Использование метода «Микроструктура» при инженерно-геологической оценке глинистых и лессовых грунтов (на примере изысканий в районе правобережного примыкания Академического моста г. Иркутска)

To assess the impact of acid deposition on forested loess and clay soils in the Netherlands, changes in base saturation and soil solution concentrations were simulated with the dynamic soil acidification model ReSAM for 38 loess soils and 16 clay soils. The selected locations represent the range in geographical position and diversity in parent material occurring in forested loess and clay soils in the Netherlands. Two deposition scenarios were used for the period 1992-2050: a business as usual scenario (BAU) and a scenario in which deposition was reduced according to present Dutch policy plans (MV-3). A comparison of simulated and measured soil solution concentrations and base saturation in 1992/1993 showed that the model simulated concentrations and base saturation in the loess soils quite good. However, the model tended to overestimate acidification in the top (0-10 cm) of the clay soils. Despite the reasonable agreement between measured and simulated data some uncertainty in the validity of the model predictions remains because time trends to validate the model were not available. The model predicted a small but ongoing acidification during the BAU scenario in the loess soils as indicated by a decline in median base saturation and pH in the topsoil in 2050. Present policy plans (MV-3) lead to a slight recovery of the base saturation in 2050 and a decline in Al concentrations. In the clay soils a strong decline in base saturation is simulated in the topsoil, whereas an increase in base saturation is predicted for the subsoil.

To calculate critical acid loads or to predict elementconcentrations in the soil solution, information on weatheringrates is essential. Several studies have taken place in theNetherlands to obtain weathering rates for non-calcareous sandysoils. Recently information on weathering rates in less vulnerable loess and clay soils have become available. However,up to now no system is available to estimate weathering rates ona regional scale by relating them to regionally available soilproperties.To obtain weathering rates of loess and clay soils on a regionalscale for the Netherlands, the applicability of a statisticalregression model and the process based PROFILE model have beenevaluated. Both models were calibrated on a set of laboratoryexperiments. To evaluate their predictive power, both methodswere validated on a number of sites for which field weatheringrates were available.Predictions with the statistical model, for the individual basecations, were generally within a factor 2 of the calculatedhistorical weathering rates, except for Ca, which wasoverestimated, by a factor 3 to 4. PROFILE stronglyoverestimated all weathering rates using both standard parameters and in particular after calibration on the laboratoryrates. However, PROFILE predicted weathering rates of the loesssoils quite good after calibration on historical weatheringrates, indicating that the downscaling procedure used in PROFILEto translate laboratory to field weathering rates is inadequatefor the considered soils.The statistical model was applied to predict weathering rates,for the Netherlands on a 1 × 1 km grid scale. Weathering rates at the present pH values in forested loess and clay soilsranged from 135 to 6000 molc ha-1 a-1 in loesssoils and from 100 to 1750 molc ha-1 a-1 in claysoils.

Summary The production of sunflower grains for roasting was investigated in two soil types under different quantities of applied saline and non-saline irrigation water, different irrigation managements, soil salinity due to previous use of saline water or due to a raised water table. It was shown in one experiment, conducted in a loess type soil, that sunflowers extracted water at least to a soil depth of 120 cm, when the available water from the top layers was used up. The crop in this soil consumed all the available soil water from nearly the entire root zone, while in the clay soil limited water was consumed from deep layers, due to the high salinity and lack of aeration. No decrease in yield was found in the loess soil when 75% of the full amount of water (which was 0.8 of Class A pan evaporation rate) was applied. When only 50% was applied a significant decrease in yield was obtained. In contrast, in the clay soil even 75% of the full amount of water decreased the yield remarkably. Under dry-land con...

Nitrous Oxide and Methane Emissions as Affected by Water, Soil and Nitrogen

Woody peat addition increases soil organic matter but its mineralization is affected by soil clay in the four degenerated erodible soils

A comparative experimental study of rill erosion on loess soil and clay loam soil based on a digital close-range photogrammetry technology

Rill erosion accounts for approximately 70% of the total erosion of upland areas in China's Loess Plateau. A laboratory rainfall experiment with deionized water was conducted to examine the process of rill evolution and the relationship between runoff, rill evolution, and erosion rates for clay loam and loess soils given a fixed slope gradient (10°) and two rainfall intensities (1.5 and 2.0 mm min −1 ). The results show that rills evolved from a series of parallel drop‐pit chains along the down‐slope direction. Clay loam soil produced rills under a rainfall intensity of 1.5 mm min −1 , and loess soil produced rills only under higher rainfall intensity. The temporal change in sediment concentration and erosion rate shows good consistency with the emergence of drop pits and rills. An increase in rainfall intensity had little effect on the sediment concentration and erosion rate for clay loam soil, whereas for loess soil, both increased rapidly and exceeded those of clay loam soil, with the emergence of a rill when the rainfall intensity was higher. Rills have a much greater effect on sediment concentration and erosion rate for loess soil than for clay loam soil. This study indicates that soil texture has a major impact on rill formation; clay loam soil is more subject to rill formation, but the rills formed are generally small and do not substantially increase soil loss. In contrast, the well‐developed rills in silt loam soil can result in intensive soil loss, though rills occur infrequently. Basic understanding of these results, causes, and quantification are essential for the prediction and evaluation of soil loss.

A middle- term laboratory research was performed by monitoring three types of loess soils of NH <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> and NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3-</sub> dynamics and N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O production and denitrification. Results showed that there were no significant differences in the total amount of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O production and denitrification loss over 22 day between fertilized and unfertilized soils. This study also indicated that soil moisture had significant effect on N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O production and denitrification loss. From 80% to 110% WFPS, the amounts of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O production and denitrification loss increased by 16-41 and 17-22 folds, respectively. The maximum N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O emission rates and denitrification rates from all treatments occurred after rewetting of dry soil. The peaks maintained transitorily in the two clay loess soils, however, the higher fluxes remained for several days in sandy loess soil. The total N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O production and denitrification from the sandy loess soil were significantly higher than that from clay loess soils. Soil moisture could be the most important factor controlling N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O emissions and denitrification loss when a rich N supply existed in soil.

Impact of three soil types on afforestation in China's Loess Plateau: Growth and survival of six tree species and their effects on soil properties

ABSTRACTTo study the effects of aging time (the length of time when contaminants are sequestered in soil) and soil properties on TNT bioavailability in soil, earthworms (Eisenia fetida) were exposed to three types of soils (fluvo-aquic soil, loessal soil, and black soil) contaminated by TNT for 7, 14, 21, 28, 35, and 42 days. The Earthworm-Soil Accumulation Factor (ESAF) of TNT and soil properties were analyzed. The ESAFs in black soil were significantly lower than those in fluvo-aquic soil and loessal soil (P < 0.05). In loessal soils, the ESAF increased with aging time, while that in black soils decreased. The ESAF of TNT had a significantly negative correlation with soil organic matter content, clay contents, and cation exchange capacity, which were the main factors affecting the TNT bioavailability in soils (P < 0.01). There was more quartz and feldspar in black soil, as well as more particles and micropores on the surface, which resulted in the easy adsorption and lower bioavailability of TNT. In conclusion, TNT bioavailability in soils is affected by aging time, soil physical and chemical properties, and mineral and surface properties, which must be considered when biotreatment for TNT in soils is applied.

The red clay in northern China is also known as the Sanzhima red clay. It is discontinuously distributed under laying loess at the Loess Plateau, where is a typical slide-prone stratum. We can usually observe the exposed red clay in the valleys. The mechanical properties of the red clay can decrease with the increase of its water content. Accordingly, its deformation can increase and the sliding can occur. It is believed that all these behavior of the red clay are closely related to its creeping characteristics. Most of the recent related studies focus on the red clay in southern China. However, the engineering properties of the red clay in the south and north of China are quite different. We cannot treat them as the same. We take the red clay in Lantian County at Shaanxi Province as an example. There is widely distributed red clay. The landslides related to loess and red clay soil are also intensively developed along the loess tableland there. We study the long-term strength and deformation characteristics of the red clay taken from the section at the Lantian County. Based on the theory of unsaturated soil mechanics, the triaxial creeping test under different confining pressures and different matric suctions are conducted. The unsaturated triaxial test apparatus, FSR-60, is used. The pressure sensor is updated to improve the accuracy and long-term stability. According to the range of the volumatric water content(from 11.4%to 22.3%) of the studied red clay, the suction is controlled as 0, 100 kPa and 200 kPa respectively in the test. The step-loading method is used. The deformation less than 0.01 mm within 1 day is taken as the criterion for stability. During the process of adding load step by step, the lasting time for each step is about 1 to 2 weeks. The test and analysis results show the follows: (1)The red clay in northern China is characterized with obvious creeping property. The changes of stress with strain under different confining pressures are similar, which obey the law of power function or logarithm function. (2)When the value of deviatoric stress is less than the failure load, the instantaneous strain is first observed, and then the deformation decreased until stable. When the value of deviatoric stress is close to the failure load, creeping deformation occurs, then the deformation accelerates until the tested sample failure. When the value of deviatoric stress is bigger than the failure load, the tested sample is quickly destroyed during the loading process. (3)When the confining pressure and load are constant, the creep deformation increases with the decrease of suction, and the lasting time for stability increases with the decrease of suction. The creep probability increase and yield strength decrease under small suction. (4)The long-term strength for the saturated red clay(with the suction of 0) is about 50%lower than that of red clay with a suction of 200 kPa, indicating that the increase of water content can increase the creep deformation of the red clay and led to the occurrence of landslides. This study can provide a basis for the study on the mechanism of landslide related to red clay at the loess plateau.

Effects of overconsolidation ratios on the shear strength of remoulded slip surface soils in ring shear

We quantified the effects of the site factors pH and nitrate (NO3) concentration in soil solution and groundwater level on the vegetation of terrestrial ecosystems for the Netherlands in response to changes in atmospheric nitrogen (N) and sulphur (S) deposition and groundwater level over the period 1990–2030. The assessment was made with the SMART2 model, a simple one-layer model including geochemical buffer processes, element cycling by litterfall, mineralisation and uptake, nitrogen transformation processes and element input through deposition, weathering and upward seepage. To assess the effects of changes in abiotic site factors on the vegetation, we developed a simple plant diversity indicator for grassland, heathland and forest, based on the occurrence of target plant species and competing species. Species occurrence was calculated from the preferred ranges of each species for the NO3 concentration and pH in soil solution and mean spring groundwater level. Changes in the plant diversity indicator were assessed from effects of changes in the occurrence of target and competing plant species in response to changes in mean spring groundwater level and in pH and NO3 concentration, as calculated with SMART2. Calculations were made for combinations of five vegetation structure types (three forest types, semi-natural grassland and heathland) and seven soil types (three sandy soils, two clay soils, peat and loess soils) using a 250 × 250 m grid. We used data for atmospheric deposition and groundwater level in the past to assess trends between 1990 and 2010 and evaluated two future scenarios for the period 2010–2030: a Business as Usual and an Improved Environment scenario. Comparison of model predictions on pH and NO3 with measured soil solution concentrations for forest showed a reasonable to good agreement for pH but rather poor for NO3. The largest impacts were found for the combination of the two Improved Environment scenarios. Reductions in N and S deposition and an increase in groundwater level between 1990 and 2030 hardly caused changes in soil pH and only relatively small reductions in NO3 concentration (11–13%). Nevertheless, those changes caused a significant increase in plant diversity indicator.

1. Half shade favored the growth of seedlings of black walnut, buckeye, red oak, shellbark hickory, and hard maple but retarded growth of honey locust, boxelder, and sycamore. 2. Root systems were deeper and more branched in all cases where the seedlings grew in full insolation. 3. Transpiration rates were consistently higher in full insolation. Hard maple transpired 2.5 times more rapidly but boxelder only 20per cent more than in the shade; other species were intermediate. 4. The root systems of seedling honey locusts were 1.5 times as deep as the height of the top, and those of shellbark hickory 10 timesas deep; other species were intermediate. 5. Root penetration of all seedlings, except red oak, was greatest in loess soil, where depths of 36 to 65 inches were attained. 6. Total lateral spread of seedling roots varied from 6 to 18 inches, except those of black walnut which spread 4 feet in clay, 3 feet in alluvial soil, and 3.5 feet in loess. 7. Roots were most poorly developed in the alluvial soil by midsummer, owing to deficient aeration in spring; by September honeylocust and black walnut had penetrated deeper here than in the clay soil. 8. Honey locust has a generalized root system readily modified byenvironment. In upland soil taproots of saplings penetrated to 5 feet, but on the floodplain they penetrated only to 2 feet, and laterals extended outward 10 to 17 feet. 9. The generalized root system of boxelder is very plastic. On the upland the taproot and nearly all the major branches penetratedeeply. In alluvial soil the root system is much shallower but extends widely in the surface foot. 10. The taproots of 6-year-old sycamore saplings penetrated upland soil to about 7 feet, branched widely at all depths, and were also furnished abundantly with deeply penetrating laterals. 1. Seven- to 12-year-old black walnut saplings developed strong taproots 4-6 feet long with many oblique branches spreading 3-6 feet and often reaching similar depths. In addition numerous strong horizontal laterals extended outward to distances two or three times the diameter of the crown. 12. The root systems of 5- to 8-year-old red oaks were deep, abundantly supplied with mostly horizontal laterals in their upper course and obliquely descending ones at greater depths. A column of soil 9 feet square and 5 feet deep was usually well occupied and a few strong branches extended 6 or more feet laterally. 13. The widely spreading root system of shellbark hickory thoroughly occupied the soil within a radius of 6 feet from the treeand to a depth of 5 feet when only 6 to 8 years old. 14. Hard maple has a relatively shallow root system, that of a 10- to 16-year-old sapling extending to depths of only 2.5 to 3 feet. Large laterals were fairly numerous; a few spread beyond 3 feet, but the smaller branches were relatively few. 5. The sturdy taproot of bur oak penetrates upland clay to 15 feet in 8 years. Laterals from the upper portion were abundant and afew spread far outward and in addition gave rise to sinkers that extended deeply. Deeper laterals usually pursued an obliquely downward course. 16. The shallow rooted cottonwood of the floodplains sends its strong taproot deeply in upland soil, at the rate of 1 foot or more each year. It is well furnished with laterals throughout but these do not spread widely for 6 or more years.

Interactions of triclosan, gemfibrozil and galaxolide with biosolid-amended soils: Effects of the level and nature of soil organic matter