HYDRODYNAMIC DISPERSION IN COLUMNS OF PUMICE PARTICLES

A study was made of hydrodynamic dispersion in columns of pumice particles of different equivalent diameters and over a range of flow velocities. Dispersion is described by the first and second order moments of the elution curves. Two models are used to give a numerical analysis of the dispersion: a model using an apparent hydrodynamic dispersion coefficient and one using mixing cells with exchange (MCE). The part played by the stationary phase is described, and the molecular diffusion coefficient within the porous particles is calculated.     

土壤水动力弥散系数的室内测定

用粉砂壤土进行了室内非饱和水动力弥散试验 ,依据质量守恒原理 ,推导了水动力弥散系数的计算公式 ,根据垂直土柱法测定的土壤水盐动态数据 ,计算了非饱和粉砂壤土的水动力弥散系数 ,并建立了该土壤水动力弥散系数与孔隙流速之间的关系。该方法物理概念清楚 ,计算公式简单实用 ,使用常规仪器就可测定     

多孔介质溶质运移边界层理论初探

研究了溶质运移边界层条件和边界层运动方程。采用一个小的运移通量脉冲定义边界层应满足的特征值。应用加Ｌａｐｌａｃｅ变换方法求解边界层问题的浓度解，并推导出边界层运动方程。边界层问题浓度解与精确解比较表明在计算浓度方面误差很小。边界层运动方程的一个重要应用是估算溶质运移参数。这个估算参数的新方法是应用边界层随时间运动的观测信息。这个方法简单，节省时间，并能充分利用边界层运动观测资料。     

伴有吸持反应的土壤溶质综合扩散系数的测定

土壤溶质综合扩散系数Ｄｓｈ的测定是进行土壤溶质运移定量分析的必要条件。本文用水平土柱法进行了ＫＨ２ＰＯ４在五种非饱和土壤中的入渗实验,测定了磷离子综合扩散系数Ｄｓｈ讨论了测定方法及结果。     

FREEZING AND MELTING TEMPERATURE HYSTERESIS OF WATER IN POROUS MATERIALS: APPLICATION TO THE STUDY OF PORE FORM

A theory is developed for the influence of pore form on the equilibrium freezing and melting temperatures of water in porous materials. This is supported by calorimetry and uses the hysteresis between freezing and melting temperatures for two clays and undried synthetic organic textile fibres in which the pore geometry is that of intersecting cylinders. For most water-saturated clay systems, analysis of the low temperature endotherms gives a better appreciation of the pore size distribution than analysis of the exothermic data, unless the width of rectangular pores is known.     

AN OSMOTIC METHOD FOR STUDYING THE SUCTION/MOISTURE CONTENT RELATIONSHIPS OF POROUS MATERIALS

Zur's osmotic method was simplified by placing 2 g particulate samples of finite size (e.g. 1–2 mm) in 6·5 mm diam sacs made of semi-permeable membrane tubing and suspending these in solutions of polyethylene glycol (PEG), molecular weight approx. 20,000. Moisture content was measured daily by weighing the sacs. PEG solutions of low pF were calibrated by hanging sacs containing water in them, and observing the difference in height of the liquid surfaces at equilibrium. The range was thus extended from pF 3·0-4·2 to pF 1·5-4·1. Wetting over the whole range takes 8 days and drying, from saturation, 16 days. Six polythene boxes (each holding 3·25 1 of PEG) used simultaneously, give the equivalent of wetting curves for 24 samples per day. In the isopiestic method, used for comparison over the range pF 3·5-4·0, nickel crucibles containing 1 g samples were partly immersed in control solutions of sodium chloride, in vacuum desiccators, in a temperature controlled double water-bath. Structural stability is a problem with certain soils, and more durable membranes are desirable.     

关于水稻土研究中的某些认识

讨论了测定土壤总孔隙度的有关简易方法失误渊源的辩正,论证了水稻土的地貌分类以及由此引出的一些问题。     

磷比色测定的某些问题

磷的比色测定在文献中常见的有钼黄和钼蓝法。钼黄生色的原理是在某种浓度的酸溶液中,若有钼酸根、钒酸根和磷酸根存在,能结合成一种深黄色的络合物P₂O₅·R₂O₃·22MoO₃·nH₂O。钼蓝生色的原理是在一定条件下,磷酸和钼酸所结合成的杂多酸(hetropoly acids)H₃[P(Mo₃O₁₀)₄]·nH₂O(磷钼酸)在还原剂的作用下能还原成深蓝色的复杂氧化物(MoO₃+Mo₂O₃)。     

THE USE OF MICROPEDOLOGY IN THE STUDY OF SOME ONTARIO PODZOLIC PROFILES

By adopting a micropedological approach, in which samples were taken at intervals as small as 5 mm, very acute changes in soil pH with depth were revealed. For certain Ontario podzolic profiles under long-established coniferous forest, pH values changed from around 4 in the topmost humus layer to around 6 at a depth as little as 15 to 20 cm, with little change below this depth. Because much of the magnitude and sharpness of these gradients in properties could be lost by conventional horizon-sampling, the micropedological approach—used so profitably in some branches of soil science—warrants wider adoption, particularly in shallow profiles.     

浙江稻田施用煤灰柴灰问题的研究

一.引言浙江省钱塘江上游地区,包括金华、建德二专区所属的大部分及临安、新登、富阳、馀杭等县,至少约有六、七百万亩水稻田普遍探用石灰作为肥料。在这些地区的稻田土壤一般多为红壤性母质,故缺乏石灰。栽培水稻又常用未腐熟的有机质肥料如青刈紫     

酸性硫酸盐土酸消长的水动力机制研究

以不同土壤湿度、不同干湿交替周期和原状土自然风干 8个处理进行酸性硫酸盐土 (简称ASS)室内模拟实验。通过对模拟过程内土壤pH、总硫化物性酸度和未氧化双氧水可氧化硫、交换性酸度、硫派生的实际酸度、KCl可提取硫等指标的动态变化过程的跟踪测定和分析显示 ,土壤水分条件是制约ASS酸度及酸形态转化的重要动力机制 ,可导致ASS酸度和酸形态的有规律变化。ASS产酸量和洗酸量受干湿交替周期制约     

THE USE OF ORIENTATION DIAGRAMS IN DESCRIBING PLASMIC FABRICS IN SOIL MATERIALS

Orientation diagrams are used to show differences in the orientation of birefringent domains in the S-matrix, and in sub-cutanic features of the vo-insepic fabric of two West Indian soils. Such orientation diagrams could prove useful in helping to characterize plasmic fabrics.     

关于几种土壤脲酶抑制剂的作用条件

近10年来,几种有效的脲酶抑制剂如N-丁基硫代磷酸三胺N-（n-butyl）thiophosphrictriamide（nBPT）、苯基磷酸二胺phenylphosphorodiamidate（PPD）和氢醌hydroquinone（HQ）受到广泛的关注。脲酶抑制剂能够抑制尿素的水解,因而减少了尿素氮的氨挥发损失。然而,脲酶抑制剂的有效性与环境条件（如土壤pH、通气性以及作物残茬有无）有关。目前的研究表明,脲酶抑制剂用在氨易于挥发的土壤上和脲酶抑制剂的作用环境满足时显示了良好的应用前景。因此应用脲酶抑制剂可能对节省尿素肥料施用量,同时确保提高作物产量、减少环境污染提供一种可持续的农业生产技术。本文论述了几种脲酶抑制剂对尿素氮的转化、作物氮吸收和产量等的影响,使对脲酶抑制剂的潜在农用价值、使用条件及其有效用量有所认识。     

THE WEATHERING OF CHLORITIC MINERALS IN SOME SCOTTISH SOILS

The mineralogy of 14 chloritic soils of various drainage classes developed on different parent materials from the Loch Awe area of Argyllshire, Caithness, and the Southern Uplands reveals only minor variations'in clay mineralogy with profile depth, the frequent presence of primary minerals indicating that all the soils are immature, and that weathering is at an early stage. Iron-rich chlorite generally persists throughout the profiles, varying little in amount or chemical composition between horizons; where identifiable, the polytype is II b. Oxidation of iron modifies the thermal characteristics of the chlorite in all the freely-drained soils but usually only in the surface horizons of gleys. Irrespective of soil type or drainage class, in most profiles chlorite weathers only slightly, probably by vermiculitization around the edges of flakes.     

THE EFFICIENCY OF AGGREGATION INDICES IN THE COMPARISON OF SOME ENGLISH AND CANADIAN SOILS

The efficiency of indices of aggregation was tested by assessing the accuracy with which they reflected observed differences between selected samples from a variety of Albertan and Derbyshire soils. The most efficient indices were shown to be the percentage-weight of water-stable aggregates > 3 mm, > 2 mm, > 1 mm, > 0.5 mm, the coefficient of aggregation, and the mean-weight diameter. Indices also showed highly significant variations in aggregation between fourteen soil groups, ranging from humus-iron podzol to brown solodized-solonetz. The Derbyshire soils showed significantly higher aggregate stability than those from Alberta. These differences may be the result of variations in clay mineral type, sodium content and climatic factors.     

DISTRIBUTION OF SOME CHEMICAL ELEMENTS IN THE SOILS OF NORTH WEST PEMBROKESHIRE

Total amounts of Mn, Fe, Ni, Cu, Zn, As, Bt, Rb, Si, Y, Zr and Pb were determined in soil samples from approximately 250 profiles. Examples of automatically plotted maps show the distribution of some of these elements in topsoils and subsoils. Element distribution in the soils is related to land units based on underlying rock-type and air photograph interpretation; these units distinguish soils of different lithological and drainage status and many are dominated by a single soil subgroup. Agricultural and pollution aspects of the work are discussed. The survey indicates the present levels of the elements, and may be used as a comparison in future pollution studies.     

THE GENESIS OF SOME BASALTIC SOILS IN NEW SOUTH WALES

Field and laboratory investigations of 182 soil samples and their underlying basalts in the Inverell area indicated that not all of the red soils in the area are relicts of Tertiary laterization as was previously thought. The soils on basalt were divided morphologically and mineralogically into shallow (black, brown/ chocolate, and red) and deep (krasnozems and lateritic soils) profiles. The mineralogy of the sand fractions of the shallow soils, which were similar in all respects except colour and location, suggests that they are young soils as the heavy minerals in the sand fractions are dominantly pyroxene, olivine, and the black opaque minerals which weather quite rapidly. The shallow black and brown/chocolate soils occupy whole slopes under grassland vegetation or grassland with trees, while the shallow red soils are restricted to steeper well-drained slopes and crests where trees tended to dominate grass. In similar areas throughout the New England region red soils are found on basalt in areas receiving 75 cm or less average annual rainfall, although previous workers have assumed that red soils develop from basalt at present only in areas receiving more than 140 cm average annual rainfall. The deeper soils, which were characterized by a lower pH, occupied upper or upper and middle slopes. The dominance of the resistant altered opaque minerals in these soils suggests that they are relict soils. The krasnozems showed little horizon differentiation apart from a slight darkening of the upper 8–10 cm. The lateritic soils had marked horizons, with laterite overlying mottled and pallid zones, the whole sequence being deeper than the krasnozems. The lateritic soils contained a high percentage of heavy minerals in the sand fractions in contrast to all the shallow profiles. Only one period of laterization is indicated in the area, although the laterite levels were not always accordant.