermine, hexadimethrine, tyramine, phenyltrimethylammonium, and hexadecyltrimethylammonium) were incorporated into Na-rich Wyoming montmorillonite (SWy-2) and Ca-rich Arizona montmorillonite (SAz-1) at two different loadings (50% and 100% of the cation exchange capacity of the clays) as a strategy to enhance the affinity of the clay minerals for three herbicides widely used in olive groves: terbuthylazine, diuron, and MCPA. The modified montmorillonites were characterized and tested as adsorbents of the herbicides through batch adsorption tests. At the experimental conditions used, some of the modified montmorillonites removed more than 95% of the herbicide initially present in aqueous solution, whereas the unmodified clays removed less than 15%. All three herbicides displayed very strong affinities for SAz-1 exchanged with hexadecyltrimethylammonium cations, particularly when these were incorporated at 100% of the cation exchange capacity of the clay mineral. Terbuthylazine and diuron also displayed very strong affinities for SWy-2 exchanged with L-carnitine and spermine, respectively. The chemical characteristics of the organic cation greatly influenced the adsorptive properties of the resultant organoclay. The herbicides were in general reversibly adsorbed by the modified clays. The results indicate that some of the tested modified clays could be suitable for the removal of the assayed herbicides from contaminated water and also as possible supports for the design of slow release formulations of such herbicides to attenuate their environmental impact when used in high-risk scenarios such as olive groves.  相似文献   

3.
The clay fractions of the soils of two toposequences derived from gneissic rocks (Peninsular gneiss) in southern India consist chiefly of kaolinite and amorphous ferrialuminosilicates (AFAS). The cation exchange capacity of the amorphous constituents, ranging between 21.4 and 107.6 mequiv./100 g, has been explained on the basis of a structural model. Considerable amounts of smectite were present in the clays of soils on the toeslopes. Two hypothetical pathways for the formation of the clay minerals are proposed.  相似文献   

4.
Influence of two- and three-layered clay minerals on the Dehydrogenase-, acid Phosphatase and Urease Activity in model experiments The influence of different Ca-homo-ionic clay minerals as well as humic acid (Roth) on the dehydrogenase activity (DHA) as well as on urease and acid phosphatase were examined in model experiments. The following results were obtained: 1. The DHA of a fertile soil and the activity of urease and acid-phosphatase decreased remarkably and specifically with increasing amounts of sorbents. Generally speaking, inactivation was complete at approximately 0.6 g of each additive. Both urease- and acid phosphatase activity were inactivated specifically. The inactivation of urease decreased in the sequence humic acid < montmorillonite < illite < pyrophyllite < halloysite < kaolinite < bentonite, whereas the following order of succession pyrophyllite < montmorillonite < bentonite < halloysite < kaolinite < illite was recorded with acid phosphatase. The yellow colour of humic acid excluded it from experiments with acid phosphatase. 2. No relationship could be found between the degree of inactivation and the cation exchange capacity (CEC) or the total surface area of the clays. However, nearly the same sequence of inactivation with the three enzyme systems was revealed, if their activity was related to the specific surface charge of the clay minerals. Apparently, both the total surface area as well as CEC are involved in the specific sorption of cells and enzymes. The possible mechanisms of sorption on clay surfaces are discussed.  相似文献   

5.
The effects on a number of soil physical and aeration parameters of compaction during spring pre-sowing operations were measured on a clay soil (49% clay). A soil-tyre contact stress of 200 kPa was applied by tractor tyres.
Yield of an oat crop was reduced by 30% as a result of compaction. Total porosity of the soil was reduced by 6% v/v owing to loss of pores > 60 μm, and water retention was increased. The resultant decrease in air-filled porosity greatly reduced gas diffusion and air permeability coefficients of the soil, and, for a time, O2 content of the soil atmosphere was significantly lowered in the compacted treatment. Penetrometer resistance after sowing was 3.5 MPa in the control and 4.5 MPa in the compacted treatment; in the latter, root growth was inhibited until the soil dried and cracked. By the end of June, canopy temperature measurements indicated water stress in the oat crop on compacted soil but not in that on the control.
The results obtained indicated that air permeability, measured in the field, of 1 mm s−1 provides a satisfactory single value below which crop growth is likely to be reduced.  相似文献   

6.
Short-term effects of high axle load traffic on soil total porosity and pore size distribution were examined in field experiments on a clay (Vertic Cambisol) and an organic soil (Mollic Gleysol) for 3 years after the heavy loading. The clay soil had 48 g clay (particle size less than 2 μm) per 100 g in the topsoil and 65 g per 100 g in the subsoil. The organic soil consisted of well-decomposed sedge peat mixed with clay below 0.2 m depth down to 0.4–0.5 m and was underlain by gythia (organic soil with high clay content). The experimental traffic was applied with a tractor-trailer combination in autumn 1981. The trailer tandem axle load was 19 Mg on the clay and 16 Mg on the organic soil. There were three treatments: one pass with the heavy axle vehicle, with wheel tracks completely covering the plot area, four repeated passes in the same direction, and a control treatment without experimental traffic. During loading, the clay was nearly at field capacity below 0.1 m depth. The organic soil was wetter than field capacity.

One and four passes with the high axle load compacted both soils to a depth of 0.4–0.5 m. On the clay soil the total porosity was reduced by the heavy loading nearly as much as macroporosity (diameter over 30 μm) to 0.5 m depth. On the organic soil, macroporosity was reduced and microporosity (under 30 μm) increased in the 0.2–0.5 m layer by the heavy loading. Total porosity did not reveal the effects of compaction on the organic soil. The compaction of the clay below 0.1 m persisted for 3 years following the treatment despite annual ploughing to a depth of 0.2 m, cropping and deep cracking and freezing. Likewise, in the subsoil (below 0.2 m) of the organic soil, differences in pore size distribution persisted for a period of at least 3 years after the heavy loading.  相似文献   


7.
The cation exchange capacity (CEC) and specific surface properties were investigated in four particle‐size fractions < 50 μm from three loess (one Kastanozem and two Phaeozems), a holocene (Fluvisol) and a basalt soil (Nitisol) before and after destruction of organic matter. Particle‐size fractions were separated by sedimentation after chemical and physical dispersion of the soil samples. Illite, amorphous minerals, mixed layers, smectite and kaolinite were the predominant clay minerals. They were detected in all size fractions. The CEC increased with increasing organic matter contents and this effect was more pronounced in coarser fractions. The organic matter content per unit surface area was two or three times larger in coarse silt than in clay, irrespective of the soil type.  相似文献   

8.
The role of colloidal constituents in soil structure and its resistance to compaction was studied in two acid forest soils of contrasting pH, clay type and texture. The soils were trafficked with an eight‐wheel‐drive forwarder, and undisturbed topsoil samples were taken on trafficked and control plots. Shrinkage analysis was used to assess the soil's physical behaviour, and in addition texture, organic carbon content and exchangeable Al3+ (Alex) and amorphous Al oxide (Aloxa) contents were determined. The effect of each constituent on the soil's physical properties was assessed with covariance analysis. The hydro‐structural stability and coarse pore (> 150 µm radius) and structural pore volumes of control samples were strongly determined by organic carbon and the forms of Al, whereas the plasma porosity was determined by clay content only. Organic carbon and Aloxa increased the structural pore and coarse pore volumes and modified their susceptibility to compaction; organic carbon provided a protecting effect, whereas it was the opposite with Aloxa. We observed contrasting effects of the colloidal constituents and of the behaviour of the pore systems on compaction. The situation is complex and we need to take into account the effects of the colloidal constituents to determine the effects of compaction on the soil's porosity. A simplified approach in which we used the water content at ?10 hPa as a covariate predicted soil bulk density as accurately as with all the analytical covariates, and it seems to be an inexpensive way to assess compaction.  相似文献   

9.
Neither the specific surface area values (from N2 sorption) nor the ethylene glycol monoethyl ether (EGME) retention values of 21 soil samples from New Zealand and Fiji could all be accounted for by the sum of the contributions from their component minerals. Much EGME is probably retained by internal surfaces of inter layered and interstratified clay minerals. EGME retention correlated well with cation exchange capacity (CEC) and a number of measures of water content of these soils. The water contents of air-dried soils (measured as ‘moisture factors’ or the ratios of air-dry and oven-dry weights) showed almost as close a relationship to CEC as EGME retention for this set of 21 subsoils. Moisture factors and CEC were closely related, within groups defined by dominant clay mineralogies, for a much wider selection of 1318 New Zealand soil horizons with low carbon contents. The relationships between surface area and a number of other soil properties including dispersibility of soils were also examined.  相似文献   

10.
北京香山地区褐土粘土矿物的研究   总被引：1，自引：0，他引：1  
陈佐忠 《土壤学报》1979,16(4):387-396
我国褐土作为一个独立的发生学土类是1958年以后被确定了的(Герасимов1958)。在这前后,李连捷、华孟、文振旺、许冀泉等都曾从不同角度、对褐土分布地区的土壤进行调查研究,得出一些有意义的结论1-2)(文振旺等,1959;中国科学院土壤及水土保持研究所等,1961;许冀泉,1961)。而对褐土中粘土矿物的研究,许冀泉的工作,是极其有益的。本文报告的是作者1961-1964年对北京香山地区褐土粘土矿物进行研究的结果。  相似文献   

11.
It is generally accepted that broken bonds are the major cause of cation exchange in kaolin minerals, although the studies of a “fireclay” type of kaolin mineral (8) and hydrated halloysite (12, 15) seem to indicate that lattice substitutions, such as that found for 2 : 1 type of clay minerals, account for the fairly large parts of the cation-exchange capacities of some kaolin clays, particularly with poor crystallinity.  相似文献   

12.
Analyses of the sorption of five polysaccharide cleaving soil enzymes by Na-homoionic clay minerals revealed a dependency on the cation exchange capacity of the clays: montmorillonite displayed the highest sorbing capacity, followed by palygorskite and kaolinite. Variation of the experimental conditions using cellulase and montmorillonite showed a maximum sorption at pH 4.8 and temperatures between 25°C and 45°C. Urea had no effect on the sorption, whereas humic acids and acetylation of enzymes lead to a decrease. No sorption was observed in the presence of bivalent cations. A discussion of possible binding mechanisms lead to the conclusion that interactions can be ascribed to van der Waals forces rather than to ionic reactions. It is assumed that the enzymes penetrate into the interlayers of montmorillonite, but not of palygorskite and kaolinite.  相似文献   

13.
Adsorption of Water, Ethylene Glycol Monoethyl Ether as well as Nitrogen and its Relation to Properties of German and Israeli Soil Samples To determine the specific surface area, samples taken from 140 soil horizons were selected and the significant physical and chemical properties were investigated. The specific surface area of the samples was determined by adsorption of H2O, ethylene glycol monoethyl ether (EGME) and N2. A comparison of the three methods shows that the specific surface area determined by the adsorption of H2O and EGME does not differ significantly. However, the specific surface determined by N2-adsorption differs markedly from the results obtained using the polar substances. As a dependent variable the specific surface area is mainly influenced by the clay content and clay mineral type. Further, the organic substance content as well as the iron- and manganoxide content have a more significant influence on the specific surface area the lower the clay content is, or the content of three layer minerals. As an independent variable, the specific surface area determined by adsorption of EGME, proved to be the characteristic soil factor which reflects the effective cation exchange capacity as well as the hygroscopicity with the highest degree of accuracy.  相似文献   

14.
辽宁省西部是低山丘陵区,年平均温度7.1℃,年平均降雨量400—500毫米,降雨集中在夏季,具有明显的大陆性气候特征,干燥度小于1,属半干旱类型.植被为油松柞木和草原灌木丛林.土壤属棕色森林土向栗钙土过渡的褐土地带.母质主要为花岗片麻岩风化物.山麓缓坡和河谷两岸为黄土丘陵.在黄土沉积物覆盖层下,常见红色风化壳露头,即红色粘土层.此外,并有松软易风化岩层,如砂岩、页岩和变质岩等.本区近百年来,由于自然植被受到严重破坏,大量水土流失,土壤侵蚀严重,土壤有机质含量低,成为辽宁省的低产区.因此,鉴定本区不同母质的土壤矿物胶体组成及其特征,不仅可以研究这一特定自然条件下土壤矿物的转化和形成,并且有助于了解土壤特性和肥力特征.  相似文献   

15.
Contaminant adsorption properties of clays are markedly influenced by the type of clay minerals, the nature of the exchangeable ions, and the type of clay microstructure present. Clay soils, due to their high buffering capacity and low permeability, are very helpful materials as barriers in waste disposal projects. On the other hand, the different microstructures of clay soils, due to their different surface areas and the different quantity of these surfaces exposed to the water, cause different contaminant attenuation levels for clay minerals. Even though the dispersive structures of soils might cause some geotechnical problems, in geo-environmental projects they might be of use as an excellent contaminant absorbent due to the fact that their clay particles are well-exposed to the soil pore fluid. The present study investigates the role of various types and concentrations of pore fluid on the microstructure and contaminant adsorption of illite. A series of pH measurements, a turbidity experiment, an XRD analysis, batch equilibrium testing and soil adsorption evaluation were performed to achieve the aforementioned objective. Homo-ionic illite mineral was prepared and some experiments were performed on it to support the findings. The results of this study show that although the theoretical calculation of the double layer theory does not take into account the effect of different anion types on the variation of the thickness of double layer, the anion type has a major impact on the microstructure variations of clay minerals. In addition, the turbidity measurement and the monitoring of XRD peak intensity of the major basal spacings of illite are appropriate tools for evaluating its dispersivity behaviour. It is shown that the PDI treated illite has more capacity for adsorption of heavy metal contaminant than that of illite or Ca–illite. It is concluded that the observed geo-environmental behaviour is noticeably a function of changes in the microstructure of illite.  相似文献   

16.
本文研究了中南地区不同纬度带花岗岩母质发育的黄棕壤、红壤、砖红壤的胶体表面性质与粘土矿物组合、14×10-10m矿物、氧化物的关系。结果表明:(1)黄棕壤、红壤、砖红壤粘粒的阳离子交换量、比表面和内表面占总表面的比例依次减小,这与其高岭石、粘粒氧化物含量依次增加,14×10-10m矿物含量依次减少有关,且也与14×10-10m矿物在黄棕壤中主要是蛭石,在红壤中主要是14×10-10m过渡矿物,砖红壤不含14×10-10m矿物的结论相符合。(2)在其他矿物类型和含量相近下,14×l0-10m矿物是蛭石的土壤与14×10-10m矿物是14×10-10m过渡矿物的土壤相比,前者的阳离子交换量、比表面、内表面占总表面的比例比后者高些,但土壤的活性酸度弱些,交换性铝含量比后者低些。  相似文献   

17.
The main objective of this study is to determine if bottom ashes of dried sludge cakes (SCbash) could be used as landfill cover or liner, a function which is normally performed with clay. Laboratory tests were performed to determine its particle size distribution, Atterberg limits, compaction characteristics, hydraulic conductivity, and shear strength parameters. The effects of desiccation and freeze–thaw on the hydraulic conductivity of SCbash were also examined. The results of this investigation proved that properly compacted and stabilized SCbash has the required properties to be used in landfill covers or liners. The SCbash can be compacted into a dense mass with a low hydraulic conductivity of the order of 1.15×10−7 m/s. The compacted SCbash showed also a good resistance to the increase in hydraulic conductivity caused by desiccation and freeze–thaw as compared to other compacted clays. The results also indicated that the compacted SCbash has greater shear strength as typically expected for compacted clay, and therefore is likely to remain stable on a typical landfill slope designed and based on clay shear strength.  相似文献   

18.
Abstract

The aggregate stability of several surface soils from Thessaly plain, Central Greece, was studied using an instability index which classified the soils according to the stability of their aggregates to water. This index was correlated to the basic soil properties influencing aggregate stability. It was found that soil aggregate stability was positively correlated with clay content, total specific surface area, cation exchange capacity, base saturation, and free silicon oxides content. Silt, very fine and fine sand, and the ratio (sand+silt)/clay influenced negatively the aggregate stability. Organic matter content and sesquioxides have no effect on aggregate stability. It was also observed that the fraction of carbonates with silt dimension influenced negatively the aggregate stability. From the results of this study it was concluded that the factors affecting water aggregate stability were specific surface area and cation exchange capacity of the soils.  相似文献   

19.
Four pedons of Arenic/Grossarenic Paleustalf (Denteso Series), in the Volta Lake drawdown area in Northern Ghana, were described and sampled just before seasonal floodings commenced in the area. After 5 years of periodic flooding the soils were re-examined and sampled. Soil properties required for soil classification, including the clay mineralogy, of both the pre-flooding and the post-flooding samples were determined. One of the main objectives was to identify changes in soil properties which result from the periodic flooding. X-ray diffraction (XRD) indicated that before flooding the main clay minerals of the Denteso were kaolinite and smectite, and there were also some mica and quartz in the total clay fraction. Comparison of the pre-flooding with the post-flooding data revealed that practically all the smectite disappeared from all the three sampled pedons that were flooded for 5 to 20 weeks during each flood cycle, while the smectite persisted in the non-flooded pedon. With the disappearance of the 2 : 1 lattice clays there occurred a considerable decrease in cation exchange capacity (CEC) and in base saturation of the flooded pedons ranging from 0.04 to 3.63 cmol kg −1. Also, there was an increase in pH by 0.4 to 1 unit in most horizons of the flooded pedons in spite of the general decrease in base saturation. These changes in CEC, base saturation and pH support the XRD evidence that the seasonal floodings caused pedochemical weathering of the smectite in this loamy sand soil at a very fast rate during the 5 year period and this had resulted in the lowering of the buffering capacity and a general impoverishment of the soil series.  相似文献   

20.
渭北果园土壤物理退化特征及其机理研究   总被引：2，自引：0，他引：2  
【目的】针对我国渭北苹果主产区出现的随植果年限增加,果园土壤质量严重退化,树势衰弱、树体过早衰老、抗性降低、腐烂病及早期落叶病频繁发生,果品产量与品质下降等问题,开展了渭北苹果园土壤物理质量退化特征、退化机理及危害程度等问题的研究,以期查明制约果业可持续发展的因素,为果园土壤科学管理提供依据。【方法】在渭北黄土塬区选取了10 a、10 20 a、20 a 3个园龄段果园各4个,并以土壤条件相同的农田作对照,在果树冠层投影范围内距树干2/3处采取土样,测定土壤剖面不同层次容重、紧实度、孔隙度、饱和导水率、粘粒含量等物理性指标。【结果】渭北果园土壤容重和紧实度随园龄和土层深度的增加而增大,尤其在表层(20 cm)以下,土壤容重已经达到了1.45 1.61 g/cm3,紧实度达到933 2433 k Pa,严重超出果树健康生长的阈值。土壤孔隙度仅在0—20 cm土层能够保持在50%以上,属于良好状态,而20—60 cm土层维持在40%46%,已处于紧实和严重紧实状态。土壤饱和导水率在果园表层和紧实层均表现出随植果园龄的增大而减小的趋势,尤其是10 20 a和20 a的果园亚表层土壤饱和导水率低至46.88 cm/d和20.89 cm/d,制约着降水入渗和土壤蓄墒。3个园龄段果园土壤剖面上粘粒含量随土层深度呈递增趋势,且在0—30 cm土层随园龄的增加而明显减少,而在30 cm以下则随园龄的增加而呈递增趋势。进一步分析发现,粘粒含量与土壤容重、紧实度以及孔隙度之间呈极显著的相关关系。以压实密度(PD)为指标,对渭北果园土壤压实程度进行评估,发现渭北果园20 cm土层以下的土壤压实密度都在1.40 g/cm3以上,均达到了中度压实的程度,严重影响果树根系的健康生长及对养分的吸收。【结论】渭北果园20 cm以下的亚表层土壤孔隙密实、容重和紧实度增大,土壤饱和导水率递减是其土壤物理性质退化的主要特征,表层土壤粘粒的深层移动与淀积是土壤物理退化的主要过程和机理,果园土壤翻耕扰动少、对物理退化干预少是其土壤物理退化程度逐渐加剧的外在原因,土壤团聚体稳定性差是土壤物理状态退化的根本原因。  相似文献   

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