摘要:

SummaryThe exchange of Na, Mg, Ca, Sr, and Ba ions has been studied in the temperature range 25° C‐70° C.Vermiculite shows a preference for divalent ions over Na ions at 25° C and the preference increases very greatly at higher temperatures. The preference is largely determined by the increase in entropy which accompanies the replacement of monovalent ions by divalent ions in the vermiculite. Preference is less marked between divalent ions. These ions are similarly hydrated in vermiculite, which differs in this respect from resins and most other clay minerals. The greater affinity of Mg ions compared with other divalent ions is explained by their closer approach to the silicate surf

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1964.tb02214.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SummaryBiological transformations have been responsible for formation of Na2CO3and resultant high alkalinity in some of the salt‐affected soils of the Sacramento Valley, California. Environmental factors favouring Na2CO3formation are high ground‐water level to provide an anaerobic environment, supply of Na2SO4, and organic matter. Under these conditions, anaerobic micro‐organisms reduce sulphate to sulphide and oxidize organic matter to CO2. The sulphides hydrolyse to produce free OH which combines with CO2to form HCO3. Reduced Fe in the system inactivates the sulphides and allows accumulation of NaHCO2. Loss of CO2from NaHCO2during dry periods of the year results in formation of Na2CO3.In the laboratory an anaerobic environment and a supply of readily decomposable organic matter have been shown to be essential for development of HCO3and CO3. Ultimate development of high alkalinity depends upon inactivation of soluble and exchangeable divalent bases as precipitated carbonates. Inactivation of divalent bases favours a high exchangeable Na content as well as build up of soluble NaHCO3and Na2CO3.There is an equivalent relationship between the amount of SO4reduced and HCO3formed by the processes involved. The anaerobic organisms involved in the transformations obtain oxygen from the SO4and in turn oxidize carbon of the organic matter to CO2.Development of HCO3and CO3is favoured in situations where organic matter and Na2SO4concentrations are both high, but is limited in systems with a relatively low organic matter content and a high concentration of Na2SO44, or conversely, when a high content of organic matter is combined with a low salt concentr

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1964.tb02215.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SummaryA field and laboratory examination has been made of the soils of the Pilliga district of New South Wales, with particular reference to those showing solonetzic morphology. The area consists largely of alluvium from the Jurassic sandstones of the Warrumbungle Range, and grading diagrams for the sandfraction suggest that distribution of the soils follows the changes in depositional pattern.It seems probable that a soil type can occur, morphologically and chemically similar to that which has been described as solodized‐solonetz without ever having been through the stages of solontchak and solonetz. The conditions under which such a profile could develop are:(a) a semi‐arid to sub‐humid climate, where the mean soil temperature is too high to permit either accumulation of organic matter or the long persistence in the groundwater of organic compounds capable of chelation;(b) a parent material sufficiently coarse textured to allow movement of clay and of fine silt simply by the mechanical action of percolating water, but not so coarse that the clay is washed completely out of the column;(c) a parent material extremely low in calcium‐bearing minerals. This condition would obviously be met when the parent material of the present soil was part of a fossil profile formed in a humid or strongly leaching environment;(d) the presence of vegetation capable of absorbing silica from the soil water and returning it to the surface in leaf fall in a sufficiently finely divided form;(e) a source of sodium ions.The solodized‐solonetz could consequently be considered as the normal soil found on coarse‐textured parent material in the semi‐arid to sub‐humid zone of the warm tempera

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1964.tb02216.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SummarySurface areas of soil clays can be determined by adsorption of cetyl pyridinium bromide (CPB) from solution. The method is best used with peroxidized, air‐dry samples which have been treated with dithionite‐citrate‐bicarbonate to remove iron and some aluminium oxides, and made homo‐ionic with respect to the exchangeable cation. Apparent CPB areas derived from the plateau of the CPB adsorption isotherm agree with nitrogen areas when no expanding lattice material is present in the sample and when no large proportion of oxides of low surface density of charge remain after the dithionite treatment. When expanding lattice material is present CPB can provide an accurate measure of the internal surfaces provided that the external area is determined independently. Real variations in the crystal size, and hence ratio of external to internal area, are found with montmorillonite, and are exceptionally large for Wyoming bentonite. Specific surface areas determined by the ethylene glycol adsorption method agree reasonably well with areas of non‐expanding lattice clays determined by CPB and nitrogen provided that the specific surface coverage by each adsorbed ethylene glycol molecule is taken as 23Å2. When expanding lattice material is present the agreement is less satisfactory, but is improved in most instances by correcting the area on the basis that molecules adsorbed on external surfaces cover 23Å2but those on internal surfaces cover 46Å2. Within the range of surface densities of charge found for mica‐type materials the adsorption of CPB is much less sensitive to differences than is ethylene glycol, and therefore enables surface areas to be determined more accurately. CPB is also considerably more convenient to use, since well‐defined adsorption plateaux are formed after o

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1964.tb02217.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SummaryThe surface areas of a number of soils have been determined before and after removal of organic matter by treatment with hydrogen peroxide. The external area as determined by low‐temperature nitrogen adsorption increased after peroxidation. The total area derived from the nitrogen area and cetyl pyridinium bromide (CPB) adsorption generally decreased. Part of the clay‐organic complex was separated from some soils, and the external and total surface areas of this material before and after peroxidation determined similarly. Both the external and total areas increased after peroxidation. These results indicate that soils contain organic materials which are not part of the clay‐organic complex and which adsorb large amounts of CPB on surfaces not accessible to nitrogen molecules. A sample of peat showed a correspondingly high CPB adsorption and low nitrogen area. The large differences that occur in the nitrogen and CPB areas after peroxidation show the importance of removal of organic matter prior to the determination of the surface areas of soil clays. The surface areas were only slightly greater when carbon was completely removed by 30 per cent peroxide than when it was partly removed by 6 per cent peroxide. Organic compounds associated with the clay in the clay‐organic complex are apparently able to prevent access of nitrogen molecules to many of the clay surfaces, and also probably exclude CPB from some of these s

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1964.tb02218.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SummaryHumic acids extracted from decomposing plant and peat core samples and changes in them during the process of humification were investigated in terms of their elementary composition, the acidity and the equivalent weight, the infra‐red, visible and ultra‐violet spectra and the shape and size of the molecules and their weight. With progressive humification in peat and decomposing plant samples, increases were noted for the carbon content and the aromatic character of the humic‐acid molecules and in the number of their alcohol and ether groups, aliphatic side chains and double bonds, while decreases were observed for the hydrogen content, the molecular weight, the equivalent weight, and the hydrophilic character of the humic acids and possibly to a minor extent also for the ionization constant and the alkoxyl and alkimide groups. It was noticed that the presence of charcoal and, to a minor extent also, of clays in decomposing plant material promoted the formation of humic acids which were very similar to those found in older peat deposits, while the presence of ash did not seem to have much effect. Humic acids derived from different peat materials were found to be very similar in structure and composition, but when different types of plant material were mixed, the humic acids formed during the first stages of decomposition were very similar to those from more decomposed samples containing only the separate compo

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1964.tb02219.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SummaryAs a first step in identifying the agents responsible for the mobilization of ferric iron by an aqueous extract of pine needles, the extract is divided into three fractions, an amino‐acid fraction, an organic‐acid fraction, and a neutral fraction. The principal constituents of the amino‐acid and organic‐acid fractions are then identified and their contents determined by means of paper and column chromat

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1964.tb02220.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SummaryThe organic‐acid fraction maintains iron in solution from pH 4 to at least pH 9.5, with a maximum of 15 mg iron per gram of dried pine needles at pH 8; the amino‐acid fraction is inactive above pH 4.5. The constituents of the organic‐acid fraction are examined individually and their effectiveness com‐pared. Of the active acids, all except phosphoric acid are α‐hydroxy carboxylic acids. A synthetic solution, with a composition that corresponds to the analysis of the organic‐acid fraction, is used to demonstrate that all the major active constituents have been identified. The activity of the individual acids and the organic‐acid fraction is due to their ability to form water‐soluble complexes with iron and to stabilize ferric hydroxide sols. The water‐soluble complexes are formed over a wide range of pH and in the presence of calcium ions. The formation of ferric hydroxide sols, however, is greatly influenced by pH and by the presence of calcium ions. These findings are related to soil processes and to the morphological character of the soils on which Scots Pine t

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1964.tb02221.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SummaryA catena on the Mid‐Tertiary surface near Salisbury, Southern Rhodesia, has developed over granite. Both land form and rock form indicate a two‐cycle landscape. The climate is sub‐tropical with a 33‐in. rainfall and the vegetation is a variant of Braclzystegia savannah woodland. Profiles of good and imperfect drainage have three main horizons, namely, M (mineral); over, F/S (ferricrete and stones); over, W (weathered rock) horizons. Poorly drained soils exhibit G (gley) horizons. The W horizon of a hill‐top soil comprises material at an early weathering stage below 12 ft having a platy structure, well‐developed clayskins, and fresh minerals, but older material above that depth does not correspond to Van Wambeke's criteria for ante‐Pleistocene materials. Dynamic soil‐forming processes include lateral movement of the M horizon by sheetwash and truncation of the W horizon by

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1964.tb02222.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SummaryThe three profiles occurring at the highest levels are moderately fine‐textured and the remainder are coarse‐textured. Sandy topsoils are a feature of the whole catena. Low values of cation‐exchange capacity indicate two‐layer clay minerals. High anion‐exchange capacity values in profile I (highest level) indicate surfaceactive sesquioxides. Low percentage base saturation and high exchangeable A1 distinguish the hill‐top profiles from the remainder. This distinction is much less clearly shown by pH values. An eluvial horizon at shallow depth is distinguished by low base saturation and relatively high exchangeable Al values. Exchangeable bases from this horizon have probably been carried upwards by plants to enrich surface layers. High values of mobile iron are found only in topsoils indicating that iron enters the vegetation cycle. By contrast, high values of mobile A1 are associated with subsoils above the ground‐water table and topsoils only of profiles 6 and 7. Mobile aluminium is correlated with soluble silicon and cationexch

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1964.tb02223.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY