摘要:

SummaryRecent work on the origin of soil polysaccharide and its biological stability in soil is reviewed. It is concluded that much of the constituent hexose and deoxyhexose sugars are of microbial origin, whereas the pentose sugars are derived from plant residues. The stability of soil polysaccharide in its native state is not related to its chemical composition but to its unavailability. This is caused by inaccessibility within undecomposed biological residues and to insolubility resulting from adsorption on clay, the formation of metal complexes, or tanning by soil humic substances. Complexing by metals and tanning may also inhibit enzymic hydrolysis.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1977.tb02290.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SummaryA comparison was made of the physical properties of pairs of silt soils differing only in organic matter content. Within the textural group studied, the member of the pair with more organic matter had better physical properties relating to both plant growth and soil management. Increased organic matter give higher water holding capacities and porosities, and decreased compaction, breaking strength and bulk densities. Organic matter content alone was not sufficient to explain differences in aggregate stability to water.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1977.tb02291.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SummarySamples from field plots of silty soils in East Anglia, which were high and low in organic matter, were subjected to mild ultrasonic vibration. In soils high in organic matter particles in the 2–20 μm or 20–50 μMm size range contained most humified organic matter, whereas in soils low in organic matter, most was present in the clay sized fraction. Scanning electron micrographs of the ultrasonically separated particles showed that those from the high organic matter soils had more extensive surface coatings. Clean fragments were left after peroxide and calgon dispersion trea

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1977.tb02292.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SummaryThe adsorption of oxalic acid on synthetic goethite (α‐FeOOH) was studied using adsorption isotherms. Infrared spectra were obtained for goethite‐oxalate complexes at several points on the isotherms. On a goethite preparation with a phosphate sorption capacity of 200|μmolg−1the amounts of oxalate strongly adsorbed varied from near zero at pH 8 to about l00μmolg−1at pH 4 and below. At pH 3.4, the first l00μmolg−1of oxalic acid added was strongly adsorbed as a binuclear complex (FeOOC–COOFe), replacing two singly‐coordinated OH groups by ligand exchange. At higher concentrations a further 200 μrnol g−1of oxalic acid formed a monodentate complex (FeOOC–COOH) so that more oxalate could be accommodated.Benzoic acid was weakly adsorbed on goethite with one benzoate oxygen replacing one singly‐coordinated OH. The other oxygen of the COO group fitted into the goethite surface so that the benzene ring was at a high

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1977.tb02293.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SummaryAdsorption isotherms, the infrared spectra of adsorbed species, and the amount of hydroxyl released when oxalate is adsorbed, all indicate that adsorption of oxalate, benzoate and phosphate at low solution concentrations occurs only on A1(OH)(H2O) sites exposed on edge faces of the platy gibbsite crystals studied. This is confirmed by the finding that the vibrations of surface hydroxyl groups on the principal plate faces are unaffected when excess oxalate is present, and further supported by the low affinity for oxalate of imogolite, a tubular mineral with a very large gibbsite‐like surface, but with a very low concentration of edge sites.Infrared spectra indicate that oxalate is adsorbed in bidentate form. Near neutrality and at low solution concentrations, gibbsite adsorbs more oxalate than does goethite of comparable surface are

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1977.tb02294.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SummaryMeasurements of equilibrium phosphate concentrations, adsorbed phosphate and isotopically exchangeable phosphate (Et) were made on suspensions of acid soils at initial P concentrations ranging from 1–1000 μM and pH values between 4.2 and 6.8. At low P concentrations (1–100 μM), the affinity of the adsorption reaction was greatest at pH 5.2–5.5. This result, which was inconsistent with the ligand‐exchange hypothesis of Kingstonet al.(1967, 1972, 1974), was interpreted in terms of the formation of basic aluminium phosphates of varying composition that depended on the OH/P ratio in solution. At the highest P concentrations (1000 μM), when the affinity of adsorption was least at pH 5.2–5.5, it appeared that basic calcium phosphates were precipitating at pH values>5.5.In suspensions containing 1–100 μM P initially, values of Etdid not change consonantly with values of adsorbed P over the pH range 4.8 to 5.5. It is suggested that the Etvalues were underestimated due to the presence of labelled complexes in solution which were detected by scintillation counting but not by the analysis for orthophos‐phate. Evidence from solution studies (Whiteet al., 1976) suggested that as much as one‐third of the phosphate could be complexed with aluminium in solutions between pH 4.7 and 5.4 at P/A1 mole ratios of 0.075 to 7.5. It was apparent that the interpretation of the physical significance of E values in acid soils is complex and requires careful appraisal of the experimen

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1977.tb02295.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SummaryAmounts of inorganic phosphate (P) sorbed by two unfertilized soils, during times less than required to reach equilibrium, were affected by the ionic strength and cation species of the matrix solution. For non‐equilibrium conditions the amounts of P sorbed increased with increasing ionic strength and were greater with Ca2+than Na+. For higher P additions, resulting in equilibrium solution P concentrations greater than 30 to 40μrnole 1−1, the effects of the matrix solution on P sorption were maintained at equilibrium, whereas at lower P additions the dependence of sorption on matrix solution composition was eliminated at equilibrium.Equilibrium sorption isotherms for each soil and matrix solution were described by three Langmuir equations, which corresponded to distinct concentration ranges or regions (I, II, and III) on the overall isotherm. The free energies of sorption (ΔG) for each region, were essentially independent of the soil matrix solution. The sorption maxima for regions I and II of the isotherm for a particular soil were also virtually independent of the matrix solution used. The sorption maximum for region III, however, was markedly dependent on the matrix solution, implying a potential‐determining (p.d.) sorption me

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1977.tb02296.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SummaryData for the sorption of added inorganic phosphate (P) by contrasting soils and iron oxide gel were resolved by a method of successive approximation of the Langmuir sorption constants. Three distinct Langmuir equations described the overall isotherm irrespective of the experimental conditions used. Free energies of sorption (ΔG) for a particular region were similar for each soil and for iron oxide gel under all experimental conditions. In contrast, the sorption maximum for each region was influenced by the sorbent and experimental conditions.Because of the pronounced similarities in their P sorption characteristics iron oxide gel was used as a model surface for P sorption by soils. Three mechanisms for P sorption by iron oxide gel and by soils are proposed: (i) chemisorption at protonated surface sites, (ii) chemisorption by replacement of surface hydroxyls, and (iii) a more‐physical sorption of P as a potential‐determining

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1977.tb02297.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SummaryRelationships between the adsorption ofp‐chloroaniline and the original adsorbate concentration were investigated for five soils ranging in organic matter content from 1.7 to 8.1 per cent and in clay content from 0.5 to 21 per cent. Adsorption data were analyzed applying the linear form of the Freundlich equation. To evaluate the general relationship between adsorption ofp‐chloroaniline by soils and the solution concentration (C0), values of partition coefficient (Kp), reflecting the magnitude of distribution of chemical at equilibrium between soil colloids and solution were calculated.The experiments showed that the regression parameters were significantly correlated with the soil organic matter content. A comparison of the experimental results obtained with other soils and the calculated values gave satisfactory agreem

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1977.tb02298.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SummaryWhen copper sulphate and zinc oxide are granulated with ordinary superphosphate, insoluble copper phosphate and soluble zinc phosphate are formed. The copper phosphate has the approximate chemical composition NaCu6H3(PO4)5Cl. 6H2O and a structure similar to that of the mineral sampleite. When such fertilisers are applied to soils the development of an acid phosphate solution within granules dissolves most zinc and some copper. Subsequently, diffusion and leaching release zinc and copper from within the granules.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1977.tb02299.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY