土壤矿物学研究综述

土壤矿物是土壤物质组成的主体 ,是土壤微量元素的主要来源。土壤矿物的研究是土壤学研究的前沿基础领域。通过对土壤矿物尤其是粘土矿物的研究 ,可以揭示土壤的发生学特性、母质特征、成土过程及环境 ,揭示土壤的发育程度和肥力水平 ,为环境保护、优质生产和土壤改良提供基础依据。本文指出了土壤矿物学的研究意义 ,综述了土壤矿物学的研究进展 ,总结了不同类型土壤矿物的组成特征及其与成土作用、风化程度和生物气候条件间的变化规律     

Utilization of fly ash for stabilization/solidification of heavy metal contaminated soils

Pozzolanic-based stabilization/solidification (S/S) is an effective, yet economic remediation technology to immobilize heavy metals in contaminated soils and sludges. In the present study, fly ash waste materials were used along with quicklime (CaO) to immobilize lead, trivalent and hexavalent chromium present in artificially contaminated clayey sand soils. The degree of heavy metal immobilization was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) as well as controlled extraction experiments. These leaching test results along with X-ray diffraction (XRD), scanning electron microscope and energy dispersive X-ray (SEM–EDX) analyses were also implemented to elucidate the mechanisms responsible for immobilization of the heavy metals under study. Finally, the reusability of the stabilized waste forms in construction applications was also investigated by performing unconfined compressive strength and swell tests. The experimental results suggest that the controlling mechanism for both lead and hexavalent chromium immobilization is surface adsorption, whereas for trivalent chromium it is hydroxide precipitation. Addition of quicklime and fly ash to the contaminated soils effectively reduced heavy metal leachability well below the nonhazardous regulatory limits. Overall, fly ash addition increases the immobilization pH region for all heavy metals tested, and significantly improves the stress-strain properties of the treated solids, thus allowing their reuse as readily available construction materials. The only potential problem associated with this quicklime–fly ash treatment is the excessive formation of the pozzolanic product ettringite in the presence of sulfates. Ettringite, when brought in contact with water, may cause significant swelling and subsequent deterioration of the stabilized matrix. Addition of minimum amounts of barium hydroxide was shown to effectively eliminate ettringite formation. Overall, due to the presence of very high levels of heavy metal contamination along with sulfates in the solid matrices under study, the results presented herein can be applied to the management of incinerator and coal fly ash, boiler slag and flue gas desulfurization wastes.     

Seismic response of adjacent dense and loose saturated sand columns

Compaction or densification of loose saturated soils has been the most popular method of reducing earthquake related liquefaction potential. Such compaction of a foundation soil is only economical when limited in extent, leading to a case of an ‘island’ of improved ground (surrounded by unimproved ground). The behavior of the densified sand surrounded by liquefied loose sand during and following earthquakes is of great importance in order to design the compacted area rationally and optimize both safety and economy. This problem is studied herein by means of dynamic centrifuge model tests. The results of three heavily-instrumented dynamic centrifuge tests on saturated models of side-by-side loose and dense sand profiles are discussed. The test results suggest the following concerns as relates to ‘islands’ of densified soil: (1) there is a potential strength degradation in the densified zone as a result of pore pressure increase due to migration of pore fluid into the island from the adjacent loose liquefied ground; (2) there is a potential for lateral deformation (sliding) within the densified island as the surrounding loose soil liquefies.     

Effects of random variations of soil properties on site amplification of seismic ground motions

This paper investigates the effects of random variations of soil properties on site amplification of seismic waves. First, based on attenuation laws and the filtered Tajimi–Kanai spectrum, seismic motion at the base rock of a soil site is stochastically generated according to an assumed earthquake with a given magnitude and epicentral distance. Motions on the surface of this layered random soil site are calculated by nonlinear wave propagation methods, and by assuming the incoming seismic wave consisting of SH wave or combined P and SV waves. Soil properties, including shear modulus, damping ratio and mass density, as well as ground water level are considered as random in the numerical calculation. The Rosenblueth method is used to solve the random dynamic responses of the soil site. Parametric calculations are performed to investigate the effects of various parameters on site amplification of seismic waves. The mean and maximum ground motions on surface of the site are estimated. Numerical results indicate that the estimated surface motions differ substantially if the random variations of soil properties and soil saturation level are taken into consideration in the analysis.     

典型干旱区荒漠戈壁陆面参数的观测研究

根据目前流行的陆面过程模式的需要，利用２０００年５－６月敦煌陆面过程野外观测实验加强期的观测资料，分析了西北典型干旱区荒漠戈壁的一些关键陆面过程和土壤参数的特征和规律。并且利用相对反射为权重加权平均，计算得到典型干旱区敦煌荒漠戈壁的平均反射率为０.２５５±０.０２１；剔除建筑物干扰后，利用对数平均法计算的粗糙度长度平均值为０，００１９±０。０００７１ ｍ；剔除绿洲影响后，用无降水影响的资料确定出土壤湿度影响因子为０．００４５；剔除降水影响后，用观测资料计算的敦煌典型干旱区荒漠戈壁的热容量平均值为１．１２×１０~６ｍ~（－３）Ｋ~（－１），比“黑河试验”在戈壁和在其它沙漠观测的有关值略小一些，但热扩散率和热传导率都比“黑河试验”在戈壁观测的值小一倍左右；观测的敦煌戈壁典型天气条件下的土壤含水量非常小，基本上不超过１％。     

UPLAND EROSION MODELING WITH CASC2D-SED

1 INTRODUCTION Erosion and sedimentation embody the processes of detachment, transport, and deposition of soil particles. Erosion and subsequent deposition can cause major problems. Erosion reduces productivity of cropland, sediment degrades water quality and may carry soil adsorbed polluting chemicals. Deposition in irrigation canals, stream channels and reservoirs reduces structural capacity and requires costly removal. Ideally, an erosion model should describe the physical processes…     

Quantifying CO2 fluxes from soil surfaces to the atmosphere

Measurements of CO₂ fluxes from ground surface of the atmosphere (soil respiration) are needed to quantify biotic and abiotic reaction rates in unsaturated zones and to gain insight into the importance of these processes on global warming. The use of three techniques (dynamic closed chambers, static chambers, and gradient calculations) to determine soil respiration was assessed by measuring fluxes of microbially produced CO₂ from an unsaturated mesocosm (2.4 m dia.×3.2 m thick) and two unsaturated minicosms (0.58 m dia.×1.2 m thick), one maintained at 18–23 °C (HT) and the other at 5 °C (LT). By injecting known and constant CO₂ fluxes into the bottom of the HT minicosm and measuring the resulting fluxes, it was shown that the dynamic closed chamber (DCCS) technique yielded accurate measurements of fluxes over the range observed from natural unsaturated media. Over this same range, results showed that the concentration gradient method yielded reasonable estimates of fluxes but its accuracy was limited by uncertainties in both the concentration gradient and the gaseous diffusion coefficient in the soil atmosphere. The static chamber method underestimated the actual flux at higher CO₂ fluxes and when adsorption times of >24 h were used.     

华南亚热带山地土壤有机质更新特征定量研究

选择鼎湖山自然保护区森林植被带（SL）、灌丛一草甸过渡带土壤剖面（GC）进行薄层取样，根据土壤有机质^14C放射性水平，运用模型计算土壤有机质更新速率（m）。结果表明上部0－10cm土层有机质更新速率（m）最高；向下,m锐减；剖面下部m值极低，这说明土壤有机质由不同更新周期（T）组分构成。表层快循环组分占绝对优势，向下，慢循环组分为主，剖面下部为稳定组分。根据m、有机碳含量、有机碳含量、土壤容重、土层厚度计算有机质更新CO2产量，表层0－10cm层段CO2产量约为整个剖面的98％。SL剖面m值及有机质更新CO2产量均明显大于GC剖面相应值。分析表明在同一气候植被是制约土壤有机质更新及CO2产量的第一要素，这为通过绿化加强土壤碳汇功能提供重要依据。     

湿地土壤有机质和全氮含量分布特征对比研究——以向海与科尔沁自然保护区为例

研究了土壤有机质及全氮在霍林河中下游的科尔沁和向海两个自然保护区湿地表层土壤中的水平分布及其在土壤剖面中的垂直分布特征。结果表明，与科尔沁自然保护区相比，向海自然保护区的空间分异程度较高，其表层对有机质及全氮的持留作用较强，碳的固定速率比氮累积更慢一些；盐碱化程度较高，湿地植被净化效应较显著；pH值对有机质和全氮的影响也更为显著。     

新丰江水库消涨带岸坡侵蚀研究

水库消涨带是随水库水位涨落不时出没的库岸，坡面裸露，泥沙侵蚀强度大，生态环境恶劣。本研究采用野外点定观测方法，研究了新丰江水另消涨带花岗风化泥沙侵蚀机理，实测各类坡面的侵蚀模数，估算了总侵蚀量，并把塌岸与陆上花岗岩石风化壳的崩岗和滑坡发生机理作比较。