PORE SIZE DISTRIBUTION IN CRITICAL POINT AND FREEZE DRIED AGGREGATES FROM CLAY SUBSOILS

Using aggregates from 2 clay soils over a range of water contents from pF 1 to oven dry, shrinkage and water release curves were measured and pore size distributions found by mercury porosimetry after critical point and after freeze drying. Freeze drying caused less shrinkage, the maximum being 6 cm³ 100 g^?1 from pF 1, but gave a large increase, up to 10 cm³ 100 g^?1, of pores in the 0.1–10 μm size range. Critical point drying produced more shrinkage from pF 1, more than half of which was attributed to loss of interlamellar water and the rest to the collapse of pores larger than 10 μm. In these clays the volume of pores of over 3 μm diameter was very small (<3 cm³ 100 g^?1) and most of the plant available water was released by collapse of narrower pores and not by pore emptying.     

WET AND DRY PORE SIZE DISTRIBUTION IN A KAOLINITIC SOIL BEFORE AND AFTER REMOVAL OF IRON AND QUARTZ

A kaolinitic soil was treated chemically to remove iron and quartz. Before and after treatment the properties of the soil were, respectively: iron content, 7 and 1%; quartz content, 21 and 0%: water content at saturation (water/kaolin content, g/g), 0.40 for both, of which 0.34 was in pores for which the Kelvin radius r_j, was ≤35 nm. Porosity and pore size distribution (PSD) up to this pore size were studied using nitrogen sorption, mercury injection, pressure membrane equilibration and low temperature scanning microcalorimetry (DSC). These analyses justified interpretation in terms of kaolinite content alone. The PSD was unaffected by the removal of iron or quartz or the moisture content of this soil. New DSC techniques show that the pore spaces within the treated samples (r_j≤ 35 nm) are largely unconstricted, and thus, an experimental curve relating temperature depression for melting to pore size is possible using only one sample.     

宜川县油松人工林集水区水文状况分析

通过对人工油松（Pinus tabulaeformis）林集水区水文特征与产流特征的分析发现:人工油松林集水区产流有三种类型:坡面和沟道不发生径流;沟道产生径流;坡面和沟道均产生径流。     

SIZE FRACTIONATION, DISSOLUTION ANALYSIS, AND INFRA-RED SPECTROSCOPY OF HUMUS COMPLEXES IN ANDO SOILS

Eight samples of Ando soil A₁ and buried A₁ horizons of different ages were fractionated into clay-, silt-, and sand-size separates, and the yields and carbon contents of these separates were determined. The clay-size separates were subjected to two series of successive extractions, 1) 0.1 M Na₄ P₂ O₇/2% Na₂ CO₃/0.5 M NaOH and 2) dithionite-citrate/2% Na₂ CO₃/0.5 M NaOH; and to difference infra-red spectroscopy for identification of the extracted constituents. The result indicated that humus evolves from forms with a very low complexing ability for Al and Fe into forms that complex Al and Fe in the A₁ horizon, and that humus further interacts with allophane-like constituents, allophane and imogolite in the buried A₁ horizon. These reactions between humus and inorganic constituents result in formation of silt- and sand-size aggregates which are stable to sonic wave treatment, but are broken down into finer particles upon boiling with H₂ O₂.     

孔隙结构图像分析中不同试验因素对分析结果的影响

研究了不同试验因素 (包括图像分辨率、土壤切片定向性、分析区域大小等 )对孔隙结构图像分析结果的影响以及试验误差 ,并简要介绍了用于分析土壤孔隙结构的土壤切片及数字图像的制备技术。结果表明 :不同试验因素对分析结果均会产生一定的影响 ,试验误差约在 1 0 %。这表明同一研究中应保持试验条件的相对一致以保证分析结果的可靠性和可比性     

甘肃黄土高原植树造林水分条件分析

本文采用气候学方法计算了甘肃黄土高原林木生长期的蒸散耗水量,与实测资料对照表明,计算值较符合实况.根据乔木生长期的耗水量指标,以及降水量和水土流失的观测资料,对甘肃黄土高原乔木生长期的水分条件进行了较详细地评述。提出了“实际干燥度”和“实际湿润度”的概念,并根据后者确定了甘肃黄土高原各类气候植被区林木的适生程度,以及在各种地形下应当选择的乔,灌木树种。     

微观尺度上土壤孔隙及其分维数的SEM分析

对两类不同质地土壤的SEM图像,利用数字图像技术分析孔隙的大小、数量及其分布规律,由测量数据给出了微观尺度上土壤孔隙的质量分维数Dm和表面分维数Ds。结果表明:Dm与土壤质地、容重、孔隙度、孔径分布等之间存在一定的相关关系,土壤质地越细、容重越大、孔隙度越低、小孔隙越多,Dm越大,Dm与土壤容重和孔隙度均存在显著线性回归关系;Ds反映了土壤孔隙轮廓边界的曲折程度,孔隙轮廓越不规则,Ds越大,土壤中各孔隙的Ds分布符合总体正态分布形式。Dm和Ds的数值大小对不同利用方式和耕作制度下的土壤较为敏感,分维数可为土壤科学管理提供依据。     

赣南环境平衡与人类活动关系的分析

本文简要地阐述了赣南的自然条件,人类活动与环境平衡的关系。环境平衡破坏后的表现及引起环境平衡破坏的原因。     

PORE SPACE VARIABILITY IN A SUB-SURFACE HORIZON OF TWO SOILS

Image analysis was used to investigate the variability of pore space in soil thin sections. Two fine-textured soil profiles (or pedons) were sampled by inserting eight Kubiena tins (7.5 × 6 × 4 cm) in ledges at 50 cm depth. From each soil block three horizontal thin sections (7.5 × 6 cm) were made and photographed. Each photograph was then divided into nine ‘frames’ so that the voids in each of these frames could be measured using the Quantimet 720 Image Analysing Computer. The results show the variability of three specific pore-space characters and the consequent need to sample a number of large thin sections from several sample blocks for each soil horizon to obtain estimates of sample means with suitable accuracy.     

MEASUREMENT OF PORE SIZES IN FINE-TEXTURED SOILS: A REVIEW OF EXISTING TECHNIQUES

Pore size distributions obtained from the relationship between moisture content and suction are not dependable in fine-textured soils because of shrinkage. To overcome this problem, methods such as nitrogen sorption, mercury intrusion porosimetry, non-polar liquid desorption and thin sectioning have been used. In order to pre-dry samples without changes in the pore system, freeze-drying, organic liquid replacement of soil water, and critical point drying techniques have been employed. These methods of soil drying and pore size measurement are described and compared, and the validity of their use in soil studies is examined. The measurement of pore sizes by water desorption is also discussed.     

山区温度场立体模式与地形影响分析方法的探讨

为了得出山区温度场的空间模式,本文选用代表站资料进行三元(纬度、经度和海拔高度)线性回归。对全国范围,九个省(区)和广西六个河谷流域片的气温场立体模式都进行了统计分析。这些回归分析结果充分证明了这一方法有广泛的用途,不仅能明确显示不同尺度范围热量资源的空间分布规律,对比地形影响,而且极大地有利于克服山区气候研究中经常遇到站点稀少资料不足的困难。     

THE EFFECT OF MOLECULAR SIZE ON DIFFUSION CHARACTERISTICS IN SOIL

Measurements of the apparent self-diffusion coefficients of, poly(vinyl pyrrolidone) mol. wt. 40 000, polyethylene glycol) mol. wt. 4000, and chloride ion, were used to determine the effect of molecular size on diffusion characteristics in soil. The measurements were carried out on the same soil, at a range of moisture contents, and indicated that the mobility of large molecules in soils depends, to a large degree, on the inter-aggregate pores. Any drop in moisture content which caused these pores to drain, produced a sharp decrease in the apparent self-diffusion coefficient of the poly(viny) pyrrolidone) 40 000. Neither poly(ethylene glycol) 4000 nor chloride, which exhibited similar diffusion characteristics, were as sensitive to variation in moisture content. The results are interpreted in terms of certain parts of the pore volume being inaccessible to the diffusing molecule. Possible reasons are outlined.     

坡面水土流失观测分析

本文作者在实地观测资料的基础上,分析了降水量、雨强、土壤入渗及不同植被对水土流失的影响,认为雨强是影响径流速率的主导因子,雨量是影响径流量的关键,建造植被、增强土壤入渗是防止水土流失的有效途径。     

利用土壤切片的数字图像定量评价土壤孔隙变异度和复杂度

研究结果表明 :利用土壤切片的数字图像 ,以孔隙周长和面积为基础数据 ,可以定量评价小尺度上的孔隙变异度 ,也可以对孔隙复杂度进行研究 ;土壤孔隙在mm尺度上也具有较高的变异度和复杂度 ;粒径 1～ 3mm和粒径 <2cm的重组土壤的孔隙在 2D空间多呈现网络状 ,而原状土壤的孔隙则多呈不规则的枝状或椭圆状 ;不同处理及不同土壤类型之间在孔隙周长、孔隙度以及孔隙变异度和复杂度方面存在不同程度的差异。     

玉米密码子用法分析

生物中普遍存在密码子使用偏性,这对外源基因的表达强度有着较大影响。本研究运用Codon W软件和CUSP程序对玉米基因组中的7402个蛋白质编码基因序列进行了分析,计算了编码氨基酸的密码子使用频率,并将其与人、酵母、大肠杆菌、果蝇等不同种类的模式生物及与拟南芥、烟草、水稻、小麦等双、单子叶植物进行比较,结果显示玉米密码子偏爱性与模式生物有不同程度的差异,与拟南芥、烟草双子叶植物的密码子使用频率差异较大,与水稻、小麦单子叶植物的密码子偏爱性一致。分析结果对玉米基因的转化及高效表达系统的选择等具有重要指导意义。     

滇中高原地区地膜覆盖种植花生的增产与增温效应分析

在滇中海拔1870米地区地膜覆盖种植花生试验表明:与无膜对照区比较,地膜区(A)增产124％,柴灰加盖地膜区(B)增产145％,其中B比A区又增产约10％。文中讨论了盖膜增温效应,云南省花生产量与气候的关系,以及盖膜种植在云南南、中、北部推广应用中应注意的问题。     

盐渍土中盐分的X射线分析

土壤溶液是由各种阴离子和阳离子所组成的复杂盐溶液,通过土壤溶液中盐分的分析,可以确定盐分的类型和含量,了解盐渍土的性质,研究盐渍土的利用和改良对策。土壤盐分的常规分析方法是用水浸提液来测定可溶性盐分的阴阳离子组成,这种方法不能指出盐分在土中的实际化学特征,因此,常应用化学中的溶度积法来探求盐分的类 型,如Duff和Doneen^[5]应用溶度积的概念来预测含有石膏的土壤溶液中的盐分组成;Nakayama^[6]利用溶度积常数解决土壤中碳酸钙、硫酸钙的溶解性问题,研究了混合盐溶液中的盐分组成。