长三角经济高速发展地区土壤pH时空变化及其影响因素   总被引：13，自引：0，他引：13  

邵学新  黄标  顾志权  钱卫飞  金洋  毕葵森  严连香 《矿物岩石地球化学通报》2006,25(2):143-149

通过调查和分析长三角地区张家港市2004年和第二次土壤普查时(1980)的土壤pH,探讨了该市近20年来基于经济高速发展影响下的土壤pH变化及影响因素。结果表明,自第二次土壤普查以来,该市土壤pH变化明显。南部人为土地区绝大部分土壤pH值都下降了一个单位,平均值由7.39降至6.33;北部雏形土区,两个时期的土壤pH值分别为7.92和7.98。土壤pH的降低可能同该地区长期施用化学肥料、酸雨及工业酸性“三废”排放的增加有关。此外,土地利用和田间管理也对土壤pH变化起着较为重要的作用,而土壤地球化学性质差异则是导致南北地区土壤pH变化不同的内在因素。  相似文献   

Geobotanical and biogeochemical reconnaissance of the ultramafics of Central Iran     

S.M. Ghaderian  A.J.M. Baker 《Journal of Geochemical Exploration》2007

In Iran, ultramafic rocks cover substantial areas at many locations in the country. These rocks consist predominantly of peridotite which has been serpentinized to some degree. Anarak and Nain are two ultramafic areas in Central Iran comprising about 180 and 270 km², respectively, located in a coloured melange zone. There is little information available regarding the geobotany and biogeochemistry of these areas. They have a dry climate, with low rainfall and high temperatures in summer which encourages mostly annual and perennial herbaceous types of plants. In this paper, we report a reconnaissance study of these two ultramafic areas of Iran. Soil analysis of total elements indicates that typical concentrations of Ni, Cr, Co, Mn, Fe, Mg and Ca are about 1500, 300, 75, 800, 45.000 150.000 and 2000 μg g^− 1, respectively. During this study 176 plant species were collected, belonging to 29 families. The species diversity at Anarak is more than at Nain, possibly due to microclimatic differences and a greater precipitation. The number of plants endemic to ultramafic soils of these two areas is very low. The herb Cleome heratensis (Capparaceae) appears to be an indicator of ultramafics in Central Iran. Populations of this plant cover quite extensive areas during summer and autumn when there is no rainfall. Analysis of the dry matter of the leaves of all plants collected did not reveal any hyperaccumulator of nickel or any other ‘serpentine’ metals. The ultramafic endemic plant C. heratensis contained low concentrations of all metals and thus it possesses exclusion mechanisms to restrict excessive metal uptake. The Mg/Ca ratio for some plants collected is high—up to 4.9. This initial survey suggests that a more complete investigation of the ultramafic areas of Iran would be valuable.  相似文献   

Hydraulic and compaction characteristics of leachate-contaminated lateritic soil   总被引：2，自引：0，他引：2  

Sitaram Nayak  B.M. Sunil  S. Shrihari   《Engineering Geology》2007,94(3-4):137-144

Large quantities of leachate-contaminated lateritic soil results from dump yards in the southwest coast of India. These dump yards receive large quantities of municipal solid waste which includes chemical, industrial and biomedical wastes. Large areas of land are currently being used for this purpose. An extensive laboratory testing program was carried out to determine the compaction characteristics and hydraulic conductivity of clean and contaminated lateritic soil. Batch tests were used to study the immediate effect of leachate contamination on the properties of lateritic soil. Contaminated specimens were prepared by mixing the lateritic soil with leachate in the amount of 5%, 10% and 20% by weight to vary the degree of contamination. The results indicated a small reduction in maximum dry density and an increase in hydraulic conductivity due to leachate-contamination. The change induced by chemical reaction in the microstructure of the soil was studied by scanning electron microscope before and after contamination of soil with leachate. The structure of the leachate contaminated soil sample appeared to be aggregated in scanning electron microscope analysis. The aggregated structure increases the effective pore space and thus increases the hydraulic conductivity. Fifty percent increase in hydraulic conductivity was observed for specimens prepared at standard Proctor density and mixed with 20% leachate. Compaction characteristics did not change much with the presence of leachate up to 10%. With 20% leachate the maximum dry density decreased slightly indicating excess leachate in the soil. However the changes are not significant.  相似文献   

Residual strength of slip zones of large landslides in the Three Gorges area, China   总被引：2，自引：0，他引：2  

B.P. Wen  A. Aydin  N.S. Duzgoren-Aydin  Y.R. Li  H.Y. Chen  S.D. Xiao 《Engineering Geology》2007,93(3-4):82-98

Slip zones of the large landslides in the Three Gorges area are commonly composed of fine-grained soils with substantial amount of coarse-grained particles, particularly gravel-sized particles. In this study, residual strength of the soils from slip zones of these landslides were examined in relation to their index properties based on a survey of 170 landslides. It was found that laboratory-determined residual friction angle using gravel-free fraction of the disturbed soils from the slip zones was closely related to clay content, liquid limit and plasticity index. On the other hand, in-situ residual friction angle of these soils (i.e. including gravel fraction) showed very weak correlations with clay content and Atterberg limits, but was largely dependent on gravel and fines (clays + silts) contents, increasing with gravels and decreasing with fines, and displayed strong linear correlation with the ratio of gravel to fines contents. These observations indicate that among the index properties, clay content and Atterberg limits can be used to estimate residual strength of the soils finer than 2 mm, but they are not appropriate evaluate the residual strength of the soils containing considerable amount of gravel-sized particles. For the latter, particle size distribution (particularly the ratio of gravel to fines contents) appears to be a useful index. Additionally, it was found that there was no identifiable correlation between relative abundance of individual major clay minerals and residual friction angles of both gravel-free fraction of disturbed and in-situ soils, suggesting that influence of clay minerals on residual strength of these soils can not be simply evaluated based on their abundance.  相似文献   

层状地基端承桩扭转动力阻抗研究     

王海东  尚守平  童桦 《地震工程与工程振动》2007,27(1):171-175

本文采用Novak薄层法推导粘弹性地基的扭转动力阻抗,并将其用于考虑桩土相互作用的单桩扭转动力阻抗,又通过传递矩阵法将此公式推广到求取层状地基单桩扭转动力阻抗。而且本文以工程中常用的端承桩为例,推导了层状地基中端承桩扭转动力阻抗的简化计算公式。根据此公式,分析了频率、上覆软土层厚度、上覆软土层刚度等因素对单桩扭转动力阻抗的影响,分析结果表明,随着振动频率提高,层状地基中端承单桩的扭转动力阻抗的实部有缓慢下降的趋势,而虚部则增大;随着上覆土层厚度的增加,层状地基中端承单桩的扭转动力阻抗的实部和虚部均减小;随着上覆土层刚度的减小,层状地基中端承单桩的扭转动力阻抗的实部减小,虚部在低频段减小,而在较高频率段则增大。  相似文献   

Extractable and total Fe and Mn contents of three sand dune soils in NW Nigeria     

B.A. Raji  V.O. Chude  I.E. Esu 《Journal of Arid Environments》1998,38(4):585-596

The profile distribution of total, diethylene triamine penta-acetic acid (DTPA)- and 0·1 HCl-extractable Fe and Mn were determined in 12 pedons formed on three contiguous sand dunes in the semi-arid savanna of Nigeria. The total Fe and Mn contents varied from 100 to 3750 and 40 to 11,375 μg g⁻¹, respectively. Values of 0·1 HCl-extractable Fe and Mn varied from 8·0 to 123 and 1·5 to 43·5 μg g⁻¹, respectively. The corresponding values of DTPA-extractable Fe and Mn were 4·5 to 16·0 and 1·0 to 38·8 μg g⁻¹. Total Fe and Mn correlated significantly with clay in nearly all the dunes (p≤ 0·01) but were not significantly correlated with organic matter. The 0·1 HCl-extractable Mn had a positive significant correlation with soil pH (r= 0·58*) in Illela dunes but a negative significant correlation with pH in the Sangiwa dunes (r= −0·75***). The values of extractable Fe and Mn in the sand dune soils are above the critical limits reported in other literature, thus deficiencies of these micronutrients do not pose a problem to crop production in the study area.  相似文献   

土壤中溶质运移模拟的理论与应用^*   总被引：11，自引：0，他引：11  

许秀元  陈同斌 《地理研究》1998,17(1):99-106

可溶性化学物质在土壤中的运移和分布一般可以反映出多孔介质中溶质随着水分运(流)动的规律。文中系统地回顾了近二十年来土壤中溶质运动理论的发展和有关模型的应用概况,以期对地下水污染、海水入侵、水盐运动等溶质运移模拟的理论和应用问题进行较全面的分析;讨论了水动力学弥散、宏观弥散、层状介质中的弥散、多组分溶质运移和非饱和带中溶质运移等问题,以及描述土壤中溶质迁移的主要模型和模拟方法。  相似文献   

Dating of post-glacial landforms in the central howgills     

A. M. Harvey  F. Oldfield  A. F. Baron  G. W. Pearson 《地球表面变化过程与地形》1981,6(5):401-412

Little is known of Holocene landform development in Upland Britain. This paper describes a site at Middle Langdale in the Howgill Fells of Cumbria where large, but now stabilized and inactive gullies cut through periglacial material. At the base of the gullies large debris cones have buried earlier alluvial sediments on the valley floor. On these sediments and buried by the debris cones is a well-developed organic soil from which two ¹⁴C dates have been obtained in an attempt to estimate the age range of the soil. These dates range from 2580±55 years BP for the fine particulate fraction from the base of the organic horizon to 940±95 years BP for fossil rootlets from the uppermost organic layer, immediately below the overlying debris cones. The pollen evidence suggests that the valley floor site was initially dominated by alder carr and later by a Juncus marsh with birch, alder and hazel nearby. The pollen, from the surrounding upland area suggests woodland on the valley sides, dominated by oak and elm that was later replaced by a more open environment rich in heath species and in which disturbed ground species were present. The magnetic evidence indicates a stable local environment during soil formation but shows a sudden inwash of unweathered debris at the top of the buried soil. The evidence suggests that the valley floor was geomorphologically stable throughout the period of soil formation, although there was a local change in valley floor vegetation and a reduction of woodland cover on the valley sides at sometime during the period. The evidence then points to major geomorphological changes; a wave of soil erosion, gully development and debris cone deposition, perhaps following the Scandinavian introduction of sheep farming in the tenth century A.D.  相似文献   

A meshfree method for fully coupled analysis of flow and deformation in unsaturated porous media     

A. Khoshghalb  N. Khalili 《国际地质力学数值与分析法杂志》2013,37(7):716-743

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ACMEG‐TS: A constitutive model for unsaturated soils under non‐isothermal conditions     

Bertrand François  Lyesse Laloui 《国际地质力学数值与分析法杂志》2008,32(16):1955-1988

This paper introduces an unconventional constitutive model for soils, which deals with a unified thermo‐mechanical modelling for unsaturated soils. The relevant temperature and suction effects are studied in light of elasto‐plasticity. A generalized effective stress framework is adopted, which includes a number of intrinsic thermo‐hydro‐mechanical connections, to represent the stress state in the soil. Two coupled constitutive aspects are used to fully describe the non‐isothermal behaviour. The mechanical constitutive part is built on the concepts of bounding surface theory and multi‐mechanism plasticity, whereas water retention characteristics are described using elasto‐plasticity to reproduce the hysteretic response and the effect of temperature and dry density on retention properties. The theoretical formulation is supported by comparisons with experimental results on two compacted clays. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献