摘要:

SummaryThe linear diffusion of H ion from a series of soil blocks, containing essentially H and Ca only as exchangeable cations, into a sink solution maintained at pH 5·2, has been studied.In three separate series of experiments, first the total concentration of diffusible H, then the amount of diffusible H in the pore solution, and finally the amount of exchangeable H associated with the solid phase have been successively varied. Account has also been taken of the variation in activity ratio:aH/√aca. The effect on the resulting flux and diffusion coefficients of the ion has been related to the H buffer power of the soil.The impedance factor of the ion through the liquid pathway is slightly lower than that for other cations determined in soil. The diffusive flux of H occurs through the liquid pathway, and the contribution of solid‐associated H is small, except possibly at low H ion solution concentrat

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01147.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryDiffusion coefficients of soil phosphate calculated from flux to chloride form of anion‐exchange resin‐paper, assuming total depletion of the labile pool at the boundary, were too small and unrealistic. Thus not all the phosphate in the labile pool contributed to the diffusion process while being desorbed at constant pH in the presence of an indifferent anion—Cl—from the resin‐paper. Desorption relationships under these conditions, using CaCl2at atmospheric CO2pressure, were markedly different from the relationship between the long‐term32P‐exchangeable phosphate and the corresponding pore‐solution concentrations. In the same soil containing different amounts of labile phosphate, a different desorption relationship was found for each phosphate level.The constant proportionality between amount of phosphate diffusing into resin‐paper and square root of time was indicative of a constant concentration at the boundary. The resin‐paper: soil system was therefore considered as an infinite composite medium in which diffusion through both resin‐paper and soil were rate‐limiting. The constant boundary concentrations were estimated by the use of the diffusion coefficients in the resin‐paper, the phosphate adsorption isotherm for the resin‐paper and the desorption relationship for each phosphate level in the soil.Diffusion coefficients, calculated using the boundary concentration appropriate to each phosphate level, were related to the slopes of the corresponding desorption relationships, resulting in values of the impedance factor similar to those found for K diffusion under similar conditions.The resin‐paper method, however, does not provide an accurate enough measure of the diffusion coefficient of soil phosphate to be of any practical use. Until better and simpler methods are found, the diffusion coefficient may be calculated using the slopes of the desorption relationship and the separately determined

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01148.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummarypH values in CaCl2suspensions of some acid Scottish soils increase with time, in some cases by 0·4 units in 24 h. This is attributed to proton uptake by a complex ion displaced into solution, and to obtain unambiguous values, pH in CaCl2suspensions should be measured within an hour of making up the suspensions.In moderately to strongly acid soils, lime potential (LP) and aluminium hydroxide potential (AHP) vary with salt concentration and soil: solution ratio. Unique values for these ion‐activity ratios can be obtained by equilibration with a single solution only when the reference cations, i.e. (Ca2++Mg2+) for LP, and Al3+for AHP, are the dominant exchangeable cations. Otherwise, equilibrium values should be obtained by interpolation from an exchange isotherm at the point where no exchange occurs, i.e. where Δ(Ca+Mg) = o for LP values and ΔA1 = o for AHP va

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01149.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryThe exchange reaction between NH4+and Mn3+was studied on a montmorillonite clay at several temperatures and different ionic strengths.Manganese was preferred to ammonium; this preference increased with the temperature and dilution of the dialysate. Comparison with published data concerning exchanges involving NH4+and the alkaline‐earths showed that in the sequence of increasing selectivity: Mg2+

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01150.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryThe coefficient of diffusion of air through the pore water of clay soils has been measured directly and has been shown to be markedly less than for free water and to decrease with water content.It has been shown that these low coefficients of diffusion are not accounted for by the sinuosity of the flow channels, or by any important departure from Henry's law of solution at curved air‐water interfaces. The main factors appear to be constrictions in the flow channels and the reduced viscosity of the adsorbed water. It is concluded that air‐water equilibrium in partly saturated soils will be attained much more slowly than is generally assu

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01151.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryMethods of dispersion used in Japan and New Zealand for soils formed on recent volcanic ash (Andepts) which involved adjusting the pH of organic matterfree soil suspensions to 4 or 10·5 were not effective on similar soils in the Caribbean. Partial dispersion was obtained by adjusting the pH to between 2 and 3 but lower (down to pH 1) and higher (up to pH 11·1) pH values were ineffective. Substantial amounts of Al dissolved at pH 1–3 probably as a result of some disintegration of the allophanoid minerals. Zirconium nitrate solutions were very efficient in causing dispersion, a concentration of 12 me Zr being necessary for complete dispersion of 20 g samples of soil. Excess Zr did not adversely affect dispersion but resulted in depression of pH of the suspensions. The high ionic charge, small atomic radius, and low ionization potential of Zr apparently resulted in saturation of the cation exchange capacity and some isomorphous substitution of Al leading to a net positive charge of the clay and an increase in anion exchange capacity. This was considered to be responsible for dispers

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01152.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryPhosphate adsorption data for 24 soils showed that although the Langmuir equation gave a good fit, there was significant curvature. Of the alternative equations examined, that of Freundlich provided a better description than that of Langmuir in 22 soils, but the best fit, accounting for more than 99·8 per cent of the variation in phosphate adsorption, was given by introducing a square‐root term:wherey= adsorbed phosphate,c= equilibrium concentration of phosphate in solution,B, A, andDare constants. The phosphate adsorption maximum, obtained from I/B, gave values in the range 325 to 1427 μg P/g soil which were 1·39 to 2·40 times those obtained from the Langmuir equation.The inclusion of a square‐root term in the Langmuir equation could be taken to imply that the soil will adsorb a little phosphate firmly, a slightly greater amount of phosphate less firmly, and so on until a limiting value is reached when all the components of the phosphate adsorption system are sa

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01153.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryApatite, magnetite, ilmenite, and magnetite‐ulvöspinel inclusions were identified in certain primary minerals in a rhyolitic pumice ash and beach sands from New Zealand using an electron microprobe. In addition to being present in apatite inclusions, P was uniformly distributed throughout the matrix of plagioclase feldspars. Included apatite was particularly common in hypersthene and also occurred within Fe and Fe‐Ti rich phases in hypersthene. Quantitative data for Ca and P and the presence of Cl and F indicate the similarity in composition between the apatite inclusions and a chlorofluorapatite from Kola (U.S.S.R.). The coexistence of various mineral inclusions in hypersthene reflects magma composition, oxygen fugacity, and temperature conditions at the time of crystallization.The presence of included apatite and lattice‐P within certain primary minerals adequately explains the low results reported previously for total P in these samples, obtained by HClO4digestion as compared to Na2O3fusion. Apatite and lattice‐P present within magnetite, ilmenite, and magnetite‐ulvöspinel inclusions are expected to be pedogenically inert in weakly and moderately weat

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01154.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryCharacteristics of the soils include well‐defined horizons, very low pH values and base saturation percentages, and a slight but general increase in the silt‐plusclay content down the profile. X‐ray diffraction shows that the soil clays are rich in mica and chlorite with subsidiary amounts of kaolinite, goethite, and lepidocrocite. The general distribution of the clay minerals in the profiles studied suggests that the weathering of chlorite leads to the formation of kaolinite in the A horizons and to the accumulation of crystalline iron‐oxide minerals in the B horizons. The presence of kaolinite, taken in conjunction with recent clay mineral studies of Scandinavian and Canadian podzols, indicates that the Ben Lawers soils may pre‐date the last glaci

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01155.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SummaryTwo pyrimidine nucleoside diphosphates have been isolated from sodium hydroxide extracts of soils. They were initially detected in fractions which had been separated by ion‐exchange chromatography, and were purified by a combination of ion‐exchange and paper chromatography. Their ultraviolet spectra indicated that one ester contained thymine and the other uracil, and this was confirmed by hydrolysis. The ratio of P to pyrimidine was 2, but their acid stability showed that the esters were not nucleoside‐5’ pyrophosphates. Both gave a positive reaction to a colour test for deoxypentose and comparison with reference samples prepared from calf‐thymus DNA showed that they were thymidine‐3′: 5’ diphosphate and deoxyuridine‐3′:5’ diphosphate.The nucleoside diphosphates may be artefacts, derived from polynucleotides by acid and alkaline hydrolysis, but their isolation confirms, for the first time, the existence in soil of characteristic st

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1970.tb01156.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY