摘要:

SummaryCalibrations enabled controlled application of a range of known dispersive energies to a selected soil sample. The corresponding levels of dispersion were measured in terms of the weight fraction of particles<2 μm equivalent spherical diameter produced, and are used to define a dispersion characteristic for the test soil.Interpretation of this characteristic in terms of a microaggregate theory provides the energy value associated with complete ‘primary dispersion’ of microaggregates, which under normal field conditions is a direct practical measure of soil stability. This leads to a definition of the specific stability index (σ) of a soil which for the gleyed brown earth used in this work has the value (25±3)

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb02014.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryIn a field experiment on a weakly structured, almost stone‐free loamy sand, the depths of leaching of chloride and nitrate were measured after sprinkler irrigation at 8 mm/h. The modal depth of movement of the two ions was about half the mean depth of movement, indicating a highly skewed distribution and a pronounced leading tail of chloride and nitrate. The marked asymmetry of the salt distribution is attributed to uneven downward movement of water, including movement down earthworm channels, which results in part of the nitrate and chloride being deeply leache

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb02015.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryThe neutral polymer, polyvinyl alcohol, has been shown to be adsorbed by the hydrated oxides gibbsite and goethite. A reduction in adsorption on gibbsite is observed when it is dried prior to the adsorption measurements. Evidence from electron microscopy suggests that this is caused by a reduction in the accessible surface area due to aggregate formation, rather than a change in the surface properties of the substrate. Changes in either the pH or the ionic strength of the medium do not significantly alter the amount of PVA adsorbed. Electrophoretic data indicate that the thickness of the adsorbed layer on both clays and oxides is in excess of 10 nm at high concentrations of polymer.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb02016.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryIron (III) was extracted by EDTA and ammonium oxalate from a model substance consisting of amorphous iron oxide, goethite, and hematite precipitated in the presence of quartz sand. Even by varying the EDTA concentration between 0.02 and 0.1 M, pH between 4.40 and 6.00, the solid:solution ratio between I:25 and I:250, and using extraction times up to go days, it was found that EDTA was able to extract only a limited amount of iron. In contrast, 0.2 M ammonium oxalate at pH 3.0 is able to dissolve all the iron compounds if the extraction time is sufficient. Nevertheless, the amount of EDTA‐extractable iron is equal to the amount of iron extracted after 4–5 hours with ammonium oxalateat pH 3.0.From X‐ray analysis, DTA curves, a solubility product determination, and a kinetic investigation, it is concluded that the EDTA‐extractable fraction consists of X‐ray amorphous iron oxide, less soluble than polymeric iron hydroxide, and presumably only one compound.Therefore, it is concluded that it may be possible by means of EDTA to carry out a selective extraction of X‐ray amorphous iron oxides mixed with goethite a

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb02017.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryAn apparatus, based on an optical microscope system, has been constructed for the subjective observation of cathodoluminescence, and the value of the technique has been determined for the examination of minerals and soils. The use of cathodoluminescence for the specific identification of minerals was found to be limited by the observation of different luminescent colours from the same minerals, and the same luminescent colour from different minerals. However, a sufficient variety of luminescent colours is believed to exist to allow the method to be used in conjunction with others for the identification of mineral grains. An examination of the trace element levels in a small group of mineral separates was found to be uninformative in trying to explain the variations in luminescent colours found.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb02018.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryThirty‐eight termite mounds (about 1.6 m high and 7.6 m basal diameter) and the same number of adjacent soils were sampled in three rainfall zones: low (below 700 mm annual rainfall), medium (700 to 1000 mm annual rainfall), and high (above 1000 mm annual rainfall). Higher amounts of clay, silt, and fine sand, and lower amounts of coarse sand occurred in termite mounds than in adjacent soils of all rainfall zones. Extractable cations (Ca, Mg, and K), calcium carbonate, pH, electrical conductivity, and organic carbon were also higher in termite mounds than adjacent soils of all rainfall zones.Wide differences in extractable calcium between termite mounds and adjacent soils of low and medium rainfall zones indicated weak leaching of termite mounds; narrow differences in the high rainfall zone indicated strong leaching of the mounds.The ‘umbrella effect’ of termite mounds in shedding rainfall and retarding leaching is clearly displayed in the medium rainfall zone where high concentrations of extractable calcium in termite mounds and low concentrations in adjacent soils indicate weak and strong leaching respect

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb02019.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryIn two chronosequences of soils, total organic phosphate (P0) accumulated rapidly during the first 50 years of soil development, when organic matter increased and pH decreased. The rate of P0accumulation then declined with age of soil until a ‘steady state’ was reached. The amounts of phospholipid, inositol phosphates and humic acid—P0followed the same trends as the total P0.Parent materials and very young soils contained largely citric acid‐soluble P0, but after less than 50 years, surface horizons accumulated sufficient organic matter to complex a considerable proportion of the P0. An upper limit of 20–5 per cent citric acid‐soluble P0and 70–80 per cent NaOH‐soluble P0was attained within 50 years of soil formation in the surface layers, and this slowly extended down the profile so that, after 10000 years, the soil had 20 per cent citric acid soluble‐P0and 70 per cent NaOH‐soluble

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb02020.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryThe mineralogy of ten profiles developed from hornfelsic rocks on the summit areas of the Merrick and Kells Hills has been investigated by X‐ray powder diffraction, thermal, infra‐red, and optical methods.The soil clays of the C horizons of all profiles contain 6 to 37 per cent of gibbsite but this mineral is not found in the A horizons. Optical observations reveal that gibbsite is associated with hematitic rock fragments which are considered to represent older soil material–i.e. are pedorelicts. It is suggested that the Merrick soils are polygenetic and consist of two soil stratigraphic units, recent pedogenic effects being superimposed on a basal horizon that has been strongly influenced by preglacial or interglacial weath

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb02021.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryChemical and mineralogical properties of brown podzolic soils, brown earths, a podzol, and an Andept have been studied with particular reference to the kinds and distribution of amorphous materials.In addition to pyrophosphate extractable (Fe + Al)/per cent clay, brown podzolic soils can be distinguished from brown earths by Fe‐oxalate/Fe‐dithionite and Fe‐pyrophosphate/Fe‐dithionite ratios, fluoride reactivity, and the presence of intergrade 2:1‐2:2 and smectite‐like clay minerals in surface horizons.Significant amounts of amorphous alumino‐silicates resembling allophane were found in the Bs horizons of the brown podzolic soils, particularly those on igneous rocks. These amounts are sufficiently large to suggest the recognition of an Andic sub‐group of brown podzolic soils in En

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb02022.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

SummaryA small scarp foot valley cut in blocky Coombe rock contained three layers of calcareous material which had been washed into it, the middle one of which was soil material. Mineralogical analyses showed that there was a lithological discontinuity immediately beneath the soil material but not above it. It seemed possible that there had been a complete inversion of soil horizons by successive erosion phases upslope and deposition in the valley bottom.Micromorphological analyses showed that the particular arrangement of soil fabric in three profiles due to decalcification, gleying, and the reorganization of clay plasma varied logically according to slope position and inferred water regimes. The soil, although thin, had been developed in place. Charcoal flakes from the soil gave a radiocarbon date of 3910±220 years BP. The material that buried the soil is a combination of slopewash and ploughwash initiated by man's clearance and cultivation of the land begun in the late Neolithic or early Bronze Age

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1976.tb02023.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY