摘要:

SummaryA 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 know

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02090.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryA 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 radiusrj,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 (rj≤ 35 nm) are largely unconstricted, and thus, an experimental curve relating temperature depression for melting to pore size is possible using only one sam

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02091.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe shrinkage potential of natural clods from a variety of clayey soils was measured and related to their physical, chemical and mineralogical properties. It is shown that the most important factors affecting shrinkage are initial bulk density, clay content, organic carbon content and cation exchange capacity of the peroxidised clay, and mica‐smectite content on a whole soil basis. Multiple regression equations involving the initial bulk density, clay content, organic carbon and cation exchange capacity accounted for 87 and 82 per cent of the variation in total shrinkage of topsoils and subsoils respectively.Because of restrictions on shrinkage imposed by factors such as climate, crops, ground‐water and moisture release characteristics of soils, soils with a high shrinkage potential may not behave very differently to soils with a much lower potential. On these grounds it is concluded that the shrinkage criteria used in US Taxonomy are not applicable in Brit

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02092.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryVolumetric water contents of 17 mineral and 3 peat soils were measured at 15 bar pressure using the ceramic plate and the pressure membrane apparatus. There was no overall significant difference between the results from the two types of apparatus and both ranked the soils in essentially the same order. Although soils of high clay or organic matter content retained up to 13.5% more water on the ceramic plate than on the pressure membrane, available water capacity (AWC) of a clay soil would be decreased by only 1–2%, and that of a peat soil by 3–4%. Due to its greater reliability, the ceramic plate is an acceptable alternative to the pressure membrane when used to determine the 15 bar water cont

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02093.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryPhosphate adsorbed on an anion exchange resin was titrated with sodium hydroxide. The inflection point which corresponds to the second pK value of phosphoric acid in solution, was lowered 0.9 pH‐unit when the acid was absorbed on the resin. This shift was fully explained by the exclusion of H+from the resin due to a Donnan equilibrium.The adsorption characteristic of the single and double charged phosphate ion on an anion exchange resin was examined at different pH values and phosphate:resin ratios. A model was suggested for the observed adsorption patter

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02094.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryFormation of hydroxy‐Al (HA) and hydroxy‐aluminosilicate (HAS) ions was studied in solutions of A1C13, orthosilicic acid and NaOH. Evidence for incorporation of Si into HA is that HA retarded the development of silicomolybdate colour and Si was retained by a cation‐exchanger. The reaction is believed to be mainly a condensation reaction between the hydroxyl groups in Al–OH–Al and Si–OH groups. The HAS with Si/Al ratio 0.3–0.6 showed infrared spectra similar to allophane‐like constituent

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02095.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryCadmium sorption was measured in 10 agricultural soils with pH ranging from 4.5 to 7.9, and total Cd content from 0.27 to 1.04 μg g−1dry soil. With initial Cd concentrations of 0.5 to 100.0 μM, sorption from 0.002 M CaCl2was described by the Freundlich adsorption equation but the gradients of the isotherms increased when the initial concentrations were below 0.5 μm. This indicates that there are specific sites of differing sorption energy; differences between soils in the gradients of the isotherms at low initial concentration could largely be accounted for by their contents of ‘free’ Fe2O3. When initial concentrations were below 0.5 μm there was a linear relationship between the quantity of Cd sorbed and the final concentration in solution. This relationship held with all soils except that of lowest pH from which there was a net loss of Cd to the solutions. Desorption was measured from three soils with contrasting pH. With the soil of lowest pH, over 80 per cent of sorbed Cd was desorbed to 0.002 m CaCl2and up to 30 per cent to 100 or 500 μm solutions of heavy metal chlorides. In contrast, only very small proportions (<1.25 per cent) were desorbed from the other soils with pH 6.7 and 7.8.The results indicate that Cd is strongly sorbed by soils of pH of above 6.0 when added in amounts comparable to additions in sewage sludges or phosphatic fertilizers, and illustrate the importance of liming as a means of reducing the mobility of this meta

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02096.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe monosaccharide composition of Ando soils, which originate from volcanic ash and have high organic matter content (8–21% carbon), was quite different from that of non‐volcanic ash soils (1.2–1.9% carbon), being richer in mannose, fucose and ribose, whereas there was less glucose in cellulose‐like form, arabinose, xylose and rhamnose. The Ando soils were also characterized by a lower percentage of organic carbon in the form of saccharide (4.4–7.4%) in comparison with non‐volcanic ash soils (10.5%), though the former soils contain a greater amount of saccharides.The monosaccharide composition of Ando soils was unrelated to the vegetation, land usage, or climatic conditions, and is presumed to be a soil characteristic resulting from the preferential accumulation of microbial poly

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02097.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryModification of the electrode assembly of a counter current paper electrophoresis method kept the pH of the suspensions stable, and gave a method suitable for studying the electrophoretic behaviour of soil colloids.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02098.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SummaryThe effect of three microbial dextrans of defined molecular weight, on shrinkage and porosity inside clods has been studied on two Italian clay soils, a Fluvisol and a Vertisol.Shrinkage was determined on dried soil samples using an electro‐optical apparatus. The same apparatus was also used to measure porosity and pore size distribution inside the clods. For this purpose large thin sections were prepared from cracked soil samples after shrinkage measurements.Dextrans influenced shrinkage and the size distribution of clods and cracks in the two soils. The major effect was found in the Fluvisol where the arrangement of cracks was changed visibly.The dextrans caused a marked increase in total porosity in the Fluvisol but had only a small effect in the Vertisol. In both soils the pore size distribution was changed resulting in a greater number of larger pores in the dextran treated sample

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1980.tb02099.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY