摘要:

SummarySand‐, silt‐, and clay‐size organo‐mineral fractions were isolated in bulk from surface horizons of five soils following ultrasonic dispersion in water. Good clay separation was achieved for all except one highly organic, calcareous clay soil. Organic‐N and ‐C were concentrated in the clay and silt fractions but for each soil the organic C : N ratio decreased in the order sand>silt>whole soil>clay. Acid hydrolysis of the silt and clay fractions revealed a slight concentration of amino acid‐N and NH4‐N in the clays but only small differences in the distribution of individual amino acids were observed. The results suggest that both silt and clay fractions may be important in the stabilization of soil

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01096.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryOrgan‐mineral particle‐size fractions, isolated from five soils by ultrasonic dispersion in water, were extracted with anhydrous formic acid/acetylacetone before and after treatment with aqueous HF partially to destroy silicate material. The resulting residues from two of the clay fractions, one montmorillonitic the other kaolinitic, were extracted further using the same reagents and also with 0.5M NaOH. The pattern of nitrogen extraction and nitrogen distribution data for the size fractions of four soils was similar but those of a fifth soil, with a high content of amorphous oxides, were quite different. There was evidence that the increasing nitrogen contents of successive samples of extracted material were mainly due to an increased amino acid content, especially dibasic acids. A serial extraction of clay fractions using formic acid/acetylacetone followed by HF followed by formic acid/acetylacetone and finally NaOH dissolved approximately 90 per cent of the organi

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01097.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe desorption of specifically adsorbed (ligand exchanged) anions, such as phosphate, selenite, and fluoride, from the surface of gibbsite and goethite has been studied by repeatedly washing the adsorption complex with solutions of constant pH and ionic strength but containing no specifically adsorbable anions. The desorption of the anions varies between complete reversibility and almost complete irreversibility. Measurements of surface charge by the uptake of Na+and Cl‐revealed that, on washing the adsorption complex, the surface charge returned to its value at the given pH in the absence of specifically adsorbed anions. Thus when the isotherm was irreversible, OH‐was desorbed (or H+adsorbed) in preference to the desorption of the specifically adsorbed anion, whereas when the isotherm was reversible the specifically adsorbed anion was desorbed.Irreversibility appears to involve the nature of the adsorption complex at the surface. Where only monodentate ligands form, for example fluoride adsorption, the isotherm is reversible, whereas bridging or multidentate ligands and the formation of ring structures at the surface favour irreversibil

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01098.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryExperiments, designed to test the non‐uniqueness which has been reported in the relationship between moisture content and suction in porous materials during transient flow conditions, are escribed. When a vertical column of sand was brought to uniform moisture content and uniform suction in a draining condition by percolating a constant flow through it until apparent equilibrium conditions ensued and then placed horizontally at the same time as the flow was stopped, the suction was found to decrease with time over a period of a day, indicating that the sand was now wetting up. This decrease was smaller the drier the sand. However, when the column was left in a vertical position with the water percolating through it for three hours after apparent equilibrium conditions were reached, a small adjustment of moisture content and suction was observed; when it was then placed horizontally as in the previous experiments little decrease of suction was observed. No change in suction was observed in either case if the equilibrium condition was reached in a wetting porous material.These experimental results and those of previous workers are explained by the hypothesis that, during drainage, some water is left in pores from which the air‐water interface has already retreated to drain through film flow, more slowly, subsequently to the continuous water body.Additional experiments showed that the release of entrapped air may have a small effect on the uniqueness of the moisture characterist

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01099.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryA method for routine particle‐size analysis of soils is described which is quicker than methods using peroxide. Organic matter is destroyed by ignition at 400°C and an ultrasonic bath is used for disaggregation.The efficiency of ultrasonic baths for this purpose is affected by the temperature, aeration status, and depth of water in the tank; the nature, size, and depth of immersion of the sample vessel; and also the ratio of solid to liquid in the sample vessel.Standardization is preferably based on the effect of treatment on standard materials, rather than the energy output of the apparatus used.It is difficult to differentiate between aggregates and primary particles, and to choose a method applicable to all soi

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01100.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummarySoluble phosphorus was allowed to age in contact with four colliery shales for up to 6 months. The ageing process apparently involved three stages–(i) a rapid initial drop controlled by pH; (ii) a steady‐state period; and (iii) an exponential decline whose rate was proportional to buffering capacity. Using this relation‐ship a model was derived to predict soil phosphorus requir

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01101.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryA comparison has been made of the sorption of inorganic orthophosphate and inositol hexaphosphate by six acidic surface soils from arable land in north‐east Scotland. The sorption of inorganic P increased with increasing quantities added and tended towards a maximum, but was never complete. In contrast, the organic P was completely sorbed up to an added quantity which varied with the soil, and above this level the absolute sorption decreased, probably due to the formation of soluble complexes involving iron and aluminium. The sorption sites were apparently the same for the two P forms and, particularly at high levels of addition, the organic P depressed the sorption of inorganic P. Inorganic P did not depress the sorption‐of organic P, which was preferentially adsorbed. The results help to explain the extreme stability of inositol hexaphosphate in these so

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01102.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryTechniques for preparation and preservation of peat soil monoliths for display purposes are described. Impregnation with a low molecular weight polyethylene glycol polymer has been found to be extremely effective in stabilising the natural structural features of peats.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01103.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe clay mineralogy of two red‐black soil toposequences on basic igneous rocks in Kenya has been investigated. Besides some illite and amorphous material kaolinites predominate in the slope soils (ultisols) whereas smectites are the main clay minerals in the soils of the depressions (vertisols). The kaolinites are poorly crystalline and have high surface area. According to chemical analysis, IR spectroscopy, and D.T.A. the smectites appear to be a ferriferous member of the montmorillonite‐beidellite series having approximately 0·5 Fe3+in octahedral and 0·2 Al per O10(OH)2in the tetrahedral position. The profile and slope distribution of kaolinites and smectites led to the conclusion that the smectites are the first weathering product and, depending on hydrological conditions governing the soil solution composition (Si, Mg, pH), either persist (depression) or are decomposed (slope) and followed by kaoli

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01104.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SummaryThe mineralogical composition of clays (<2μm) in representative profiles of all soil types of Israel was investigated. The soils were classified according to their clay mineral assemblages into three groups.I.Montmorillonitic soils.Montmorillonite is the dominant mineral and exceeds 65 per cent of the total minerals found; each of the other minerals comprises less than 15 per cent.2.Montmorillonitic‐kaolinitic soils.The soil clay fractions contain 50‐60 per cent montmorillonite and 15‐25 per cent kaolinite, generally adding up to more than 75 per cent of the clay fraction.3.Montmorillonitic‐calcitic soils.The clays contain more than 10 per cent calcite. Montmorillonite is the dominant clay mineral (except for one soil type, mountain rendzina, where calcite is dominant).The first and second assemblages are typical of the soils of the Mediterranean zone, whereas the soils of the desert zone are characterized by the third assemblage.The origin of montmorillonite, kaolinite, and illite, the three main clay minerals, was found to be detritic, as was the origin of palygorskite which was mainly found in the calcite rich soils of the desert zone.The cation exchange capacity of montmorillonite seems to be higher under higher precipitation. Montmorillonite content and cation exchange capacity of the clays were found to be highly correlated. The carbonate content of the clay fraction and the amount of carbonate in the soil were also highly co

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1974.tb01105.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY